1939
STOUT TROPHY
WINNER
This model's 36-minute flight won the Stout Trophy and
qualified the builder as captain of the American Moffett team.
Bob Toft. Has won a second in gas, first in rubber at Nationals.
BY BOB TOFT
THIS is a typical American model. It was finished at
five o'clock in the morning, a few hours before it won first place in the
Minneapolis Model Aero Club's eliminations for the Nationals. It won for
the builder an all-expense air-lines trip to Detroit, where he gained the
Stout Trophy. The 12-3/4-minute average of three flights that the model
hung up was one of the outstanding marks of the contest. The model is
extremely simple, and the inclusion of full-size parts in the plans should
make every beginner reach instinctively for his favorite razor.
CONSTRUCTION
Fuselage. A plan view of the fuselage should be
drawn up. All measurements are given on the plans, but any not supplied
may be had by multiplying the size of the part on the plan by four, the
plans being one-quarter full size. Two sides of the fuselage should be
built simultaneously to insure duplicate shapes, and after the cement has
dried they should be removed from the drawing and checked. If one or both
of the fuselage sides has warped out of line, insert one or two diagonals
in the proper places to straighten it out. The two fuselage sides should
be connected at the extreme rear and the cross braces added. If rubber
bands are stretched around the fuselage after two opposite braces have
been added, the next two may be cemented in without waiting for the last
set to dry. The landing gear is bent to shape and embedded between the
full-size gussets given on the drawing. After the nose and tail ends of
the fuselage have been filled in with 1/16" sheet balsa, the corners of
the longerons are sanded slightly round and the fuselage covered with
tissue.
Wings. After nineteen ribs have been cut from 1/16"
balsa, bamboo wing tips are bent to the outline shown on the full-size
plate. After assembling the entire wing, the bottom spar, leading, and
trailing edges should be cracked slightly for dihedral. The top spar and
sheet covering will have to be cut out a little to provide the necessary
gap to be taken up by the wing when the tips are raised. When covering,
make sure that the wing does not warp. If the shrinking of the tissue
after it has dried causes a warp, it can be removed by holding the wing in
the proper position while doping.
Tail. The stabilizer is made in much the same
manner as the wing, and it also should be free from warps. After it has
been assembled and covered, cement it to the tail plug at the proper
angle, a small incidence block being cemented under the leading edge. The
incidence block should be slightly more than 1/8" thick. The rudder is
flat, having been built up from 1/8" square and 1/8 x 3/8". When cementing
the rudder to the top of the stabilizer, offset it slightly, as the model
is intended to fly in large circles.
The wing mount and nose plugs are illustrated in
detail. Be sure to brace the tail plug securely, and the cross pieces it
is cemented to should form a T section.
Propeller is carved from a medium-hard 2 x 2 x
9-3/4" block and should be doped and then sanded with successively finer
grades of sandpaper. After the hinge parts have been carefully cut and
bent to shape, they are cemented to the prop in the proper position and
bound with thread. Three or four coats of cement should follow on the
bound portion to insure long use with little fraying or wear. The
counterweight should be oversize, so that it may be trimmed down to
balance. In cutting the prop at the point at which it folds, a very fine
jig or scroll saw will not rip the wood excessively. In positioning the
prop for folding, the nose plug should be inserted so that the stop is in
such a position that the prop folds flat against the left upper fuselage
side (looking from the rear).
The motor used in the original was composed of twenty
strands of 3/16" rubber, 50" long. A good grade of lubricant should be
used, and it is necessary to employ rubber tubing on the prop hook and
rear hook.
FLIGHT
The original model was adjusted by setting the wing and
tail at a definite angle to each other -- two degrees angular difference
-- and maintaining that relation during all adjusting. The wing was
shifted to produce the best glide possible. The center of gravity was
about an inch behind the trailing edge of the wing when the best glide was
had. The wings were perfectly straight with no warps for adjustment. The
rudder was warped slightly for a right turn. The nose plug was offset to
produce the correct climb adjustment. The model did not climb very fast,
but a long motor run gave it more time to strike a thermal. Even without
the help of thermals, the glide stretched out the time pretty well. The
model circles to the right under power and in the glide. The circles are
about one hundred feet in diameter, because the designer thinks that too
tight a circle will induce an unnecessarily steep glide. The maximum turns
are twelve hundred, a few of which remain after the prop has folded.
BILL OF MATERIALS
Fuselage |
5 pcs. |
1/8 sq. x 36" |
longerons |
8 pcs. |
1/8 sq.. x 36" |
cross braces |
1 pc. |
1/16 x 3/16 x 11" |
bamboo wing runners |
1 pc. |
1/16 x 3/4 x 12" |
wing mount |
1 pc. |
.045 x 36" wire |
wing mount |
2 pcs. |
1-3/4 sq. x 1/4" hard balsa |
nose plug |
1 pc. |
1-1/4 sq. x 1/4" hard balsa |
nose plug |
4 pcs. |
2 x 2 x 1/16" |
wheels |
1 pc. |
1/16" hole x 1" brass tubing long |
wheel hub |
1 pc. |
2 x 1/16 x 16" |
balsa fill-in |
|
Wing |
3 pcs. |
1/8 sq. x 36" |
leading edge and spars |
1 pc. |
1/8 x 3/8 x 36" |
trailing edge |
1 pc. |
1/16 x 2 x 36" balsa |
ribs |
2 pcs. |
1/16 sq. x 12" bamboo |
wing tip strips |
1 pc. |
1/20 x 3 x 36" balsa |
leading-edge covering |
|
Stabilizer |
1 pc. |
1/16 x 2 x 12" |
ribs |
2 pcs. |
3/32 sq. x 36" |
spars |
1 pc. |
1/20 x 3 x 36" |
leading-edge covering |
1 pc. |
1/8 x 5/16 x 36" |
trailing edge |
2 pcs. |
1/16 sq. x 12" |
bamboo stab tips |
|
Rudder |
1 pc. |
1/8 sq. x 36" |
rudder ribs |
1 pc. |
1/8 x 1 x 36" |
leading edge, trailing edge, rudder base
rib |
1 pc. |
1/16 sq. x 12" |
bamboo rudder tip |
|
Miscellaneous |
1 pc. |
1/16 diam. x 36" |
landing-gear, prop shaft |
1 pc. |
1/32 x 3/8 x 2" |
brass prop hinge |
1 pc. |
2 x 2 x 9-3/4" |
prop block |
1 pc. |
rubber or cambric tubing |
for shaft |
4 pcs. |
1/4" diameter |
copper washers |
4 sheets |
|
colored tissue paper |
Solder for prop counterbalance, Cement, dope,
thread, plastic wood |
Scanned From December 1939
Air Trails
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