On Fri, 09 Apr 2004 14:59:24 GMT, Ernest Christley
wrote:

So let's take an example. I have an aileron that was designed for a
medium weight fabric (which is 4oz/sq yard?). A 2oz FG woven finish
fabric would still be much stronger by far, but it will be much thinner.
Being thinner, it won't need as much "filler" (whether that be epoxy,
dope, or paint).

The process would go like this. I cut a piece of fabric the dimension
of my aileron with an inch or so overlap. I wet out the glass on a
sheet of 6mil plastic, set the aileron on top of it and bring the
fabric/plastic up around the aileron sides...just wrap it over. The
fabric is bonded to the ribs and around all the edges. No shrinkage
necessary, since it will be the exact size. Once that cures, I repeat
the process for the other side. The FG will add no more to the
structrual integrity than the fabric did. It's bonded to the ribs, so
no more attachment work or possibility of fretting. It has the smooth
FG look, and even with an exterior coat of paint will be thinner and
hopefully lighter than the medium weight fabric. Concerning Corky's
excellent point about the aerodynamics, a suitably flexible epoxy will
allow the fabric to have just a slight amount of give just like a fabric
covering.

This seems like a way to make a stronger, lighter skin without as much
work. But on the other hand, I'm dreadfully afraid of falling out of
the sky. How could this technique be safely tested?

Ernest, from what I've read and seen in the world of fabric covered
airplanes, it's really hard to substitute something for the fabric
itself and do any better in the weight saving department.

I've heard of people laying up fiberglass as a sheet and applying it
to fuselages, but the airplane ended up being heavier than when it was
covered with just fabric.

Fabric works fine by the way, it was used right through WWII on a
number of airplanes including bombers and fighters. The Corsair, one
of the most powerful fighters to fly originally had a portion of the
wing covered with fabric and even during the Korean War still flew off
carriers with a fabric covered rudder. The P-51 Mustang, one of the
fastest fighters of the war had a fabric covered rudder.

Are you trying to save money or weight, or both? When you wet out the
fiberglass fabric, it sometimes takes a lot of primer to fill the
weave, depending on the weight of the cloth. That could make for a
looonnnnggggg time of finishing to make it look good.

So what's the thought process you're going through? Why are you
interested in making the substitution? If you are looking for
additional strength, you don't really have to. Here's why: When a
friend of mine was covering his biplane, he thought it would be
interesting to test the fabric for strength, just for fun. He had a
metal stool with two loops on either side so he glued fabric across
the loops and taughtened it with the iron just like he did with the
wing. He then reached into his toolcabinet and pulled out a 16oz
ballpeen hammer. He made a half hearted swipe at the fabric and the
hammer bounced off without a mark. He swung harder and got bounced
off harder. So he stepped back and lunging forward, put every ounce
of his strength behind the swing. He hit the fabrice right in the
middle and was rebounded so hard he almost hurt himself. The fabric
was undamaged. Try that with an aluminum wing. ;-)

Corky Scott