I received the PM below from GreyCoyote and, because it contains so much useful and detailed info, am posting it here with permission.
Sent: Sun Mar 16, 2014 6:04 am
Hey: Wanted to share something I learned using very similar material to what you have posted in the "Teepee" thread.
I prototyped a dome cover using a type of housewrap (cheapo stuff, too) that looks exactly like the sample you posted except for the aluminum covering layer. Believe it or not, the stuff was very durable. I was shocked. So I think what you've got will work nicely, and not be disposable after just one burn. But sewing it can be a little tricksy.
I found out the hard way you want to play with this stuff before you do the whole project. There are some non-obvious traps waiting. Follow:
1). Do not use a cotton or cotton-poly thread. Use only polyester. The cotton very quickly degrades in the sunlight. It took just two weeks for my samples to start having problems. When I switched to UV-stablized polyester, the thread became bulletproof.
2). Use a heavy-duty thread. Gutermann makes the best IMHO. You can get it at JoAnns or any other large supply place. Not a quilting or upholstery thread, just a good heavy-duty "normal" thread.
3). Use a semi-flat-felled seam. When you get the seam made, run another line of stitching down the middle of it. Keeps it flat, but also serves to strengthen the seam.
4). Use the smallest needle you can get away with. This is contradictory advice at first glance (you are using heavy-duty thread!), but you want the smallest hole you can get by with. I think I wound-up using a 100 needle, but that was because I'm a total spaz when it comes to sewing. She-Who-Must-Be-Obeyed was able to use considerably smaller and get good results.
5). Test various stitch-per-inch configurations. Try 6 tpi, 8 tpi, etc. Pull-test them to failure using the semi-flat-felled seam design in 4-inch wide pieces. You will learn a LOT about this material. If you're doing it right, it should take two people pulling to get a failure.
6). Do a double-back-stitch at the ends of your seams. Loads accumulate at the ends under wind, and you want to prevent a "zipper-like" failure of the seam. If I had it to do all over again, I would also incorporate a strip of canvas or something in the last 6 inches of any top or bottom seam as a load-spreading/anti-punch-through device within the the stitch.
7). Thread tension is everything. You will find a very narrow range that provides a good stitch. It's going to be different for every machine. For me it was a little higher than the "center-of-the-dial". (Singer commercial machine).
. You may need a lot of foot-tension after you fold-over the seam. Dunno why, but the material I was using was *easy* to punch through in 2 thicknesses, but became a right sticky bastard anytime I was trying to do 4 or more. YMMV.
9). Consider using this stuff for your seams. http://www.sailrite.com/Seamstick-3-8-f
... yWdzYXLLf0 If you want to try a little first, you can get seam-stick tape at WalMart in 10 foot lengths. The WalMart stuff is inferior, but will give you an idea if you like it. If possible, assemble your seam with the sticky-stuff down the full length. It keeps everything lined-up and you can sew right through it. This stuff is DA BOMB on canvas. Should work good for your stuff, too. (Disclaimer-no financial interest)
FWIW, my test-cover spent six months on the dome, in Texas heat and light and winds. It survived 50 MPH winds on several occasions. Eventually, the "fabric" frayed-out and started coming apart, but the seams were still pretty good.
- Maybe consider sewing-in a narrow webbing in all of your vertical seams? It would give you a good anchor point.
- Have you contacted the company to see if this material can be heat-sealed? If so, how much? (Might make for really strong seams if done right).
- Will your inner fabric be canvas? If so, you NEED to talk to these guys: http://www.bigduckcanvas.com
When I did my "real" dome cover, they were an amazing resource. Lots cheaper than anyone else I could find, and a really good product. I used this 10.10 oz "Army Duck" called SunForger with a fire retardant. Link: http://www.bigduckcanvas.com/canvas-for
... ent-canvas It is amazingly strong but you can still sew it on a good consumer machine. In 100 yard x 60 inch rolls I think I paid $7/yd + shipping. They will send you free swatches of anything they sell, too. (Disclaimer-no financial interest)
Good luck. Hope this helps. See ya in the dust!!!
Hey: One other thing I saw from your post this PM that you may benefit from: Try using a narrow-gauge (relatively speaking) denim needle. These are thicker than a normal needle, but they have a blunter, spade-shaped point that tapers to a narrower shaft. This design tends to spread the fibers instead of piercing them outright. This may leave you with a stronger base material.
Another thing would be to see if you can use a zig-zag stitch. It may also leave the base material stronger. (The problem with some poly is once you get a hole, it will "run" from the hole).
Finally, try using a waxed thread. Sounds funny, but a waxed (or siliconized) thread will be less prone to tear through your base material.
Take care! Glad you found my rant useful.