On Thu, 08 Apr 2004 19:01:51 GMT, 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?

Not sure that the fiberglass cloth plus the resin would be lighter
than the cloth plus the paint. For one thing, you left out the paint
on the fiberglass, or were you going to leave it the opaque look that
the fiberglass gets after wetting out and curing?

The other thing is that the fabric covered wing was designed for a
fabric covering. In some cases where a wing was "metalized" the
airplane ended up with a performance that was not as good as the
fabric covered wing.

Finally, as was pointed out already, there is no benefit to putting a
stiff panel around the wing. You don't save weight because the wing
is structurally designed for a fabric covering so it's internally
braced. If you wanted to use a stiff skin to cover the wing, you
should redesign the wing such that it gets it's stiffness from the
covering, not the internal bracing, and save weight.

For instance, the wing I built is fabric covered. The spars are wood,
and the ribs are wood. The wing is braced with drag and anti drag
wires that are actually 1/4" drill rod. Because they tend to try to
draw the spars together, the spars need to be held apart with steel
tubes called compression tubes. There are around six of them.

There's also a diagonal brace at the wing root to prevent the wing
from swaying back and forth, or in my case, a plate of sheet aluminum
instead. All this is to make sure the wing is stiff enough to
withstand the forces it's expected to encounter in flight. It's the
result of many years of aviation experience and engineering.

If I were to cover the wing with metal instead of fabric, I could do
away with all of the braces mentioned above.

Corky Scott