Orval Fairbairn wrote:
In article ,
Ernest Christley wrote:


Most of the fabric covered aiplanes I've seen didn't seem that hard.
That is, you could walk up to them and push the fabric in with your
hand. The way I understand the fabric process, it is basically a
composite structure. You have a nylon cloth with a paint "epoxy".

Could a much stronger and lighter covering be made by wetting out some
2.5oz glass cloth on plastic, waiting till it's tacky and then wrapping
it around the airframe? The epoxy would be much lighter than paint, and
fiberglass cloth is MUCH stronger than nylon.

I've seen some places where builders used composites in place of fabric,
and it seemed that they all aimed for a multlayer, stiff panel, putting
the weight far above the original. I just don't understand why?




There have been some fibreglass/dope coverings around for at least 45
years. I remember a couple of Stearmans that the University of Illinois
had that were covered in glass/acetate dope. They looked like wrinkled
shirts whenever theweather was coll & humid. I understand that CAB dope
works bettere here. The shrinkage of the butyrate dope provides the
taughtness that the fabric needs.

Another disadvantage of this process is weight -- glass weighs more than
Dacron.

The glass process is also more susceptable to "ringworm" -- little
ring-shaped cracks in the finish.

As others have posted, fabric provides very little in the way of
structural loads -- all it really does is help to provide aerodynamic
shape.

There have been a lot of very informative responses in this thread, but
they don't seem to address the question I have; therefore, my
conclusion is that I didn't ask the question very clearly.

Razorback has been mentioned several times. Everyone seems to agree
that it's heavy, the glass will last forever...IF it is supported
properly, and that the dope which makes it taught needs some care.

Corky and several others make the point that the fabric doesn't need to
be strong, it's just there to catch the wind.

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?

--
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"Ignorance is mankinds normal state,
alleviated by information and experience."
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