wrote:

Ernest, it isn't the dope that provides the strength, not with
Razorback fabric or with any fabric. The fabric itself is what gives
the wing it's strength and/or stiffness against the wind. The initial
application of the correct dope, in the case of the Razorback fabric,
or a calibrated heating iron, in the case of the Polyfiber fabric, is
what shrinks it.

The application of paints on top of the fabric serve to protect it
from UV rays, make it waterproof, and look nice, but do not add
strength.

You should participate in one of Ron Alexander's fabric covering
sessions and see for yourself how it's done. They offer hands on
experience and you learn how to properly apply fabric to wings and
control surfaces. You will discover that the fabric is incredibly
taught, once properly shrunk. The skin of a drum comes to mind.

You can shrink the fabric too much and actually crush or bend the
framework beneath it, the fabric has that kind of strength.

Corky Scott





Corky, the polyester fabrics have long chain molecules that 'curl up'
when you heat them. This makes the actual threads shorter, so that
after the actual fabric is shrunk to size.

The butyrate doesn't shrink the fiberglass threads. It just grabs a
couple and pulls them closer together. "Chain is only as strong as its
weakest link" comes to mind. Until a butyrate coated covering stretches
enough to take out the slack that was there when the fabric was first
put on, it is only being held together by the butyrate.

That is the mental picture I have. I could be wrong, and I don't even
know if it is good or bad. For starters, I don't know how strong
butyrate dope is. It could be much stronger than polyester, and just
needs the fabric to give it some shape. I'm in unknown territory and
just need a compass and a map, or maybe just a practice kit to play with.

Didn't I read somewhere that butyrate dope can be found in most hardware
stores under a different name?

--
http://www.ernest.isa-geek.org/
"Ignorance is mankinds normal state,
alleviated by information and experience."
Veeduber