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#11
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Fiberglass cloth weight vs 'finished' weight
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 |
#12
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Fiberglass cloth weight vs 'finished' weight
Fred the Red Shirt wrote:
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. I'd guess it would work ok (as per below) but ONLY on fabrics that have a nap. That rules out dacron in favor of cotton. (with all that that implies as well) Recall Steve Wittman's accident - doped alone won't hold dacron as a structural attachment. 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. I'm not completely sure that assumption would be valid. Durability, UV resistance, chemical compatability, cost, longevety... All these may have more impact than just weight alone... Richard -- (remove the X to email) Now just why the HELL do I have to press 1 for English? John Wayne |
#13
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Fiberglass cloth weight vs 'finished' weight
On Apr 4, 9:12 pm, cavelamb himself wrote:
Fred the Red Shirt wrote: 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. I'd guess it would work ok (as per below) but ONLY on fabrics that have a nap. That rules out dacron in favor of cotton. (with all that that implies as well) Recall Steve Wittman's accident - doped alone won't hold dacron as a structural attachment. 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. I'm not completely sure that assumption would be valid. Durability, UV resistance, chemical compatability, cost, longevety... All these may have more impact than just weight alone... Good quality dewaxed shellac has good durability, is impervious to petroleum based solvents, relatively cheap, and while it may not last as long as some others, it can be refreshed just by wiping it down with fresh alcohol. I'd only use it on a small patch somewhere like on the fuselage for a long time before doing a while plane with it though. -- FF |
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