Tarp French Seam Allowance?

[Spokes]

I’m confused on how much extra to allow for the ridgeline French seam. My initial thought was to use a 1/4” basting stitch to hold the two sections together but from there the math gets fuzzy to me when doing the folds. Can anyone help?

[Shug]

Can't say for sure as I did mine long ago.
I would suggest doing several practice french seams before committing to the final.
That is what I did and believe me...my first few were failures.
Shug

[MAD777]

Great advice from da man! Good use of scraps!

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[gargoyle]

DIYGS-Seams-Binding-lowres.jpg

5/8” or 3/4” is good.
“Modified or Hybrid French Seam” is the technique.

[Spokes]

Can't say for sure as I did mine long ago.
I would suggest doing several practice french seams before committing to the final.
That is what I did and believe me...my first few were failures.
Shug

I may have to resort to this. I’ve yet to find any instructions online answering this question. It’s not listed in the DIY instructions for RipStopByTheRoll, DIYGear, or even Dutchgear. They just say “do the French seam...”. You’d think it’d be sorta important to know the allowance when cutting your fabric.

*ugh

[carmen2kayak]

When I build tarps, my first seam has a 1/4 inch seam allowance. Second seam is 1/2 inch seam allowance. The third seam is determined by the second seam since you are folding it back on itself.

Five tarps later, they are all performing well. A couple were built for friends, but no failures or complaints so far.

But make it the way you want it. That's the beauty of DIY.

My $0.02

Nancy

[Cruiser51]

TBH ... if you allow 1" and use 1.5" ...that's .5" on a 10' or 12' foot tarp, so short story is "you need to make seam allowances to get close, but don't overthink them on a tarp".

If you see "french seam the ridge line" in instructions ... it may not be an accurate description and it could really mean a flat felled french seam, which is most common on ridge lines ... if you are in doubt call RSBTR and see if they can clarify what the ridge line is using. A standing french seam can be used, but then there is usually a wrap of grosgrain or similar material to strengthen and protect the seam ...

Brian

[MAD777]

An option is to sew a standing French seam, then fold it over and sew it down.

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[jellyfish]

I am pretty sure I describe seam allowances here.

https://youtu.be/XuAhiHFKtV0

Good luck.

[mab0852]

Looking at diagram linked by gargoyle, if you are doing a standing French seam, 1" seam allowance per side. To make it flat felled as most tarps would be, side A is 1" and side B is 1 5/8".