Oh mighty tarp gurus.....help....

[thepikey]

So, I had my mother in law up from Colombia recently to help with our new baby and immediately set up my own little sweatshop on the dining room table. In between cranking various little cute outfits and blankets and whatnot, I was able to get her make me one sweet HH clone. But "we" didn't get to my tarp before she left. So I'm looking at taking on the task myself. I scored some PU coated ripstop, I know I know, not the lightest, but it was the cheapest. And I didn't want to invest too much into this just yet without knowing what I was getting into. Anywho...

Now, I've been reading up some of the designs and whatnot and I've got myself a cat cut hex ready to get stitched up. I know this maybe a matter of opinion, but should I really hem a border of grosgrain? Does it really improve the structural integrity of the tarp or is just aesthetically pleasing? I was going to reinforce the tie-outs, but I wasn't sure about the whole grosgrain thing.

[NewtonGT]

Ive seen alot of tarps without the grossgrain but I dont know as to weather it helps the structure of the tarp or not im interested myself. so heres a free bump for your thread haha

[gargoyle]

You can hem.
It is tough do around the curve/cat cuts. Keep them small, work in short sections, stopping to roll the hem every few inches. You'll basically end up stair-stepping the material around the curve, since its impossible to roll it evenly.
By keeping the hem small, if when your done you dont like it, you can cover the hem with grosgrain.

Practice on some scraps that are cat cut to perfect the technique.

[RootCause]

IMO, grograin is extra weight, but seems to be easier to apply than a hem.

For me, it's no contest. Hemming= no additional material to buy, run out of, mess up. If I mess up the hem, well- at least it blends better because it's the same color as the tarp!

[turnerminator]

IMO, grograin is extra weight, but seems to be easier to apply than a hem.

For me, it's no contest. Hemming= no additional material to buy, run out of, mess up. If I mess up the hem, well- at least it blends better because it's the same color as the tarp!

I'm no tarp God, but I've just finished my first Cat cut tarp with doors out of PU coated ripstop. I'm thinking differently to RootCause in that my next will be hemmed with grosgrain.

I hemmed the new tarp all round but getting the hem right on the Bias was difficult on the doors without excessive pinning. I also feel that adding tie-outs is much easier on GG and needs less re-inforcement work. It will certainly add a little weight, but will be offset slightly by using less re-inforcement patches. I spent as much time reinforcing it as making the basic tarp!

A PU coated tarp is never going to be the lightest, so the GG weight penalty is proportionally less too.

These are just my present thoughts and after making a GG hemmed tarp, I may well change my mind again

[Ramblinrev]

It's a matter of personal choice. Some people like the look. I don't particularly. Personal choice I do roll some twill tape into the hem for a little extra strength. But I suspect that is more for my peace of mind than necessity.

[hppyfngy]

I'm far from knowing enough about it, having only made a few tarps and hammocks myself and never putting any of them to extreme wind and weather tests.

I have never understood, however, the concept of hemming a stretchy material with a less stretchy one like grosgrain. Doesn't that lead to loose flappy bits in your tarp?

I don't suppose it's a "one size fits all" answer but it just seems that hemming is enough...

(don't let my lack of practical experience suggest that I know what I'm talking about.)

[Ramblinrev]

I have never understood, however, the concept of hemming a stretchy material with a less stretchy one like grosgrain. Doesn't that lead to loose flappy bits in your tarp?

One of the reasons for using a "cat cut" (catenary) on the sides is to take up that slack. The cat cut allows the bias of the fabric to stretch and the whole thing pitches tighter. Since the bias is allowed to funtion the stretch of the grosgrain really is not a problem. The idea behind the reinforcement of the hem is to keep the fabric from ripping. Cutting on the bias makes the cuts a little more vulnerable because the strength of the grain is somewhat compromised.

[hppyfngy]

Cutting on the bias makes the cuts a little more vulnerable because the strength of the grain is somewhat compromised.

Thanks RR, I actually do understand it conceptually. I guess I'll have to experience a blowout to really get it.

[Ramblinrev]

Thanks RR, I actually do understand it conceptually. I guess I'll have to experience a blowout to really get it.

If you do a proper rolled hem you should not have a problem. If you put grosgrain on the hem you might only do a folded hem meaning you would be trying to rip two layers of fabric. With a proper rolled hem you are trying to rip three layers. Not likely. I usually sew in the twill tape because it makes the cat cuts easier to manage in the sewing machine for me. But I'll justify it by claiming added strength. Do I need it? Not likely.