straight grained spruce. At the center each member is of approximately
circular cross section, and is ¹⁄₄″ in diameter. The members taper to
about ³⁄₁₆″ at the ends, the circular cross section being maintained
throughout. The frame is braced by a strip of bamboo of streamline
form, extending from one side member to the other, 18″ from the apex of
the frame. The ends of this frame are bent to run parallel to the side
members of the frame where they are secured by binding with silk thread
and gluing. Piano wire hooks are also secured to the side members of
the frame adjacent the ends of the cross brace, and from these hooks
extend wires of steel (No. 2 music wire) which run diagonally to the
rear brace or propeller spar where they are secured.
[Illustration: Diagram 11]
The frame is braced further by an upwardly arched strip of bamboo, as
shown in diagram 11, this strip being 2¹⁄₂″ in height. At the top of
this brace are two bronze strips of No. 32 gauge brass, one above the
other, one on top of the brace and the other below.
Adjacent the ends of these strips of metal are perforations through
which pass bracing wires, one of which wires runs to the front of
the frame where a hook is mounted for its reception, and the other
two wires extend to the rear of the frame where they are secured
to the propeller brace. The propeller brace consists of a strip of
streamlined spruce 11³⁄₄″ in length, the propellers being at an angle,
thus clearance is allowed ¹⁄₄″ wide at the center, tapering to ³⁄₁₆″
at the ends. The ends of the propeller brace extend out one inch from
the side members of the frame, to allow room for the rubber strands to
be used as motive power. In order to avoid slotting the ends of the
side members of the frame so that the propeller brace can be secured
therein, thin strips of bamboo are secured above and below the end of
each side member, by binding with silk thread and gluing, the space
between these bamboo strips being utilized for the brace which is
securely bound and glued therein. The propeller bearings consist of
strips of very thin bronze (No. 32 gauge), about ³⁄₁₆″ in width, bent
over ⁵⁄₈″ strips of German silver tubing, the tubing being soldered to
the bronze strips and the propeller brace, which fits between the upper
and lower portions of the bronze strips, is securely bound and glued
thereto.
The propellers are cut from solid blocks of pine, and are 12″ in
diameter. The blade, at its widest portion, measures 1³⁄₈″. The blades
are cut very thin, and in order to save weight, they are not shellacked
or painted.
The propeller shafts are of piano wire (No. 20 size) to fit the tubing
used in the bearings, pass through the propellers and are bent over
on the outer side to prevent turning. A few small bronze washers are
interposed between the propellers and the outer ends of the tubing to
minimize friction when the propellers are revolving. Twelve strands of
rubber are used for each propeller, the rubber being ¹⁄₈″ flat.
[Illustration: Wallace A. Lauder distance and duration model]
[Illustration: Wallace A. Lauder R. O. G. Model]
The wings are both double surfaced, and are of the swept back type. The
span of the main wing is 28¹⁄₂″, with a chord of 6¹⁄₂″. The elevator
has a span of 15″ with a chord of 4³⁄₄″. The main wing has eleven
double ribs, these ribs being built up on mean beams of spruce ¹⁄₁₆″ ×
³⁄₁₆″, the front beam being placed 1¹⁄₄″ from the entering edge, and
the second beam being 2″ back from the front beam. The entering and
trailing edges are formed from a single strip of thin split bamboo, all
the joints being made by binding with thin silk and gluing.
The elevator is constructed in like manner, except that it only has
seven ribs, and the measurements are as above set forth. Both planes
are covered with goldbeater’s skin, sometimes known as “Zephyr” skin,
which is first glued in place and then steamed, which tightens the same
on the plane, and given a coat of preparation used for this purpose.
THE HITTLE WORLD RECORD
MODEL
(SINGLE TRACTOR MONOPLANE, 116 seconds
DURATION RISING FROM WATER)
The Hittle World record model hydroaëroplane, designed and constructed
by Mr. Lindsay Hittle of the Illinois Model Aëro Club, is perhaps
one of the most interesting types of models yet produced. The
establishing of this record illustrates the value of careful designing
and construction and offers to the beginner an example which might
be followed if good results are sought. In having broken the world’s
model hydroaëroplane record with a tractor type model Mr. Hittle
accomplished a feat of twofold importance. First, in having advanced
the possibilities of the tractor model, and, second, in illustrating
the value of scientific construction. The previous record for this
type of model has been but 29 seconds, just one-fourth of the duration
made by Mr. Hittle’s model.
Mr. Hittle’s model shows many new and original features not hitherto
combined on any one model. Note diagram 12. The model is of extremely
light weight, weighing complete but 1.75 ounces. The floats and their
attachments have been so designed as to offer the least possible wind
resistance. In fact every possible method was utilized in order to cut
down weight and resistance on every part of the model. As a result of
this doing away with resistance an excellent gliding ratio of 8³⁄₄ to 1
has been obtained.
For the motor base of the model a single stick of white pine ⁵⁄₆″
deep and 45″ in length is used. On the front end the bearing for the
propeller is bound with silk thread and a waterproof glue of the
constructor’s own composition being used to hold it secure. For the
bearing a small light weight forging somewhat in the shape of the
letter “L” is used, this being made streamline. At the rear end of
the engine base is attached a piano wire hook for the rubber. The
stabilizer consisting of a segment of a circle measuring 12″ × 8″ is
attached to the under side of the engine base. The rudder measuring
3¹⁄₂″ × 3¹⁄₂″ is attached to the stabilizer at the rear of the engine
base.
The wing is built up of two beams of white pine with ribs and tips of
bamboo and has an area of 215 square inches.
The wing which has a total span of 43″ and a chord of 5¹⁄₈″ is built up
of two beams of white pine with ribs and tips of bamboo and has a total
area of 215 square inches. The wing is given a small dihedral and the
wing tips are slightly upturned at the rear.
The trailing edge is longer than the entering edge the ribs being
placed somewhat oblique in order to secure an even spacing. The wing is
attached to the frame by two small bamboo clips which hold it rigidly
and permit easy adjustment and is set at an angle of about 4 degrees
with the line of thrust.
[Illustration: Diagram 12]
Both the floats which take practically the whole weight of the machine
are situated directly under the wing just far enough behind the center
of gravity to prevent the model from tipping backward. These floats
are attached to the engine base by means of streamlined bamboo struts.
Bamboo is also used in the construction of the float frames. A single
float of triangular sections is situated just behind the propeller. The
entire weight of the floats and their attachments is but .23 ounces.
The propeller which consists of four blades is built up of two
propellers joined together at the hubs and securely glued, the
completed propeller having a diameter of 10″ with a theoretical pitch
of 14″. The blades are fairly narrow, tapering almost to a point at the
tips. The propeller is driven by five strands of ³⁄₁₆th″ strip rubber
at about 760 r.p.m. when the model is in flight. At the time when
the model made its record flight of 116 seconds the rubber was given
1500 turns which is not the maximum number of turns. At other times
the model has flown satisfactorily with less turns of the rubber.
While in the air the model flies very slow and stable notwithstanding
its light weight and large surface. On three occasions the model has
made durations of approximately 90 seconds which rather dispenses the
possibility of its being termed a freak.
THE LA TOUR FLYING BOAT
One of the most notable results of the National Model Aëroplane
Competition of 1915 was the establishing of a new world’s record for
flying boats. Considering that the model flying boat is a difficult
type of model to construct and fly, the establishing of this new world
record of 43 seconds is remarkable. Credit for this performance is
due Mr. Robert La Tour of the Pacific Northwest Model Aëro Club, who
designed, constructed and flew the model flying boat which is herewith
described and illustrated. Diagram 13.
The frame is made of laminated spruce 40″ in length, made of two strips
glued together. They are ³⁄₈″ × ¹⁄₈″ at the center tapering to ³⁄₁₆″ ×
¹⁄₈″ at the ends. The cross braces are of split bamboo and are fastened
to the frame side members by bringing them to a wedge at the ends and
then inserting them into slots in the sides of the frame side members
and are finally drilled and bound to the latter. The rear brace is
of streamlined spruce ¹⁄₄″ × ¹⁄₈″; this butts against the frame side
members and is bound to them. The propeller accommodations are made of
brass.
The propellers are 10″ in diameter with a 19″ pitch. These are carved
from a block of Alaska cedar 1¹⁄₄″ wide by ³⁄₄″ thick. Of course the
propellers may also be made from white pine. To turn the propellers 15
strands of ¹⁄₈″ flat rubber are used.
Bamboo about ¹⁄₁₆″ square is used to obtain the outline of the wings.
The main wing has a span of 33″ with a chord of 5¹⁄₂″. Split bamboo
is used for the making of the 9 ribs. The wing spar or brace is of
spruce ³⁄₁₆″ × ¹⁄₈″ and is fastened below the ribs as illustrated in
diagram 13. The elevator is constructed in like manner but has a span
of only 17″ × 4³⁄₄″ and has only 5 ribs. A block ³⁄₄″ high is used for
elevation. Both wings have a camber of ¹⁄₂″ and are covered on the
upper side with silk doped with a special varnish and a few coats of
white shellac.
[Illustration: Diagram 13]
The boat is 20″ long, 3″ in width and shaped as shown. The slip is
¹⁄₂″ deep and is located 7″ from the bow. The rear end is brought down
steeply to avoid the drag of the water on this point when the boat is
leaving the surface of the water. Spruce ³⁄₆₄ths of an inch thick is
used for the making of the sides, but the cross bracing is of slightly
heavier material, there being six braces used throughout. The rear
brace is much heavier in order to withstand the pull of the covering
and to receive the ends of the wire connections. The outriggers or
balancing pontoons are constructed of the same material as that of the
boat and are held together by a spruce beam 18″ long, ¹⁄₂″ wide by
³⁄₁₆″ thick, streamlined. This beam is fastened to the boat by means
of three brads to permit changing if necessary. The lower edges of the
outriggers should clear the water about ¹⁄₈″ before the steps on the
boat leave the water. The boat and outriggers are covered with silk,
shrunk with a special solution and then coated several times with white
shellac. It is a good plan to shellac the interior walls of the boat
and pontoons before covering to prevent them from losing their form by
becoming soft from the influence of water in the case of a puncture.
The boat is connected to the frame at its front by two steel wires,
their ends being inserted into the cross members of the boat, and then
brought up along the sides, crossed and then bound to the frame. A
similar pair of connecting wires are used to connect the rear end of
the boat to the rear end of the frame. A U-shaped wire is bound to the
outrigger beam and frame. A single diagonal strip of bamboo is also
fastened to the outrigger beam with a brad, its upper end being bound
to the cross bracing of the frame, making a very solid connection.
Under ideal weather conditions this model will fly on 12 strands of
rubber with the possibility of a better duration than has been made.
But, however, with 15 strands the model will rise at every attempt.
More rubber, however, causes the bow of the boat to nose under and to
accommodate this increase of power the boat should be lengthened.
THE COOK NO. 42 WORLD
RECORD MODEL
(TWIN PROPELLER HYDROAËROPLANE, 100.6
SECONDS RISING FROM WATER)
During the National Model Aëroplane Competition of 1915 held under
the auspices of the Aëro Club of America, a number of new world
records were established, one of which was for twin propeller
hydroaëroplanes. The credit for this record is due Mr. Ellis C. Cook
of the Illinois Model Aëro Club, who succeeded in getting his model
hydroaëroplane—which by the way is a rather difficult type of model to
operate—to rise from the water and remain in the air for a duration
of 100.6 seconds. This model is of the common A frame design with the
floats or pontoons arranged in the familiar fashion, two forward and
one aft. The model is fairly light, weighing, when complete, 3.33
ounces, ¹⁄₂ ounce of which is made up in rubber strands for motive
power. Diagram 14.
The frame is made of two sticks of white pine for side members, each
member measuring 38¹⁄₄″ in length, ⁵⁄₁₆″ in depth, by ¹⁄₈″ in width.
These are cut to taper toward the ends where they are only ¹⁄₈″ in
width by ³⁄₁₆″ in depth in the front and rear respectively. Three “X”
strips of streamlined bamboo measuring ³⁄₁₆″ in width by ³⁄₆₄ths of an
inch in depth, are used for bracing the frame between the front and
rear and are arranged as shown in diagram 14. The propeller bearings
are of small streamlined forgings of light weight, and are bound to the
rear end of each side member first by gluing, then binding around with
thread. The front hook is made of No. 16 piano wire and is bound to the
frame as shown in diagram 14. The chassis which holds the floats or
pontoons is made of ³⁄₃₂″ bamboo bent to shape and bound to the frame
members. By the use of rubber strands the floats are attached to the
chassis; the forward ones being attached so that angle may be adjusted.
The main wing has a span of 36″ and a chord of 5″ and is constructed of
two white pine beams each 39″ long, with bamboo wing tips. The ribs,
seven in number, are also made of bamboo and are spaced along the edges
of the wing at a distance of 4¹⁄₂″ apart. The “elevator” or front wing
has a span of 14″ and a chord of 3¹⁄₄″, the framework of which is made
entirely of bamboo. The entering edge of this wing is given a slightly
greater dihedral so that the angle of incidence at the tips is greater
than at the center. By this method the added incidence in the front
wing is obtained. By the use of rubber bands both wings are attached to
the frame.
[Illustration: Diagram 14]
The two forward floats are spaced eight inches apart and are of the
stepped type, the step being 3¹⁄₂″ from the front and has a depth of
¹⁄₈″. These two floats are separated by two bamboo strips as shown
in the diagram, which are tied to the rounded portion of the under
carriage by small rubber bands. By the sliding of these strips back
and forth the necessary angle of the floats may be obtained to suit
conditions. The floats are built up with two thin pieces of white pine
for sides, separated by small pieces of wood about one-half the size
of a match in cross section. Chiffon veiling which is used for the
covering of the wings, is also used for the covering of the floats,
after which it is covered with a special preparation to render both the
wings and the floats air and water-tight.
The two ten-inch propellers with which the model is fitted have a
theoretical pitch of twelve and one-half inches. The propellers are
carved from blanks one-half inch thick, the blades of the completed
propellers having a maximum width of one inch at a radius of three
inches. The propeller shafts are made from No. 16 piano wire and have
small washers for bearings. Each propeller is driven by three strands
of ¹⁄₄″ strip elastic. The rubber is given 1700 to 1750 turns and
revolves the propellers at 1150–1200 r.p.m., when the model is in
flight.
The model usually runs over the surface of the water for a distance of
from two to three feet before it rises, after which it climbs at a very
steep angle to the necessary altitude. The model seems, when in flight,
to be slightly overpowered but this is misleading. The rubbers usually
unwind in from 85 to 90 seconds. On four out of six flights this model
has made a duration of between 98 and 100 seconds which is rather
unusual for a model of this type.
THE RUDY FUNK DURATION MODEL
Of the many different types of duration models that have made their
appearance during the year of 1915 perhaps the model described
herewith, constructed and flown by Mr. Rudolph Funk, of the Aëro
Science Club, was one of the most successful. Unlike most models the
propellers of this model are bent and not cut. This model made its
appearance during the latter part of 1915, on several occasions having
flown for over 100 seconds duration. Diagram 15.
While retaining the important characteristics of his standard model,
slight changes have been made. Instead of the usual wire for the
construction of the frame of the wings, bamboo is used in its place for
lightness and strength. The wing frames are single surfaced, China
silk being used for covering. The “dope” which is used to render the
silk airtight is made by dissolving celluloid in banana oil. This in
turn is applied to the silk with a soft brush.
The camber of the main wing is ³⁄₄″ at the center, with a slight
reduction towards the negative tips; it also has a dihedral angle of 2
degrees. The main beam, which is secured to the under side of the frame
for rigidness, is of spruce 1″ by ⁵⁄₆₄″, tapering to ³⁄₄″ × ⁵⁄₆₄″.
The ribs for the main wing and small wing or “elevator” are cut from
solid pieces of bamboo ³⁄₁₆″ thick by ¹⁄₄″ wide. These pieces of bamboo
are first bent to the proper camber and are then cut into strips each
¹⁄₁₆″ wide. The ribs are next tapered to a V at the bottom, toward the
trailing edge, as shown in diagram 15, and also toward the entering
edge. To accommodate the entering and trailing edges of the frame, each
rib is slit slightly at both ends. Both edges of the frame are then
inserted in the slots at the ends of the ribs and bound around with
silk thread.
[Illustration: Diagram 15]
The frame is composed of two sticks of silver spruce 38″ in length,
⁵⁄₁₆″ × ³⁄₁₆″, tapering to ¹⁄₄″ × ⁵⁄₃₂″, held apart by a streamline
bamboo cross brace in the center. An additional brace of bamboo is
securely fastened across the frame toward the front. The propeller
brace consists of a streamline-cut piece of bamboo 12¹⁄₂″ in length
by ³⁄₈″ in width at the center, tapering to ¹⁄₄″ toward the ends. The
propeller brace is inserted in slots cut in the rear ends of the frame
members, then bound and glued.
The propellers are bent from birch veneer, the bending being done
over an alcohol flame as illustrated in diagram 15. But first of all
the blades are cut to shape, sandpapered and finished before they are
bent. As shown in the drawing a slot is filed in the hub of each blade
to enable the propeller shaft to pass through when both have been
glued together. The blades are then glued and bound together, first by
placing a piece of wire in the slots to insure their being centered and
also to prevent their being filled with glue. After this has been done
each propeller is given three coats of the same dope as is used on the
wings.
The propeller bearings are turned out of ¹⁄₃₂″ bronze tubing, the
length of each bearing being ¹⁄₂″. Steel washers are slipped over the
propeller shaft, between the bearing and propeller to insure smooth
running. The propeller shafts are made from steel hatpins which are
heated at both ends, one end of which is bent into a loop to receive
the rubber strands, the other end being bent around the hub of the
propeller to prevent the shaft from slipping during the unwinding of
the rubbers. Two strips of brass, each ¹⁄₄″ × 2″, are bent around the
one-half inch bearing and soldered. The brass strips are then glued and
bound onto the ends of the propeller brace as shown in diagram 15.
[Illustration: Rudy Funk speed model]
[Illustration: Schober compressed air driven monoplane. McMahon
compressed air driven tractor (right)]
THE ALSON H. WHEELER WORLD RECORD MODEL
(TWIN PUSHER BIPLANE 143 SEC. DURATION
RISING FROM THE GROUND)
Since the beginning of model flying very little attention has been
paid to the model biplane. Practically all records are held by
model aëroplanes of the monoplane type. With this fact in view, the
record established by Mr. Wheeler with his Twin Pusher Biplane is
extraordinary, in so far as it surpasses many of the monoplane records.
This model is a very slow flyer, and has excellent gliding ability. At
the time when this model flew and broke the world’s record, the greater
portion of the flight consisted of a beautiful glide of 86 seconds’
duration, after the power gave out, making it possible for the model to
remain in the air for a duration of 143 seconds.
The frame consists of two I-beams, each 48″ in length, running
parallel, and spaced by cross pieces, each piece 11¹⁄₂″ long. The
bearing blocks used made it possible for the propellers to clear by
one-half inch. Two 12″ expanding pitch racing propellers are used and
these are mounted on ball bearing shafts. The main upper plane has a
span of 34″ with a chord of 5″, the lower plane being 26″ by 5″. The
elevator consists of two planes, each measuring 14″ by 5″. Cork wheels
are used, each being one inch in diameter. For motive power one-eighth
inch flat rubber is used, this being coated with glycerine to prevent
sticking.
[Illustration: Alson H. Wheeler twin pusher Biplane]
[Illustration: C. V. Obst tractor model]
A MODEL WARPLANE
The model shown in the accompanying photograph was constructed by
Master R. O’Neill, of Montreal, Canada. The machine was designed
after one of the leading warplanes now in active service abroad and
in carrying out the entire features he did not fail to include the
identification marks which are of utmost importance in the war zone.
The dimensions of the model are as follows: Length of fuselage, 23″;
span of top wing, 33″; span of lower wing, 29″, both having a chord of
7″. Motive power is derived from two ¹⁄₈ inch square elastic strands
which operate a multiple gear to which is attached a 10″ propeller.
In coloring the model a dull aluminum was selected. Complete the model
weighs 12 ounces. Perhaps the most interesting feature of the model
is the ability to change it to a monoplane by the removal of the
upper wing after which the lower wing is raised to the sockets in the
fuselage which were especially arranged for that particular purpose.
[Illustration: Model warplane]
A SIMPLE COMPRESSED AIR ENGINE
During the past few years model flyers in America have shown a tendency
toward the adoption of compressed air engines for use in connection
with model aëroplanes. Hitherto, England has been the home of the
compressed air engine, where a great deal of experimenting has been
carried on, to a considerable degree of success. Flights of over 40
seconds have been made with models in which compressed air power plants
were used. But, however, the desire on the part of a large majority of
model flyers in America to build scientific models, that is, models
more closely resembling large machines, has made it necessary to find a
more suitable means of propulsion; rubber strands being unsatisfactory
for such purposes. Many different types of compressed air engines have
made their appearance during the past few years, among which the two
cylinder opposed type is very favorably looked upon, because it is
perhaps one of the easiest to construct.
To make a simple two cylinder opposed compressed air power plant, as
illustrated in Figure 1 of diagram 16, it is not necessary that the
builder be in possession of a machine shop. A file, drill, small gas
blow torch and a small vise comprise the principal tools for the making
of the engine.