So I'm planning my first MYOG shelter. I'm thinking six-sided shaped tarp, supported by two hiking poles, mesh skirt and door. Catenary ridgelines. 1.1 oz silnylon (would like to use 2nds). Shooting for about 13 oz finished weight.

Couple questions I'm having: 1) Should I use seam binding (eg, grosgrain or bias tape) or flat felled seams for ridges? I'm a pretty competent sewer, but have never worked with silnylon. 2) Is alignment of the fabric warp and weft important? If not, I think I can do layout more efficiently and save some material.

1) Flat felled seams worked fine for me

2) Yes, 1.1oz is pretty elastic at angles between the warp and weft. I would try to align the main stress with the warp or weft.

Sewing silnylon is not too hard, you will get plenty practice when making a tarp/tent. Good luck!

I use 2nds 1.1 ounce silnylon

It's possibile there is slightly more misting with 2nds, but regardless you get some condensation that can be knocked off the inside of the tent that produces more water on you than the misting so it doesn't really matter, in my opinion. Regardless, you should probably have a water resistant sleeping bag, but your body heat will evaporate a little water regardless.

I use catenary ridgelines. See the article in MYOG about making silnylon tent, there are a couple possibly useful ideas there including how to do catenary ridgeline

Flat felled seam is fine.

I always aligh the warp and weft, but I'm not sure that it makes any difference. They typically spec different warp and weft strengths, so maybe they stretch differently which might make a difference. Silnylon is fairly stretchy so it probably doesn't matter. If you're using 2nds, it's fairly cheap, so maybe you shouldn't cut that corner.

Maybe it's more important to align a diagonal cut on one piece to a diagonal cut on the adjacent piece, but even that isn't probably critical because silnylon is fairly stretchy.

We want to see pictures of your finished product : )

+1 for flat felled seam. Just use plenty of pins along the stitch line to maintain tarp panel aligned at the end of the seam.

Definitely you need to take care of alignment. As pointed out, silnylon (as many fabrics) is more elastic diagonally.

Cheers.

Thanks for the information. I'll probably start the project in a couple weeks--will definitely post pics.