Looking at Thru-hiker, it appears I only have a few options for "officially" downproof fabrics. M50 sounds like it's a bit to airtight for an inside layer, and could trap water vapor. Pertex is described as being more breathable, does anyone know if it has much (if any) stretch/give on the bias? What about M50 (if it's breathable enough), does it have any give?
I haven't yet figured out how to (efficiently) make large sheets of bias grain fabric (Google only shows how to make tape
), but I'm guessing it's tedious and involves Frankensteining big chunks of bias-cut squares together. If anyone knows of a pattern for doing this that wastes the least material, that'd be very helpful. With the inner layer taught/stretched, I don't think the fabric would need to be much over 3ft wide.
I could do a down-proof layer (M50) and a breathable layer atop that (between hammock and quilt) from thinsulate or something, but that seems like a lot of extra weight/bulk, that could be avoided if I use a breathable downproof fabric. Would a vapor barrier setup like this be needed for a 20F quilt?
(I also gotta find a line on some 1" grosgrain so I can continue production on the hammock; I need to stop putting the cart before the horse with this UQ project!)