March 2001 117
SiNcE rETurNiNG from my
wonderful trip to the United Kingdom, I
have been very busy building models in
between finishing the Cub wings.
(I have been corrected. The Cub does
not have a Clark Y airfoil, as I stated in the
last column; it has the USA 356. I am not
familiar with this airfoil, except that it is
supposed to have a bit of undercamber.)
Those of you who know me realize I
cannot build one airplane at a time; I have
at least 10 going at any given point. I go
from one to another, enjoying the
construction of each model. Often, one
will give a temporary headache when a
hurdle comes in. It is good for me to leave
the problem and approach it later, when a
solution is reached.
I wrote an earlier column regarding
the many areas on plans where errors can
be located. With all the building I have
been doing in the last couple months, I
can’t believe how many mistakes I have
encountered. No matter how great the
plans look, each set has its share of
inaccuracies.
I am not mentioning this to put blame
on the individuals who drew up the
plans; heaven knows I can’t draw plans
worth a hoot. I just want you to be aware
so you don’t have to redo something, or
even give up on a model.
I’ll review a few major areas where
errors tend to crop up.
On a low-wing model, there is usually a
cradle where the wing sets. If you cut the
airfoil in the cradle using the drawing
shown on the fuselage profile, the
following might happen.
Somewhere on the plan will be a
drawing for the actual airfoil. You build
the wing using this airfoil. When the time
comes to put the wing onto the cradle,
guess what? It doesn’t fit.
I learned to use the airfoil parts that
were removed from the cradle for the root
part of the wing. This assures that the wing
will fit correctly.
For some reason, the width of the
stabilizer shown on the side view never seems
to correspond with the stabilizer drawing. I
have encountered this many times.
By being aware of this fact, I can
adjust the fuselage structure to ensure
that the stabilizer will set properly on the
fuselage.
Full-size fuselage bulkhead drawings
are also an area of concern; one side rarely
matches the other side. Sometimes the
error is subtle, and doesn’t show up until
stringers are being installed.
To eliminate this, I draw half the
bulkhead onto a folded piece of paper. The
fold of the paper is positioned on the
centerline of the bulkhead on the drawing.
When the paper is unfolded, the result is an
accurate and symmetrical bulkhead.
Even though wing halves are shown
on the plans, I usually use one depicted
half to build both wings. I spray WD-
40™ on the drawing and let it soak
through, then I wipe off the excess WD-
40™ with a paper towel. This allows the
wing drawing to be seen on the back side
of the plan, producing a mirror image of
the wing half.
The WD-40™ will evaporate long after
the wing has been constructed, returning
the plan to its original state.
There are many more possible plans
errors, but these are some of the more
common ones.
how many of you have covered a model
with Japanese tissue followed by silk? I’ll
bet many of you.
What is the advantage of doing so? It
makes doping the silk much easier, and it
takes much less dope to do it this way.
Doping silk is a rather time-consuming
procedure, since silk is a rather porous
material. If you hurry the doping, you will
have a real mess on your hands; it can
ooze through and glob on the back side,
making a mess of the silking.
At the British Nationals, I asked Terry
Manley (well-known Free Flight and
Radio Control Scale modeler) how he
covered his very large Blackburn Torpedo
biplane. (He worked at Blackburn for 40
years.) The model had an eight- or ninefoot
wingspan.
I couldn’t believe it when he told me he
used tissue and silk! There had to be a
small fortune in all that silk.
Terry irons the silk, then he applies it to
the doped tissue using wallpaper paste.
Yes, wallpaper paste!
He dabs the paste through the silk until
there is total adhesion. His comment is that
it looks awful until the paste dries.
The paste is mostly water, and the
surface would be ready for doping after the
water has evaporated.
I will try this method, and pass on
what I experience. I will compare
weights using this system to others, to
see it there is an advantage.
From the fertile mind of Derek Knight
comes a nifty idea.
When Derek is ready to cut letters or
numbers from tissue, he makes templates
from 1⁄64 plywood first. This thin wood is
easy to cut with scissors. He uses an XActo
™ knife to cut out the centers of the
letters and/or numbers.
This technique makes cutting the letters
much easier. I saw Derek do it with very
small characters. You can use these
templates repeatedly.
as promised some time ago, following
is the method for plotting an airfoil. You
can use this technique for any airfoil, as
long as the ordinates are given. This is
for the RAF 34.
The nifty drawings and chart were
Fernando ramos, 19361 Mesa Dr., Villa Park CA 92861; E-mail: [email protected]
FREE FLIGHT SPORT and SCALE
118 M ODEL AVIATION
done for me by my good friend, Blair
Reardon.
1) Determine the desired chord for the
wing you are building.
2) Draw a horizontal line a bit longer
than the chord required.
3) Use a ruler with divisions of
tenths, to simplify the actual plotting.
Starting at the left-hand side of the line,
divide it into the required percent of
chord. These points represent percents
from zero to one hundred.
4) Calculate the percent of chord. If
the number is less than 10%, add a zero
and put a decimal to the left of the
number (i.e., 1.25, 0125). If the number
is less than 1%, add two zeros (i.e., 0.64,
0064). If the number is greater than 10%,
add a decimal before the number (i.e.,
15% = .15).
5) Multiply the proper number from
step 4 by the chord dimension (in this
illustration, the chord is 7.5 inches). For
station 7.5%, change to .075 and
multiply it by the chord—7.5 inches.
This equals .562, which is the dimension
used for this station
6) Lay out dimensions from step 6
along horizontal line from step 2.
7) To plot the vertical points required
to complete the airfoil, multiply the
percentile heights given in the airfoil data
by chord dimension. Upper goes above the
horizontal line, and lower goes below the
horizontal line.
8) After you have all the plot points
calculated and placed on the drawing,
connect all the dots with a french curve or
a flexible spline. Now you have your
desired airfoil.
9) Choose leading edge, trailing edge,
and spar material size, and draw them on
your drawn airfoil.
Step 10 on the airfoil drawing shows
these materials drawn on the plotted airfoil.
On monoplanes, the spars are usually
positioned at 25% of the chord from the
leading edge. Biplane wing spars are
120 M ODEL AVIATION
positioned to attach to cabane and
interplane struts.
I hope this information is not too
complicated to follow.
dan and Kerin Galloway of Flying Scale
report that this plans company is still in business.
You might remember that Dan’s father,
Bill Galloway, drew up incredibly detailed
plans of more than 80 airplanes from World
War I, the Golden Age, and World War II.
Some show retracts that work and an array
of details that can make a winner from any
of these exquisite drawings.
Bill passed away approximately eight
years ago, and Dan and his wife have
continued with the business.
However, the new neighbors didn’t want
to be helpful when Dan’s mother sold her
house, so any mail they received regarding
the business went by the wayside.
To get a plans listings, send an SASE
to Flying Scale, 1908 Colony Rd., Metairie
LA 70003. You won’t regret it.
You can purchase a great video of the Flying
Aces Club Nationals Mark XII (2000) from
Jim Cagle. He has five formats: regular VHS
for $30; super VHS for $35; 8mm for $30; hi 8
for $35; and mini-DV Digital for $40.
This high-quality video is professionally
done. Jim’s address is 648 Andover Village
Pl., Lexington KY 40509. Include $4.95 for
shipping and handling. MA
