DIY Hex Tarp - Diagonal (Bias) Stretch Woes

[BCBob]

I'm working on my first hex tarp. Fabric is RipStopbytheRoll 1.1 oz Silpoly - Mil Woodland Camo (with ripstop grid).

The four diagonal (cut on the bias) sides have a lot of stretch in them. Not too surprising, since it's a 45 degree angle (bias) to the grid pattern.

I see hex tarp kits out there with the same material that just have a rolled hem on all sides.

I'd rather not, but I'm considering sewing 1/2" grosgrain on the diagonal sides (at least).

What's the best solution?

hextarp.jpg

[jellyfish]

Yeah, there is a fair bit of bias stretch to the 1.1 Silpoly. I used a rolled hem foot to put the rolled hem on mine, but that technique takes some practice.

https://youtu.be/8n0ZVwKmW3Q

Grosgrain will add a lot of weight.

If you take care not to tug on the fabric, and give the weight of the tarp plenty of support in the table, you should be able to do a tidy rolled hem on the bias.

[BCBob]

Sorry, I guess I wasn't all that clear. I'm not having any problems sewing the rolled hem. (I do the limited-skills 2-step process. Fold once, sew. Fold again, sew a 2nd time.)

But after that's completed, there is a lot of stretch on the four diagonal side edges.

(view the second image, it's smaller)

[jellyfish]

That looks really nice. Once you pitch your tarp, it should work fine.

[BCBob]

OK, thanks. I'll give it a pitch once I get the loops attached.

[C_Claycomb]

Resurrecting an old thread, but I have had exactly the same problem, same material, first hex, and having finished the rolled hems all around, I pitched, and three out of four bias sides had almost no tension in them and just flopped around in the wind. I had about 2" of catenary cut. I am baffled how anyone could have a straight cut hex with rolled hem edges and get a taut pitch. Have spent hours looking at the one bias side that turned out okay trying to see what was different. Was less puckered, but not by much and I haven't figured out what caused that difference. Maybe sewing from the ridgeline down to the tie out, but can't do that for all four sides.

Don't want to use grosgrain edging, but the commercial hex tarps that I have both use a binding, and both pitch tighter.

Any tips on how to sew the rolled hem to work on a hex? Maybe one needs 4-5" of cat cut?

[2tarps]

Whilst waiting on delivery of materials to make a 12' hex tarp, I've had time to slide from happy-go-lucky optimism to reading endless posts on the potential difficulties ahead.
My diy hammocks are fully functional but I'd rather others viewed them from a distance! I now see that, beyond keeping the slippery yardage under control at the machine, any mistakes aren't likely to be as inconsequential as the odd pucker and wavy stitching on my hammocks.
I plan on taking the maximum depth cat cut and doing rolled hems. But I'm half curious if grosgrain (I've not fully researched the idea) may be a shortcut of some description... Or is that another can of worms and perhaps stick to the steady improvement of my rolled hems?

[C_Claycomb]

Guess an update is in order.

I tried EVERYTHING to get the hex to pitch taut with rolled hems. It wouldn't. The winter-esque tarp with doors that I made immediately before starting the hex was fine with just rolled hems (1.6oz silpoly), but, it is basically rectangular so none of the hems is really on the bias. The hex on the other hand has four edges on the bias and they just flopped and flapped and none of the tension in the tie outs got carried by the bias edges. Even when I increased the depth of catenary cut. Not really surprising when you think about it. Bias cut fabric has a LOT of stretch. If the edges cannot tighten up and carry tension, they can't transmit it to the rest of the sheet. The result is floppy hems and the weirdest looking ridge seam shape when you tension the guy lines. |''''\___/''''|

What did work and work well, was over binding the bias edges with folded 15-16mm grosgrain tap. I just went over the existing rolled hem. Two rows of stitching and the tarp pitches tight. Folding the tape was a PITA. Used a hot iron to press it into a rough fold, but keeping the fold even was difficult. The result of a just slightly off folded ribbon was stitching that had to weave and meander to keep the ribbon sewn down on both edges.

I got so fed up with un-picking black thread from black ribbon and dark tarp that I used orange for the final stitching, yeah, showed up all the mistakes, but would have been SO much easier to unpick if I had used it from the start.