,transcriber's ,notes3 ,underscores 80 before and after a word or phrase indicate italics in the original text4 ,equal signs 80 before and after a word or phrase indicate bold in the original text4 ,small capitals have been converted to ,,solid capitals4 ,illustrations have been moved so they do not break up paragraphs4 ,typographical and punctuation errors have been silently corrected4 ,many of the illustrations are not in numerical order4 ,this is not a mistake1 it is part of the original book4 ,,model ,,aeroplanes ,the ,building of ,model ,monoplanes1 ,biplanes1 etc41 together with a ,chapter on ,building a ,model ,airship ,,by ,f4 ,j4 ,,camm ,,with #aij ,,illustrations ,,new ,,york ,,funk ,,wagnalls ,,company ,,editor',s ,,preface ,this is a practical handbook on the principles1 constructional details and methods of building model aeroplanes1 written by a well-known model aeroplane designer and builder4 ,it deals with every part of a machine and describes a number of different types1 including monoplanes1 biplanes1 collapsible machines1 tractor monoplanes1 hydro-monoplanes1 aeroplanes driven by compressed air1 etc41 etc4 ,the concluding chapter explains how to build a model airship1 and1 as in the case of all the others1 is based on the results of practical experience4 ,readers in need of further information on the subject should address their inquiries to 8,work10 ,la ,belle ,sauvage1 ,london1 ,e4,c41 through whose columns 7but not by post71 assistance will be gladly given4 ,b4 ,e4 ,j4 ,,contents ,,chapter ,,page #a4 ,,why ,,an ,,aeroplane ,,flies #a #b4 ,,types ,,of ,,model ,,aeroplanes #ab #c4 ,,practical ,,construction3 ,,model ,,aeroplane ,,fuselages #ai #d4 ,,practical ,,construction3 ,,carving ,,air-,,screws #ce #e4 ,,practical ,,construction3 ,,bending ,,air-,,screws #db #f4 ,,practical ,,construction3 ,,planes #dg #g4 ,,simple ,,twin-,,screw ,,monoplane #ed #h4 ,,simple ,,twin-,,screw ,,biplane #fa #i4 ,,winders ,,for ,,elastic ,,motors #fi #aj4 ,,collapsible ,,monoplane #gc #aa4 ,,tractor ,,monoplane #hj #ab4 ,,hydro-,,monoplane #hg #ac4 ,,compressed-,,air ,,engine ,,for ,,model ,,aeroplane #id #ad4 ,,biplane ,,driven ,,by ,,compressed-,,air ,,engine #ajd #ae4 ,,general ,,notes ,,on ,,model ,,designing #abj #af4 ,,general ,,notes #abd #ag4 ,,easily-,,made ,,tailless ,,kites #acf #ah4 ,,building ,a ,,model ,,airship #ada ,,index #aed ,,model ,,aeroplanes ,,chapter ,i ,why an ,aeroplane ,flies ,why does an aeroplane fly8 ,the question is worthy of close examination4 ,there is one common enemy to aeroplanes--the force of gravity4 ,were it not for the existence of this force1 which1 as ,newton put it1 8is unseen and unheard and yet dominates the universe10 the problem of the aeroplane would have been solved years ago4 ,illustration3 ,fig4 #a4--;,bristol ,monoplane and ,biplane ,most readers have handled the toy kite1 and since the principles governing the flight of a kite are precisely the same as those which apply to the aeroplane1 the latter will be the more readily understood if the principles are explained through this medium4 ,full-size aeroplanes to which certain models approximate are shown in ,fig4 #a4 ,illustration3 ,fig4 #a;,a4--,forces ,acting on ,kite ,if a kite is launched in a wind it speedily attains a certain height or altitude1 at which it remains so long as the wind does not drop4 ,the wind is overcoming gravity1 which constantly endeavours to bring the kite to earth1 and hence1 since the kite remains in the air1 the forces acting on the kite are said to be in equilibrium--that is1 balanced4 ,the forces are shown diagrammatically in ,fig4 #a;,a1 and include gravity1 which is practically constant and remains unaltered under all conditions1 the air pressure which1 when sufficiently intense1 lifts the kite against the action of gravity1 and the pull of the string4 ,the air pressure is really a combination of two forces--lift and drift4 ,the drift or resistance tends to move the kite in the direction of the wind1 and lift to raise the kite in opposition to gravity4 ,since1 therefore1 drift is an undesirable factor1 the resistance of the machine must be made as low as possible1 as it absorbs power1 as will clearly be seen4 ,if the velocity of the wind drops1 the kite drops also1 increasing its angle with the horizon1 thereby causing it to capture and force down more air until equilibrium is again restored4 ,if the string of a kite breaks1 the balance of the forces is destroyed1 drift and gravity taking command and so bringing the kite to earth4 ,if it takes a wind of fifteen miles an hour to lift a kite1 similarly it would lift to exactly the same elevation if the holder of the kite-string commenced to run at a rate of fifteen miles per hour in calm air4 ,now1 an aeroplane is merely a kite with a mechanical arrangement 7the engine and propeller7 which supplies the motion necessary to fly it1 and eliminates the necessity for a wind4 ,this statement can easily be followed4 ,in the aforementioned parallel it was seen that it was immaterial whether the kite-flyer was standing still with the wind moving at fifteen miles per hour1 or whether he was moving at the rate of fifteen miles per hour in still air4 ,the result in each case is the same--the kite flies4 ,it has been stated that if the kite-string fractured the kite would fall to the ground4 ,if1 however1 it were possible at the moment of rupture to attach a weightless engine and air-screw to the kite capable of exerting a forward push equal to the drift1 the kite would still remain in the air4 ,again1 if the wind were suddenly to stop1 and the engine and air-screw were capable of moving the kite forward at the same rate at which the wind was blowing1 the kite would fly1 and in all important respects would constitute an aeroplane4 ,the kite1 it will be assumed1 requires a minimum speed of fifteen miles per hour in order to sustain itself4 ,if the wind be blowing at fifteen miles an hour the operator can remain stationary4 ,if it blows at ten miles an hour he must run at five miles an hour against the wind4 ,if it blows at five miles an hour he must run at ten miles an hour against the wind1 or twenty miles per hour with the wind to maintain the kite4 ,hence an aeroplane really has two speeds--its speed relative to the earth and its air speed4 ,the former is the rate of which it would travel a given distance1 and the latter is the sum of the speed relative to the earth and the velocity of the wind4 ,it can readily be seen that an aeroplane travelling at ten miles an hour relative to the earth against a fifteen-mile-an-hour wind has really an air speed of twenty-five miles an hour4 ,when the aeroplane1 however1 is travelling with the wind1 the air speed is the speed relative to the earth minus the velocity of the wind4 ,it is also convenient to draw a parallel between the ship and the aeroplane4 ,the weight of a ship must equal the weight of water it displaces in order to float4 ,similarly an aeroplane1 by its motion through the air1 must deflect a volume of air equal at least to its own weight4 ,the aeroplane then would just lift itself from the ground2 and the more air it deflects the higher does it ascend4 ,now1 if a #a-lb4 weight be laid on a table1 the table presses against the weight with a force of #a lb4 ,if the hand is pressed against the wall1 the wall presses back with an equal pressure4 ,if a person fires a revolver1 the force of explosion tends to force the revolver and the person in the opposite direction to the travel of the bullet4 ,these are merely illustrations of the law that action and reaction are equal and opposite4 ,it is in reality due to this law that the aeroplane can resist gravity4 ,illustration3 ,fig4 #b4--;,deflection of ,air ,fig4 #b represents an end view of a kite--or1 for that matter1 of an aeroplane4 ,the arrows indicate the direction of motion of the wind4 ,upon contact with the kite the air has a downward action1 and the consequent reaction lifts the kite4 ,hence the motion of an aeroplane through the air causes a pressure on the latter1 and the resultant is what is termed lift4 ,so far1 then1 the reason why an aeroplane lifts has been dealt with4 ,further considerations have to be dealt with after the machine has left the ground4 ,in technical language these could be summarised into a single sentence--that is1 the centres of pressure and gravity must be made to coincide1 and the machine must also be stable in both lateral and longitudinal directions4 ,illustration3 ,fig4 #c4--,position of ,centre of ,gravity ,an ordinary paper glider1 cut from a stiff sheet of cartridge paper1 will serve admirably to demonstrate this statement1 which at first sight will convey as much to the reader as ,choctaw or other remote language4 ,cut the paper to the dimensions given in ,fig4 #c and make sure that it is flat1 by pressing between the leaves of a book4 ,then project it horizontally into the air4 ,it does not attain gliding motion4 ,it performs a series of evolutions1 too quickly for the eye to perceive2 but what happens is this4 ,after launching1 the front edge turns up and the sheet glides back4 ,now the back edge turns up and the glider dives forward4 ,again the front edge turns up1 the glider slides back1 the back edge turns up1 it glides forward1 and so on until the glider reaches the ground4 ,now fix a couple of small brass paper-fasteners in the front edge 7the correct number of fasteners can however only be found by experiment1 but two will usually be sufficient for the size of glider indicated71 and launch the glider again4 ,it will be noticed that it glides steadily at a small angle to the ground4 ,the explanation of this phenomenon is simple4 ,when it was launched in the first place1 the centre of gravity of the plane lay along a line running through the geometrical centre1 parallel with the front edge1 and the glider merely rocked or oscillated about this axis4 ,the centre of pressure of the surface would be approximately in the position shown in the illustration4 ,when the correct number of paper-fasteners1 however1 are fixed1 the centre of gravity is moved forward to a position coincident with the centre of pressure1 the result being that the glider came to earth in steadiness and poise4 ,but1 even though it is now balanced1 it will still show a tendency to rock sidewise or laterally1 and if the wings are bowed up to the dihedral angle shown in ,fig4 #d1 the rock will be eliminated1 and the machine is said to be laterally stable4 ,either of the dihedral angles may be used1 although ,b is much to be preferred4 ,what of stability in a longitudinal direction8 ,just as important this1 but not quite so easy to obtain4 ,illustration3 ,fig4 #d4--,various ,forms of ,dihedral ,fig4 #e is a side elevation of two surfaces fixed to a spar1 and shows how stability is obtained longitudinally4 ,the surfaces of the elevator or tail1 according to whether the machine is 8canard0 or tractor 7canard being the term for propeller-behind or 8pusher0 machines71 is placed at a positive angle with the horizon4 ,the correct angle can1 of course1 only be found by experiment4 ,now1 from the foregoing certain laws can be deduced4 ,firstly1 in order to be stable longitudinally1 the centre of pressure must be kept as near to the centre of gravity as possible1 and secondly1 the main surface of the aeroplane must be inclined to preserve lateral stability4 ,with full-size aeroplanes there are1 however1 several exceptions to this rule1 as the faster a machine travels the more stable does it become1 and hence the dihedral angle is really unnecessary4 ,it may be well at this point to describe the action of a plane4 ,strictly speaking1 the terms 8plane0 and 8aeroplane0 are misnomers1 since no full-size machine has surfaces which even approximate to planes4 ,illustration3 ,fig4 #e4--;,disposition of ,angles ,illustration3 ,fig4 #f4--;,air-flow ,round ,plane ,illustration3 ,fig4 #g4--;,air-flow ,round ,cambered ,surface ,illustration3 ,fig4 #h4--;,air-flow ,round ,streamline ,strut ,illustration3 ,fig4 #i4--;,air-flow ,round ,square ,strut ,the reason why a perfectly flat plane is never used on full-size aeroplanes will be followed from ,fig4 #f1 which shows the flow of air over an inclined plane1 the term 8plane0 being used here in its technical sense4 ,it will be noticed that a region of 8dead air0 or partial vacuum is caused1 which seriously affects the lift of the plane4 ,fig4 #g shows the flow of air over a cambered aerofoil 7or to use the popular colloquialism 8plane074 ,less disturbance occurs in this instance1 the air following very approximately the contour of the surface4 ,it has been proved by test in the ,wind ,tunnel at the ,national ,physical ,laboratory at ,teddington that an efficiently-designed aerofoil section has a lift two-thirds greater than a true plane4 ,for a similar reason all struts or aeroplanes are 8streamlined10 as shown by ,fig4 #h4 ,the air flow1 it will be seen1 is less disturbed than by a square strut 7,fig4 #i74 ,illustration3 ,fig4 #aj4--;,flow of ,air over ,ends of ,plane ,fig4 #aj shows the air flow round a square-ended and taper-ended plane respectively4 ,it will be noticed that the air has a tendency to leak over the end of the square plane1 which is obviated by the tapered wing4 ,it may be thought that such details as these are unimportant2 but when it is remembered that an aeroplane1 correctly streamlined1 will fly for one-half the power required to fly a machine not so designed1 the enormous saving in power will be manifest4 ,the actual thrust required to lift a model aeroplane is roughly equal to a quarter of its total weight4 ,thus a model weighing #f oz4 will require #a-oz4 thrust4 ,,chapter ,,ii ,types of ,model ,aeroplanes ,with a view to illustrating some of the models described in this book complete1 some drawings are given of the more successful designs which have come into prominence during the past eight years4 ,fig4 #aa shows the ,ridley ,monoplane1 which secured several well-merited rewards in open competition1 and is an excellent machine for distance4 ,birch should be used for the longerons1 preferably of channelled section4 ,the main plane is of piano wire1 covered with proofed silk1 and the elevator is entirely of extremely thin veneer4 ,bentwood screws are used fairly short in diameter and of long pitch4 ,the machine is capable of flying a quarter of a mile4 ,the ,fairey type of model aeroplane typified in ,fig4 #ab is a most successful type1 and has achieved much in open competition4 ,it has what is known as a floating tail1 with no leading stabilising surface1 but a small vertical fin is used4 ,this is a practice the waiter is not personally in favour of1 as through such a long lever the slightest wind will cause great instability4 ,if a vane or fin must be used1 it should be placed as far to the rear of the machine as possible1 preferably just behind1 or in front of the propellers for pusher machines1 and the extreme end of the tail for the tractor type4 ,the swept-back wing tips should have a negative angle of about two degrees1 and the tail should be quite flat in relation to the horizontal4 ,illustration3 ,fig4 #ac4--;,clarke ,type ,monoplane ,illustration3 ,fig4 #ab4--,the ,fairey ,monoplane ,illustration3 ,fig4 #aa4--,the ,ridley ,monoplane ,it has been stated that this machine is a highly successful one2 it is also exceedingly intricate in adjustment1 and requires very calm weather indeed to secure successful flights4 ,it has also been flown with great success by ,mr4 ,houlberg1 who at one time held the official duration record of #hi secs with his machine4 ,the long unrelieved length of spar projecting forward of the main surface detracts much from its appearance in the air4 ,a machine of this type should not weigh more than #h oz41 and is capable of a flight of at least a minute in duration4 ,the simple #a-a-,p type drawn in ,fig4 #ac was formerly popularised by ,mr4 ,t4 ,w4 ,k4 ,clarke1 of ,kingston1 who used all-wooden surfaces1 a solid spar and bentwood screw built up in two halves4 ,this method of screw manufacture is unique1 since it enables the two blades to be prepared from jigs to a greater degree of accuracy than when it is bent from one piece4 ,moreover1 the lapping of the two halves at the boss imparts strength to the boss where it is most needed4 ,fig4 #ad is a type of tractor monoplane very successful for duration1 capable of doing a minute at an altitude of forty feet4 ,the rudder of tractor machines must always be placed above the thrust line and also above the centre of gravity1 so that should a side gust strike the machine1 the latter does not rock laterally in the air1 as a couple is set up between the underhung load and the rudder4 ,the winner of the ,wakefield ,gold ,challenge ,cup is shown in ,fig4 #ae4 ,it was designed by ,mr4 ,e4 ,w ,twining1 one of the early experimenters1 for duration1 and in the winning flight scored a duration of sixty-five seconds4 ,it is a very pretty and stable flyer1 and will rise from the ground after a run of about five feet4 ,illustration3 ,fig4 #ad4--,tractor ,monoplane ,illustration3 ,fig4 #ae4--,twining ,monoplane ,illustration3 ,fig4 #af4--;,bragg-,smith ,biplane ,fig4 #af is of the ,bragg-,smith biplane1 which first came into prominence at ,wembley in #aiji4 ,the original machine was a huge machine some four feet in span1 possessing a propeller of large diameter1 large blades1 and large pitch--quite the antithesis to ordinary practice4 ,latterly1 however1 ,mr4 ,smith has developed his machines into twin-screw1 and no doubt is entertained that even better results are obtained with this arrangement4 ,illustration3 ,fig4 #ah4--,tandem ,monoplane ,illustration3 ,fig4 #ag4--,tractor ,hydro-,biplane ,illustration3 ,fig4 #ba4--;,fuselage ,biplane ,illustration3 ,fig4 #bb4--;,blriot ,type ,tractor ,monoplane ,illustration3 ,fig4 #bj4--,tractor ,biplane ,illustration3 ,fig4 #ai4--,twining ,hand-launched ,biplane ,it should be pointed out1 in passing1 that this machine is the subject of a patent for stability1 it being claimed that greater lateral stability is obtainable from the curved lower mainplane4 ,a sketch is also given in ,fig4 #ag of a tractor hydro-biplane4 ,this should weigh about #ab ozs4 finished4 ,the tandem monoplane shown by ,fig4 #ah is another machine which has scored many successes in the early days of model aeroplaning at the ,crystal ,palace4 ,figs4 #ai1 #bj1 #ba1 #bb show the ,twining hand-launched biplane1 a tractor biplane built by the writer1 a fuselage biplane 7canard or screw behind71 and a ,blriot type tractor monoplane4 ,a tractor machine is one having the screw in front1 and a 8canard0 or 8pusher0 machine has its screw behind4 ,it is best to designate the machine by the type formula4 ,thus1 a pusher monoplane with twin screws would be a #a-a-,p-#j type4 ,if it had a tail it would be #a-a-,p-#a4 ,a twin-screw 8pusher0 biplane with or without tail would be #a-b-,p-#a and #a-b-,p-#j respectively4 ,a pusher monoplane with only one screw is a #a-a-,p type4 ,a tractor monoplane with single screw is ,p-#a-a2 a tractor biplane with single screw is ,p-#b-a4 ,if a biplane tail is also used it becomes ,p-#b-b4 ,if twin screws are used it would then become ,p-#b-b1 and so on4 ,,chapter ,,iii ,practical ,construction3 ,model ,aeroplane ,fuselages ,in no other portion of a model aeroplane has standardisation become more marked than in the design and construction of the fuselage or main frame1 both with regard to general details1 methods1 and materials4 ,this fact is singular1 because in other components contributing in a greater degree to the success of the model great diversity of opinion exists4 ,it is difficult to ascribe this lack of uniformity to any particular reason1 unless it is the failure on the part of zealous amateurs to appreciate the meaning of the term 8efficiency40 ,very few1 it is thought1 endeavour to extract the maximum amount of work for a minimum expenditure of power from the propellers1 surfaces1 and so forth1 and the writer1 in judging and tabulating some of the model aeroplane competitions held in different parts of the country1 has found models giving excellent spectacular results which1 judged on an efficiency basis1 such as 7distance flown duration of flight7 ------------------------------------- 7weight of rubber7 show a very poor result4 ,the model should be made to fly the longest possible distance1 and to remain in the air the longest possible time with the smallest possible amount of elastic4 ,this chapter is devoted to the various types of fuselage for flying models 7as distinct from 8scale0 models of full-size prototypes7 and methods of constructing them1 and the list is as representative of best practice as it has been possible for the writer1 in his extensive connection with this subject1 to make it4 ,the first shown is the ,a frame 7,fig4 #bc71 brought into prominence by ,mr4 ,r4 ,f4 ,mann4 ,it should have birch longitudinals and spruce cross members4 ,quite the best section wood to employ is that shown at ,b1 which forms a convenient seating for the cross members1 the latter being pinned and glued into position4 ,the middle bay of such a frame requires to be braced1 to counteract the torque or distortion caused by the elastic skein when the latter is in torsion4 ,diagram ,a shows the joint at the juncture of the longerons or longitudinals4 ,the hooks which embrace the elastic skeins are formed from one continuous length of wire following round the nose of the machine4 ,the bearings may be of brass1 with a lug to follow round the end of the longeron to which it is bound4 ,fig4 #bd shows the ,t or cantilever frame1 so named because of its resemblance to that letter4 ,it is usual to make the spar of this hollow1 by channelling out two pieces of wood1 and gluing and cramping them together under pressure4 ,where the bracing kingpost passes through the channel should be packed1 previous to gluing the two half spars together1 with a piece of hard wood1 so that the assembled spar is not weakened by the piercing necessary for the insertion of the kingpost4 ,such a spar should not exceed #d ft4 in length4 ,c is a section of the spar4 ,illustration3 ,fig4 #bc4--;,a ,frame ,illustration3 ,fig4 #bf4--,t ,frame ,illustration3 ,fig4 #be4--;,a and ,t ,frame ,illustration3 ,fig4 #bd4--,t ,frame ,a much stronger twin-screw fuselage1 which is a combination of the ,a and ,t frames1 is shown by ,fig4 #be4 ,here1 again1 a single-channelled longeron should be used1 although the propeller bar and supports should be solid4 ,the channelled spar can be of silver spruce or birch1 and the bar and supports of mahogany4 ,a section of the spar is given at ,d4 ,fig4 #bf shows a ,t frame made from a hollow spar1 having the ends splayed out to give the required support to the elastic skein4 ,no propeller bar is used but there is a tension wire from bearing to bearing to prevent the splayed section of the spar from spreading when the rubber is wound up4 ,e shows a section of the spar4 ,it should be pointed out that the greatest width of a spar should be placed vertically4 ,never use a square-sectioned spar4 ,moreover1 the bearing centres should only exceed the propeller diameter by in41 since1 apart from consideration of weight1 greater rigidity is obtainable from short spars than from long ones4 ,it is in details such as this that not only is a considerable saving in weight effected1 but also a material increase in strength and efficiency4 ,the ,t frame adapted to a 8rise-off-ground0 fuselage is shown in ,fig4 #bg4 ,a hollow spar should be used for preference1 but the spar cut from the solid is shown1 as most amateurs will not be in possession of a joiner's plough1 which is the tool required for this job4 ,f is a section on the vertical line of the spar4 ,illustration3 ,fig4 #bg ,illustration3 ,fig4 #bh ,illustration3 ,fig4 #bi ,illustration3 ,fig4 #cj ,figs4 #bg to #cj4--,various ,forms of ,fuselage ,in bracing such frames as those dealt with1 fine ,no4 #ce ,s4,w4,g4 7,standard ,wire ,gauge7 should be used1 fixed to small hooks bound in suitable places on the spar2 the hooks should be made from ,no4 #bb ,s4,w4,g4 ,fig4 #bg shows at ,g a perspective view of a ,t-frame propeller bar and support4 ,as there shown1 the propeller bar fits into a slot cut in the spar end4 ,if the spar is hollow1 the channel should be filled with hard wood1 such as birch1 before the slot is cut1 to strengthen the spar at this point4 ,so much for twin-screw fuselages4 ,fig4 #bh is a perspective view of a boat-shaped tractor fuselage1 it being understood that a tractor machine is one with the air-screw in front4 ,a model built on such lines is extremely neat in appearance and has a pleasing aspect in the air4 ,the three longerons are attached to a three-way brass bearing at the front end1 and are simply bound together at the rear1 the hook for the elastic being inserted between the two top members and turned round the end of one of them for security1 as shown at ,h4 ,the bottom member should be cut #a in4 longer than the two top ones1 to compensate for the shortening due to the curve1 which is effected by compressing the bottom member to the same length as the top ones4 ,the curved cross members are of bamboo1 bent to the required shape over a lamp flame2 or they could be made from piano wire4 ,their shape should be drawn full-size to use as a template during the bending operation4 ,as will be seen1 a skid is used to protect the tractor screw from damage4 ,this should extend for #b in4 beyond the bearing1 and must be attached to the bottom longitudinal directly beneath the first cross member1 so that the latter absorbs the shock of landing4 ,at the point of intersection between the skid and the axle1 the former should be bound to the latter with fine florist's wire and neatly soldered4 ,a two-membered fuselage can be adapted from this design by omitting the bottom member and skid4 ,such a fuselage would be suitable for a light machine4 ,it is an essential point with tractor models to fit a chassis2 the purpose thus being twofold4 ,first1 it protects the propeller1 and secondly1 it obviates the characteristic tendency of tractor machines to ascend 8nose first10 by keeping the weight low 7in technical language1 providing a low centre of gravity74 ,hand-launched tractor machines that are unprovided with a landing gear are seldom successful and notoriously troublesome4 ,furthermore1 the centre of thrust 7literally the axis centre1 or centre of rotation of the bearing7 should always be above the centre of resistance4 ,the centre of resistance can usually be taken 7although not quite accurate7 as being on a level with the planes4 ,an exceedingly strong two-membered tractor fuselage of the fusiform or cigar-shaped type is that shown by ,fig4 #bi1 the bearing1 which is bracketed and cut from brass1 being shown in detail at ,i4 ,in this instance the greatest width of the top spar should be disposed horizontally1 the bottom member1 with the two cross members1 providing rigidity and a girder-like form of construction4 ,the bottom member need be only one-half the weight of the top one1 as it will be in tension and so acting as a tie4 ,silver spruce should be used throughout4 ,a simple single-spar chassis1 consisting of a hollow spar1 is shown by ,fig4 #cj4 ,a kingpost and bracing is fitted underneath the spar1 to counteract the tendency of the twisted skein to bow it4 ,the chassis should be 7and this applies to all models7 of piano wire of from ,no4 #ag ,s4,w4,g4 to ,no4 #ah ,s4,w4,g4 ,a twin-screw propeller-behind fuselage of the cantilever type that is exceedingly strong1 although more difficult than it appears to construct1 is shown by ,fig4 #ca4 ,this can be made exceedingly light from a hollow spar 7packed solid at the point where the kingposts are let through71 and braced with ,no4 #ce ,s4,w4,g4 piano wire4 ,the bracing is the difficult operation1 as the tension on each wire requires to be very delicately adjusted to maintain the truth of the spar4 ,the box-girder type of fuselage shown by ,fig4 #cb is more suited to models which aim at an accurate representation of some prototype4 ,it is intricate in construction yet of neat appearance1 the difficulty being in the adjustment of the large number of bracing wires necessary4 ,the illustration gives a view of a ,blriot type of fuselage1 ,j being a detail of the cross member and compression-strut joint4 ,fig4 #cc gives some spar sections which are in common use by some of the crack aero-modellists4 ,all spars should taper in a fore-and-aft direction1 so that it virtually becomes a cantilever4 ,the greatest cross-section should be one-third of the total length from the front end of the spar4 ,illustration3 ,fig4 #ca ,illustration3 ,fig4 #cb ,illustration3 ,fig4 #cc ,illustration3 ,fig4 #cd ,figs4 #ca to #cd4--,various ,forms of ,fuselage ,another form of spar construction is that given by ,fig4 #cd4 ,q shows a spar fretted out1 the sides being covered with a thin veneer glued and cramped into place1 and ,r the method of making a slotted spar4 ,fig4 #ce is the simplest possible form of model aeroplane fuselage1 if such it can be called4 ,choice of materials and the method of utilising them to the best advantage1 so that the machine is strong without being unduly heavy1 is a phase of model aeroplaning that calls for some care and judgment4 ,there is a very erroneous impression prevalent among novices that packing-case wood or similar material is suited to the requirements peculiar to model aeroplanes4 ,nothing could be farther from the truth2 and the fact that #ej per cent4 of the total marks awarded in competition are for design and construction should show that this matter is of primary importance4 ,the true test of any model is the way it 8stands up0 to a nose dive1 for then the care and forethought of the builder in providing for anticipated eventualities will manifest itself4 ,it is to be feared that those who had lavished much care and infinite pains in the scientific construction of models were woefully handicapped in competition1 the flimsy freak that could flutter aloft for a minute or so1 with three strands of rubber wound to nearly breaking point1 gaining priority over the properly built machine4 ,there are three salient points to be borne in mind on which the durability of the machine largely depends3 7#a7 its capacity for resisting the torque of the rubber motor2 7#b7 of absorbing the shocks of rough landing2 and 7#c7 the provision that has been made for the rigid attachment of the various parts4 ,if the machine is at fault with regard to point one1 fuselage distortion is likely to occur1 and resulting from this there will be lack of alignment of the surfaces and attendant troubles4 ,point two calls for suitable bracing of the spar or spars1 and careful choice of timber4 ,it is inadvisable to use wood of square cross-section1 an oblong section with the greatest measurement placed vertically being preferable4 ,if no arrangement has been made to fix rigidly the wings1 chassis1 etc4 7point #c71 these parts are likely to rock or sway when the machine is in the air1 and so occasion bad stability1 apart from which a couple of landings would shake the machine out of truth4 ,illustration3 ,fig4 #ce4--,simple ,fuselage ,to obviate these difficulties a knowledge of the strength of the various timbers will be found useful1 and there is appended a table of the weights of various timbers4 ,the writer prefers birch for fuselage members over #c ft4 #f in4 in length4 ,although on the heavy side compared with spruce1 it will stand a great amount of rough usage4 ,spruce is also suitable for fuselages up to this length1 while maple is more suited for main planes4 ,bamboo can be used more efficaciously for cross members1 struts1 etc4 ,some model-makers use bamboo for planes1 the joint of the rib to the spar being by means of glue and cross-binding4 ,although planes so built are exceedingly strong1 it is not possible to make quite so neat a job of them as with spruce or maple4 ,another method of building main planes is to use spruce or birch spars with piano-wire ribs1 these latter being bound to the former4 ,for single-spar models the main spar should be tapered fore and aft from a point one-third of the length from the front of the machine4 ,where it is necessary to pierce the spar of a model aeroplane for the reception of a kingpost or other member1 silk tape binding should be used1 the joint being soaked with clean1 weak glue4 ,to resist fuselage distortion the spar must be suitably braced in a lateral direction1 the outrigger carrying the bracing wires being situated just forward of the centre of the spar4 ,no4 #ce ,s4,w4,g4 is quite strong enough for fuselage bracing4 ,silk fishing-line or ,japanese silk gut is admirably suited for wing bracing1 and is not so liable to stretch as the tinned-iron or brass wire sometimes used4 ,piano wire is generally used for elevators1 tail planes1 chassis1 and propeller shafts1 of a gauge ranging from ,no4 #ag ,s4,w4,g4 to ,no4 #bb ,s4,w4,g4 ,a clock-spring or piano-wire protector fitted to the nose of a model aeroplane will also prevent a broken spar should it strike any object during flight4 ,illustration3 ,fig4 #cf4--;,built-up ,plane ,illustration3 ,fig4 #cg4--,wing ,plans ,illustration3 ,fig4 #ch4--,types of ,bearings ,illustration3 ,fig4 #ch;,a4--,twin-screw ,bearings ,,weight ,,of ,,woods ,,chiefly ,,used ,mahogany #ce lb4 per cubic foot ,birch #de 0 0 0 ,maple #df 0 0 0 ,spruce #ca 0 0 0 ,bamboo #be 0 0 0 ,building ,scale ,models4--,models of well-known machines should be built to correct proportions1 if as perfect a resemblance as possible is aimed at4 ,the best way to do this is1 of course1 to adopt a definite scale4 ,the particular scale will depend principally on the size the builder requires his model2 but the size of the prototype must1 of course1 be considered1 because the large machines differ so much in point of size4 ,taking the span or width across the planes as the base from which to start1 it is assumed that the width of the model is desired to be from #be in4 to #ce in41 which is perhaps the best all-round minimum and maximum to adopt4 ,then having decided on the prototype1 multiply the span of the real machine by a fraction1 which brings the model span somewhere between the two figures4 ,for instance1 suppose it is desired to model an ,antoinette monoplane1 the span of which is about #df ft41 and multiplying by the model span becomes #cd2 therefore the scale is in4 to the foot4 ,if the model is to be a ,blriot1 then as the original has a span of #bh ft41 the model may be built to a scale of #a in4 to the foot4 ,the ,wright machine has a span of #da ft41 so a model to in4 to the foot would have a span of #cj in4 ,in this case1 perhaps1 #a-;in4 scale would not be considered too large4 ,odd scales such as in4 to the foot can1 of course1 be adopted2 but whatever the scale is to be1 the model should be set out full-size on a sheet of cartridge paper1 and the scale drawn accurately at the foot4 ,the ribs should be built up as in ,fig4 #cf4 ,in designing a rubber-driven model1 absolute scale must of necessity be departed from1 except in the principal measurements and in the distance of centres apart of spars and other important members1 which if not reproduced in their proper form and position would mar the otherwise correct appearance of the machine4 ,many of the spars will1 of course1 need to be increased in cross-sectional dimension in order to make them of sufficient strength4 ,some efficient wing plans are given by ,fig4 #cg4 ,stated briefly1 there are essentially three kinds of model aeroplanes4 ,first1 the scale model1 which is a reproduction to scale of a real machine2 second1 a modified copy of a large machine1 which is so designed as to resemble in general form some well-known prototype1 while retaining by means of a suitable motor1 generally twisted rubber1 some ability to fly2 third1 a machine which does not in any way follow the lines of full-size machines1 and is built for flight only4 ,the first of these is essentially an exhibition model2 it is more often built either to illustrate points in the design and construction of large machines1 or to demonstrate the functions of the various parts to technical classes1 etc4 ,scale models1 as a rule1 are unsatisfactory flyers1 and if they fly at all the flight is so short that little can be learned from their performance4 ,some serviceable types of bearings are given by ,figs4 #ch and #ch;,a1 on p4 #ca4 ,,chapter ,,iv ,practical ,construction3 ,carving ,air-screws ,one of the most important units of an aeroplane1 whether full-size or model1 is the screw1 since excellence of design with regard to the other portions of the machine are rendered void if the means of converting the power of the engine into work are inefficient4 ,the action of an air-screw may be likened to a bolt turning in a nut 7the screw being the bolt and the air the nut71 the difference being that whereas one turn of a bolt with1 say1 a ,whitworth pitch of #ad threads per inch in a nut is bound to advance a distance equal to the pitch _/ in41 an air-screw may only advance #ge per cent4 of its theoretical pitch1 owing to the yielding nature of the air4 ,this loss in efficiency is called 8slip10 and is usually expressed as a percentage of the theoretical pitch4 ,thus a screw with a theoretical pitch of #d ft41 which possesses #ge per cent4 efficiency1 has an effective pitch of #c ft4 ,that is to say1 each turn of the screw will take the aeroplane forward #c ft4 ,if1 however1 the screw were working in a solid1 it would advance its theoretical pitch #d ft4 ,a greater efficiency is obtainable with screws working in water1 owing to the difference in density of the two media1 namely1 air is to water as #hjj3 #a4 ,probably no air-screw has yet exceeded #hj per cent4 efficiency1 #gj per cent4 being a fair average4 ,it may1 perhaps1 not be amiss to outline some of the factors involved in the design of an air-screw4 ,having decided on the diameter of it1 the proportions of the block from which the screw is to be carved are required4 ,it is a very good rule to make the pitch from one and a half to twice the diameter for single-screw machines1 and from two and a half to three times the diameter for twin-screw machines4 ,it is possible to use much longer-pitched screws with twin-screw machines 7it being understood that the screws revolve in opposite directions71 since the torque1 or tendency of the screw to capsize the machine in the opposite direction to which it revolves1 will be balanced4 ,for the purposes of this chapter1 however1 it is presupposed that a screw is required for a single-screw machine1 and a diameter of #ab in4 has been decided on4 ,one and a half times #ab in4 gives #ah in4 as the pitch4 ,remembering the formula for pitch1 7thickness of block7 ,p #c_/ ,d --------------------1 7width of block7 where ,p pitch1 ,d diameter of screw1 and using a ratio of width of blade to diameter of screw of #f3 #a 7which gives #b in4 as the width of block7 gives #bb #ab 7thickness of block7 #ah ---- ---- ------------------1 #g #a #b #fa from which thickness of block #ied ---- approx4 #fd ,illustration3 ,fig4 #ci ,illustration3 ,fig4 #dj ,illustration3 ,fig4 #da ,illustration3 ,fig4 #db ,illustration3 ,fig4 #dc ,illustration3 ,fig4 #dd ,illustration3 ,fig4 #de ,illustration3 ,fig4 #df ,illustration3 ,fig4 #dg ,illustration3 ,fig4 #dh ,figs4 #ci to #dh4--;,carving ,air-screws4 ,the block may now be prepared from these dimensions4 ,american whitewood1 silver spruce1 mahogany1 or walnut are the most suitable woods to use4 ,the block should be planed up true and square1 and a hole drilled axially through its geometrical centre4 ,the first operation is to rough the block out to the shape shown by ,fig4 #ci1 which shows the ,chauvire type4 ,of course1 other shapes may be used as desired1 but the method of manufacture is the same4 ,now1 with a flat chisel or woodworker's knife pare the wood away 7see ,fig4 #dj7 until the hollow or concave side of the blade is formed 7see ,fig4 #da74 ,the obverse side of the other blade is then similarly treated 7see ,fig4 #db71 which clearly shows how the blade is hollowed out4 ,fig4 #dc shows the method of forming the boss of the screw1 and ,fig4 #dd how the reverse or convex side of the blade is shaped4 ,fig4 #de shows the screw roughed out1 and ,fig4 #df indicates the glass-papering operation4 ,at this stage the screw has to be balanced4 ,this is of great importance1 since the screw that is unbalanced loses a great amount of efficiency owing to the consequent vibration when it rotates4 ,in full-size practice it would be highly dangerous to use a screw that is not balanced4 ,a piece of wire is passed through the hole previously drilled1 and the heavier blade carefully glasspapered down 7with ,no4 #jj glasspaper to finish7 until the screw poises in a horizontal plane4 ,fig4 #dg shows the sort of brush to use for polishing1 and ,fig4 #dh the finished screw4 ,for models that require a good finish an excellent form of construction 7incidentally it may be remarked that full-size screws are made in this way7 is that shown by ,fig4 #di1 the laminated type4 ,these laminated screws are exceedingly strong1 as the grain1 by virtue of the splayed blanks1 follows the blade4 ,screws carved from the solid block are a trifle weak near the boss owing to cross grain4 ,the lamin could be alternate layers of whitewood and mahogany1 which give a pleasing finish to the screw4 ,a is an end view of a carved screw4 ,illustration3 ,fig4 #di4--,laminated ,air-screw ,the method of obtaining the pitch angles at various points along a screw-blade is shown diagrammatically in ,fig4 #ej4 ,it will be obvious that the pitch of a screw should be constant along the whole length of blade1 so that the air is deflected or driven back at a constant velocity4 ,an efficient screw will deliver a solid cylinder of air1 whereas an inefficient one delivers a tube of air4 ,if1 for instance1 the pitch at the propeller tip is #cj in41 whilst at1 say1 #c in4 from the centre it is only #be in41 obviously the tip of the screw will be imparting a higher velocity to the air than the portion approaching the boss1 and thus this latter would be acting as a drag upon the other portion4 ,illustration3 ,fig4 #ej4--,setting ,out ,pitch ,angles ,the method is to lay off a distance1 equal to the pitch1 to some convenient scale1 and to erect another line vertically and to the same scale equivalent to the circumference of the disc swept by the propeller1 which may be called the peripheral line4 ,subdividing this line into a convenient number of equidistant parts 7three or four are sufficient for screws up to #ad in4 in diameter71 and connecting up the points so obtained to the right-hand end of the base line1 gives the pitch angles at the corresponding points of the blade4 ,it is the subtended angles which are required1 as indicated by the arrows4 ,templates should be cut to these angles 7which1 of course1 are the angles made with the axis7 with which to check the angles along the blade during construction4 ,this checking is more necessary with bentwood screws than with carved ones4 ,,chapter ,v ,practical ,construction3 ,bending ,air-screws ,great diversity of practice exists with regard to the construction of model air-screws1 some aero-modellists favouring small diameter with long pitch1 others long diameter and short pitch1 and still others who adhere to either bentwood or carved screws in either of the above forms4 ,generally speaking1 a screw with a large diameter in proportion to short span has a short pitch1 say one and a quarter times the diameter1 while those having a short diameter in relation to span should have a fairly long pitch1 from one and a half to twice the diameter4 ,it is a useful rule to make the diameter approximately one-third the span of the machine for either single-screw or twin-screw machines4 ,this relation seems to give a very small effect on lateral stability1 whereas when the diameter is made larger1 the machine has a tendency to capsize laterally in the opposite direction to which the screw revolves4 ,this force is known as torque4 ,it can1 however1 be fairly claimed that1 for a given torque or turning power1 better results are usually obtained with carved screws1 whether short or large ones are used4 ,the writer personally prefers a large diameter and short-pitched screw1 because1 as the screw thrust is equal to the weight of air displaced1 the larger the screw the greater is the proportion of air driven back in proportion to diameter4 ,that is to say1 double the diameter and four times the volume of air is displaced for only a double expenditure of power4 ,illustration3 ,fig4 #ea4--;,bentwood ,screws ,illustration3 ,fig4 #eb ,illustration3 ,fig4 #ec ,figs4 #eb and #ec4--,standard ,types of ,bentwood ,screws ,it is difficult to speak positively on the question of the best speed at which a screw should rotate1 as the loading per square foot of surface enters into the proposition4 ,if a model has #a sq4 ft4 of surface for every ounce of its weight1 there is a speed at which the main surface will give a maximum of lift for a minimum of power1 and a screw must be fitted whose pitch1 multiplied by its revolutions per minute1 equals the distance per minute the model should fly4 ,if a screw that is too fast is fitted the model will show a tendency to 8stall10 or ascend nose first1 and if too slow a one is used the model will appear to be under-powered4 ,the writer has outlined these points to emphasise the fact that no definite rules1 but only approximations1 can be laid down1 owing to the large number of unknown quantities which would have to be taken into consideration4 ,as the aero-modellist1 however1 becomes accustomed to puzzling out the many little problems connected with model aeroplaning1 he speedily diagnoses the complaint of a refractory machine1 and applies a remedy accordingly4 ,illustration3 ,fig4 #ed4--;,bentwood ,shaft ,attachment ,illustration3 ,fig4 #ef4--,safety ,hook ,illustration3 ,fig4 #ee4--;,carved ,screw ,shaft ,illustration3 ,fig4 #eg4--,proportions of ,camm ,air-,screw ,the accompanying illustrations 7see page #dc7 show the method of making bentwood and screws4 ,fig4 #ea is a view of a finished pair of propellers4 ,to the left of this illustration is given the method of setting out the blank in terms of pitch and diameter relations4 ,the maximum blade width should be located one-third of the radius from the screw tip1 and should be about one-eighth the diameter4 ,this latter1 in turn1 should be two-thirds of the pitch4 ,inversely1 therefore1 the pitch should be one and a half timed the diameter4 ,with twin-screw machines this may be extended to twice the diameter1 or even more1 but should never exceed three times the diameter4 ,fig4 #eb is a view of the ,camm type of bentwood screw1 which has a high thrust to power ratio4 ,birch should be used for bentwood screws1 as this bends easily and yet has a tenacity which is lacking in other woods4 ,ash or hickory may be used as an alternative1 but neither of these is as satisfactory as birch4 ,before bending1 the blanks should be filled with gold size to keep the blade as rigid as possible1 and prevent it from going back or flattening out after bending4 ,fig4 #ec shows the ,twining type of screw1 which has long1 narrow tapering blades and fine pitch4 ,under test this has given extremely satisfactory results1 and can be recommended4 ,fig4 #ed shows the method of attaching spindles to bentwood screws1 a strap of tin being wrapped round the blank centre to which the shaft is soldered4 ,care should be taken to ensure that the shaft is quite central sectionally and diametrically4 ,a method of securing carved screw shafts is shown by ,fig4 #ee1 and is self-explanatory4 ,when the elastic skein is in tension it has a tendency to pull the hooks out straight1 so releasing the skein1 with sometimes painful consequences to the hand4 ,the safety hook shown by ,fig4 #ef has a brass-tube collar which slides over the end4 ,all the hooks should be covered with valve tubing1 to prevent the elastic cutting through4 ,fig4 #eg gives the proportions of the ,camm bentwood blank1 and will require no explanation beyond the fact that it is bent along the dotted lines4 ,,chapter ,,vi ,practical ,construction3 ,planes ,there is little difference of opinion regarding the construction of the planes of a model aeroplane1 and the methods of making can be classified under three headings--cane1 wood1 and wire4 ,there are advocates for each form of construction1 and it is difficult to state definitely which is the best practice1 each having equally good results4 ,the wire plane1 especially when steel wire of the music or piano variety is used1 is much stronger1 offers less resistance to the air1 and has a neater appearance than the others1 but it is slightly the heavier4 ,a wooden plane can also be made extremely neat and light1 although it is a little weak4 ,birch is the best wood to use for this purpose1 as it is extremely tough and not too heavy4 ,where cane is used for the frame1 pinning and gluing is out of the question1 hence binding and gluing must be resorted to4 ,a plane so made is very strong and flexible1 and will withstand a great amount of rough usage4 ,it is1 however1 not neat in appearance and hardly to be recommended1 although many prizes have been won by models possessing such planes4 ,yet another form which can be considered good practice consists of a combination of umbrella ribbing and piano wire4 ,this gives a very rigid and almost unbreakable plane1 but its weight for small machines is prohibitive4 ,it should chiefly be used for power-driven machines1 power in this instance meaning any form of motive power other than elastic4 ,illustration3 ,fig4 #eh4--,wooden ,planes ,the ,wooden ,plane4--,in constructing wooden planes it is usual to adopt the method shown by ,fig4 #eh4 ,the spars are set out to their correct positions but left overlapping1 so that the pinning operation does not split the ends out4 ,the pins should be driven through to secure the frame to bench1 so that it remains true until the glue has set4 ,whereupon it may be prised up with a pocket-knife1 and the pins clinched over as shown in the joint analysis ,a4 ,the centre rib should be trimmed up as shown at ,b1 to provide a means of attachment of the completed plane to the fuselage or body of the machine4 ,two spars are sufficient for models up to #cf-;in4 span1 but over that three spars should be used1 as in the part plan 7,fig4 #ei71 or two spars spaced closer together1 as in ,fig4 #fj1 may be used1 with a thread trailing edge4 ,this gives a neat appearance to the finished plane and greater rigidity4 ,illustration3 ,fig4 #ei4--,three ,spar ,plane ,illustration3 ,fig4 #fj4--,two ,spar ,plane ,illustration3 ,fig4 #fa4--;,cane ,plane ,illustration3 ,fig4 #fb4--,umbrella ,ribbing ,plane ,the ,cane ,plane4--,another form of construction that is very light is that shown by ,fig4 #fa4 ,here a length of thin cane is bent to the form of the outline1 the ribs being bent to align with the leading and trailing edges4 ,gluing and binding is used here4 ,such a plane can be made light1 but it always has an appearance anything but neat4 ,it cannot be advocated for machines over #cj in4 in span4 ,the ,umbrella-ribbing ,plane4--,umbrella ribbing can be utilised1 in conjunction with piano wire1 for plane construction as shown by ,fig4 #fb4 ,the channel of the ribbing should be thoroughly cleaned with emery cloth1 so that the leading ends of the ribs can be soldered therein4 ,three spars should be used for spans over #cj in4 ,for the planes of model flying machines steel wire offers exceptional advantages1 as it is practically unbreakable and can be bent to any desired shape4 ,another advantage is that it offers a minimum resistance when travelling in the air4 ,to the uninitiated1 the making of steel-wire planes is a difficult undertaking2 but if the following instructions are carefully carried out the planes will prove very satisfactory4 ,first procure a piece of wood about in4 thick and slightly larger than the plane to be made1 and draw on it a plan of the plane as shown in ,fig4 #fc4 ,for example1 it will be assumed that a plane #cj in4 span and #e in4 wide1 having four ribs1 is to be made4 ,for planes approximately this size1 ,no4 #ag ,s4,w4,g4 steel wire is employed4 ,before beginning the work the wire should be straightened as much as possible4 ,then lay the wire over the plan1 beginning at ,a 7,fig4 #fc7 and passing round to ,b4 ,as the wire is bent to the shape of the plan1 it must be fastened down to the board by means of small staples4 ,then cut four pieces of wire for the ribs ,c1 ,d1 ,e1 and ,f1 allowing in4 each end for turning at right angles as in ,fig4 #fc4 ,illustration3 ,fig4 #fc ,illustration3 ,fig4 #fd ,figs4 #fc and #fd4--,making ,wire ,planes ,the framework is now ready for soldering together4 ,it is essential that the wire and soldering bit must be perfectly clean4 ,apply a little killed spirits of salt to the parts to be soldered1 and then place a piece of solder in position and touch with the hot soldering bit4 ,care must be taken to see that the wires lie close together4 ,when the plane is soldered together remove all the staples and clean up all the joints with a file4 ,the joints must now be bound round tightly with fine iron wire1 which must be perfectly clean4 ,the plane must now be fastened to the board again1 and all joints soldered again4 ,when the soldering is completed the plane is once more removed from the board1 straightened1 the dihedral angle given1 and the ribs bent to the desired camber4 ,if the soldering has been carefully accomplished there is no fear of the joints giving way4 ,illustration3 ,fig4 #fe4--,swept-,back ,wing ,for covering planes it is far better to purchase a waterproof silk especially manufactured for the purpose than to attempt to use ordinary silk4 ,the silk varies in weight from #a oz4 to #a oz4 per square yard4 ,when cutting the silk about in4 must be allowed for turning over for fastening4 ,at the curved ends of the plane slits about in4 apart must be cut in the edge of the silk1 as shown in ,fig4 #fd4 ,apply a thin coating of glue to the silk 7use seccotine7 to be turned back1 and allow sufficient time for the glue to get tacky4 ,then stick over the plane1 beginning at ,a 7,fig4 #fd7 and finishing at ,b4 ,allow time for the glue to set1 then fasten the opposite end in the same manner4 ,care must be taken to stretch the silk tightly1 so that it is free from wrinkles4 ,then fasten first one side of the plane and lastly the other4 ,another method of covering steel-wire planes is to lace the silk to the framework4 ,the silk must be cut about in4 larger than the framework1 and the edges hemmed with a sewing machine4 ,the silk cover when hemmed should be slightly smaller than the framework4 ,first sew the silk roughly in position1 and then carefully sew it1 beginning at one end1 following with the other end1 and lastly the sides4 ,the stitches should first be passed through the silk1 and then round the wire at intervals of about in4 ,fig4 #fe is the plan of a swept-back wire plane4 ,the plan should be drawn full-size on a board by means of squares1 the contour of the plane being contiguous in relation to the squares as that in the illustration and the method outlined above followed4 ,the ribs should also be fitted up to the outline1 being bound and soldered to the piano-wire frame4 ,for machines above #cj-;in4 span a third strengthening spar should be fixed in the position of the dotted line to obtain rigidity4 ,two central ribs should be fitted to provide a spar-attachment4 ,the tips require to be set at a slight negative angle as at ,c4 ,,chapter ,,vii ,simple ,twin-,screw ,monoplane ,the accompanying illustrations show as simple a type of model aeroplane as it is well possible to make1 excluding the now obsolete single-stick hand-launched #a--a--,p#a4 ,it is thus a suitable model for beginners1 flights of well over a quarter of a mile being easily obtainable4 ,the main spar 7see ,fig4 #ff7 is cut from straight-grained birch1 to the dimensions given1 each end of it being tapered down to _/ in4 square4 ,the propeller bar is of silver spruce1 in4 by in4 in cross-section4 ,the end of the main spar is slotted to receive the propeller bar1 this latter being pinned and glued into position4 ,the propeller bar support is similarly slotted to take the bar1 a pin being driven through the two and clinched over on the under-side4 ,fig4 #fg clearly shows both joints4 ,at #f in4 from one end the main spar is mortised to receive two tenons which are cut on the ends of the bar supports4 ,these tenons should be so cut that they butt to one another in the centre of the mortise4 ,an idea of the shape of the tenon will be gathered from ,fig4 #fh1 a view of the joint assembled being given4 ,illustration3 ,fig4 #ff ,illustration3 ,fig4 #fg ,illustration3 ,fig4 #fh ,illustration3 ,fig4 #fi ,illustration3 ,fig4 #gj ,figs4 #ff to #gj4--;,details of ,simple ,monoplane ,two brass propeller bearings will now be required4 ,they should be cut from ,no4 #bj gauge brass1 a hole being drilled in each to allow the ,no4 #ah gauge propeller shafts to rotate freely4 ,each bearing is bound on with three-cord carpet thread1 a portion of each being left overhanging the bar to provide clearance for the revolution of the shaft4 ,these projections should be bent at an angle of #ij to the skeins of rubber1 so that the bearing faces present true surfaces for the screws to revolve on4 ,details of the bearings are given by ,fig4 #fi4 ,two hooks bent from one continuous length of wire are bound to the nose of the machine1 to embrace the skeins of rubber4 ,all bindings on the machine should be smeared with weak glue4 ,in ,fig4 #gj details are given of the spar bracing outrigger4 ,the binding1 for the sake of clearness1 is omitted4 ,a piece of wire 7hard-drawn brass is suited to the purpose7 is passed through the spar1 a portion being bent to align with each side of this4 ,it is then bent outwards1 the ends being pulled round a piece of ,no4 #bj gauge wire secured in the vice1 to form eyes1 through which the bracing passes4 ,the outrigger arm is #b in4 long1 the cranked portion of it being bound to the spar4 ,the bracing is attached to small ,no4 #bj ,s4,w4,g4 hooks bound to each end of the spar at the points shown4 ,care should be taken to apply equal tension on each wire1 or the spar will become warped4 ,the elevator is built from ,no4 #ah ,s4,w4,g4 piano wire4 ,all joints are bound with fine wire and soldered4 ,the centre rib continues over the leading edge1 being bent downwards and backwards as at ,a 7,fig4 #ff74 ,this projection fits into a hole drilled in the nose of the model2 and1 being bent at an angle1 the trailing edge binds on the spar with sufficient friction to retain it in place1 but yet permitting it to swivel should it strike any object when flying4 ,illustration3 ,fig4 #ga4--,plane ,fastening ,illustration3 ,fig4 #gc4--;,elevation of ,main ,plane ,illustration3 ,fig4 #gd4--;,finished ,screws ,illustration3 ,fig4 #gb4--;,detail of ,plane ,bracing ,the main planes are built from birch in4 by _/ in4 in cross section1 the trailing spar being bent in a jet of steam1 so that its ends sweep forward1 as shown in the plan view4 ,the ribs are pinned and glued to the spars1 the pins being clinched on the under-side4 ,the centre rib is left overhanging the spars1 as shown in ,fig4 #ga1 to enable the tin straps 7lapped and soldered together as at ,a7 to slide over them and secure the wing to the spar4 ,a section of the joint is given by ,b4 ,by removing these straps it is thus possible to alter the disposition of the main surface1 when it is desired to adjust the elevation of the complete model4 ,fig4 #ga is a perspective view of the centre rib1 the strap being shown black4 ,to move the main plane each clip is forced off the extensions of the centre rib and thus releases the wing4 ,each clip is cut from tinfoil to the dimensions given at ,a 7,fig4 #ga71 being bent to a rectangular shape1 and soldered up4 ,b is a section of the joint4 ,fig4 #gb indicates the method of attaching the diagonal wing bracing1 which imparts a dihedral angle of #a in4 to the plane4 ,a #a-;in4 dihedral means that each wing tip is #a in4 above the level of the spar4 ,an elevation of the main plane is given by ,fig4 #gc4 ,two propellers1 of right-handed and left-handed pitch 7for the reason1 see p4 #cf71 must be bent from birchwood #ab in4 dia4 #a in4 wide1 by _/ in4 thick2 a finished view of the two screws is given by ,fig4 #gd4 ,for more comprehensive details of air-screw construction see chapters ,,iv and ,v4 ,illustration3 ,fig4 #ge4--,plan of ,model ,illustration3 ,fig4 #gf4--,outrigger ,details ,illustration3 ,fig4 #gg4--,view of ,elevator ,figs4 #ge to #gg4--;,another ,simple ,monoplane ,design ,some details are also given of a similar design1 the difference being that the former machine is built for distance1 whilst the latter 7see ,fig4 #ge7 is built for duration4 ,the main spar is of spruce in4 in4 in cross-section and of the length shown in ,fig4 #ge4 ,the main plane1 as with the previous machine dealt with1 is adjusted by means of the tin clips and extending centre-rib2 a plan of the outrigger is also given in ,fig4 #gf4 ,the main plane has a dihedral angle of #a in4 ,a is a side elevation of the elevator1 showing its angle of incidence in relation to the spar1 and ,fig4 #gg a perspective sketch of the elevator4 ,an idea of a model of this type flying can be gathered from ,fig4 #gh4 ,illustration3 ,fig4 #gh4--;,finished ,model ,,chapter ,,viii ,simple ,twin-screw ,biplane ,according to the type formula1 the machine illustrated on p4 #fc is of the #a-b-p#b type1 which signifies that it has two superposed main supporting surfaces and twin screws1 and that it flies with the small plane leading4 ,the writer1 in testing the model from which the drawings were made1 found that #cjj yards were easily obtainable at every flight at an altitude of #dj ft4 or so4 ,although its construction is slightly more complicated than a monoplane1 this is amply compensated for by its majestic appearance in the air4 ,the central spar is hollow1 and measures #cf in4 by in4 by _/ in4 ,fig4 #gi shows a cross-section of it4 ,spruce was used for this1 a groove in4 by _/ in4 being ploughed in the spruce1 and a _/-in4 strip being glued over the open side4 ,the spar should be tapered off from a point #ab in4 from the front end to in4 by in41 to give additional strength4 ,the propeller bar is mortised into one end of the central spar1 and is stayed from a point #f in4 from the rear end to in4 in from each end of the propeller bar1 to which projection the bearings1 cut from sheet brass1 are lashed4 ,these latter are shown in ,fig4 #hj4 ,to the front of the spar are bound two hooks1 formed from one continuous length of wire4 ,these embrace the rubber1 and should be covered with valve tubing4 ,four birch struts should next be cut1 in4 by _/ in4 in section and #g in4 long1 to support the main aerofoils on the spar4 ,they should fit over the spar in the position shown1 small blocks uniting them top and bottom1 and should be so fixed that their upper ends are #c in4 off the spar4 ,notches are to be cut in them #b in4 below the spar1 to form a convenient fixing for the lower main plane4 ,fig4 #ha clearly shows the struts united to one of the blocks2 the saw cuts or notches will also be apparent from this4 ,a cane skid is bound to the lower blocks1 and to the spar at the position indicated in ,fig4 #hb4 ,a half-section of a round cane is quite suitable for this purpose4 ,a plan view of the model is given by ,fig4 #hc1 from which the relative position of ribs1 planes1 etc41 will be seen4 ,fig4 #hd is an end elevation looking through from the propeller end4 ,it will be observed that the screws rotate from approximately the centre of resistance4 ,the measurements given should be carefully followed to see that this is so in the completed model4 ,the dihedral angle of the planes should be made #a in41 which is ample to provide lateral stability4 ,longitudinal stability is provided by an angle of incidence on the elevator 7,fig4 #he74 ,illustration3 ,fig4 #gi ,illustration3 ,fig4 #hj ,illustration3 ,fig4 #ha ,illustration3 ,fig4 #hb ,illustration3 ,fig4 #hc ,illustration3 ,fig4 #hd ,illustration3 ,fig4 #he ,illustration3 ,figs4 #gi to #he4--;,general ,arrangement and ,details of ,biplane ,the elevator is constructed from one continuous length of ,no4 #ah gauge piano wire4 ,it is rectangular in plan1 the joint being a soldered one at the centre of the trailing edge4 ,the centre rib projects downwards for #a in41 which projection fits into a hole bored in the nose of the machine with just sufficient friction to retain it in place4 ,it should also be bent back at an angle to cause the trailing edge to bind on the spar sufficiently to allow it to swivel in the event of it striking any fixed object4 ,from this centre rib the elevation of the complete machine is adjusted4 ,the main planes are constructed from birch in4 by _/ in4 in cross-section1 five ribs connecting the longer spars4 ,no camber is given to the ribs2 they should be cut off #a in4 or no longer than is necessary1 pinned to the spars1 so that the latter are #e in4 apart1 and cut off flush after the glue is dry4 ,the top plane1 it will be noticed1 has an overhang of #c in4 ,the planes are covered underneath to eliminate the undulations which would otherwise be caused by the ribs4 ,fabric should be sewn to the elevator frame4 ,the top plane is lashed to the struts in the manner shown in ,fig4 #hf1 the centre rib resting on the small wooden blocks1 while the bottom plane is sprung into the notches previously referred to4 ,four ,no4 #bj ,s4,w4,g4 wire stanchions1 with eyes bent in them top and bottom1 as shown in ,fig4 #hg1 will next be required to form an anchorage for the wing bracing1 and to maintain the 8gap0 at the tips of the wings4 ,brass wire will do for them1 and when made their ends should be forced through the spars in the position shown in the end elevation1 and then clinched over4 ,bracing the wings should next be undertaken1 and carpet thread should be requisitioned for this purpose4 ,it is the easiest matter possible to warp the wings in this operation1 so that too much care cannot be taken in this respect4 ,it should be understood that the bracing is fixed to holes in the wooden stanchions1 where it must be securely tied1 and not continued to the opposite side without1 or the wings will rock laterally1 and so cause instability4 ,sufficient tension should be placed on the threads which pass to the wing tips of the bottom plane to impart a #a-;in4 dihedral angle4 ,illustration3 ,fig4 #hf ,illustration3 ,fig4 #hg ,illustration3 ,fig4 #hh ,figs4 #hf to #hh4--;,details of ,biplane ,the last1 and perhaps the most important1 unit of the model should be made--the propellers4 ,cut a pair of blanks1 as shown in ,fig4 #hh1 to shape from _/-in4 birch to form the propellers4 ,strips of tinfoil are wrapped round their centres1 to which the spindles are soldered4 ,bend the blades at the dotted lines under a jet of steam from a kettle1 making them to revolve in opposite directions4 ,they rotate on steel-cupped washers placed on the spindles4 ,motive power is supplied from eight strands per side of -in4 strip rubber well lubricated with soft soap emulsified with water4 ,these skeins will stand #fej turns each1 which number should be gradually worked up to on new rubber1 and not applied at the first flight4 ,a perspective view of the finished model is given in ,fig4 #hi4 ,flying the ,model4--,having selected a large open space clear of trees1 give about #ajj turns on the propellers in order to adjust the elevator4 ,if the model points its nose in the air it is elevated too much4 ,if the model flies too low it is not elevated enough4 ,in each case it requires adjustment until the precise position is arrived at4 ,the elevator should never be at a greater angle than #h or less than #e4 ,if the machine still flies too low with the elevator at #e the main planes will have to be moved forward slightly2 but the exact position is only found by experiment4 ,if it flies too high with the elevator at #e the planes will have to be put back4 ,illustration3 ,fig4 #hi4--,the ,finished ,biplane ,much depends on the way a model is launched4 ,the proper way is to hold it by the propellers1 with the thumb and forefinger along the main sticks1 taking care not to bend the propeller hooks2 then hold at about the angle shown in the photograph 7,fig4 #ij74 and launch as near as possible with the wind4 ,illustration3 ,fig4 #ij4--,launching the ,model ,it is necessary when flying in windy weather to launch the machine high and smartly1 as the wind has a tendency to beat it to the ground4 ,both propellers must be released at exactly the same time4 ,it should be carefully watched while it is flying1 and if it persists in turning1 say to the right1 the fault will probably be that the left propeller is more effective1 or the planes on the left side of the machine are elevated more4 ,for straight flights it is most important that all the planes should be in perfect alignment2 but to succeed in making a twin-propelled model fly perfectly straight is largely a matter of perfect construction4 ,the model can be steered by means of the elevator 7looking at the machine from the propeller end72 if the elevator is lowered on the left side it will fly round to the left1 and vice versa4 ,the adjustment necessary to effect this can be accomplished by means of the slot in one of the elevator uprights4 ,,chapter ,,ix ,winders for ,elastic ,motors ,to a model aeroplane enthusiast a winder is an enormous acquisition4 ,the converted egg-beater type of winder1 so much in evidence1 leaves much to be desired1 the chief fault being that the bearing spindles wear so quickly1 apart from the fact that they are awkward to manipulate single-handed4 ,a second person is generally required to support the model4 ,the winder here illustrated bears the distinct advantage that one person can wind1 keep the model in alignment with1 and forced into1 the chuck simultaneously4 ,the construction and general details will be fairly obvious from the accompanying illustrations1 so that it will only be necessary to give a brief description4 ,it consists of an ash stump1 #ac in4 by #a in4 by #a in41 tapered at one end1 as in ,fig4 #ia1 to facilitate its being forced into the ground4 ,a gear and pinion 7see ,fig4 #ia71 which may be requisitioned from some of the cheaper type of clockworks1 are mounted at the top end of the stump in a casting of ,no4 #ah ,s4,w4,g4 brass1 which is secured to the ash by means of two round-headed screws 7see ,fig4 #id74 ,it will be found that for general purposes a gear ratio of six to one will be most suitable4 ,thus the pinion may have ten teeth and the gear sixty4 ,the handle should be bent to shape after being passed through the stump4 ,copper ferrules are used on the spindles to keep the gears central between the casing1 as shown in ,fig4 #ic1 and should allow a little play to ensure easy rotation4 ,the pinion spindle must be flattened out after the gearing is put together1 and the hardwood chuck then driven on4 ,a glance at ,fig4 #ib will show clearly what is meant4 ,the slot in the chuck should be made sufficiently large to take a carved propeller4 ,illustration3 ,fig4 #ia ,illustration3 ,fig4 #ib ,illustration3 ,fig4 #ic ,illustration3 ,fig4 #id ,figs4 #ia to #id4--;,a ,model ,aeroplane ,winder ,illustration3 ,fig4 #id;,a4--,the ,winder ,illustration3 ,fig4 #ie4--;,an ,egg ,whisk ,illustration3 ,fig4 #ie;,a4--,using ,twin ,winder ,a ,double ,winder4--,as each propeller of a twin-screw machine requires to be wound up #djj to #ejj times1 it is obviously necessary to use a geared-up winder4 ,this can easily be constructed out of an ordinary egg-beater1 and one converted into a very useful instrument is shown by ,fig4 #id;,a4 ,the great advantage of using a winder of this type is that both propellers can be wound simultaneously4 ,figs4 #ie and #ie;,a clearly show how the alteration is made2 it is quite simple1 and all the tools required are a three-cornered file1 a drill1 and a soldering bit4 ,the egg-beater can be obtained for a few pence at any ironmonger's4 ,the two hooks at the nose of the machine are attached to the cross-pieces on the winder1 and the rubber is wound in the same direction as the propellers revolve 7see ,fig4 #ie;,a74 ,the winder shown is geared #e to #a1 so that #ajj turns on the winder gives #ejj turns on the propellers4 ,geared-up winders may be purchased fairly cheap4 ,,chapter ,x ,collapsible ,monoplane ,the difficulty of carrying a fairly large model to a convenient flying ground prevents many would-be makers taking a practical interest in model flying4 ,the necessity of overcoming this difficulty has resulted in several excellent designs1 one of the best being the monoplane designed and constructed by ,mr4 ,a4 ,b4 ,clark1 the secretary of the ,south-,eastern ,model ,aero ,club4 ,when this model monoplane was built the objects aimed at were extreme reliability and easy conveyance to and from the flying grounds situated some distance away4 ,the model is fitted with a chassis to enable it to start off good ground under its own power2 but this starting-gear is so constructed that the whole model will pack up flat and make a convenient parcel4 ,in fact1 the complete model will easily go into a cardboard box measuring #b ft4 #aj in4 by #a ft4 #b in4 ,referring to the accompanying illustrations1 ,fig4 #if shows the plan view of the complete machine1 ,fig4 #ig a side view1 and ,fig4 #ih a front view4 ,the body 7fuselage7 is made of two pieces of silver spruce1 #c ft4 #f in4 long1 in4 deep1 and _/ in4 thick4 ,these gradually taper towards each end1 where they measure in4 by _/ in4 ,two distance pieces of bamboo are shaped to streamline form and placed at equal distances along the fuselage2 the front piece is #b in41 the other #b in4 ,these pieces should be pointed at the ends1 and fit in a slot made in the side lengths1 as indicated at ,a 7,fig4 #ii71 and then bound very tightly with glued narrow silk tape or ribbon1 as indicated at ,b4 ,this is the neatest and also the strongest method of making joints for model aeroplane frames4 ,the ends of the two long lengths should be bound together with strong thread and carefully glued4 ,the tail 7used in place of the familiar elevator7 is built on to the rear end of the fuselage1 and is composed of two pieces of yellow bamboo1 #i in4 by _/ in by in41 tapering to in4 square at the end to which the propeller bearings are attached4 ,these bearings are made of ,no4 #ah or ,no4 #bj ,s4,w4,g4 piano wire1 and their shape is clearly shown in ,fig4 #ajj4 ,the bearings are bound to the inner edge of the wood with glued thread or fine flower wire4 ,the wide ends of the bamboo lengths are held over a bunsen 7the blue flame of an incandescent burner is very suitable71 and bent to the angle shown in ,fig4 #if4 ,the trailing edge of the tail is made of ,no4 #bf ,s4,w4,g4 piano wire1 or a ,g banjo string4 ,the wire is taken right through the end of the fuselage1 a small hole being carefully drilled in4 from the end4 ,a bead of solder should be run on the wire on both sides of the hole1 to prevent movement in a lateral direction1 and the two ends are taken through the bearings and bound to the bamboo with fine wire1 leaving sufficient to form hooks for the two bracing wires to be afterwards attached4 ,the whole of this tail framework is covered with proofed silk on both sides1 thus forming an approximate streamline surface1 which has proved remarkably efficient4 ,two triangular pieces of silk should be cut out1 just large enough to give sufficient overlap4 ,they should be attached with fish glue1 and stretched as tightly as possible4 ,illustration3 ,fig4 #if ,illustration3 ,fig4 #ig ,illustration3 ,fig4 #ih ,illustration3 ,fig4 #ii ,illustration3 ,fig4 #ajj ,illustration3 ,fig4 #aja ,figs4 #if to #aja4--;,arrangement and ,details of ,collapsible ,monoplane ,at the other end of the fuselage is attached the hooks for the elastic1 and the wire forming them is also utilised as a protector4 ,the whole construction is made from a #aj-;in4 length of ,no4 #ah ,s4,w4,g4 piano wire1 reinforced with a strip of thin bamboo1 bent to shape over a blue flame and bound with silk tape4 ,the part is shown unbound in ,fig4 #aja1 and ,fig4 #ajb shows an alternative protector2 but it is not so effective4 ,the main plane is made of bamboo and piano wire of ,no4 #ah ,s4,w4,g41 and measures #b ft4 #aj in4 by #f in4 ,the leading edge is of bamboo #c ft4 #b in4 long1 _/ in4 wide1 tapering to in4 at the ends1 with a uniform thickness of in4 ,when planed down the length should be heated over a blue flame1 and bent to the shape shown in ,fig4 #if1 the outside of the bamboo being kept on the outside of the curve4 ,the trailing edge should now be attached to the ends of the leading edge1 a length of in4 being bent up at each end of the wire1 and securely bound to the bamboo4 ,the ribs should now be cut from the same gauge wire4 ,the ends should be bent out at an angle so that they may be bound to the leading and trailing edges1 as shown in ,fig4 #ajc2 the projecting ends should be about in4 ,illustration3 ,fig4 #ajb ,illustration3 ,fig4 #ajc ,illustration3 ,fig4 #ajd ,illustration3 ,fig4 #aje ,illustration3 ,fig4 #ajf ,illustration3 ,fig4 #ajg ,illustration3 ,fig4 #ajh ,illustration3 ,fig4 #aji ,figs4 #ajb to #aji4 ,details of ,collapsible ,monoplane ,the two centre ribs are shaped as shown in ,fig4 #ajd4 ,it will be seen that the leading edge is raised in4 above the fuselage1 and the rear edge is level with it4 ,the ends of the ribs are fitted into small holes drilled in the top of the fuselage1 and kept in position by means of small metal clips1 as shown in ,figs4 #aje and #ajf4 ,four of the clips are required1 and they may be easily made from thin tinplate and soldered4 ,the ribs should be soldered to the trailing edge so as to make them secure4 ,the framework should be covered with proofed silk1 and neatly glued on all edges4 ,illustration3 ,fig4 #aaj4--,rear ,skid ,illustration3 ,fig4 #aaa ,illustration3 ,fig4 #aab ,figs4 #aaa and #aab4--;,details of ,screw ,the chassis is shown by ,fig4 #ajg1 ,no4 #ah gauge piano wire being used for the framing1 and an ordinary cycle spoke for the axle4 ,figs4 #ajh and #aji show the flexible joints of the chassis1 which folds up flat when the hooks at ,c 7,fig4 #ajg7 are withdrawn4 ,the wheels are #b in4 in diameter1 and are rubber tyred1 the ends of the spoke being burred over to keep them in position4 ,the rear skid is shown in ,fig4 #aaj1 and is made of ,no4 #ah gauge piano wire4 ,a single length is used1 being bent to shape1 passed through the end of the fuselage1 and held to its work by the projecting end ,d1 which fits in a hole in the under-side of one of the pieces of wood4 ,when not in use the skid may be folded flat4 ,the two propellers are of the simple bentwood type1 #aj in4 in diameter and #a ft4 #h in4 pitch4 ,they are made of _/-in4 birch in the usual way4 ,the shape of the blades is shown in ,fig4 #aaa1 and the angle at which the blades are bent is shown in ,fig4 #aab4 ,six strands of strip rubber should be attached to each propeller1 ordinary soft soap being used as a lubricant4 ,,chapter ,,xi ,tractor ,monoplane ,some of the competitions arranged by the ,kite and ,model ,aeroplane ,association have been for duration models of a minimum weight of #a lb41 capable of rising from the ground under their own power1 carrying a dead weight of a quarter of their own total weight4 ,such a model is that here illustrated and described4 ,it has flown repeatedly for thirty-eight seconds after rising from the ground1 while its hand-launched duration is about half a minute1 by no means a small accomplishment for a #af-oz4 model4 ,it will be seen that it has somewhat larger dimensions than the ordinary rubber-driven model4 ,the top main spar is of spruce1 #d ft4 #f in4 long and in4 by in4 in cross-section1 the bottom one being #b in4 longer and in4 by _/ in4 in section4 ,the bottom member is to be bent by steam approximately to the shape shown in the side view of the machine 7,fig4 #aac71 and then fitted to make a clean butt joint to the top spar ,b 7,fig4 #aad74 ,bearings for the two -in4 gears1 details of which are shown in ,fig4 #aae1 are bent to shape from ,no4 #bj gauge sheet-brass1 a lug being left projecting to engage with the bottom member of the fuselage4 ,the holes for the shafts should be drilled so that the gears make a fairly tight mesh4 ,the spindles are to be of ,no4 #af gauge piano wire1 on to which the gears are to be soldered4 ,the propeller shaft is continued forward of the bearing for #a in41 and is bent back at an angle 7as shown in detail at ,a in ,fig4 #aaf7 to grip tightly in the propeller boss4 ,the gears are kept central between the two bearings by means of pieces of brass tubing1 which are slipped on the spindles at each side of the bearing and soldered in position4 ,illustration3 ,fig4 #aac4--,side ,elevation ,illustration3 ,fig4 #aad4--,spar ,joint ,illustration3 ,fig4 #aae4--;,gearing ,illustration3 ,fig4 #aaf4--,shaft ,attachment ,illustration3 ,fig4 #aah4--;,chassis ,illustration3 ,fig4 #aai4--,main ,plane ,attachment ,elastic hooks1 formed from ,no4 #af gauge wire1 are fixed at the rear end of the fuselage1 and serve the double purpose of providing an anchorage for the bottom spar1 which is whipped and glued with the hooks to the top spar4 ,fig4 #aad shows clearly what is meant4 ,bamboo1 of _/-in4 by -in4 cross-section1 is used for the tail skid1 which is secured to the fuselage by thread binding4 ,piano wire is used for the landing chassis1 and of the same gauge as hitherto used on the spindles4 ,the triangular side struts of the chassis should first be framed up from one continuous length of wire1 lugs being bent at the point where they meet the fuselage1 to be bound with fine tinned iron wire and soldered to the spar4 ,figs4 #aac1 #aag and #aah clearly show its construction4 ,make the axle of such a length that a #ab-;in4 wheel-base may be left after the wheels are placed on4 ,the writer found that #b-;in4 rubber-tyred disc wheels left nothing to be desired for rising off short grass4 ,care should be taken that the measurement from the periphery of the wheel to the top spar1 measured1 of course1 in a vertical direction1 shall be #i in4 7see ,fig4 #aac74 ,illustration3 ,fig4 #aag4--,plan ,illustration3 ,fig4 #aba4--,kingpost ,illustration3 ,fig4 #abb4--,wing ,bracing ,attachment ,as twin gears of equal size are used1 the torques of the oppositely revolving skeins of rubber will be balanced4 ,hence no bracing will be found necessary on the motor spar4 ,the gearing1 by the way1 is bound to the top and bottom members of the fuselage with tinned iron wire1 and soldered as shown in ,fig4 #aae4 ,the main plane is of rather a large span1 and it is essential that birch be used1 in4 by _/ in4 in section4 ,the wing spars are bent at their centres1 to impart a tapering wing plan analogous to the ,martinsyde monoplane4 ,seven ribs connect the spars1 and these are cambered to in4 ,the wing tapers from #aj in4 at the centre to #g in4 at the tips1 the centre rib projecting for in4 fore and after of the wing4 ,the tin clips shown in detail in ,fig4 #aai slip over these1 and so provide a means of adjustment to the centre of pressure of the complete machine4 ,choice of covering must be left to the builder2 but yellow ,japanese silk1 proofed with varnish1 will be found quite suitable1 and of a rather pleasing amber hue4 ,a birch kingpost passes through the fabric1 and to this the wings are braced by ,no4 #ce gauge music wire4 ,sufficient tension should be placed on the top wires to give the wings a #c-;in4 dihedral angle1 as in ,fig4 #abj4 ,the detail illustration of the kingpost 7,fig4 #aba7 is self-explanatory4 ,the bracing wires are anchored to wire hooks forced through the wing in the manner shown in ,fig4 #abb4 ,the correct position of the main plane should be found by trial4 ,the kingpost can then be permanently fixed to the main spar by pinning and gluing4 ,no4 #ah gauge wire of the music or piano variety should be used for the tail and rudder4 ,draw the plan form of the wing full-size on a board2 pins may then be driven partly home on each side of the line at spaces of about #c in4 ,the wire may now be pushed between the pins1 cut off1 and lapped for in4 ,the two cross ribs can be soldered to the tail before the tacks are withdrawn4 ,it will be found on releasing the tacks that the wire will remain true to the shape of the template4 ,this may seem a rather laborious process2 but it is far quicker and easier than attempting to guess the correct curvature4 ,the rudder may be made to any convenient shape1 preferably that shown4 ,the two ends should be sprung outwards after the form of the letter ,a to form a clearance for the rubber hooks1 and then soldered to the tail4 ,a very slight adjustment of this will be found necessary to obviate propeller torque4 ,illustration3 ,fig4 #abj4--;,front ,elevation ,no provision has been made for the adjustment of the lift on the tail4 ,indeed1 none was found necessary1 it being quite an easy matter to bend the tail flaps up or down to increase or decrease the elevation4 ,they should always1 however1 have a slight negative angle to maintain longitudinal stability4 ,the tail should be bound to the fuselage with copper wire4 ,the propeller1 of the usual integral type1 is carved from the solid block1 which measures #ae in4 by _/ in4 by #b in4 ,it should be made of right-handed pitch1 and must be placed on the right-hand gear1 so that thrust balances torque4 ,on each side1 nine strands of -in4 strip rubber1 lubricated with diluted soft soap1 supply the motive power4 ,this will stand approximately #fjj turns4 ,vaseline will suffice to minimise friction on the gears4 ,it is advisable to test the model down the wind with about #ej per cent4 of the maximum turns4 ,the main plane should be moved forwards to increase the elevation1 and backwards to decrease it4 ,illustration3 ,fig4 #abc4--;,complete ,tractor ,monoplane ,fig4 #abc shows the model in perspective4 ,,chapter ,,xii ,hydro-monoplane ,the present machine is capable of making a flight of about sixty seconds after rising from the water1 which it does after travelling from #h ft4 to #aj ft4 under normal conditions4 ,this model is what is known as the 8,a0 frame 7see ,chapter ,,iii47 type of monoplane fitted with a loaded elevator4 ,the framework or fuselage is not constructed in quite the orthodox manner1 but in the manner shown in section at ,d and ,e 7,fig4 #abd74 ,these side members are made from two pieces of best silver spruce #c ft4 #c in4 long1 in4 by in4 at the forward or elevator end1 in4 by in4 in the middle1 between the elevator and the main plane1 and in4 by _/ in4 at the propeller end4 ,this tapering is necessary in order to make the wood proportionate to the strain to which it will be subjected4 ,this is called a cantilever4 ,after each stick has been planed to the above sizes1 a hollow chisel is used to channel out the wood on one side1 the finish being given with a woodworker's file4 ,the opposite side is rounded off after the inside is finished4 ,the front ends are bound together and glued1 the forward hooks 7to which the rubber is attached71 and the protector1 shown by ,fig4 #abe1 being incorporated at the same time2 these are made of ,no4 #ah and ,no4 #bj ,s4,w4,g4 piano wire respectively4 ,the other extremity of the fuselage is held #i in4 apart by means of a bamboo distance strut1 measuring _/#af in4 by _/#af in4 ,this strut1 together with the three others1 is carefully shaped1 the ends sharpened1 and then fitted into a split in the side members as indicated in ,fig4 #abf4 ,considerable care is needed in making this form of joint2 but when the joints are glued and bound over with -in4 strip silk1 they are wonderfully strong4 ,the propeller bearings are made of ,no4 #ah ,s4,w4,g4 wire1 and resemble a lady's plain hairpin bent at right angles midway1 with a cupped washer soldered on the round end to take the thrust 7see ,fig4 #abg74 ,these washers1 known as ,french clock collets or cupped washers1 may be procured at any watch repairer's at #c;d4 per dozen4 ,the propeller bearings should be bound to the fuselage at the same time as the end distance piece is fixed4 ,the frame is trussed with two diagonal bracing wires2 ,no4 #cj ,s4,w4,g4 piano wire should be used1 this being strained with the aid of hooks as shown in ,fig4 #abh4 ,to tighten the wire1 twist the hooks with a pair of round-nose pliers4 ,the main plane is #cg in4 in span1 with a maximum width of #g in4 at the centre1 tapering to #f in4 at #c in4 from the tip4 ,the camber is in4 at the centre and in4 near the tip4 ,the frame is constructed of bamboo1 the leading edge and the end ribs being one long piece of selected yellow bamboo1 _/ in4 by _/ in41 and is bent to the shape by holding over an incandescent gas burner4 ,the trailing edge is made of similar material2 but is straight when looked at in plan4 ,this piece measures #cd in4 by _/ in4 by _/ in41 and is joined to the end ribs as shown at ,c 7,fig4 #abi71 afterwards being bound with strip silk4 ,the ribs are all _/ in4 by _/ in41 being bent in the manner suggested above and split-jointed into the spars4 ,illustration3 ,fig4 #abd4--,plan ,illustration3 ,fig4 #abe4--,nose of ,model ,illustration3 ,fig4 #abf4--;,cross ,member ,joint ,illustration3 ,fig4 #abg4--;,bearings ,illustration3 ,fig4 #abh4--;,bracing ,anchorage ,illustration3 ,fig4 #abi4--,rib ,attachment ,the main plane has a dihedral angle of #a in #g2 that is1 the tips are about #b in4 higher than the centre of the plane4 ,the plane is covered with proofed silk secured with fish glue4 ,the elevator is a miniature edition of the main plane1 being #ac in4 in span and provided with a chord of #c in4 ,the camber is in4 at the centre and _/ in4 at the tips4 ,it is attached to the framework in the following manner3 ,two straight pieces of thin bamboo #e in4 long are attached to the under-side of the elevator1 and run parallel to the tapered end of the fuselage1 and the projecting ends of these pieces are attached to the frame with elastic bands4 ,to give an increased angle1 blocks of wood are placed under the bamboo strips as shown in ,fig4 #abe1 these pieces being in4 high4 ,a greater or less angle may be given by moving the blocks either backwards or forwards as required4 ,illustration3 ,fig4 #acj4--,side ,elevation ,illustration3 ,fig4 #aca4--;,floats ,illustration3 ,fig4 #acb4--,rear ,float ,illustration3 ,fig4 #aca;,a4--,rear ,float ,illustration3 ,fig4 #acc4--,screw ,eye ,illustration3 ,fig4 #acd4--,rear ,elevation ,the floats are three in number1 and are of equal dimensions1 #f in4 by #b in4 by in4 at the greatest depth1 which is about three parts of the way from the front4 ,to construct the floats1 two side pieces of _/-in4 birch are cut to the shape given in ,figs4 #acj to #aca;,a1 and these are nailed to the ends of a piece of whitewood measuring #b in4 by in4 by in4 ,joining each end of the side pieces is a piece of whitewood1 cut to fit so as to form a nice entry1 the forward piece being flat on top and the rear piece flat on the bottom4 ,at the place marked ,g 7,fig4 #acj7 there is an additional piece to strengthen the float and keep the silk covering taut4 ,running from front to back there is a -in4 by _/-in4 strip of bamboo to keep the silk from sagging when running on the water4 ,the front floats are nailed to the bamboo cross-piece1 and the adjustment is made by bending the small pieces of piano-wire ,f4 ,the rear float attachment is shown by ,fig4 #acb1 and the adjustment is made in the same way4 ,the wire is attached to the floats with small hooks as shown by ,fig4 #acc1 these being screwed into the distance pieces of the float4 ,the connecting wires are bound to the fuselage with strip silk and glued4 ,the flat portion of the under-side of the front floats has an angle of incidence of #a in #f1 the rear float angle being #a in #h4 ,another type of float is quite practicable1 if preferred4 ,illustration3 ,fig4 #ace4--,model ,hydroplane ,the propellers are #aj in4 in diameter with a pitch of #bc in41 and are carved from a solid piece of mahogany4 ,the blades are glasspapered to a thickness of about _/ in41 and are strengthened with silk stuck on one side4 ,the floats are covered with the same proofed silk as the planes2 but to ensure complete imperviousness to water1 coat with a mixture of #b parts of boiled oil and #a part of gold size4 ,fig4 #acd is a rear elevation4 ,the main plane rests flat on the fuselage1 and is held in place by means of two #i-;in4 by -in4 by _/-in4 pieces of bamboo1 which are secured to the framework with elastic4 ,this method allows the plane to be readily removed4 ,there are six strands of thick -in4 strip elastic to each propeller1 and the number of turns given is about #ijj when well lubricated4 ,the total weight of the complete model is only #f oz41 and in making the machine every effort should be made not to exceed this amount4 ,fig4 #ace shows a model hydro-monoplane in perspective4 ,,chapter ,,xiii ,compressed-air ,engine for ,model ,aeroplane ,signs are not wanting that compressed air as a motive power for model aeroplanes will become equally as popular as the twisted skein of rubber1 which has practically held the field since it was introduced about the year #ahgj by ,alphonse ,penaud4 ,one of the chief disadvantages of the rubber motor is that experiments of a full-size scale nature cannot be undertaken1 owing to the length of frame required in order that the necessary power and duration of run may be obtained1 and also owing to the disposition of weight1 and consequently of the centre of gravity1 not being tantamount to that obtaining in full-size practice4 ,with a compressed-air plant these disadvantages are eliminated1 since the weight can be kept well forward1 thus making possible the designing of a model which represents in essential proportions a full-size machine4 ,particulars are here given of a highly successful plant1 for which the machine described in the next chapter was especially designed4 ,several of the illustrations in this present chapter are exaggerated to render the construction clear1 and it is thought that the details given will be found comprehensive4 ,illustration3 ,fig4 #acf ,illustration3 ,fig4 #acg ,illustration3 ,fig4 #ach ,illustration3 ,fig4 #aci ,figs4 #acf to #aci4--;,arrangement and ,details of ,engine ,fig4 #acf gives a plan view of the engine1 which is rotary with1 of course1 a stationary crank-shaft4 ,the five cylinders are soft-soldered to what may be termed the crank-case1 which consists of two circular brass discs of the gauge indicated4 ,in order that the cylinders may be accurately located round the plates1 a wooden jig should be made with slots to receive the cylinders1 and a recess to take the plate4 ,five lightening holes are drilled in the two plates as shown4 ,the front plate1 that is1 the one carrying the propeller bolt1 is1 however1 left off until the pistons1 crank-shaft1 and sleeve are assembled4 ,illustration3 ,fig4 #adj4--;,details of ,crank ,illustration3 ,fig4 #adb4--;,connecting ,rod ,illustration3 ,fig4 #ada4--,section of ,cylinder ,illustration3 ,fig4 #adc4--,piston ,tongues ,fig4 #acg gives a side elevation of the engine1 with the crank-shaft and sleeve shown in section4 ,it will be seen that the sleeve butts to a shoulder1 a slight undercut being given to the shaft when turning this portion to ensure a good joint4 ,from this figure the inlet and exhaust principle will be manifest4 ,it will be noticed that as each inlet pipe coincides with the right angular inlet in the shaft1 so does it receive a charge of compressed air4 ,the pressure on the piston revolves the engine1 thus shutting off inlet to that particular cylinder and bringing the next cylinder in line with the inlet4 ,as soon as the first cylinder nears the bottom of its stroke it begins to exhaust through the diametrically opposed exhaust port4 ,needless to say1 the crank-shaft and sleeve must be turned a good running fit1 otherwise there will be considerable waste of power4 ,the best method to employ is to turn the shaft a push fit within the sleeve1 and then to grind it in with rottenstone4 ,when soldering the inlet pipes into the sleeve1 care must be taken to ensure that they do not become 8choked0 with solder4 ,the sleeve should afterwards be reamed out to remove all superfluous solder4 ,when soldering the sleeve into the back plate care must also be exercised to ensure that it is truly at right angles to the plate4 ,it must be clearly understood that the engine revolves with the sleeve as a bearing4 ,the five holes which are drilled round the sleeve to receive the inlet pipes must be equidistant1 so that the periods of inlet are synchronous4 ,fig4 #ach gives an enlarged view of the crank-shaft and sleeve1 and is self-explanatory4 ,observe that the exhaust port is larger in diameter than the inlet4 ,details of the pistons are shown by ,fig4 #aci4 ,the connecting-rods are soldered to tubular distance pieces1 which rock on the _/-in4 silver-steel gudgeon-pins1 which pass through the pistons1 being cut shorter than the outside diameter of the piston to avoid possible scoring of the bore of the cylinders4 ,the gudgeon-pins are soldered into position1 the superfluous solder being scraped from the piston walls4 ,to ensure airtightness of the pistons and cylinders1 cupped leather washers are fixed to the piston-heads by means of tin tongues soldered to them1 and which are forced through the washer and bent over4 ,the ordinary cycle-pump washer is admirably suited to the purpose1 but the height of the washer when within the cylinder should not exceed in4 ,illustration3 ,fig4 #add4--;,container ,fig4 #adj gives dimensions of the crank and throw1 to exaggerated scale1 to avoid crowding the details4 ,the important point to bear in mind when beginning this portion of the construction is to obtain the correct stroke1 since the cylinders are designed to take a stroke of in4 only4 ,see also that the crank-pin revolves truly1 that is1 at #ahj to the shaft4 ,fig4 #ada is a longitudinal section of the cylinder4 ,as there shown1 the cylinder-head is 8let in0 the head and soldered there4 ,the inlet pipes should be packed with resin prior to bending1 this being afterwards melted out4 ,the connecting-rods are shown by ,fig4 #adb1 the important dimension1 obviously1 being the centre distance of the holes for the crank-pin and gudgeon-pin respectively4 ,these are of ,no4 #bj ,b4,w4,g4 brass4 ,the tin clips used to secure the cupped leather washers to the piston head 7four of which are used for each piston1 so that twenty in all will be required7 are shown by ,fig4 #adc4 ,they are of ,no4 #cj ,s4,w4,g41 and are bent along the dotted line to a right angle1 the -in4 portion being the end to be soldered to the piston4 ,the compressed-air container shown by ,fig4 #add is made from copper foil of the thickness shown4 ,this is folded round a wooden former of circular cross-section1 and tied tightly in place while the lapped joint is being soldered4 ,the two faces of the joint that are in contact should first be tinned1 using ,fluxite or resin as a flux2 spirits of salt should on no account be used1 as this has a deleterious effect on metal of so fine a gauge2 and a mediumly heated iron should be used to solder the joint4 ,wind the body with the ,no4 #ce ,s4,w4,g4 piano wire1 soldering each spiral at each revolution so that it maintains its correct pitch4 ,now attach one of the half-balls 7which for preference should be provided with a stepped flange as shown7 while the body is still on the wooden former1 first tinning the two surfaces in contact1 and then 8running0 the solder round with a mediumly heated soldering bit1 and so sealing the joint4 ,prior to attaching the second half-ball to the other end1 a tension wire must be attached to the flange1 either of the valve or the tap 7according to which half-ball was attached first71 by soldering4 ,this is then passed through the body of the container 7the wooden former1 of course1 now having been removed71 and threaded through a hole drilled in the half-ball at a convenient point near the centre4 ,tension is now applied to the wire and the second half-ball eased into position1 and while still pulling on the wire it is soldered into the hole through which it passes1 afterwards being cut off sufficiently long to form a coil on the end4 ,it will1 of course1 be clear that the valve 7of the ,lucas type7 and tap are soldered to the half-ball before the latter are affixed to the container body4 ,the container should be inflated and immersed in paraffin to test for leakages1 and when these are stopped up the container and engine may be connected by a short length of tubing4 ,the engine is then ready for running4 ,thin machine oil should be used for lubricating purposes1 and where necessary the connecting-rods must be staggered for clearance4 ,in conclusion1 it should be pointed out that the plant should not weigh more than #aj oz4 complete1 and is capable of flying a machine weighing #b lb41 provided that it is efficiently constructed4 ,the container should be inflated to a pressure of not less than #ajj lb4 ,fig4 #ade shows a similar compressed-air model aeroplane engine complete4 ,illustration3 ,fig4 #ade;,a4--,compressed-air ,plant for ,model ,aeroplane ,the accompanying photographic reproduction shows a model compressed-air plant for model aeroplanes which is similar in general design to the one illustrated4 ,the difference is that inlet takes place through hollow connecting-rods1 which are ball-ended and fit into ball seatings4 ,the cylinders oscillate1 and the connecting-rods1 being rigidly attached to the pistons1 by their angularity during revolution form the inlet and exhaust mechanism4 ,the propeller is geared up in the ratio #b3 #a4 ,illustration3 ,fig4 #ade4--,three-cylinder ,engine ,the design is analogous to a very early ,french engine much in evidence in the early days in model experiments4 ,it is thought that the photograph will give the reader an idea of the general arrangement of the plant previously described4 ,driving ,small ,biplane4--,fig4 #ade is a front elevation1 with the front plate removed1 of a #c-;cylinder engine on similar lines1 which would be sufficiently powerful for models up to #ab oz4 weight4 ,as will be obvious1 the three cylinders are fixed 7by solder7 to two circular discs of ,no4 #bj gauge brass forming the crank chamber4 ,the cylinders and various component parts should be assembled before the front plate is fixed4 ,a length of brass tube is soldered into the back plate1 and equidistant round its periphery three -in4 holes must be drilled to receive feed pipes which pass to the cylinder heads4 ,a piece of brass rod to form the crank-shaft must be turned to make a good running fit within the tube and inlet1 and exhaust holes drilled as indicated by the dotted lines4 ,the pistons should be made an easy fit4 ,pieces of by-pass tubing are soldered into the small ends of the connecting-rods4 ,through these tubes pass the gudgeon-pins which are anchored to the piston walls4 ,the position of the connecting-rods in relation to the piston is thus maintained4 ,the container 7into which air is compressed with a foot pump to from #ajj lb4 to #abj lb4 per square inch7 is constructed from copper foil of three-thousandths 7#jjc7 of an inch thickness1 and is of the same dimensions as the five-cylinder one4 ,,chapter ,,xiv ,biplane ,driven by ,compressed-air ,engine ,the model aeroplane illustrated by ,fig4 #adh has been designed to suit the compressed-air plant fully illustrated and described in the preceding chapter4 ,it is from the results obtained from the testing of the plant that the dimensions of a suitable model for it are determined2 and while the design may suit the majority of the plants constructed from the illustrations shown in pp4 #ie to #aja1 it is chiefly given to show the correct method of designing a 8power-driven0 machine1 since the power unit 7unlike the elastic motor7 cannot be varied1 and recourse to some established line of reasoning becomes essential4 ,the first thing to do1 then1 once the plant has been 8tuned up10 is to ascertain the thrust obtainable from it4 ,this is found by suspending the plant by the valve on a balance1 with a container fully inflated1 the weight registered being carefully noted4 ,the container pressure should now be released1 and the weight registered when the motor is running observed4 ,by subtracting the former from the latter the thrust is obtained4 ,thus1 assuming the plant1 at rest1 to weigh #h oz41 and when running #ab oz41 it is clear that the thrust is equal to #d oz4 ,now1 it is necessary to know the average thrust developed1 since1 as hitherto explained1 the thrust is not constant1 but gradually diminishes as the density of the air in the container approaches normal atmospheric conditions2 that is1 #adf lb4 per square inch 7known as an atmosphere74 ,it is possible to obtain some very interesting data by plotting a graph of the thrust given off at various moments from the release of the pressure in the container4 ,meanwhile it can be taken as a good rule that the thrust registered after one-third of the effective run of the motor represents approximately the average thrust2 and the figure given above 7#d oz47 will serve for the purpose of illustration4 ,it is next necessary to know the weight of the model it will lift4 ,it is well established that a plant will fly a machine weighing from four to six times the weight of the thrust it develops1 although1 of course1 much depends on the efficiency of the model2 the greater the complexity of frame members the lower the lift drag ratio1 and consequently the lower the ratio between the thrust and the weight of the model4 ,compromising1 and taking #e3 #a as the ratio1 #bj oz4 is obtained as the total weight of the plant and model4 ,the next point to be decided on is the loading1 and as the model is to be a biplane a comparatively light loading can be used4 ,in the case of the machine shown in side elevation by ,fig4 #adf and in front elevation by ,fig4 #adg1 #d oz4 has been taken as the loading per square foot4 ,so that the total area of the wings will be #bj #e sq4 ft4 #gbj sq4 in4 ---- #d ,a span of #ed in4 for the top plane and #df in4 for the bottom one has been decided on1 and by using a chord of #h in4 the total area of the wings vies very approximately with this figure1 allowing a small margin for excess weight4 ,the area of the tail1 which is non-lifting1 need not be taken into account4 ,although the 8gap0 is given as being equal to the chord1 it could be made1 if anything1 in4 greater4 ,now with regard to actual materials4 ,birch is to be used for the longitudinals1 straight in the grain and of the cross-sections illustrated4 ,the lower member is bent under steam to the curvature shown--of #f-;in4 radius4 ,two vertical struts support the wings1 and these should be cut from hickory4 ,a short tie-strut secures the bottom longitudinal to the front inter-strut1 the joint being made by means of side angle-plates bound into place4 ,it will be found good practice to make a full-size drawing of the machine in side elevation1 so that it can be used as a template to fit up the cross members--particularly with regard to the cutting of the angles4 ,the joint of the longeron to the cross member is shown separately at ,a 7,fig4 #adf74 ,the usual fish-plates are employed1 so made that a small wiring plate is left protruding from the binding1 to which the cross-sectional and longitudinal-sectional wires are made off4 ,illustration3 ,fig4 #adh4--,plan ,view of ,biplane ,driven by ,compressed ,air ,the plant itself is slung into the framework by means of eight wires1 each being made off to the wiring plates4 ,each should also be provided with a small -in4 wire strainer to enable the plant to be fixed quite rigidly--albeit permitting of its being removed for inspection or repairs4 ,the wires from the engine itself are taken off from the four small eyes soldered to the stationary portion of the crank-shaft4 ,great care should be taken to ensure that the plane of rotation of the screw is at right angles to the main planes4 ,a #a-;in4 dihedral is given to the bottom plane by means of the bracing wires passing between the inter-struts1 and shown on the preceding page4 ,it has been thought advisable to attach a small rear wheel1 to enable the model to rise off the ground with as little loss of power as possible4 ,such a wheel1 with attachments1 need weigh no more than oz41 and is a great improvement over the cane skid usually employed4 ,illustration3 ,fig4 #adf4--,side ,elevation of ,biplane ,driven by ,compressed ,air ,in bracing the outriggers1 or longerons1 some care will be required to ensure their being quite true4 ,it will be easier to finish each section off first1 so that they are quite parallel at the joints4 ,the part plan view of the model 7,fig4 #adh7 will make the relative position of the various component parts quite plain4 ,the two top tail outriggers pass through the fabric at the point where the spar is located1 their front ends being pinned and cross bound to the wing spar1 which is made of greater cross-section in the centre1 so that its strength is not materially impaired through the piercing of it4 ,birch is to be used for the wing spars and ribs of the sections indicated4 ,the planes are ribbed at periods of #f in4 and given a camber of in41 the greatest depth of which is #b in4 from the leading edge4 ,it is far easier to impart the camber after the wing framework is made than to camber each rib separately4 ,each rib should be cut #a in4 longer than necessary1 and pinned and glued to the spars1 with in4 overlapping each of these latter4 ,when the glue is quite set1 the pins may be clinched over by supporting the wing on an iron weight and tapping them back flush to the spars4 ,the full-size section of the camber should be drawn upon a board1 with which to check the accuracy of the first rib to be cambered 7the end rib74 ,the ribs are cambered in a jet of steam1 the convex or top sides being placed nearest to it4 ,having cambered the end rib carefully to agree with the drawing1 the others may be matched to it4 ,it will thus be easy to ensure that every rib is of the correct curvature1 as any mistake in the steaming of the rib will distort the wing spar at the point of its attachment4 ,if1 however1 it is thought advisable to camber the ribs first1 a wooden bending jig should be made1 to enable several ribs to be bent at one operation4 ,the ribs should be tied down to the jig with string1 and thus held under the steam jet1 being well dried in front of the fire before they are detached from the jig4 ,all three spars pass underneath the ribs4 ,a very light fabric should be chosen1 such as can be obtained from the model-aero accessory warehouses1 or an unproofed ,japanese silk can be used and varnished when on the wing4 ,if this latter is used1 it will be found advantageous to use a yellow hue1 as this colour is least affected by the action of the varnish4 ,but the covering of the wings must be left for the time being1 for the reason that the sockets to which the inter-struts are made fast must first be attached4 ,further1 the top plane must be covered after the tail outriggers have been assembled1 as it is so much easier to make the joint between the wing spars and these latter before the fabric is attached4 ,to render it unnecessary to refer to the point further1 it may be noted that the fabric is brought over the leading spar of each wing to pocket it out4 ,it is much neater to sew the fabric along on the leading edge1 as when glue is used an unsightly black smear shows through4 ,the fabric should be stretched from end to end first1 the fabric overlaps being glued on the bottom face of each end rib4 ,drawing-pins should be partially pressed into the ribs to secure the fabric until the glue is set4 ,at ,b in ,fig4 #adh is shown the method of securing the bottom plane to the inter-struts4 ,convenient notches are cut in the struts into which the plane is sprung4 ,it will have been noticed from the side elevation 7,fig4 #adf7 that the width of the inter-struts increases towards the bottom or lower ends1 and also that they incline slightly2 this is to provide for the entry of the lower plane1 since the top plane is attached outside the struts1 while the bottom is placed inside them4 ,at ,c is shown the method of attaching the inter-struts4 ,the tail is built up from split bamboo1 in4 by _/ in4 in cross-section1 and the rudders are framed up from ,no4 #bj gauge piano wire4 ,the ends of the rudder frames are forced through the longerons1 and the ends bent back in alignment with them2 they are then bound to the longerons with black three-cord carpet thread4 ,the rudders are covered after being fixed to the outriggers4 ,when it is necessary to adjust them1 the piano wire will be found sufficiently ductile to admit of a warp being placed thereon4 ,illustration3 ,fig4 #adg4--;,front ,elevation of ,compressed-air-driven ,model ,eleven ribs connect the spars of the top plane and nine those of the lower1 the camber of each being the same2 that is1 the same depth of camber is maintained throughout4 ,before the wings are covered1 the angle-plates to which the inter-struts are fixed must be bound on2 and these are cut from ,no4 #cj gauge sheet tin4 ,they should be cut less in width than the spar to which they are attached1 in order that their sharp edges shall not cut through the binding4 ,to prevent the plates from moving1 they should be lightly sunk into the wing spar with two centre-punch dots1 and a film of glue should also be spread over the face of the plate coming in contact with the spar4 ,the inter-struts are streamlined in cross-section 7see ,fig4 #adi72 but they are to be left rectangular in section at their ends1 to provide a flat surface for the plates to bed home on4 ,the ends of the plates are turned back over the binding1 which may be of the light machine variety4 ,the lower ends of the inter-struts are cut off to the same angle as the dihedral on the lower plane1 to avoid distortion of the plane4 ,spruce or ,american whitewood may be used for them1 the greatest cross section being in4 by in4 ,the greatest cross-section is situated at the middle of the strut1 whence it tapers to _/ in4 by in4 ,fig4 #adi shows the attachment of the inner strut to the wing spar4 ,in ,fig4 #aej are shown the brackets forming the guides for the axle1 and also the supports for the rubber shock-absorbers4 ,piano wire is used for them4 ,the width of the guide should be such that the umbrella-ribbing1 which constitutes the inner portion of the axle1 rides freely within it4 ,the wheel axles are cut from ,no4 #af gauge piano wire1 and they are soldered to the umbrella-ribbing1 being sunk into the channel of the latter1 bound with ,no4 #cj gauge tinned iron wire1 and then soldered4 ,ordinary elastic1 as used for a rubber-driven model1 can be used as the shock-absorber1 and it should be neatly and fairly loosely bound to the vertical guide1 the axle of course being first seated therein4 ,in order that the absorber brackets may maintain a vertical position1 their ends are shaped to a form similar to the letter ,u4 ,they are wire-bound to the skids and lightly soldered4 ,illustration3 ,fig4 #adi4--;,details of ,inter-struts4 ,illustration3 ,fig4 #aej4--;,detail of ,axle ,guides4 ,illustration3 ,fig4 #aea4--,outrigger and ,wing-spar ,joint4 ,illustration3 ,fig4 #aeb4--,tail ,crossbar ,joint4 ,illustration3 ,fig4 #aec4--;,detail of ,front ,skid ,angle-plates4 ,illustration3 ,fig4 #aed4--,tail ,incidence-quadrant4 ,illustration3 ,fig4 #aee4--;,details of ,axle4 ,illustration3 ,fig4 #aef4--,rear ,chassis ,details4 ,illustration3 ,fig4 #aeg4--;,inter-strut and ,longeron ,joint4 ,the bottom plane only must be covered2 it will be easier to cover the top plane when the machine is assembled1 for it would be a difficult matter to secure the top outriggers to the spars were the fabric attached4 ,having assembled the outriggers and completed the bracing of it1 it will be possible to attach it to the wings4 ,small elliptical holes are cut in the fabric of the lower wing1 through which the central supports or stanchions pass1 and the bottom plane is seated home in the notches alluded to in ,fig4 #adh4 ,next1 the top outrigger ends are fitted up1 being cut off to correct length and halved on to the wing spars1 as shown in ,fig4 #aea4 ,the vertical support is then glued1 pinned1 and cross-bound to the outrigger4 ,great care will be necessary to ensure that the outriggers are quite central with the planes4 ,a point to be made clear is that if in the fitting of the top outriggers one is cut even _/ in4 short1 the tail end of the machine may be in4 out of centre4 ,in order to check inaccuracy in this direction it would be advisable to mark the centre of the horizontal tail member1 insert a drawing-pin1 and take the measurement to the corner of the wing tip1 on both sides of the model2 the outriggers should be temporarily lashed to the wing spars1 and gradually adjusted until they are located centrally with the planes4 ,perhaps it may be interesting to here mention that this is the method employed in locating the fuselage of full-size machines4 ,the bracing of the planes should now be undertaken4 ,all lift wires should first be fixed1 beginning from the wing tips4 ,just sufficient tension should be placed on each wire to ensure rigidity4 ,a wooden straightedge should be used to reveal any distortion of the spar4 ,the top plane must be given a slight dihedral1 so that when the anti-lift wires are inserted it assumes a perfectly parallel position4 ,illustration3 ,fig4 #aeh4--;,biplane ,driven by ,compressed ,air ,the upper and lower longerons are spanned at the tail end with light spruce cross-bars1 -in4 by -in4 section1 which are let into mortises cut in the longerons2 and two vertical posts are halved on to these cross members 7see ,fig4 #aeb71 to provide the fulcrum about which the tail swings in the quadrant1 to be referred to presently4 ,they are spaced #d in4 apart1 which is equivalent to the distance between two ribs2 and on the outside of them a groove is cut in the centre of each to provide a seating for the two central tail ribs4 ,these grooves must be cut ,v-shaped1 the apex of the ,v facing the trailing edge of the post4 ,the object of the groove is to form a guide for the tail when it is desired to alter the angle of it4 ,a pin should be driven through the rib and into the groove to constitute the pivot on which the tail swings2 and the ribs must be bound with fine thread on each side of the pin to prevent the rib from splitting4 ,it will be found that it is better to bind the ribs before inserting the pin4 ,the central inter-struts are attached to the skids by angle-plates1 and in ,fig4 #aec the form of these is given4 ,it must be understood that there are two plates to each joint1 one on each side of it1 and for neatness and simplicity they can be cut from one piece of tin1 both plates being thus formed in the one4 ,no4 #cj gauge tinplate is suitable4 ,the plates are pinned1 clinched1 and bound into place1 and constitute an exceedingly rigid piece of construction1 which is needed in this portion of the machine1 bearing as it does the impact of landing4 ,glue should be neatly brushed into all the joints4 ,the tie-strut is to be streamlined as far as practicable without materially impairing the strength of it4 ,a very neat finish can be given to the binding if it is just brushed round with japan black1 which shows up in pleasing contrast to the light brown varnish with which the framework is coated4 ,fig4 #aed gives the shape of the quadrant1 which makes possible the variation to the angle on the tail4 ,it is cut to a radius of #d in41 and is pinned into position4 ,the pitch of the teeth is in41 and this facilitates a very fine adjustment4 ,it should be so fixed that the tail springs tightly into notches1 but not so tightly as to render adjustment difficult4 ,trial and error will be found the best method of locating its position4 ,illustration3 ,fig4 #aei4--;,compressed-air-driven ,monoplane ,it was mentioned in the preceding chapter 7see pp4 #id to #ajc7 that the axle is composed of two portions1 umbrella-ribbing and piano wire1 and ,fig4 #aee shows the construction4 ,it will be seen that the piano wire beds into the channel 7which is fixed in a trailing position71 wherein it is bound and soldered4 ,the wheels are spaced apart by means of small brass-tube collars1 soldered to the piano-wire axles in their respective positions4 ,the axle itself1 as mentioned earlier in the chapter1 is attached between the shock-absorber brackets1 being held there by means of suitable radius wires secured to any convenient part1 the rubber binding forming the absorber4 ,the radius wires are essential in order to maintain the lateral position of the axle relatively to the planes4 ,sufficient rubber binding is to be used to absorb the shocks the model is bound to receive1 the exact quantity1 of course1 being impossible to define4 ,the rear wheel members are fixed to the longerons in the following manner4 ,the ends are bent back parallel to align with the frame member4 ,the apices of the ,v chassis members are soldered to the short axle carrying the back wheel1 the axle being cut a length suitable to the hub of the wheel4 ,no4 #bj gauge wire is used for all portions of the rear chassis4 ,fig4 #aef makes this clear4 ,fig4 #aeg shows the joint of the trailing central inter-struts to the top longeron4 ,it will be seen that the joint is a halved one1 pinning and binding forming the security4 ,all woodwork may be polished by filling the grain with gold size1 and finishing with a good varnish4 ,in flying the model the writer would point out that full pressure should not be given to the plant until adjustment has been completed1 also the importance of tuning the machine by starting it from the ground1 thus obviating many vexing smashes4 ,further1 the rudder must be set to counteract torque2 if the screw is of left-hand pitch1 then torque will tend to bank the machine to the right1 and the rudder must therefore be set to the left1 and vice versa4 ,a sketch of the finished machine is given by ,fig4 #aeh1 and a design for a monoplane driven by the same plant in ,fig4 #aei4 ,,chapter ,,xv ,general ,notes on ,model ,designing ,calculations in ,designing a ,plant for a ,model ,aeroplane4--,the correct method to adopt in designing a model is to build the machine exclusive of the motor1 weigh it1 and design the plant to suit2 or to build the plant first1 determine the thrust it develops1 and vary the dimensions of the machine 7and hence the weight7 to suit4 ,it can now be taken as a general rule that a plant will fly a machine three times the weight of its thrust4 ,hence a plant developing #c-oz4 thrust would fly a machine weighing #i oz4 or #aj oz4 ,but1 since the thrust of a compressed-air engine is not constant1 gradually diminishing as the pressure in the container grows less1 for a machine weighing #i oz4 7assuming the machine to be built first7 the plant will require to develop about #e oz4 initial thrust4 ,the diameter of the propeller is dependent on the most efficient speed of the particular motor employed4 ,assuming that the model does not weigh more than #ag oz41 a four-cylinder engine constructed would answer admirably4 ,it would require a container #bd in4 long and #c in4 in diameter1 constructed of copper or hard-drawn brass foil #jjb in4 thick4 ,should1 however1 the reader particularly desire to fit a rotary motor1 doubtless the five-cylinder rotary previously described will suit4 ,building ,scale ,models4--,the great difficulty in building scale models to fly with rubber motors is to get the centre of gravity in the same relative position that it holds in the prototype4 ,this is due to the long length of rubber motor required to give the requisite power1 and also to ensure a reasonable time-length of flight4 ,it is in connection with the fixing or arranging of the rubber motor that the most radical departures in the design of the prototype will have to be made1 although the writer has evolved an arrangement whereby even this need not entail much departure from the lines of the original4 ,this arrangement consists in providing a separate strut or frame to take up all strain from the rubber1 it only being necessary to arrange suitable fastenings for the strut1 which may take the form of clips1 so making it possible either to remove the motor for the purpose of changing or repairing the rubber1 or substituting a motor of different power or length4 ,this is a great advantage on tractor monoplanes 7with the main plane in front71 where the rubber is more or less inaccessible by reason of the closed-in frame or fuselage of the machine4 ,another important advantage to be gained from the use of a detachable motor is that its position fore and aft on the machine can be varied1 in order to bring the centre of gravity into the proper position to obtain correct balance1 or1 speaking with more technical accuracy1 to make the centres of pressure and gravity coincide4 ,with regard to the type of motor to adopt1 this depends very largely on the machine which is being modelled4 ,whenever possible it should be of the simplest possible kind1 consisting of the main strut to take the tensile strain1 compressive1 of course1 so far as it affects the strut1 and the torsional strain put on by the twisting of the rubber4 ,at one end of this strut a hook of wire or other form of metal is formed to hold the rubber skein1 whilst at the other end is fixed a plain bearing4 ,through this the propeller spindle is passed1 having a hook at its end1 over which the other end of the rubber is placed4 ,on certain types such a simple motor is not possible4 ,in order to concentrate the weight more at one point1 the rubber and its struts have to be shortened2 and to get the necessary number of revolutions of the propeller a gearing of two to one1 three to one1 or four to one1 as the case may be1 must be used4 ,by this means the small number of turns which can be got on a short thick skein of rubber of great power will still give the number of propeller revolutions required to make a good flight1 just the same as with a motor of ordinary thickness and of great length4 ,of course1 some power is lost in the gearing4 ,to resist fuselage distortion the spar must be suitably braced in a lateral direction1 the outrigger carrying the bracing wires being situated just forward of the centre of the spar4 ,no4 #ce ,s4,w4,g4 is quite strong enough for fuselage bracing4 ,silk fishing-line or ,japanese silk gut is admirably suited for wing bracing1 and is not so liable to stretch as the tinned iron or brass wire sometimes used4 ,piano wire is generally used for elevators1 tail planes1 chassis1 and propeller shafts1 of a gauge ranging from ,no4 #ag ,s4,w4,g4 to ,no4 #bb ,s4,w4,g4 ,a clock-spring or piano-wire protector fitted to the nose of a model aeroplane will also prevent a broken spar should it strike some object such as a tree or wall during flight4 ,the ,kite and ,model ,aeroplane ,association1 which is the paramount body to observe and control model flying in ,england1 and which is recognised by the ,royal ,aero ,club1 stipulate that protectors must be fitted to all machines competing in their contests4 ,,chapter ,,xvi ,general ,notes ,stability4--,the principles underlying the design of a successful flying model aeroplane are almost1 if not quite1 as complex as those involved in the planning of full-size machines4 ,in some respects perhaps this is more so1 owing to the fact that models must be practically automatically stable both longitudinally and laterally1 since they are not under any sort of control after they have left the hands of the person flying them4 ,the adjustments to produce this automatic stability must be made before the machine is launched1 and the fact that there are models which are capable of flying distances of several hundreds of yards1 and high up in the air1 is evidence that it is quite possible to make this adjustment accurately4 ,a useful rule to remember is that to produce a longitudinally stable effect1 the leading plane should make a greater angle 7that is1 a positive angle7 than the following plane4 ,and that conversely a condition of instability is set up when the leading plane makes a negative angle to the trailing one 7see ,fig4 #afj74 ,referring now to lateral stability1 the same principle applies1 although in the case of biplanes stability to a great extent can be obtained in another way4 ,monoplanes and sometimes biplanes are made stable by what is known as a dihedral angle shown by ,fig4 #afa1 which represents the usual method of shaping the planes4 ,this last-mentioned figure is intended to represent a front 7or back7 view of the machine4 ,in aeroplanes of this type the elevator or tail1 whichever is employed1 may also be given a dihedral1 though this is not often done4 ,illustration3 ,fig4 #afj4--,machine without ,stability ,illustration3 ,fig4 #afa4--;,dihedral ,angles ,lubricant4--,a good lubricant can be made from pure soft soap #d parts1 pure glycerine #b parts1 water #f parts1 these constituents being boiled together to the consistency of syrup4 ,another excellent lubricant is made from castile soap #a part1 boiled in water #c parts4 ,add black lead or plumbago sufficient to make a thin paste4 ,illustration3 ,fig4 #afb4--;,fixing ,skids ,illustration3 ,fig4 #afb;,a4--,fixing ,skids ,illustration3 ,fig4 #afc4--;,fitting ,wheels ,fitting ,skid4--,steel-wire skids can be fixed to model aeroplanes as in ,figs4 #afb and #afb;,a4 ,the wheels can be obtained of any model aeroplane firm1 and can be fixed to the machine as shown in ,fig4 #afc4 ,this would increase the weight of the machine1 and more rubber may have to be used and the main planes adjusted to suit4 ,use ,no4 #ba ,b4,w4,g4 wire 7steel74 ,elevator ,adjustment4--,elevators are sometimes fixed to the fuselage as shown in the accompanying sketch 7,fig4 #afd71 which shows it fixed above the spar4 ,it is claimed that1 in this position1 the elevator is more efficient4 ,illustration3 ,fig4 #afe4--;,fixing ,struts to ,biplane ,illustration3 ,fig4 #afd4--;,elevator ,adjustment ,loading per ,square ,foot4--,generally speaking1 the loading per square foot of supporting surface for rubber-driven models should not exceed #f oz41 nor be less than #c oz41 while to obtain good stability the ratio of machine length to span should be somewhere in the neighbourhood of #c3 #b4 ,fixing ,struts to ,biplane4--,one very suitable method of attaching the inter-struts to wings of model biplanes1 that admits of dismantling the model for packing1 is shown at ,a 7,fig4 #afe74 ,a short length of brass tubing of _/-in4 bore is bound with fine florist's tinned iron wire to the wing spar1 the inter-struts being bent to the shape given at ,b1 so that they spring tightly into the sockets4 ,a simpler method is illustrated by ,c4 ,here the inter-struts are bent at right angles on the ends1 bound to the wing spar1 and soldered4 ,much will depend on whether a fuselage is one-or two-membered1 but a frame attachment capable of adaptation to either is given by ,d and ,e4 ,wire crutches are bent to take the cross-section of the frame member or members1 and fixed by binding and solder to the central inter-struts4 ,yet another method is shown at ,f1 which is self-explanatory4 ,illustration3 ,fig4 #aff4--,water-,surface ,hydroplane ,water-surface ,hydroplane4--,for a water-surface hydroplane #c ft4 long try a breadth of #aa in41 same beam all the way4 ,make the depth #b in4 at the stem and #c in4 at the step4 ,the step may be in4 deep1 and would be placed about #ae in4 from the stern4 ,the writer would suggest fins as shown by dotted lines in the accompanying illustration 7,fig4 #aff7 for steering purposes1 one fin on each side at the stem1 and one on the centre line forward4 ,the fins should be made of thin aluminium and be quite sharp on the edges4 ,canvas would be too rough a surface1 producing too much skin friction2 oiled silk would be better1 but the writer would recommend thin wood1 french polished4 ,the power needed to make these boats 8plane0 is very great1 and considerable difficulty might be experienced in getting any distance out of it with clockwork4 ,illustration3 ,farman ,this ,section is inefficient ,illustration3 ,streamline ,an efficient ,section ,illustration3 ,wedge ,this formation cannot be recommended ,illustration3 ,stepped ,fig4 #afg4--,sections of ,hydroplane ,floats ,calculating ,capacity of ,hydroplane ,floats4--,the floats of a model hydroplane must be made sufficiently large to displace about three times the model's weight of water1 since it is necessary that they should be only one-third immersed4 ,a cubic foot of water weighs #a1jjj oz4 approximately4 ,then #agbh #h ---- --- #ach cub4 in4 #ajjj #a must be displaced to float #h oz4 ,multiplying this by three gives #db cub4 in4 as the total cubic capacity of the floats4 ,two front floats1 each #e in4 by #b in4 by #a in4 maximum depth1 and a rear float #h in4 by #c in4 by #a in4 would be about the correct size to use4 ,a slightly larger diameter and pitched propeller would be necessary on a hydroplane to develop more thrust to overcome the resistance of the floats4 ,some well-known hydroplane sections are given in ,fig4 #afg4 ,illustration3 ,showing ,marking of ,block ,illustration3 ,finished ,screw of ,truly ,helical ,formation ,illustration3 ,setting out the ,angles ,illustration3 ,cross-,section ,illustration3 ,showing ,halving of ,block ,fig4 #afh4--;,four-bladed ,screws ,waterproofing ,silk for ,model ,aeroplanes4--,a waterproofing solution can be made of pure coach varnish reduced in consistency with turpentine in the proportion #b3 #a4 ,it is1 however1 more important to make the fabric airtight than waterproof4 ,this solution accomplishes both4 ,rubber lubricant is made of #a part of graphite1 #f parts of pure soft soap1 #a part of glycerine1 #d parts of water1 and #a part of salicylic acid1 boiled together and allowed to cool4 ,making ,four-bladed ,air-screws4--,fig4 #afh on the preceding page shows how truly helical and also four-bladed screws are carved4 ,four-bladed screws are not so efficient for models as two-bladed ones4 ,the drawing also shows the method of marking out and also of halving the blocks together at the centre1 so that the four blades are at right angles to one another4 ,a view of an ordinary twin-blade screw of similar design is appended to give some idea of the finished shape of the blades4 ,the pitch should not exceed the circumferential measurement of the disc swept by the propeller2 that is to say1 the pitch angle1 or the angle made by the propeller tip with the axis1 should not exceed #de degrees4 ,the angles along the blade are determined in the manner illustrated by ,fig4 #afh4 ,a line is laid off to any convenient scale equal to the circumference of the propeller disc diameter4 ,the tip angle 7or pitch angle7 may now be produced and the triangle completed by erecting a line at right angles to the first1 or the pitch may be erected perpendicularly to the circumferential line to the spiral scale and the pitch angle line drawn in4 ,the circumferential line may now be divided into a number of equal parts and the points connected up4 ,in the illustration three points have been taken1 which will be enough for a small propeller4 ,cardboard templates should be cut to these angles and the blades checked at the points corresponding4 ,the balance of the screw must be attended to and is a most cogent factor in such a small design4 ,marine-screws are exceedingly inefficient when working in air1 and their use for driving model aeroplanes1 etc41 is to be strongly deprecated4 ,the formula for propeller pitch is3 p d tan ,a1 where p pitch1 #cad1 d diameter of propeller1 tan ,a tangent of pitch angle4 ,illustration3 ,fig4 #afi4--,securing ,wooden ,planes ,fixing ,planes4--,fig4 #afi shows a neat and effective method of securing the planes4 ,very little wood is now used for the planes of model aeroplanes2 but to build a plane of veneer1 it should first be cut to the shape required and then a strip of birch pinned and glued on the under-side of the leading edge for strength4 ,the veneer is then pinned and glued to the ribs which have previously been bent to the correct camber4 ,the reader may be reminded that birch is the most suitable wood for bentwood propellers1 the wood being first cut to shape with a fret-saw1 then soaked in hot water and bent over a bunsen burner to the desired pitch4 ,this requires considerable experience1 but can be done quite quickly by an experienced workman4 ,for propellers up to #ab in4 in diameter1 use _/-in4 wood2 this should gradually taper off to _/ in4 at the tips4 ,illustration3 ,fig4 #agj4--;,geared ,motor for ,model ,aeroplane ,illustration3 ,fig4 #aga4--;,fixing ,shaft of ,carved ,screw ,making ,motor for ,model ,aeroplane4--,a geared motor suitable for a model aeroplane is given by ,fig4 #agj4 ,a cage ,e for the gears ,a can be made from -in4 by _/-in4 strip iron1 and the propeller shafts ,b can be made from cycle spokes4 ,the illustration also shows a method of fixing the propeller to the shaft4 ,the piece ,c is soldered to the shaft ,b1 and engages with two holes drilled in the propeller boss1 the propeller being secured by the nut ,d4 ,the gears ,a have an equal number of teeth4 ,there is no advantage in using a geared-up motor4 ,f is the fuselage of the model4 ,fixing ,propeller of ,model ,aeroplane4--,with a carved propeller1 the motor hook can be secured to the propeller as in ,fig4 #aga4 ,if a bentwood propeller1 the best way is to fasten a strip of tin round the centre and solder the motor hook to this4 ,,chapter ,,xvii ,easily-made ,tailless and ,box ,kites ,one of the difficulties that beset the juvenile kite-flyer is the inability to get the kite to rise from the ground unless there is a fairly good wind blowing4 ,even then the services of an assistant are required1 whilst numerous trials to adjust the amount of weight on the tail1 the position of the carrying thread on the kite1 and the distance required to be run to get the artificial wind to enable the kite to rise above the surrounding buildings1 are difficulties that damp the enthusiasm of the most inveterate kite-flyer4 ,to the kites sold in the shops the foregoing remarks apply4 ,they are too heavy1 and are suitable for flying at the seaside only4 ,to make the sport interesting1 the kite should fly in the least wind1 and should be so made as to fly from the hand1 the thread or string being paid out as the kite rises4 ,it should be perfectly balanced so as to be stable in the most erratic wind4 ,the kites shown in the accompanying illustrations1 if made to the directions1 will fulfil all the above conditions1 and at the same time be easy of construction4 ,the dimensions can be varied in proportion2 but the would-be maker is advised to stick to the given sizes for the first attempt4 ,illustration3 ,fig4 #agb4--;,hargreaves ,kite ,illustration3 ,fig4 #agc4--;,frame of ,hargreaves ,kite ,illustration3 ,fig4 #agd4--,measuring ,bend ,illustration3 ,fig4 #age4--;,box ,kite ,illustration3 ,fig4 #agg4--;,joint of ,stretcher ,ribs ,illustration3 ,fig4 #agf4--;,covering with ,paper ,the ,hargreaves kite 7,fig4 #agb7 is the simplest4 ,the frame 7,fig4 #agc7 consists of a straight length of yellow pine ,a1 to which is attached a cross piece of cane ,b4 ,this cross piece is made by cutting a thin cane and splitting it1 trimming the edges off until nearly square in section1 and then bending it over a small gas flame4 ,as it gets hot1 bend it gently by grasping the ends in each hand4 ,pass it to and fro in the low flame1 and it will be found to give4 ,bend it evenly and allow to cool1 when it will remain in this shape4 ,find the centre and ascertain if the bend is equal on each side by measuring as shown in ,fig4 #agd4 ,this being so1 notch ,a and ,b 7,fig4 #agc7 slightly where they cross1 and assemble1 applying a little glue and lapping with cotton4 ,join the ends of the bent limb with linen thread1 and also take a thread round the frame1 securing it at each extremity in a notch with the addition of glue4 ,when dry the frame is covered with paper4 ,the very thin coloured paper used for making artificial flowers is just the thing4 ,gum it on with a thin flour paste1 and allow very little overlap1 keeping the paper as free from crinkles as possible4 ,cut a disc of stout paper1 and gum it over the frame at the crossing4 ,this is to strengthen the paper at this point1 as the attached thread is liable to make a wide hole4 ,secure a yard of strong thread at the crossing1 and when dry the kite can be tested4 ,if all is right the result will be eminently satisfactory1 the kite flying from the hand like a bird1 no tail whatever being needed4 ,for decorative purposes a short fish tail and fins can be added1 or a rubber balloon can be used as a tail4 ,the box kite shown by ,fig4 #age is not more difficult to construct than the kite previously described4 ,it flies with equal facility1 and is quite as steady4 ,being made collapsible it can be rolled in a small compass4 ,to make the kite1 paste two of the coloured sheets together to form a continuous length1 and spread on the floor4 ,cut the four uprights of yellow pine to the correct length and thickness1 and having liberally glued them1 place them on the paper as shown in ,fig4 #agf1 and paste a long strip over them on to the paper underneath4 ,this is to strengthen the paper round the uprights4 ,when dry and firm1 which does not take long if the glue is put on tacky1 the loose end of the paper can be joined to the upright to form a hollow long box4 ,now cut four thin lengths of wood to form cross-pieces1 secured together with a pin through the centre 7see ,fig4 #agg74 ,notch the ends and open them out so as to fit inside the box between the uprights4 ,fit one to each end1 and then secure the upright ends with a linen thread pulled tightly from one to the other1 and tied and glued at each end4 ,this takes the strain of the cross piece off the paper1 and at the same time provides a support for the paper1 which is clapped round it and gummed on to itself4 ,the kite having been completed1 a short length of thin string is attached about #c in4 from one end of one of the uprights4 ,to this the thread for flying is attached4 ,this kite will fly quite well with the thread attached to the very end of the upright1 so that there is no fixed position for it to a fraction of an inch4 ,the nearer it is brought to the centre1 the more unstable the kite becomes4 ,in a moderate wind1 with the thread attached to the top1 the kite tends to ascend more vertical than it would otherwise4 ,illustration3 ,fig4 #agg;,a ,illustration3 ,fig4 #agg;,b ,figs4 #agg;,a and ,b4--,details of ,twin ,cellular ,box ,kite ,fig4 #agg;,a shows another simple form of box kite4 ,it is made from four strips of straight grained wood 7preferably spruce71 #b ft4 #f in4 by in4 by in4 ,obtain also four other pieces1 each #a ft4 #g in4 long1 but _/ in4 wider and thicker than the foregoing1 and halve their ends to a depth of in4 by in41 in order that when the false end ,a 7,fig4 #agg;,b7 is tightly bound on1 these cross sticks will firmly grip the long pieces edgewise2 the sides of the cell are indicated by dotted lines4 ,it is advisable to make the cross-pieces a trifle long1 to ensure their straining the kite to its correct form4 ,,chapter ,,xviii ,building a ,model ,airship ,it has not for obvious reasons been possible1 in the design here presented1 to rigidly adhere to the lines of the prototype1 as in the adaptation of the design to rubber-driven model form several modifications have necessarily been introduced4 ,it has been the aim of the writer to bring the model within the constructional capabilities of the amateur2 indeed1 it is hardly possible to have simplified the construction further4 ,now1 the success of a dirigible1 whether full size or model1 depends primarily on the observance of the fact that an airship is lighter than air1 and thus1 unlike the aeroplane1 does not rely on speed to obtain lift4 ,secondarily1 the lifting power of hydrogen must be remembered1 and although this varies according to temperature and the purity of it1 it may be taken as a general rule that hydrogen will lift #hj lb4 per #a1jjj cubic feet4 ,it is a good rule to adopt a lower figure1 say #gj lb4 lift per #a1jjj cubic feet1 to allow for discrepancies4 ,in the design here submitted1 aluminium 7or what is equally as good1 magnalium7 tube forms the framework of the body or envelope4 ,the general arrangement will be apparent from ,figs4 #agh and #agi1 which show the model in plan and side elevation respectively4 ,the framework is of hexagonal cross section1 the longitudinal members of which terminate at each end in a brass cap1 to which they are riveted with soft brass pins4 ,it will be necessary to anneal the tubes before bending them to impart the conical shape to each end of the frame1 and this can best be effected in a weak spirit flame1 care being taken to keep them on the move in it1 to obviate fusing them4 ,where it is necessary in the construction to rivet the tubes1 solder should be run over the pin to take up any play4 ,fig4 #ahj shows the method of securing the longitudinal members to the brass end-caps4 ,the tubes are first flattened out1 as at ,b1 and then riveted to the caps4 ,this figure also shows the method of adjusting the angle on the rudder4 ,a piece of brass tube is soldered to the end-cap2 and it should be of such a bore that the ,no4 #ah gauge wire of which the rudder is constructed makes a bare fit through it4 ,two similar pieces of tube1 in4 long1 are soldered to the rudder1 to maintain the position of it4 ,thirteen hexagonal cross members will be required1 and each is formed from _/ in4 aluminium tube4 ,in order that they may not become out of truth1 they are cross-braced with ,no4 #ce ,s4,w4,g4 piano wire1 the ends of each wire being made off in a small hole drilled through the tube4 ,fig4 #ahj will make the detail clear2 each cross member is riveted to the longitudinal1 and the latter is flattened out at those points where the cross member is attached4 ,illustration3 ,fig4 #agh4--,side ,elevation ,illustration3 ,fig4 #agi4--,plan ,the model is driven by four elastic motors1 transmitting their power through equal gearing to the twin propellers4 ,the four motor rods may1 for preference1 be hollow spars1 of the same cross-section as the solid ones indicated4 ,if such are used1 they may be made by ploughing a groove in a length of wood of suitable cross-section so that it represents the letter ,u4 ,two will be required for each spar1 so glued together that a hollow tube is formed4 ,at the point where it will be necessary to pierce the spar to admit the bracing outrigger1 small packing pieces of birch should be placed in the grooves previous to assembling the two halves of the spar4 ,the spars1 or1 more correctly1 motor rods1 are suspended from the envelope framework by aluminium tube outriggers of -in4 diameter4 ,fig4 #aha1 which shows the machine in end elevation1 and ,fig4 #ahb1 showing the central cross-section1 indicate the form they are to take4 ,eight of them will be required4 ,the angles must be cleanly and accurately formed1 so that the two centres of thrust lie in the same plane4 ,it will be found good practice1 when forming both the outriggers and the cross-sectional members1 to make a full-size drawing of them to use as a template4 ,more especially is this needed in the construction of the cross-sectional members1 for the purpose of ensuring that1 in the operation of embracing them1 they are not strained in any way so as to become out of truth4 ,fig4 #ahc shows the joint of the motor-rod outrigger to the motor rod itself4 ,as there shown1 the tube is flattened out partly to engirdle the spar1 to which it is attached by pinning and clinching4 ,illustration3 ,fig4 #ahj4--;,joint of ,tube to ,end-,caps ,illustration3 ,fig4 #aha4--;,end ,elevation ,illustration3 ,fig4 #ahb4--;,central ,section ,illustration3 ,fig4 #ahc4--;,joint of ,outrigger to ,motor ,rod ,the gearing 7see ,fig4 #ahd7 consists of a brass framework 7bound to the ends of the motor rods7 which provides bearings for the gears4 ,the use of gears is obvious2 they eliminate torque on the spars1 or the tendency which a single skein would have to twist the spar4 ,pieces of tube are passed over the shafts to bear between the gears and the gear bearing4 ,in order to counteract the tendency of the rubber hooks to pull out straight when the rubber is in tension1 the hook ends are secured as shown at ,a4 ,when it becomes necessary to detach the skeins1 it is only necessary to slide the tubes along the shaft to open the hook4 ,in ,fig4 #ahe the kingpost attachment is shown4 ,the spar is mortised1 the kingpost forced through1 glue having previously been brushed into the slot1 and a pin tapped through from the side to secure it4 ,birch should be used for the kingposts1 and their widest cross-section should be in4 by _/ in41 tapering off towards the extremities to in4 by _/ in4 ,to the ends of each motor rod are attached small ,no4 #bb ,s4,w4,g4 piano wire hooks1 to which the spar bracing is made fast4 ,a suitable length of wire is passed through the spar1 and the hooks then formed4 ,the bracing is fastened to the kingpost by a couple of turns being taken round it4 ,next1 four twin hooks should be made1 of the form shown in ,fig4 #ahf4 ,sixteen gauge wire is to be used for them1 bent tightly to clip the spar ends1 to which they are bound4 ,all the hooks should be covered with valve tubing to prevent them from cutting through the rubber when this latter is in tension4 ,the joint of the cross members of the envelope to the longeron is given by ,fig4 #ahg1 from which the bend in the longitudinal1 hitherto referred to1 will be clear4 ,to the tail of the machine a pair of superposed surfaces or elevators are fixed4 ,these are fastened at their foremost extremities to the motor-rod outriggers1 and at the rear they are supported by the two cross ribs of the rudder4 ,small slits are to be cut in the fabric with which the rudder framework is covered to enable any slight alteration in the angle of incidence of the elevators to be effected4 ,illustration3 ,fig4 #ahd4--;,arrangement of ,gearing ,illustration3 ,fig4 #ahe4--,kingpost ,attachment ,illustration3 ,fig4 #ahf4--;,detail of ,twin ,hooks ,illustration3 ,fig4 #ahg4--;,cross ,member ,joint ,illustration3 ,fig4 #ahh4--;,end ,view of ,screw ,attention may now be given to the propellers4 ,as twin screws are used1 they may be made of fairly long pitch1 since their torques will be opposite and consequently balanced4 ,fig4 #ahi gives a perspective view of the propeller block marked out ready for carving1 and ,fig4 #ahh shows the screw in end elevation4 ,the screw is first carved as a true helix1 and then shaped up to the form shown in the sectional view 7,fig4 #ahb74 ,american whitewood should be used for the blocks1 or1 failing this1 poplar would do4 ,circular tin discs are pinned to each side of the propeller boss1 to which the shaft is soldered4 ,great care is essential to ensure that both propellers are of the same weight1 and that each is poised2 that is1 assumes an angle of #ahj when balanced on a shaft4 ,they may be finished with a coat of gold size and one of varnish4 ,each gear is driven by six strands of -in4 strip elastic1 well lubricated with soft soap and glycerine4 ,illustration3 ,fig4 #ahi4--,propeller ,block before ,carving ,illustration3 ,fig4 #aij4--;,a ,model ,airship ,the covering is to be yellow ,japanese silk1 proofed with varnish diluted with #bj per cent4 of linseed oil and #aj per cent4 of turpentine2 two coats should be given before the fabric is applied1 and two afterwards4 ,a covering strip of fabric should be glued over all seams to make the envelope as impervious as possible4 ,and where the outriggers pass through further pieces should be glued over1 and flanged on to the tube itself1 being afterwards well doped4 ,it is well to impress here the importance of making the envelope as gasproof as possible1 and although a fabric entirely impervious has yet to be invented1 it is possible1 with care1 to reduce loss of gas by percolation to a very low figure indeed4 ,a ,lucas cycle valve is soldered into the brass end-cap constituting the rear of the envelope1 for the purpose of inflation1 which is effected in the following manner3 ,a ,t-piece is fixed to a cycle pump1 and a pipe from the gas container to the ,t-piece4 ,a further tube is connected from the remaining arm of the ,t-piece to the valve4 ,to inflate the envelope1 release the pressure from the container until the pump handle is forced out to its full extent1 and then shut off pressure and force the pump down1 thereby causing ingress of gas to the envelope4 ,continue thus until the envelope 8swells40 ,of course1 this method could be adopted if hydrogen from the gas jet is used1 although this does not possess the lifting capacity of hydrogen procured from the balloon manufacturers4 ,in conclusion1 it may be pointed out that the weight of the complete model inflated should not exceed #b lb4 ,a view of the appearance of the model in flight is given by ,fig4 #aij4 ,for those who wish to design model airships of their own it may be stated that coal-gas lifts about #ce lb4 per #a1jjj cub4 ft41 or half the weight lifted by an equal volume of hydrogen4 ,a small model would not be very successful1 as the volume1 and hence the lifting power1 decreases as the cube of the diameter4 ,thus assuming a model to be built of half the dimensions given in this chapter1 the weight of it could only be of the original model1 and it would be found difficult to work to this limit4 ,the writer would point out that little success can be expected from an airship of such small dimensions1 as the following elementary calculation will show4 ,it takes #ce1jjj cub4 ft4 of hydrogen to support #a ton4 ,then #a cub4 ft4 of hydrogen supports _/ lb4 ,now1 the cubic contents of a model dirigible1 we will assume1 is #bb #e #e #cf #a ---- --- --- ---- ------ cub4 ft41 #g #b #b #a #agbh and therefore the total weight it is capable of supporting is #bb #e #e #cf #a #bbdj ---- --- --- ---- ------ ------ 4#jbf lb41 or 4#d oz4 #g #b #b #a #agbh #cejjj ,from this it will be seen that it is extremely improbable that a model can be built to this weight4 ,no more suitable covering than gold-beater's skin exists4 ,if the model is of the rigid type1 then the covering should be stretched over the framework that imparts the ichthyoid shape to the envelope4 ,strips of the fabric must be attached with mucilage over all seams to make the envelope as impervious as possible4 ,it is worthy of note that full-size airships have as many as three or four coverings to eliminate loss of hydrogen by escape through the pores of the fabric4 ,if1 however1 the reader contemplates building a model of the nonrigid type1 a wooden hull should be cut and the fabric fitted up to this4 ,the hull should represent the shape of the inflated envelope4 ,compressed air also lends itself to model airship propulsion4 ,in conclusion1 a word of warning3 do not place the model near any fire1 gas1 match1 etc41 as any small leaks may cause an explosion4 ,in building model airships1 it is advisable to remember that by doubling the diameter of the envelope we get four times the capacity and hence four times the lift for only double the weight4 ,this will be seen from the following calculation3 ,lift of airship #c ft4 long #b in4 diameter equals1 as we have just seen1 #jbf lb4 ,by doubling the diameter the calculation becomes3 #bb #e #e #cf #a #bbdj ---- --- --- ---- ------ ------ #jeb lb4 #g #a #a #a #agbh #cejjj ,from this it will be seen that if it is desired to lift a certain weight with a lighter-than-air craft1 the minimum capacity should first be calculated and the diameter 7which should always be as large as possible7 then varied to obtain the required capacity4 ,although it has been stated that the lift of hydrogen is #gj lb4 per #a1jjj cub4 ft41 it will be in order to explain two important considerations4 ,it will be clear that1 firstly1 a full-size balloon must be inflated to a much higher pressure than a model1 owing to the heavier mass of material to be forced out to form4 ,as a direct adjunct to this fact it will be seen that percolation will be high4 ,consequently the lift weight ratio #gj3 #a1jjj is somewhat a low estimate for a model1 since1 firstly1 it will only require to be inflated to less than half the pressure of a full-size balloon2 and1 secondly1 percolation will be considerably less4 ,the writer intentionally gave the full-size limit in order that1 should the builder's model fail to come within the prescribed limit of #b lb41 its flying capability would not be appreciably impaired4 ,further1 the envelope is kept to its shape by a framework inside1 and is consequently full of air4 ,now if we start pumping hydrogen in it will make the contrivance heavier instead of lighter1 because no outlet is provided for the escape of air4 ,this could easily be remedied by standing the model on its end with the cycle valve at the top1 with a valve or tap on the bottom brass cap4 ,open this bottom tap to allow the air to escape1 and allow the hydrogen to fizz in through the cycle valve4 ,hydrogen will not escape through the bottom tap until all the air has been displaced4 ,if the hydrogen cannot be had at a high enough pressure to operate the valve itself a valve should not be used4 ,it may in such a case be necessary to fit an induction valve to the pump4 ,the envelope should be inflated to as low a pressure as possible1 otherwise the lift is correspondingly reduced4 ,in all cases it is exceedingly difficult with model airships to prescribe any definite formula1 and although the lift coefficient for models exceeds the figure stated1 the conjectural nature of the purity 7and hence of lift7 of hydrogen in various parts of the country renders it a safe one to use for all practical purposes4 ,,index ,action and reaction1 #e ,aerofoil1 flow of air round1 #aj ----1 lift of1 #aj ,aeroplane1 speed of1 #d ----1 types of1 #ab-af ----3 ,why does it fly8 #a-aa ,a frame1 #bj1 #bb1 #bc ,air1 density of1 #ce1 #cf ---- flow1 direction of1 #e ---- pressure1 #b ,air-screw1 action of1 #ce ---- balancing1 #ch ----1 calculations for1 #cf ----1 efficiency1 #ce ----1 four-bladed1 making1 #acc ----1 laminated1 #ci ----1 suitable woods for1 #cf1 #ch ,bamboo planes1 #cj ,bending air-screws1 #db-df ,biplane1 fitting struts to1 #abh ----1 sample twin-screw1 #fa-fh ,blade width1 maximum1 #de ,blriot type monoplane1 #ah ,box kite1 #ach1 #aci1 #adj ,bragg-,smith1 #ae ,building airship1 #ada1 #aed ,calculations in designing aeroplane plant1 #abj ,camm air-screw1 proportions of1 #df ,canard1 meaning of1 #h ,carving air-screws1 #ce-da ,chauvire type air-screw1 #ch ,clarke1 ,t4 ,w4 ,k41 #ad ,compressed-air engine1 #id-ajb ---- ----1 container for1 #ii ---- ----1 crank for1 #ig1 #ih ---- ----1 inlet and exhaust1 etc41 of1 #ig ---- ----1 pistons for1 #ih ,compressed-air engine1 testing the container1 #ajj ---- ----1 three-cylinder1 #id-ajc ---- ----1 valve and tap for1 #ajj ,compressed-air-driven biplane1 #ajd-aad ---- ----1 bracing planes of1 #aae ---- ----1 calculations for1 #ajd-aji ---- ----1 flying1 #aah1 #aai ---- ----1 inter-struts for1 #aab ---- ----1 materials for1 #ajf ---- ----1 planes for1 #aji ---- ----1 tail for1 #aaa ,designing1 general notes on1 #abj1 #abc ,dihedral angle1 #g ,double-winder1 #gj-gb ,drift and lift1 #c1 #f ,efficiency air-screw1 #ce ---- formula1 #ai ,elastic motor1 disadvantages of1 #id ,elevator adjustment1 #abg ,equilibrium1 #b ,fairey1 #ab ,force of gravity1 #b ,forces acting on kite1 #b1 #c ,formula1 efficiency1 #ai ----1 type1 #ah ,four-bladed air-screws1 making1 #acc ,fuselages1 #ai-cd ----1 boat-shaped1 #bd ----1 box-girder1 #bf ----1 distortion1 #cj ----1 simple1 #bh1 #bi ----1 single-spar1 #bf ,fuselages1 twin-screw1 #bf ----1 two-membered1 #be ,geared motor for model aeroplane1 #acd ,general notes1 #abd-ace ,gravity and pressure1 #f1 #g1 #h ,gravity1 force of1 #b ,hargreaves kite1 #acb ,hollow spar1 #bb ,houlberg1 #ad ,hydro-biplane1 #ag ,hydro-monoplane1 #hg-ic ----1 bearings for1 #hh ----1 elevator for1 #ij ----1 floats for1 #ij ----1 fuselage for1 #hg ----1 mainplane for1 #hh ----1 weight of1 #ic ,hydroplane floats1 calculating capacity of1 #acj ----1 water surface1 #abh ,kite1 box1 #ach1 #aci1 #adj ----1 forces acting on1 #b-c ----1 ,hargreaves'1 #acb ----1 speed of1 #d ----1 tailless1 #acf-ada ,lateral stability1 #g ,lift and drift1 #c1 #f ---- of aerofoil1 #aj ,loading1 #dd ---- for aeroplanes1 #abg ,longitudinal stability1 #h ,lubricant1 #abe ,mann1 ,r4 ,f41 #bj ,materials1 choice of1 #bh ,monoplane1 ,blriot type1 #ah ----1 collapsible1 #gc-gi ----1 ----1 chassis for1 #gh ----1 ----1 mainplane for1 #ge ----1 ----1 propellers for1 #gi ----1 ----1 tail for1 #gd ----1 hydro1 #hg-ic ----1 ,ridley1 #ab ----1 ----1 twin-screw1 #ed-fj ----1 ----1 mainspar for1 #ed ----1 ----1 propellers for1 #eh ----1 tractor1 #hj-hf 7see ,tractor monoplane7 ,penaud1 ,alphonse1 #id ,piano wire1 uses of1 #cj ,pitch1 #ce1 #cf1 #ci1 #db1 #dd1 #de ---- angles1 setting out1 #dj 8,plane0 and 8aeroplane10 meaning of terms1 #h ,planes1 bamboo1 #cj ----1 cane1 #ej ----1 constructing1 #dg-ec ----1 fixing1 #acc ----1 swept-back1 #eb ----1 types of1 #dg ----1 umbrella ribbing1 #ej ----1 wire1 making1 #ej1 #ea ----1 wooden1 #dh ,plant1 calculations for designing1 #abj ,pressure and gravity1 centres of1 #f1 #g1 #h ,resistance1 air1 #c ,ridley monoplane1 #ab ,scale models1 building1 #cb1 #cd1 #aba1 #abb1 #abc ,silk1 waterproof1 #acj ,skid1 fitting1 #abf ,slip1 #ce ,small biplane1 driving1 #ajb-ajc ,spar sections1 #bf1 #bg ,speed of aeroplane1 #d ,spindles1 attaching1 #df ,stability1 #bi1 #abd1 #abe ----1 lateral1 #g1 #db ----1 longitudinal1 #h ,tailless kites1 easily made1 #acf-ada ,t frame1 #bj1 #bb1 #bc ,thrust1 #db ---- required for aeroplane1 #aa ,timber1 strength of1 #bi1 #cj1 #cb ,torque1 #bi1 #cf1 #db ,tractor hydro-biplane1 #ag ----1 monoplane1 #hj-hf ----1 ----1 chassis for1 #hb ----1 ----1 mainplane for1 #hd ----1 ----1 mainspar for1 #hj ----1 ----1 twin-gears for1 #hd ,twining1 ,e4 ,w41 #ad1 #ag ---- air-screw1 #df ,twin-screw biplane1 simple1 #fa-fh ---- ---- ----1 elevator for1 #fb ---- ---- ----1 flying the1 #ff-fh ---- ---- ----1 mainspar for1 #fa ,type formula1 #ah ---- of aeroplanes1 #ab-ah ,waterproof silk1 #acj ,water-surface hydroplane1 #abh ,winders for elastic motors1 #fi-gb ----1 double1 #gj-gb ----1 push-in-the-ground1 #fi-gj ,wing bracing1 #cj ,,printed ,,by ,,cassell ,,company1 ,,limited1 ,,la ,,belle ,,sauvage1 ,,london1 ,e4,c4#d #ej4bbj