Tarp cut size vs. finished size question...

[DannyII]

I bought the material to make a Ripstopbytheroll 12' hex tarp. This will be my 3rd tarp build, and 2nd hex tarp. The plans say to cut the ridgeline side of the fabric to exactly 144" (12 feet). Do you DIY'ers just cut it 12' long and not worry about the length lost to the rolled hem, or do you add 2-3" to the length so the finished size is closer to 12'. I know those 2-3" probably don't make a difference on a tarp that big, but it always bugs me that the tarp ends up being less that 12 feet.

[JackM]

I bought the material to make a Ripstopbytheroll 12' hex tarp. This will be my 3rd tarp build, and 2nd hex tarp. The plans say to cut the ridgeline side of the fabric to exactly 144" (12 feet). Do you DIY'ers just cut it 12' long and not worry about the length lost to the rolled hem, or do you add 2-3" to the length so the finished size is closer to 12'. I know those 2-3" probably don't make a difference on a tarp that big, but it always bugs me that the tarp ends up being less that 12 feet.

If you insist on exactly 144" finished length you have two choices:

1. Cut it to exactly 144" and use a folded grosgrain edge, i.e., grosgrain as "bias tape" to cover the edge.

2. Add a "hem allowance" of twice the nominal rolled hem dimension perpendicular to the edge all the way around. For instance, if you plan to do a 1/4" (6mm) rolled hem you need a 1/2" hem allowance which will reduce your overall width by 1" and the overall length by a little less than 1", depending on the slope of the end cuts. In the case of a typical 30" cutback on 58" wide fabric (84" outside edge length), the overall length of the fabric will be 144.888". It may look like it will cost you an extra yard of fabric, but, in my experience, if you order 8 yds. you will get enough lagniappe for the extra length. In recent orders I have gotten anywhere from 1" to 7" lagniappe.

I hope this helps

[DannyII]

"lagniappe" - Good word!

So which one do people do?

1. Cut it exactly to length, or
2. Add a hem allowance?

[Pennsy Camp and Canoe]

when i make mine i will add the hem allowance if i can

[SimonMc]

Add the hem allowance.

[JackM]

"lagniappe" - Good word!

lan-yap, see: https://en.wikipedia.org/wiki/Lagniappe Frequently heard along the Gulf coast from deep SE Texas to Mobile, but especially in S Louisiana. (baker's dozen)

[sqidmark]

Lagniappe - I recall that from Paul Prudhomme cook books.