Myog silpoly tarp help

[Sloan]

I have recently made an 8’x10′ flat tarp out of membrane silpoly. I haven’t taken it through any major bad weather but have spent a few nights in it and lots of time experimenting with different pitches. I never seem to be able to get all the fabric taught (there are always wrinkles/sagging) it seems that the edge is always pulled as tight as possible before the panel gets taught. Is this amount of sagging/wrinkling just what is to be expected from a flat tarp? Could it be caused by something with the stitching or perhaps because of how light the fabric is?

[Sloan]

[Jerry Adams]

It’s difficult to sew a tarp and have it set up taut with no wrinkles, my sympathy to you : )

When you sewed the two pieces together, as it went through the sewing machine, maybe the top piece of fabric stuck to the zipper foot a little and thus slipped relative to the lower piece.  That can cause wrinkles

[Sloan]

[Jerry Adams]

A technique is to pin the two pieces together at several places, or I prefer using hand stitches.  As you’re sewing along, hold the two pieces together at the next hand stitch and pull back just a little against the pull of the pressure foot/feed dogs to keep the two pieces of fabric aligned

[Michael B]

Cat cuts along the perimeter can mitigate some of the effects of an imperfect pitch, but in general, pitching a flat tarp tightly takes a lot of practice, and the stretch associated with not only bias, but also the fact that low denier fabrics stretch more for a given load (load seen at the tieouts) than higher denier fabrics, causes exactly what you are experiencing with your Membrane tarp. Keep practicing your pitches, and play around with the setup to see what affects the wrinkles in each of the panels.

[Jerry Adams]

In the first two pictures, the seam is sideways to the peak.  More wrinkles.

In the last picture, the seam goes from peak down to bottom. Fewer wrinkles?

Yeah, what Michael said, practice pitching to optimize pitch.

[Sloan]

Thank you Jerry and Michael for your suggestions!

Pitches that have the seam pulled tight definitely set up better than ones that dont, I think you might be right about that seam being not quite right Jerry. I have settled on 3 pitches that setup with minimal sag and (hopefully) non fatal wrinkles.

I’m going to take Michael’s advice and keep practicing those pitches, I think they’ll fill my needs for the Colorado trail this summer.

I’ll probably make another tarp over the winter and spend a lot more time on the Ridgeline seam. Would it cause problems with the later use of the tarp if you were to use double sided tape on the Ridgeline seam?

[Jerry Adams]

even though there might be a few wrinkles in some cases it’s mostly just aesthetic

double sided tape doesn’t work as good on silicone fabrics, especially for a seam that is structural like a ridge seam

I suggest stop if you can, myog is addictive : )

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