Originally Posted by
kitsapcowboy
Many thanks. The tarp is still holding up like the day it was made. After building this and several other similar tarps to test these techniques, I have reached a couple of conclusions:
1) Grosgrain-only finishing is best for hex tarps as opposed to winter tarps with vestibule doors, owing to the force vectors and the perimeter-to-ridge line ratio; you can use grosgrain to finish a rectangle tarp, which sort of splits the difference between the other two types, but the structural advantage of the grosgrain is really best exploited only when all the tie-outs on the ground edges are deployed in a colinear fashion on either side of the tarp, rather than with the corners folded in like doors.
2) The area of highest stress on a two-piece tarp seems to be right at the ridge line tie-out, where there are significant forces deployed in a variety of vectors. A tarp with no pack cloth reinforcement here can be strengthtened by anchoring thoroughly the grosgrain edges from the two panels into a sandwich at each terminus of the folded grosgrain over the RL standing seam, as well as by sewing a short additional length of grosgrain (not necessarily the same width) straddling the RL as a connector between the edging of the panels on each side.
3) It's never a bad idea to have reinforcement patches -- especially at the ridge line -- if you value trailworthiness and dependablility, even when finishing a tarp with grosgrain ribbon. I don't think I'll ever build a two-piece tarp without RL patch reinforcement again, just for peace of mind. The weight penalty is minimal, and the biggest negative I see is usually the increased build time for your DIY tarp project, which is a one-time hit in return for what should be an extended useful lifetime for your weather protection.
The next time I get a chance, I'll try to post some detail photos. HTH...
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