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by Leon J. Friedman and Arthur Ruthlein
Plans for two indoor endurance jobs suitable for a beginners' model program.
A larger indoor craft, the "E-X". has flown about for 12
The "E-Z" type indoor ship is capable of better than 10
HAVE YOU EVER sat home on the day of a
contest with your models packed and ready to go and
could not because the weather wouldn't permit
outdoor flying? In such a case, either of the models
presented here will provide a "salve" to the builder's
feelings. To steal a phase from the Post Office Dept.,
"neither rain, nor snow . " shall stop the modeler from
flying one of these ships as long as he has a fair sized
The author has done 2 min. 10 sets., in his
parlor, which is very small, with the "E-Z" model.
The advanced model is slightly more critical in its
adjustments and necessitates flying in a larger circle,
and therefore is not perfectly suited for flying in a
very small room.
No one can truthfully say he is an expert
model builder unless he has tried his hand at building
indoor models. The ships presented here are for the
purpose of acquainting the builders with a very
simple indoor model which is built fundamentally the
same as any record job, yet which a builder may make
as his first indoor ship. This job we have called the
"E-Z". We also present a real contest ship built along
the same lines, which we call the "E-X". The "E-X"
should be capable of at least 12 mins. 30 secs.
Our "E-Z" ticked off a consistent 10-1/2
minutes every flight. This time in itself is not so
remarkable but one must take into consideration it
was not built for contest work and the weights were
not watched. The economy of construction is really
amazing with these models as both of them won't cost
you more than thirty cents.
Well let's get down to building it. The "E- Z" is
suggested if you have never built an indoor model and
the "E-X" if you have built one before, or if you want
to built it after finishing the "E-Z" and acquaint your-
self with indoor construction.
indoor job is the propeller, for the basis of all high
time and consistency is a light, well balanced,
smooth, efficient prop. If desired, an 8" indoor
machine carved prop may be used but these are hard
to obtain. The best idea is to carve it from a block of
very light balsa 8" by 5/8" by 7/8”.
The block is marked out and cut down to an
"X" blank. Carve the undercamber first on both
blades and then carve the top. The prop is sand ed with
6-0 sandpaper and then finished off with 10-0
sandpaper. The shaft is then glued on. Completed it
should weigh about .004 oz.
For the "E-Z" model a solid stick 1/8" by
1/16" by 8" of very hard balsa is used. The ends are
tapered and sanded and the hook and bearing are
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cemented on firmly. A hollow motorstick made of
1/64" sheet sanded, 9/16" in width and wrapped
around a piece of dowel is used on the "E-X". The
ends are capped with 1/64" sheet and the bearing and
hooks glued on.
The indoor wing construction is very
important and is quite different from outdoor types.
The "E- Z" spars are cut from 1/20" sheet and sanded
until it tapers from 1/20" at 8" from the front to 1/32"
at the end. When you take the ruler to cut the spars
you cut so that it tapers the same in the top view. This
is the method that all tapering is done on indoor
Four spars are made this way for the "E-Z",
tapering from 1/20" square at the center to 1/32"
square at the tip. There are four spars to be made for
the "E-Z" but these are made a little differently A
center spar 31/2" long is made by the same method,
tapering from 3/64" by 1/32" at the center to 1/32"
square at the next rib. The wing tip spars are made by
sanding 1/32" sheet at the center to 1/64" and tapering
to 1/32" at the ends. The cut is made to have a spar
1/64" square at the center and 1/32" square at the tip.
For the "E-X" a template must be made of the
wing tip and the spar wrapped around it wet. The "E-
Z" may be laid out without bothering with templates.
The spars are laid directly on the plans and glued to-
gether. Ribs are made by cutting a template of
cardboard or aluminum and placing it on a sheet of
balsa; the size for the "E- Z" ribs is 1/32", and for the
"E-X", 1/64". By moving the template down either
1/32" or 1/64" and cutting along it again, a rib is cut
out. The leading edge of the rib is glued to the spar
and the trailing edge of the rib is cut to fit and then
glued. The wing clips are glued on firmly and you
may use wire or aluminum for the "E-Z" and
aluminum only for the "E-X" to hold the wing to the
motor stick.
wheels for the "E-Z" are made of 1/64" sheet sanded
to 1/100". A small piece of .010 wire is glued to the
struts and a piece of tissue is wrapped around a pin,
glued and cut in half and used as a tube through the
center of the wheel.
Another type of wheel is made of a thin strip
of celluloid about 1/32" wide glued in a circle with a
center brace of 3/64" by 1/32". The paper tube may
also be used here as an axle if desired. The landing
gear is glued to the body about 1-1/2" from the front
and about a 4" tread.
IF you have never tried making microfilm don't be
frightened at the thinness of the stuff as microfilm is
really easier to cover with than tissue. If desired a sort
of makeshift microfilm can be made from either dope
or lacquer; made flexible with a few drops of castor
oil. The amount of castor oil is determined by ex-
periment; that is, add a few drops of castor oil to
some dope or lacquer and pour on water. If the stuff
spreads out nicely and after awhile starts to crinkle
around the edges, you will have to add more castor
oil. If you add too much oil you will find eithe r you
can't pick the film up with a hoop of wire or that it
becomes too tacky and sticks to everything it touches.
There are many commercial formulas for
"mike" which will save all this bother. A hoop of wire
is needed. It may be an old clothes hanger bent to
shape or 1/16" galvanized iron wire which can be
obtained anywhere, or 1/8" aluminum wire which is
the best. About 3 inches of water should be run into
either a bathtub, tank or wash basin top. For the be-
ginner, it is best to use cold water as this produces
heavy "mike" which is much easier to handle. The
solution is poured on the water, and after about three
to five minutes of drying, a hoop is placed over the
"mike", the "mike" pushed to the edges of the hoop
and lifted in a semi-circular motion away from you. A
knack of lifting will be acquired with a little
Probably the best way to cover is to lay the
uncovered parts on an enameled surface and draw a
wet finger around them, leaving them completely
encircled by water. Then wet the frames with saliva
and place back in position. If the hoop of "mike" is
then placed over the parts it will stick to the wet
enameled sur face and to the structure.
Another way is to rest the hoop on four bottles
and, place the frames wet, right on it. The mike is
trimmed with either a hot wire or a brush with
THE CONSTRUCTION of the tail is very
simple and for the "E-X" much the same as building
the wing, except the spars aren't tapered but are made
of 1/64" square which is made by cutting from 1/64"
sheet balsa. The "E- Z" is just an outline of 1/32"
square. The rudder on the "E- Z" may be made right
on the tail boom which is made like the spars of the
wing. The rudder is first covered and glued to the tail
boom and then both are glued to the side.
The landing gear struts are also made the same
way as the wing spars from tapered sheet balsa. The
acetone or thinner. Dihedral is then put in the wing
and to get the wrinkles out a hot wire is passed
beneath it.
If the ship is made to fly in a small room, it is
advisable to glue the boom on at an angle to give the
model left turn. Assemble the ship and put in about a
10” to 12” loop of 1/32” flat brown rubber. Place the
wing in position so that it glides flat. Put in about 500
turns and launch very gently. All adjustments should
be made with the tail. The “E-Z” should be able to fly
in a very tight circle but the “E-X” may be a little
more difficult to fly in a small place. Make sure the
windows are closed.
Scanned From July,1942
Flying Aces
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