On Mar 21, 11:05 am, wright1902glider
wrote:
On Mar 20, 12:12 pm, Fred the Red Shirt
wrote:

...

I conducted a few interesting (and historical) experiments using 2.3
oz cotton a few years ago. In one of Wilbur Wright's 1899 letters to
Octave Chanute, he asks about several things including a source for
spruce and the type of dope used on Chanute's gliders (1896-97)
stating that "hitherto we have used shellac".

Fascinating. I have wondered if shellac would be good for both
bonding and sealing the fabric.

Why not?
Good question! Here's what I found:

Assuming a 3-pound cut, I used 7 coats of orange shellac to fill the
weave (might be a little less for them since their fabric was about
1.8 oz.) That roughly trippled the weight of the fabric alone. By my
rough calculations, this would have equated to an additional 8 pounds
for the 1902 glider (317 sq, ft total surface). Considering the lift
limitations of their technology and the ultra-slow launch speeds, the
gains from reduced porosity (sp?) did not equal the loss from the [DSC]
added weight.


That works out to about 4.4 oz/square yd paint, plus the 1.8 oz
fabric
for a total of about 6 2 oz/square yd.

I'll assume that typical painted cloth finishes are no heavier, else
shellac
would be popular.

--

FF