CONTROL LINE AEROBATICS - 2003/04

April 2003 143
CONTROL LINE AEROBATICS
Curt Contrata, 6783 Nightwind Cir., Orlando FL 32818; E-mail: [email protected]
A GOOD AIRPLANE is much more fun to fly than a lousy one.
This is true whether you are a Sunday flier or trying to win the
Nationals. I define “good” not just as an excellent-flying airplane,
but one that is not plagued with problems or compromises. I
describe a model that always performs well and never gives you a
hard time. A good airplane is a pleasure to fly and quickly becomes
a natural extension of you.
So how does one create such a model? More than anything, it is a
commitment of two things: attention to detail and a realization that
each model you make will be better than the previous model. Your
attention to detail must be consistent throughout the construction
process. You cannot decide to start building a straight airplane at the
time you are installing the wing into the fuselage. A straight airplane
begins when you are cutting out the parts. Just because you are
assembling the wing on a board or in a fixture does not mean you
cannot build a warp into it.
Attention to detail means that every spar slot in every rib aligns
perfectly. Take your time with the ribs, making sure that when
they’re stacked they all match at the leading edge, the spars, and the
trailing edge. (If you are building on rods, the holes for them must
be cut accurately.) During this process I mark the tops of the inboard
ribs with one color marker and the tops of the outboard ribs with a
different color. This way I can quickly put them back in the same
order when construction starts.
A straight wing starts with a set of ribs that are true. Never
assume a set of kit ribs to be perfect; stack the ribs, check them for
accuracy, and mark the tops in contrasting colors.
You want to avoid building stresses into the model. This can
occur when parts don’t quite fit together and you force them to. It
can also happen when two pieces are warped and you force them
straight during construction. A common occurrence of this is at the
trailing edge. Wings often call for 1⁄16 balsa on the top and bottom of
the trailing edge. If one straight piece of 3-inch stock is simply split
in half, it will typically generate two slightly curved pieces.
If those curved trailing-edge pieces are used to construct a wing
by being forced straight during assembly, the wing will usually
develop a warp at some point—often sooner than later. Try cutting
long parts out by cutting them a little at a time from each side, to
Speed flier Al Jones sent in this picture of his pretty orange
deBolt Super Bipe. This 1948 design spans 28 inches.
Jamie Kijeski holds her dad Mike Kijeski’s Cardinal. Mike
finished the model with Brodak Candy Colors.
Marv Babcock Jr.’s 65-inch-span Scorpion is powered by a Double
Star .60 and finished with Brodak dope. Mitch Heller photo.
sort of sneak up on a straight part. The problem is that each time you
make a long cut on a sheet, the sheet will curl. It curls less with each
cut. Alternating sides as you cut will result in straighter parts.
It is okay to waste a little wood here; use the scrap for capstrips
or stabilizer ribs, but don’t use curved pieces for trailing-edge parts.
Paying attention to detail is harder than you think. You can never
stop or be relaxed; that is the difficult part. Every part of the
construction process is important, and every part will directly
contribute to the model’s ultimate success. The more you think this
way, the easier it becomes to care about each step, and the desire to
make the next model even better becomes a natural thought process.
Have you ever had a stabilizer go crooked in the fuselage when
you glued on the top and bottom blocks? Straight parts and perfect
fits are always important. Twisted parts will twist your airplane
every time. How much is your time worth? I suspect it is worth more
than the bit of balsa you will throw away. Perfect fits with
04sig5.QXD 1.23.03 3:21 pm Page 143
unstressed parts should be your goal.
Models built this way are not just
straighter—they are stronger and lighter.
They are lighter because perfect fits require
less glue.
If ARFs (Almost Ready to Flys) are indeed
the future of this hobby, realize that each
model you build is among the last to be
built. Fewer and fewer people are doing
what we do, so enjoy every step as if you
were among the last remaining craftsmen.
Take pride in everything you do, including
making your own tools. The most important
tools you can make only take a minute. I
generally make one or two more every time
I build a model; they are my sanding
blocks.
You should have a large collection of
sanding blocks of various sizes, shapes, and
materials. Your small blocks should be
lightweight and true. A block of 3⁄8 balsa
might make a nice small block to sand with
for a while, but it will not maintain a flat
shape over time. Glue a piece of 1⁄64
plywood to the bottom of it, then sand it
flush to the edges. Use cyanoacrylate (CyA)
glue or waterproof glue, and you can wetsand
with it too.
I made my rectangular blocks in sizes
that can get nine cuts from one sheet of
sandpaper. The smaller you make the
blocks, the more cuts you will get per sheet
of sandpaper. It is best to use fresh
sandpaper, and smaller pieces are easier for
me to throw away.
144 MODEL AVIATION
Another great block I have was made
from one of the core pieces of a foam wing.
At 3 inches long and wrapped with 1⁄64
plywood, it is perfect to sand a hollow into
something, such as a scoop on a cowl. It is
better than a dowel because it won’t gouge.
Shaped like a small leading edge back to the
high point, it is a “multiradius sanding
block.” I also use it when I am blending a
canopy. That fillet is typically difficult to
use a block on.
I have several different blocks for fillets.
My first used a carbon arrow shaft. I made a
slot on one side using a cutting wheel. I
inserted 1⁄16 plywood in the slot to make a
handle, then I built up the handle flush to
the shaft with balsa and CyA. My style has
since changed, and my fillets have gotten
smaller with each model. I am finding
myself making a new fillet block for each
model. The last few have been made from
maple.
I do need to stress the purpose of using a
block in the first place. You are trying to
accurately shape something—to knock
down the high spots and reveal the low
ones. On a fillet, you are trying to maintain
the same radius on every one for the entire
model. If you make your own radius on a
maple block, make sure it is the same radius
on both ends of the block. All mine have
been approximately 2 inches long.
Make a maple sanding block for
notching your flaps for hinges. I have one
that is just wider than the hinges I use, with
a piece of 220-grit sandpaper glued to one
side and trimmed clean along the edges.
After I have the flap slotted for the hinge, I
use this block to cut the notch to inset the
hinge. As with all the blocks, I use the same
one throughout the finishing process with
finer and finer grits.
Foam blocks are a newer addition to my
block collection. 3M makes them, and they
are black foam pads that are great with
which to wet-sand. Roughly 1⁄4-inch thick,
they are thin enough for you to maintain the
feeling of the surface, but scratch less since
your fingertips are not pressing on two or
three small spots.
You should also have at least a couple
aluminum bar sanders. They come in many
sizes and shapes, but you should definitely
have a 6- and a 36-inch T-Bar Sander. (The
refill self-adhesive paper for them is great
when stuck to your bench for sanding parts’
edges.)
Accurate sanding is an important part of
accurate building. Every part I cut is sanded
before assembly. Sometimes I find it easer
to sand a part to shape than to cut it out.
Pay attention to sound and feel. When
shaping, it is common for high spots to be
the hard ones, such as glue or hardwood.
Hard spots sound different when they are
being sanded, so listen closely. A hardsurfaced,
lightweight block, used with light
pressure, will allow you to feel the shape
develop better than a heavy rubber one, and
you will be able to better hear what you are
sanding.
You will appreciate the better fit of the
parts during assembly. The assembled
accurate parts will more easily become a
straight wing and fuselage, and the perfect
fits create stronger, lighter joints. Aligning a
true wing into a true fuselage will be easier
because each will be straight. Not having to
decide “which centerline” to use, it will
almost align itself.
When you get to the finish, the care in
construction and the use of sanding blocks
throughout will have produced a model that
will be much easier to finish. And typically
when people take the time to be real
craftsmen in their construction, they are less
likely to bang a wingtip into the edge of the
bench. This means there should be fewer
dings to fill as well.
Once in the air, a well-built model is its
own reward. MA
Just call and ask for cowlings,
wheelpants or floats from
Carl Goldberg Models,
Midwest Products, Global Hobbies,
Great Planes Manufacturing,
Pica Products and many more.
Most cowlings are seamless.
Make it last
with fiberglass.
We have a large selection of
one piece, epoxy resin cowlings
and wheel pants.
Stan’s Fiber Tech
2575 Jackson, Riverside, CA 92503
909-352-4758
Call for Price List - or visit us at
www.stansfibertech.com
04sig5.QXD 1.23.03 3:21 pm Page 144