Reinforcing 0.93 osy Membrane silpoly
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After reading about the stitch elongation Hoosier was seeing with the 0.93 osy Membrane silpoly in another thread (and talking to Hoosier offline), IÂ wanted to show some results and suggestions for reinforcement patches.
Based on Hoosier’s success with radial reinforcement using the same material, I tested a 4″ radial patch – bonded with sil-net and unsewn around the perimeter. Here are some pics:
We’ve got a printer in-house, so I made up a little template in lieu of the coffee can. Makes it simple to cut out patches regardless of the tie-out shape. Applied a thin layer of sil-net to the patch, put down, then let cure overnight with some weight on top. Should be noted that I also cut the reinforcement patches in the approximate same direction as the intended force on the base tarp material to match the stretch (pic 3 above).
For testing, I vertically stitched on the 1/2″ grosgrain tie-out and then tested with 50 lbs. For extra stress, I lifted and dropped the whole thing ~2 ft. Inspected everything after and saw no evidence of stitch elongation at the grosgrain stitching or around the tie-out. Repeated a couple more times with the same result. I then made a horizontal stitch on the grosgrain tie-out and retested. Still looked good. Some pics of the test setup and close-ups of the tie-out after testing:
I also tested without reinforcements (just 1/2″ gg) under the same conditions. No catastrophic failure, but definitely some stitch elongation near the outermost stitch line on the grosgrain. No bueno. Here’s a pic of that:
Overall the silnet bonded radial reinforcement approach seemed to work very well. I don’t know if there’s an accurate way to convert wind speed to ~force on a tie-out, but I would think the wind would need to be pretty strong to produce a force that would cause this tie-out to snap. Of course there’s also the force of tension due to the pitch and that’s going to vary depending on the design or shelter type, but hopefully this gives a point of reference.
I’m going to try and rig up a way to add additional weight and test to failure. I’d like to do the same with Membrane silpoly PU4000. Will report back when I’ve got something on that front.
Thanks for doing this testing Kyle. It would be interesting to do the same testing for what would be a tieout of the ridgeline. (where the direction of the pull is on the wrap/weff, rather than in the bias). The dynamics on a corner tieout may be quite different than the one for a ridgeline.
Also for the fabrics that have mixed coatings (sil in one side and PU in the other) like silpoly PU 4000, it would be interesting to see if there is any difference of in which side the reinforcement goes (obviously using a different adhesive:Â Silnet for sil side or seamgrip fro PU side).
Thanks for your continued effort to provide more options to the DIY market.
Kyle B said “.. I don’t know if there’s an accurate way to convert wind speed to ~force on a tie-out,”.
I would love to know the answer to this question too. This would be an interesting article for BPL to produce. How much tension there is on the tieouts under different tarp configurations (the most used i.e a-fram, half pyramid, lean-to, etc)
I have done a bit of testing myself, and I had my hoodless tarp-poncho (5’x9.5′) pitched in half pyramid configuration on a day with 18-20 mph winds. I measured 32-35 lb of tension at the apex of the half pyramid and 10-15lbs on the corner tieouts.
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