Transcriber’s Note
In the following transcription italic text is denoted by _underscores_.
Small capitals in the original publication have been transcribed as ALL
CAPITALS.
See end of this document for details of corrections and other changes.
————————————— Start of Book —————————————
[Illustration: Waid Carl’s model in flight.
Courtesy Edward P. Warner, Concord Model Club]
MODEL AEROPLANES
AND THEIR ENGINES
_A Practical Book for Beginners_
BY
GEORGE A. CAVANAGH
MODEL EDITOR “AERIAL AGE”
DRAWINGS BY
HARRY G. SCHULTZ
PRESIDENT THE AERO-SCIENCE CLUB OF AMERICA
WITH AN INTRODUCTION BY
HENRY WOODHOUSE
Managing Editor “Flying”
Governor of the Aero Club of America
NEW YORK
MOFFAT, YARD & COMPANY
1917
COPYRIGHT, 1916, BY
MOFFAT, YARD AND COMPANY
NEW YORK
————
_All rights reserved_
Reprinted August, 1917
TO
M. T. H.
INTRODUCTION
History tells us—what some of us luckier ones heard the Wright Brothers
themselves tell—that the Wrights’ active work in aëronautics was a
result of the interest aroused by a toy helicopter presented to them by
the Reverend Bishop Milton Wright, their father.
Tremendous developments have taken place in aëronautics and aircraft
are fast developing in size, speed, and range of action. They have
revolutionized warfare, and seem to be destined to become a most
important factor in the reconstruction that will follow the war.
The greater the development the truer the fact that model aëroplanes
may be instrumental in bringing to aëronautics men who may make
valuable contributions to aëronautics. As a matter of fact, there are
already in active life, contributing their share to the development of
aëronautics, young men who only a few years ago competed for prizes
which the writer offered for model competition.
The young men who are now flying models will live in the new age—and
they have much to give and much to receive from it.
Through the tremendous strides forward of aëronautics there are
wonderful possibilities for the employment of ingenuity, genius
and skill, and business opportunities, as great as have ever been
created by progress in important lines of human endeavor. Problems
of engineering as huge as were solved by master builders; juridical
and legal questions to be decided as stupendously difficult as any
Gladstone would wish them; possibilities for the development of
international relations greater than were ever conceived; problems
of transportation to be solved by the application of aircraft,
as wonderful as any economist could wish; opportunities to gain
distinction splendid enough to satisfy the most ambitious person.
HENRY WOODHOUSE.
New York, June 5th, 1916.
LIST OF CONTENTS
PAGE
INTRODUCTION ix
HISTORY OF MODEL AVIATION 1
CONSTRUCTION 8
Propellers—Wings—Frame—Assembling—Launching—
Chassis—Pontoons—Launching an R. O. G. or Model
Hydroaëroplane.
WORLD RECORD MODELS 52
Lauder Distance and Duration Model—Hittle Tractor
Hydro—La Tour Flying Boat—Cook No. 42 Model—Rudy Funk
Duration Model—Alson H. Wheeler Twin Pusher Biplane.
A MODEL WARPLANE 83
A SIMPLE COMPRESSED AIR ENGINE 85–93
COMPRESSED AIR DRIVEN MODELS 94–102
The Dart Compressed Air Driven Model—The McMahon
Compressed Air Driven Monoplane—The McMahon
Compressed Air Driven Biplane.
COMPRESSED AIR ENGINES 103–109
Wise Compressed Air Engine—Schober-Funk Three Cylinder
Engine—The Schober Four Cylinder Opposed Engine.
GASOLINE ENGINES 110–117
Jopson—Midget Aëro Gasoline Engine.
STEAM POWER PLANTS 118–122
H. H. Groves Steam Power Plants—G. Harris’s Steam
Engine—Professor Langley’s Steam Engine—French
Experiments with Steam Power Plants.
CARBONIC GAS ENGINE 123–124
THE FORMATION OF MODEL CLUBS 125–138
WORLD’S MODEL FLYING RECORDS 139–141
DICTIONARY OF AËRONAUTICAL TERMS 142–152
LIST OF ILLUSTRATIONS
PAGE
Model Aëroplane in Flight _Frontispiece_
First Model Aëroplane Exhibition Opp. 4
Propellers (Diagram 1) 9
How to cut propellers (Diagram 2) 11
Designs for propellers (Diagram 3) 14
Designs for propellers (Diagram 4) 17
Wing construction (Diagram 5) 20
Members of the Aëro Science Club Opp. 22
Members of the Milwaukee and Illinois Model Aëro
Clubs Opp. 22
Frame construction (Diagram 6) 25
Model Assembly (Diagram 7) 30
C. W. Meyer and Wm. Hodgins exhibiting early type
models Opp. 32
Henry Criscouli with five foot model Opp. 32
Schultz hydroaëroplane Opp. 32
Rubber winder (Diagram 8) 35
Chassis construction (Diagram 9) 38
Pontoon construction (Diagram 10) 43
Obst flying boat Opp. 44
McLaughlin twin tractor hydroaëroplane Opp. 44
Louis Bamberger hydro about to leave water Opp. 44
E. B. Eiring and Kennith Sedgwick Milwaukee Club How
to launch R. O. G. model Opp. 48
Waid Carl, Concord Model Club Launching R. O. G.
model Opp. 48
Wallace A Lauder model (Diagram 11) 54
Lauder distance and duration model Opp. 56
Lauder R. O. G. model Opp. 56
Lindsay Hittle world record hydroaëroplane (Diagram 12)
61
La Tour Flying Boat (Diagram 13) 66
Ellis Cook R. O. G. model (Diagram 14) 73
Funk duration model (Diagram 15) 78
Rudy Funk speed model Opp. 80
McMahon and Schober compressed air driven models Opp. 80
Alson H. Wheeler twin pusher biplane Opp. 82
C. V. Obst tractor Opp. 82
Model Warplane 84
Simple compressed air engine (Diagram 16) 87
Schober compressed air driven monoplane Opp. 90
Schober compressed air driven biplane Opp. 90
Dart compressed air driven model 95
John McMahon and compressed air driven monoplane Opp. 98
Frank Schober preparing model for flight Opp. 98
John McMahon pusher biplane (Diagram 17) 102
Wise compressed air engine Opp. 104
Schober-Funk three-cylinder rotary engine Opp. 105
Schober four cylinder engine (Diagram 18) 107
Jopson gasoline engine Opp. 110
Sectional view of Jopson engine (Diagram 19) 112
Power curve of Jopson engine (Diagram 20) 115
Midget gasoline engine Opp. 116
English steam power plant Opp. 120
V. E. Johnson steam driven hydroaëroplane Opp. 120
English compressed air driven biplane Opp. 122
Tractor hydroaëroplane fitted with steam power plant Opp. 122
English compressed air engine fitted with simple
speedometer Opp. 122
The Rompel six-cylinder carbonic gas engine Opp. 124
MODEL AËROPLANES
HISTORY OF MODEL AVIATION
Model aëroplaning, as a sport, was first introduced in America during
the year of 1907. It was then that the first model aëroplane club in
America was formed by Miss E. L. Todd, with the assistance of Mr.
Edward Durant, now Director of the Aëro Science Club of America.
Prior to this the model aëroplane was considered an instrument of
experimentation or, when built to resemble a full sized machine,
was used for exhibition purposes. Noted scientists, men such as
Maxim, Langley, Eiffel and others, depended largely on models to
bring about the desired results during their experiments. Before the
Wright Brothers brought forth and launched the first heavier than air
machine their experiments, to a great extent, were confined to model
aëroplanes. There is little doubt but that a large majority of aviators
engaged in flying machines in different parts of the world were at one
time in their career interested in the construction and flying of model
aircraft, and from which no doubt they obtained their initial knowledge
of the aëroplane, in so far as the same principles and laws apply to
any aëroplane, regardless of its size.
The first model aëroplane club went under the name of the New York
Model Aëro Club and during its existence a great many of its contests
were carried on in armories. The reason for this was because of the
fact that the greater number of the models prevalent at that time
were built along the lines of full sized machines, and their manner
of construction was such as to interfere with the flying efficiency
of the model. Streamline construction was something unknown to model
constructors in those days and, in consequence, crudely constructed
and heavy models were very often evidenced, and, as a result, flights
of over one hundred feet were very seldom made. At about the same time
model enthusiasts in both England and France were actively engaged
in constructing and flying models, but the type of model used was of
a different design from those flown by the American modelists and
as a result of this innovation many of the early records were held
abroad. The type of model flown by the English modelists resembled in
appearance the letter “A”, hence the term “A” type.
It was not long after the introduction of this type of model in America
that model aëroplaning as a sport began to assume an aspect of great
interest. Models were constructed along simpler lines and with a
greater tendency toward doing away with all unnecessary parts, thus
increasing the flying qualities of the models. Flights of greater
distance and duration were the objects sought and, in their efforts to
achieve them new records were made at most every contest, until flights
of from 500 to 1000 feet were common occurrences. By the use of the A
type model and the single stick model which made its appearance shortly
after the A type model, American modelists succeeded in breaking most
of the world records for this type of model which is now termed by
English modelists “flying sticks.”
[Illustration: First model aëroplane exhibition held at Boston, 1910]
One by one model aëroplane clubs were formed in different parts of the
country until to-day there are in existence about twenty-five clubs
and all with memberships of from two to eight times that of the first
model aëro club. The work which was started by the New York Model Aëro
Club is now being carried on by the Aëro Science Club of America and
its affiliated clubs. The interest in model flying grew to such an
extent that during the year of 1915 the Aëro Club of America decided
to hold the First National Model Aëroplane Competition for the purpose
of offering to the young men of America an opportunity of becoming
acquainted with this new sport and its advantages. The results of
this competition were beyond expectation. Models were made capable
of flying distances and with durations that, to the early flyers,
seemed impossible. In the hand launched contests models were flown for
distances ranging from 2000 to 2500 feet, the winning flight being
3537 feet, and it might also be said that the contestant who flew this
model, with a model of the same design established a duration record
of 195 seconds. As this goes to press, information is received that
the World’s Record for distance for hand launched models has been
broken by Thomas Hall, of Chicago, Ill., an Illinois Model Aëro Club
member, with a flight of 5337 feet. Another interesting result of the
competition was the establishing of a world hydroaëroplane record by
a member of the Illinois Model Aëro Club with a model of the tractor
type, a four-bladed propeller being used in connection with the model.
The flying boat which is a late advent to the field of model flying
also proved a record breaker in this competition, having remained in
the air after rising from the surface of the water, for a duration of
43 seconds. This model was flown by a member of the Pacific Northwest
Model Aëro Club of Seattle, Washington. The establishing of these
records clearly indicates the advantage of scientific designing and
construction and careful handling.
So satisfactory have been the results of the First National Model
Aëroplane Competition that the Aëro Club of America has made
arrangements for holding the Second National Model Aëroplane
Competition during the year 1916. But in the announcement of the Second
National Competition the Aëro Club of America has made provision for
the holding of contests for mechanically driven models, in view of
the interest which is being shown by model flyers in the construction
of models more closely resembling large machines to be driven by
compressed air, steam and gasoline power plants. This is the outcome
of a desire on the part of model constructors to substitute for what
is now commonly known as the “flying stick,” models more closely
resembling large machines, which models can be more satisfactorily
flown by the use of compressed air, steam or gasoline power plants. As
in the early days, the best flights made by models using compressed air
and steam have been made by English flyers, the duration of the flights
ranging anywhere from 25 to 50 seconds.
Whether or not the American flyers will repeat history and achieve
greater results with this type of model motive power is something that
can only be determined in the future. But in any event the scientific
mechanically driven model will, without doubt, assume an important
position in the field of model aviation.
CONSTRUCTION
PROPELLERS
Propellers may be cut from various kinds of wood, but the most
suitable, from every standpoint, is white pine. The advantage of using
this wood lies in the fact that the propellers may be cut more rapidly
and when cut are lighter than those made from most other kinds of wood.
When coated with the proper kind of varnish they are sufficiently
strong for ordinary flying. Wood selected for propellers should be free
from knots, holes and other imperfections and it is very desirable that
it should be of perfectly straight grain.
A piece of such clear white pine 8″ long, 1″ wide and ³⁄₄″ thick should
be selected and on one side marked TOP. A tracing of the propeller
similar in design to Figure 1, should be laid on this piece of wood and
an imprint of the propeller design drawn on the TOP side.
[Illustration: Diagram 1]
To find the center of the block two lines should be drawn from the
opposite corners, their point of meeting being approximately in the
center—near enough for all practical purposes to insure greater
accuracy. Similar lines should be drawn from the corners on the BOTTOM
side of the block of wood. A hole ³⁄₃₂ of an inch in diameter should
be bored through the center thus obtained, through which the propeller
shaft will be inserted when the propeller is finished. The two sections
of the propeller blades drawn in diagrammatical form on the TOP of the
block, should be marked respectively BLADE 1 and BLADE 2, as shown in
diagram 1. The block is then ready for the commencement of the actual
cutting. In cutting out the propeller, BLADE 1 should be held in the
left hand and the knife in the other, with the blade of the knife on
the straight edge of BLADE 1. The cutting should be carried out very
carefully with attention constantly paid to Fig. 2, and should be
stopped when the line shown in Fig. 2 has been reached. The semi-blade
should then be sandpapered until a small curve is obtained by which the
propeller will be enabled to grip the air.
[Illustration: Diagram 2]
To cut BLADE 2, BLADE 1 should be held in the left hand and BLADE 2 cut
until the line shown in Fig. 3 is reached, after which the sandpapering
process is carried out in the same manner as in the case of BLADE 1.
During all of the foregoing operations it must be clearly borne in
mind that the TOP of the blank propeller must always face upward,
and the cutting should always be done on the STRAIGHT lines. Should
the straight edge be cut on one edge of the blank propeller and the
curved edge on the other, it would result in the blades of the finished
propeller having a tendency to push in opposite directions and in
consequence no propulsion of the model would be possible.
Attention should next be turned to the back of the propeller blank on
which the manner of cutting is exactly like that suggested for the top
side, with the exception that instead of cutting along the STRAIGHT
lines, the cutting is done along the CURVED lines. In this part of
the work great care is to be exercised for by the time the necessary
cutting has been done on the back of the propeller the entire structure
is very fragile and one excessive stroke of the knife may result in
destroying the entire propeller blade. By constantly holding the wood
to the light it is possible to determine with a reasonable degree of
accuracy the evenness of thickness. To complete the BOTTOM side of the
propeller the blade should be sandpapered as was the top.
The method of cutting the second propeller is exactly that used in
cutting the first propeller, only that the diagram shown in Fig. 4
should be used. This will result in two propellers being made that will
revolve in opposite directions in order to produce even and balanced
propulsion. If both propellers revolved in the same direction the
effect would be to overturn the model.
[Illustration: Diagram 3]
In diagram 1 the propellers are shown with the straight edge as the
entering or cutting edge of the blade. Some of the model builders
prefer the curved edge as the cutting edge (diagram 2). It is
significant that Mr. Frank Schober, a well known model constructor,
tested both designs on his compressed air driven model, and while
both propellers were the same in weight, diameter and pitch, the one
having the straight edge as the cutting edge was found one-third more
efficient.
When the propellers have been given a light coat of shellac they should
be laid aside until the assembling of the complete model.
By following the foregoing instructions a simple and effective set of
propellers will be produced. But in order to vary the experimental
practice of the constructor various other diagrams, Nos. 3 and 4,
illustrating suitable designs, are provided and can be made by applying
the above general theory and using the diagrams herewith.
WINGS
One of the most important considerations in the construction of a model
is the making of the wings. To obtain the greatest efficiency the
wings must be carefully designed, with due attention to whether the
model is being constructed for speed, duration or climbing ability.
Attention should be given to streamline construction; that is, the
parts of the wing should be so assembled that the completed wing would
offer the least possible resistance to the air, if the best results are
to be obtained.
For the main wing three strips of spruce, each 30″ in length, two of
them being ³⁄₁₆″ × ¹⁄₄″ and the third ³⁄₁₆″ × ¹⁄₁₆″ are required. To
make them thoroughly streamline all edges should be carefully rounded
off and all surfaces should be smooth. A strip of bamboo at least 20″
long, ¹⁄₂″ wide, ¹⁄₈″ thick, should be cut into pieces, each piece to
be 5 in. long. To secure the necessary curve, ¹⁄₂″ depth, the pieces
of bamboo should be held in steam and slowly bent in a manner closely
resembling the skids of an ordinary bobsled. When the curvature has
been obtained, care should be exercised in cutting each piece into four
longitudinal strips, from which twelve should be selected to be used as
ribs, each to be ¹⁄₈″ wide. The bending of the bamboo preliminary to
making the ribs is done in order to secure uniformity of curvature.
[Illustration: Diagram 4]
When this has been done the ribs are ready for fastening to the
sticks—entering and trailing edges—and each must be attached an equal
distance apart. In order that the ribs may be evenly spaced it is
necessary to put a mark every 3″ on the larger stick or entering edge
of the wing, and also on the flat stick or trailing edge. The main beam
which is of the same dimensions as the entering edge is afterwards
fastened across the center of the wing, and does not necessarily need
to be thus marked, as it is fastened to the ribs after the ribs have
been attached to the entering and trailing edges of the wing frame.
By holding the ribs one at a time so that the curved edge rests upon
the entering edge where the mark indicates, as shown in diagram 5,
they should be fastened thereon by means of thread and glue. The rear
end of the rib must be fastened to the trailing edge where the mark
indicates, also by thread and glue.
After all ribs have been thus securely fastened to both edges of the
frame the third stick, or main beam, should be attached to the frame
on the underside, the fastening being made at the highest point of
the curve of each rib. This main beam prevents the wing covering from
drawing in the end ribs and adds very materially to the strength of
the entire wing structure. To cover the wings fiber paper may be used
and is a suitable material, but the best results, from a standpoint of
flying efficiency and long service, are obtained by the use of China
silk.
The frame of the forward wing or elevator is made in the same manner
as is the main wing, but it is only 12″ in span by 4″ in chord, and is
constructed without the use of a main beam. This wing has only five
ribs which are made in the same manner as those for the rear wing, and
each is placed a distance of 3″ apart.
[Illustration: Diagram 5]
A piece of silk measuring 2″ longer and 2″ wider than each of the wing
frames should be used in covering the wings, and this can be held in
position by the use of pins prior to the actual sewing. The extra inch
of silk on all sides of the frame is placed around the under side of
the frame—in order that it can be made thoroughly taut when the silk
has been sewn close to the edges of the frame. After the silk has been
sewn close to the edges the pins may be removed and the surplus silk
that hangs from the under side of the frame may be cut off. To make
this silk airproof it should be coated with a thin coat of shellac or
varnish and the wings should be thoroughly dry before being used. This
coating, in addition to airproofing, will assist in making the covering
perfectly taut, and also in making the wing ready for service when the
entire model is ready to be assembled.
FRAME
As all other parts of the model are attached to the frame in addition
to its having to stand the strain of the tightly wound rubber strands
which serve as the motive power for the model, it must be made strong.
It is therefore necessary to exercise care and judgment in making
certain that the different units that make up the frame are rightly
proportioned and are of the proper material. Just as in the large sized
aëroplanes there are many types of bodies, so there are many different
types of frames in use in model construction, but the standard, and for
all practical purposes the best frame, resembles the letter A in shape,
hence the name A type. The lightness of the frame depends entirely on
the materials used and the manner in which it is constructed.
Some model flyers use but a single stick for the frame, but generally
the A type frame is preferred for the reason that it is more durable,
the wings can be more securely attached to it, and that it is possible
of developing very much better results.
[Illustration: Members of the Aëro Science Club]
[Illustration: Members of the Milwaukee and Illinois Model Aëro Clubs]
To construct such an A type frame 2 main sticks to serve as frame side
members are necessary and are made from spruce. Each member should be
36″ in length, ³⁄₈″ in depth by ¹⁄₄″ in width. By rounding the edges
and smoothing the various surfaces with sandpaper streamline effect
will be secured and will add to the efficiency of the machine as well
as to its appearance. When the side members are placed in A formation
the extremity of the sticks at which they meet should be so tapered
in the inner sides that when they meet and are permanently fastened
the result will be a continuance of the general streamline effect. The
permanent fastening of the frame side members at the point of the A
may be accomplished by using either strong fish glue or better, a good
waterproof glue and then have the jointure reinforced by securing a
piece of ³⁄₃₂″ steel wire 3″ in length and placing the center of it
at the point of the A, afterwards bending the wire along either outer
edge of the frame side members, putting as much pressure on the wire as
the strength of the structure will permit; after this the reinforced
jointure should have thread wound around it to insure even greater
strength. About ¹⁄₂″ of the wire on each side of the point should be
left clear and afterwards turned into a loop as shown in diagram 6, for
the purpose of attaching the hooks that hold the rubber strands. To
hold the side members apart at the rear end and for a propeller brace,
a piece of bamboo 10″ long, ¹⁄₈″ thick by ¹⁄₂″ in width is required
and this should be fastened to the extreme rear ends of the frame side
members, allowing the propeller brace to protrude on either side 1¹⁄₂″
as illustrated. To put the propeller brace in position a slot ¹⁄₂″ deep
by ¹⁄₈″ wide should be cut into the rear ends of the frame side members
for the reception of the propeller brace. After the brace has been
placed in position the outer edge should come flush with the rear ends
of the side members. To hold the brace in place thread and glue should
be used in the same manner as described for the point of the frame
side members. Between the point of the frame and the propeller brace
two bamboo pieces, one 9″ long and another 2¹⁄₃″ long, should be used
as braces for the general strengthening of the structure. The longest
piece should be secured across the top of the frame about 9″ from the
rear and the shorter piece about 9″ from the point.
[Illustration: Diagram 6]
When these two braces are in position the next matter that calls for
the attention of the constructor is the matter of getting into position
at the two outer extremities of the propeller brace bearings for the
propellers. For this purpose two pieces of ³⁄₃₂nd inch brass tubing,
each ³⁄₄th of an inch long, should be used, and should be fastened to
the underside of the propeller brace, at each extremity of that brace,
by the use of thread and glue. Sometimes greater efficiency is secured
by putting these pieces of bronze tubing about ¹⁄₄″ from the end. Some
model constructors make a very neat jointure here by soldering the
piece of tubing to a strip of thin brass, which is bent over the end
of the propeller brace and bound and glued thereon. In fastening the
bronze tubing to the propeller brace it should be so adjusted that it
will run parallel to the side members of the frame and will therefore
offer the least possible resistance to the shaft of the propeller when
the rubber strands have been attached.
When the frame has been completed a coat of shellac should be applied
to the entire structure to render it damp-proof.
ASSEMBLING
The proper assembling of the parts of the model is as essential to good
results as is the designing and making. Parts, although properly made,
if improperly placed in relation to each other will very often lead to
trouble. Therefore very great care must be exercised in the assembling
process.
When all the parts have been prepared and are ready to be assembled
the first thing that should be done is to mount the propellers in
position. This must be done very carefully on account of the fact
that the propeller shafts are easily bent and if bent the result is
considerable trouble, for such a bend in the propeller shaft will
cause the propeller to revolve irregularly with a consequent loss of
thrust. Before inserting the propeller shafts in the tubing 4 washers
each ¹⁄₄″ in diameter should be cut from hard metal, and a hole large
enough for the propeller shaft to pass through should be bored in the
center of each washer. The metal washers should be passed over the
straight ends of the shafts which extend from the rear of the tubing,
after they have been inserted in the tubing, and in this manner the
cutting into the hubs of the propellers which would follow is avoided.
The propellers are now to be mounted and this is accomplished by
allowing the ends of the shafts, which extend out from the rear of
the tubing, to pass through the hole in the hub of each propeller. In
mounting the propellers it is absolutely necessary to have the straight
edge of the propellers to face the point or front end of the model. The
propeller shown in Fig. 4 of diagram 1, should be mounted on the left
side of the frame to revolve to the left, while the propeller shown in
Fig. 1 should be mounted on the right side of the frame to revolve to
the right. When the propellers have thus been mounted the one-half inch
of shafting which extends out from the hubs of the propellers should be
bent over to grip the propeller hub and thereby prevent the shaft from
slipping during the unwinding of the rubber strands. For the reception
of the rubber strands to provide motive power a hook must be formed in
each shaft and this can be done by holding securely that portion of the
shaft which extends toward the point of the model, while the end is
being formed into a hook as illustrated in diagram 7.
[Illustration: Diagram 7]
Eighty-four feet of ¹⁄₈th″ flat rubber is necessary to propel the
model. This should be strung on each side from the hooks (see diagram)
at the front part of the model to the propeller shafts at the rear
of the model. In this way 14 strands of rubber will be evenly strung
on each side of the frame. To facilitate the winding of the rubbers
two double hooks made of ³⁄₃₂″ steel wire to resemble the letter S,
as shown in diagram 7, should be made. One end of this S hook should
be caught on the frame hook, while the other end is attached to the
strands of rubber, and to prevent the possible cutting of the strands a
piece of rubber tubing is used to cover over all wire hooks that come
in contact with the rubber strands providing propelling power.
The wings are mounted on the top side of the frame members by means
of rubber bands and in placing them upon the frame it should be noted
that the entering edge of each wing must face the point or front of
the model. The wings must be so adjusted on the frame that they result
in perfect side balance which means that there is an even amount of
surface on either side of the model. To secure a longitudinal balance
it will be found that the entering edge of the main wing should be
placed approximately 8″ from the propeller brace or rear of the model,
and the entering edge of the small wing or elevator approximately 6″
from the point. But it is only by test flying that a true balance
of the entire model can be obtained. To give the necessary power of
elevation (or lifting ability) to make the model rise, a small block of
wood about 1″ long by ¹⁄₄″ square must be placed between the entering
edge of the small wing and the frame of the model.
After the wings have been thus adjusted and a short test flight made to
perfect the flying and elevating ability of the model, and this test
flight has been satisfactory, the model is ready for launching under
its full motive power.
LAUNCHING
In the preliminary trials of a model close attention must be paid to
the few structural adjustments that will be found to be necessary
and which if not properly and quickly remedied will result in the
prevention of good flights or even in possible wrecking of the model.
Careful designing and construction are necessary but it is equally as
important that the model should be properly handled when it is complete
and ready for flying.
[Illustration: Charles W. Meyers and William Hodgins exhibiting models
of early design.]
[Illustration: Henry Criscouli and his five foot model. This model may
be disassembled and packed conveniently in small package.]
[Illustration: Harry G. Schultz hydroaëroplane.]
The approximate idea of the balance of a model can be secured by
launching it gently into the air. If the model dives down point first
it indicates that the main wing should be moved a little toward the
front. If it rises abruptly the main wing should be moved slightly
toward the rear. In this way by moving the wing forward or rearward
until the model glides away gracefully and lands flat upon the ground,
proper adjustment of the balance can be effected. If when launching
from the hand the model should curve to the left the main wing should
be moved slightly to the left of the frame members. And if the curve
is to the right the main wing should be moved in that direction. This
process can be continued until the model flies in the course desired.
The winding of the rubber strands to get the necessary propelling power
is an important detail. The model should be firmly held by some one
at the rear with the thumb on either side member, pressing down on
the jointure and with the four fingers of each hand gripping the under
side of the frame members, and in this way holding the model steady
and until the rubber strands have been sufficiently wound. With the
hands in this position the propellers, of course, cannot and should
not revolve. The hooks attached to the rubber strands at the point or
front of the model should be detached from the side members and affixed
to the hooks of the winder. A winder may be made from an ordinary egg
beater as is shown in diagram 8. When the hooks attached to the rubber
strands at the point of the model have been affixed to the winder the
rubbers should be stretched four times their ordinary length (good
rubber being capable of being stretched seven times its length) and
the winding commenced, the person winding slowly moving in towards the
model as the strands are wound. If the ratio of the winder is 5 to 1,
that is if the rubber is twisted five times to every revolution of the
main wheel of the winder, 100 turns of the winder will be sufficient
for the first trial. This propelling power can be increased as the
trials proceed. When the winding has been accomplished the rubber hooks
should be detached from the winder hooks and attached to the hooks at
the front of the side members as shown in the diagram.
[Illustration: Diagram 8]
In preparation for launching, the model should be held above the head,
one hand holding it at the center of the frame, the other in the center
of the propeller brace in such a way as to prevent the propellers
from revolving. When the model is cast into the air if it is properly
adjusted it will fly straight ahead.
A precaution which is sometimes worthy of attention before the
launching of the model under its full power is to test out the
propellers to find out whether or not they are properly mounted and
whether they revolve evenly and easily. To do this the rubber strands
may be given a few turns, enough to revolve the propellers for a brief
period, while the machine is held stationary. If the shafts have been
properly inserted in the hubs of the propellers and have not been
bent during the winding of the rubbers, the propellers will revolve
evenly and readily. If the propellers revolve unsteadily it indicates
that there is a bend in the propeller shafts or the propellers have
not been properly balanced. If the trouble is a bend in the shaft, it
must be removed before the model is launched on actual flight. If the
propeller does not revolve freely the application of some lubrication
(such as vaseline) to the shaft will eliminate this trouble. With these
adjustments made satisfactorily, the model can be launched with the
anticipation of good flying.
CHASSIS
The preceding instructions and discussions have dealt with different
parts of a simple model to be used as a hand-launched type of model.
The experience which will come as the result of flying this type of
model for a period will undoubtedly tend toward a desire on the part of
the constructor to make his model more nearly represent a large sized
aëroplane and will make him want to have his model rise from the ground
under its own power. Such a model is known as an R. O. G. type, that
is, rises off the ground.
[Illustration: Diagram 9]
To meet this desire all that it is necessary to do is to make a
chassis, or carriage, which can be secured to the frame of the model,
and with extra power added, will result in a practical R. O. G. model.
In constructing such a chassis or carriage it is necessary to bear
in mind that it must be made sufficiently strong to withstand the
shock and stress which it will be called upon to stand when the model
descends to the ground.
For the main struts of the chassis two pieces of bamboo each 9″ in
length are needed and these should be bent over 1″ on one end as shown
in the diagram, that they may be fastened to the under side of the
frame members, one on either side, at a point on that member 12″ from
the front. Two similar pieces of bamboo, each piece about 7″ in length,
are required to act as braces between the frame members and the main
chassis struts. Each end of each of the braces should be bent over in
the same direction and in the same manner as that described for the
main strut so that the fastening to the main frame member and the main
chassis strut may be accomplished. Steam may be used in bending the
ends of the pieces of bamboo. To make the landing chassis sufficiently
stable to withstand landing shocks a piece of bamboo 9″ should be
fastened from either side of the main chassis struts at the point where
the chassis brace on either side meets with main strut. The ends of
this cross brace should be bent in similar fashion to the other braces
to enable its being fastened easily and securely.
Two small wheels constitute the running gear for the front part of
the chassis, for which two pieces of ¹⁄₁₆″ steel wire each 2¹⁄₄″ long
are required. These small wires are fastened to the bottom ends of
the main struts, and to accomplish this the wire should be bent in
the center at right angles; one leg of the angle is attached to the
bottom end of the main strut as shown in the diagram. Disks for wheels
may be cut from a bottle cork which should be ³⁄₄″ in diameter by
approximately ¹⁄₄″ in thickness. The edges should be rounded off to
prevent chipping. Before mounting the wheels on the axles which have
been provided by the wires attached to the bottom of the main struts,
a piece of bronze tubing ³⁄₃₂″ inside diameter and ³⁄₁₆″ long should
be inserted in the center of each disk. To secure the least possible
resistance on the revolutions of the wheels, there should be placed on
the wire axles pieces of bronze tubing similar in diameter and ¹⁄₈″ in
length on either side of the wheel (see illustration). When the wheel
is thus placed in position with the pieces of bronze tubing on either
side about ¹⁄₄″ of the axle wire will extend from the outward end of
the outside piece of tubing. This should be bent over the tubing to
prevent its falling off and at the same time hold the wheel securely in
position.
For the rear skid a piece of bamboo 6″ long is used, one end of which
is curved as in a hockey stick so that it will glide smoothly over
the ground. The other end of the rear skid should be bent over about
¹⁄₂″ so that it can be securely fastened to the propeller braces,
as illustrated in the diagram. Two 7″ pieces of bamboo are required
to act as braces for the rear skid. Both ends of each brace strut
are bent over ¹⁄₂″ in the same direction, one end of each strut is
securely fastened to a side member 3″ from the rear and the other end
of each strut is fastened to the rear skid, at their point of meeting
as shown in diagram 9, the method of attaching being the same as in
the case of the forward portion of the chassis. All joining should be
accomplished by first gluing the braces and then binding with thread.
When completed, the rear skid should glide along the ground in bobsled
fashion, thus preventing the propellers from hitting the ground.
[Illustration: Diagram 10]
In making such a chassis or carriage the endeavor should be made to
use, as near as possible, the same weight of material on either side of
the model so as little interference as possible will be made with the
general balance of the model in flight.
PONTOONS
Having satisfactorily developed the hand launched model and the
model rising off the ground under its own propulsion the constructor
will next turn his mind to the question of having his model rise
under its own power from the surface of the water in the fashion of
passenger-carrying hydros and flying boats. This will be accomplished
by the use of pontoons attached to a specially designed chassis.
[Illustration: C. V. Obst World record flying boat]
[Illustration: Twin tractor Hydroaëroplane designed and constructed by
George F. McLaughlin]
[Illustration: Louis Bamberger’s hydro about to leave surface of water]
Three pontoons are necessary and these should be made as light as
possible. Each pontoon should be made 6″ long, 1″ deep toward the
forward part, by ³⁄₄″ at the rear and 2″ wide. The side members of
each pontoon are made from pieces of thin white pine wood ¹⁄₃₂nd of an
inch thick, slightly curved up at the front and sloped down toward the
rear. Small niches should be made on the top and bottom sides of the
pontoons into which the cross braces are inserted and glued. Further
reference to diagram 10 will show that at the extreme forward end of
the sides a cut is made large enough to receive a flat piece of spruce
¹⁄₁₆″ wide. Another cut of the same dimensions is made at the extreme
rear end. Still further cuts are made on the top and bottom sides of
the pontoons, the forward cuts measuring 1¹⁄₂″ from the front and the
rear cuts 1¹⁄₂″ from the rear, to join the sides of the pontoons as
illustrated in diagram 10. Six pieces of ¹⁄₁₆″ flat spruce are required
for the rear pontoon, the ends of which are held in position by glue.
For the forward pontoon only 4 braces are required in so far as the
ends of the two main brace spars of the forward part of chassis are
inserted in the cuts on the top sides of the pontoon. These brace spars
measure 10 inches in length and are made from bamboo ¹⁄₈th inch in
diameter, which necessitates enlargement of the cuts on the top sides
of the forward pontoons so that the extreme ends of the spars can be
inserted in the cuts in the place of the braces. To complete the rear
pontoon and prepare it for covering, three strips of ¹⁄₈″ bamboo are
required for struts. Two of these strips should measure 9″ in length
and should be attached to the front of the pontoon on the inner side
as shown in diagram 10. Thread and glue should be used in attaching
the ends of the strips to the pontoon. To enable fastening to the
frame the upper ends of the bamboo strips should be bent over about
¹⁄₂″. The third strip should measure 8″ in length and is attached to
the upper and lower braces toward the front of the pontoon as shown
in the diagram. It is necessary that this strip be secured in the
approximate center of the pontoon to insure a good balance. For the
purpose of securing the upper end of the third strut to the center of
the propeller brace a piece of wire 1¹⁄₂″ long should be secured to the
upper end of the strut and looped as shown in diagram 10. The three
pontoons should now be covered with fiber paper and it is necessary to
exercise care to avoid punctures. For the purpose of coating the fiber
paper to render it waterproof, a satisfactory solution can be made by
mixing banana oil with celluloid until it has attained the desired
thickness, after which it should be applied to the covering of the
pontoons with a soft brush.
For the main strut of the forward portion of the chassis two pieces of
¹⁄₈″ bamboo, each 11″ in length, are required and these should be bent
over 1″ on one end as shown in the diagram, that they may be fastened
to the under side of the frame members, one on either side at a point
on that member 11″ from the front. Two similar pieces of bamboo, each
piece 8″ in length, are required to act as braces between the frame
members and the main chassis struts. Each end of the braces should
be bent over in the same direction and in the same manner as that
described for the main struts so that the fastening to the main frame
member and the main chassis struts may be accomplished. Steam or an
alcohol lamp may be used in bending the ends of the pieces of bamboo.
To make the chassis sufficiently stable a piece of bamboo 7¹⁄₂″ should
be fastened from either side of the main chassis struts at the point
where the chassis brace on either side meets with the main strut. The
ends of this cross brace should be bent in similar fashion to the other
braces to enable its being fastened easily and permanently.
For the accommodation of the pontoons two strips of flat steel wire,
each 4″ in length, should be attached to the ends of the main struts,
about one inch from the bottom, the farthest ends should be bent to
grip the second spar which joins the pontoons. Note diagram 10.
To further strengthen the chassis a strip of flat steel wire
sufficiently long enough should be bent so that ¹⁄₂″ of the central
portion can be securely fastened to the center of the cross brace as
shown in diagram 10. The two outer ends should be bent down and are
fastened to the wires which are attached to the bottom ends of the
struts. This method of attaching the forward pontoons enables the
constructor to adjust them to any desired angle and also detach them
when not in use.
A model hydroaëroplane is one of the most interesting types of models
and if properly taken care of will afford the constructor many pleasant
moments.
[Illustration: Erwin B. Eiring about to release R. O. G. Model. (Note
manner of holding propellers.) Kennith Sedgwick, tractor record holder
Milwaukee Model Club. Courtesy Gilbert Counsell.]
[Illustration: Waid Carl releasing R. O. G. Model. Courtesy Edward P.
Warner.]
LAUNCHING AN R. O. G. OR MODEL
HYDROAËROPLANE
Although the method of determining the balance of an R. O. G. or a
model hydroaëroplane is exactly the same as that of a hand launched
model, the manner of launching is somewhat different. Instead of
holding the model one hand in the center of the frame and the other at
the rear as in the case of the hand launched model, in launching an R.
O. G. or hydro, the model should be rested upon the ground or water,
as the case may be, with both hands holding tightly to the propellers.
Then when about to let the model go release both propellers instantly.
If the model has sufficient power and it has been properly adjusted
it will glide over the surface of the ground or water for a short
distance, then rise into the air. Should the model fail to rise into
the air additional strands of rubber should be added, after which it
should be rewound and a second attempt made.
Should the model fail to respond after the addition of extra rubber,
the indications are that something requires further adjustment. Perhaps
the pontoons need further elevation if the model is a hydro, or if
it be an R. O. G. model the forward wing may require an increase of
elevation. In any event the model should be carefully examined and
adjustments made where necessary, after which the model should be
tested for balance and elevation. If satisfied with the behavior of the
model after test flights have been made, another attempt should be made
to launch the model from the ground or water.
On no account try to fly the model in the house, or see, supposing the
model is of the R. O. G. type, if it will rise from the dining room
floor. This advice may seem unnecessary, but it is not so, for there
has been quite a number of instances in which the above has been done,
nearly always with disastrous results, not always to the model, more
often to something of much greater value. The smashing of windows has
often resulted from such attempts, but generally speaking pictures
are the worst sufferers. It is equally unwise to attempt to fly the
model in a garden in which there are numerous obstructions, such as
trees and so forth. A wrecked model is very often the result of such
experimenting. The safest way to determine the flying ability of any
model is to take it out in an open field where its flight is less apt
to be interrupted.
WORLD RECORD MODELS
THE LAUDER DISTANCE AND
DURATION MODEL
After many months of experimentation Mr. Wallace A. Lauder succeeded in
producing a model that proved to be one of his most successful models.
But a few years ago flights of 1000 feet with a duration of 60 seconds
were considered remarkable. But so rapid has been the development of
the rubber strand driven model that to-day it is hardly considered
worth while to measure a flight of 1000 feet, especially in contests
where models fly over 2500 feet or 3537 feet which was the distance
flown by Mr. Lauder’s model during one of the contests of the National
Model Aëroplane competition of 1915. Mr. Lauder’s model on several
occasions made flights of over 3500 feet with a duration in each event
of over 195 seconds. It is therefore to be remembered that this model
is both a distance and duration model, both qualities being seldom
found in one model.
Reference to the accompanying drawing will give a clear idea of the
constructional details.