The only reinforcing i've done is double hem all the edges, they're all 3 layers thick and 1 inch wide. I then put the webbing side by side like (not on top of each other) and sewed the crap out of it. along the ridgeline, it's already 4 layers thick from the lap fell seam, and then i double hemmed the edge as well, so i have a total of 16 layers where i attached my webbing. The 3 layer thick 1 inch wide seam is strong enough for me to sit on when i'm getting in and out of a hammock, i figured it'd probably be good enough for the tarp too. Although I think additional strength can be had by applying 'liquid stitch' into the hemmed edges as well. That stuff is tough as nails. basically end up laminating layers together.
It's not the thickness of the hem that'll give you a problem. It's the single-layer material at the edge of the hem, where the last line of stitch is. That's why you want some sort of reinforcement patches - to spread the force over a greater area. If you attach directly to the hem and nothing else, a good strong wind will tear the hem right off the tarp body.
What kind of webbing are you using? Grosgrain? I think GG probably works fine, but using thicker nylon webbing doesn't add much weight and (I assume) is much stronger. It's also a good idea to double the webbing over/under the tarp, so you're sewing through both layers of webbing with the same stitch. This compresses the tarp material in between and distributes the force across the whole attachment area, not just on the stitches. The main force on the stitching is then also transferred to the webbing instead of the tarp, so you're less likely to get tears started.
"Physics is the only true science. All else is stamp collecting." - J. J. Thompson
you know, come to think of it, my first DIY tarp (a ray way tarp) didn't have re-enforcement at the tie-outs either. and it's still going strong.
but the main thing i would suggest is not putting grommets in the tie-outs.
they will weaken the webbing.
besides, you can do just as much if not more with out the grommets when it comes to attaching poles & sticks to hold the tarp sides up higher.
I too will something make and joy in it's making
I'm using 1" wide tie-down straps for backpacks. They're side by side, so a total of 2 inches wide, and I have them on the fabric an additional 2 inches deep. So far so good. I was thinking about sewing them over/under on top of each other, but then I read someone else recommend that the increased surface area was better. The way I have it now introduces alot of weird stress, I'm sure it's alot easier to plan for reinforcement if you're doing over/under.
Sounds like you're going in the right direction! My webbing, like yours, is lapped and sewn 2" into the tarp. From experience, I think a single 1" width, lapped 2: deep, should be plenty attachment area. I use 3/4" webbing on mine, doubled over/under, and haven't had any problems at all through two HEAVY windstorm nights. If it's something you could change easily, though, I'd definitely recommend the over/under attachment and reinforcement patches. The patches don't have to be anything major - I use the same 1.9 oz. untreated ripstop I make hammocks out of - just something with some extra strength to distribute the force more evenly.
"Physics is the only true science. All else is stamp collecting." - J. J. Thompson
Whatever way you go the poles can easily be used. I've used my poles upside down with the tip poking through the ribbon loop (this works if your poles have baskets). My last time out I tied a clove hitch with the tie out line around the pole handle right up next to the ribbon loop. Get your corners figured out the you'll find a way to use your poles.
Stoikurt
"Work to Live...Don't Live to Work!"
One option is to sew around the grommet to strengthen it up. Problem with webbing is once you have cut it to get the grommet through, you loose alot of the strength it once had. Sewing either in a square or a circle should stop the bunching and pulling.
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