Double stitching pack’s main seams

Yes. Redundancy is a good thing in pack seams.  Also, if you fell seams, load is transferred into the second line of stitches.

A second row farther in helps stop fraying. Even better is binding the seam.

Top stitching spreads the force out on both rows.

If you have weak thread, running the second stitch line on top of the first can make it stronger (unless you have weak fabric too).

Good info, thanks. I’ve been doing a second line of stitching with zigzag to stop fraying (a tip I got from Paul McLaughlin on here).

Felled seams / topstitching would be harder to do. Maybe I’ll experiment with it next time. With MYOG packs there’s always a next time, right? :)

“Next time” is the best part about MYOG – well that and the lower cost of good equipment that you custom make to fit your needs :)

“…lower cost of good equipment” only lasts till you get that nicer sewing machine!

Doug,

With a flexible, and certainly a woven fabric, a second line of stitching will spread the force between the two stitch lines.  Unless you are doing a peel, which would be asking for trouble,  I think.

Sam, what is a peel? I am not familiar with that terminology.

peel – the two pieces of fabric pulled apart – all stress on one row of stitches

shear – the two piece of fabric pulled sideways – all rows of stitches share load, friction of fabric against fabric also helps

Wouldn’t the seams in a pack be doing a peel? (first I’ve heard that term!)

some seams peel, some shear

if you sewed a pocket onto a pack, it’s peel

if you sewed fabric into a cylindrical shape, with flat felled seam, it’s shear

I don’t plan on using flat-felled seams and I think most commercial packs don’t use them either. So are regular seams, even if there are two lines of stitching, “doing a peel”?

If so, the force is not spread to the second line of stitches…unless the first line of stitches fails, it would seem to me.

Doug, it is the flexibility of, say, a nylon fabric that spreads or distributes force throughout a lap or flat felled seam, or even a faux felled seam.  Perhaps not so much with less flexible, non woven dyneema fabrics, but think the force on one line of stitching would still be shared with the other line.

One has to be creative with pack seams.  Even with tunnel tents, Roger Caffin has posted illustrations of the seams he designs for attaching pole sleeves.  Pack fabric is heavier, so one can take liberties in designing the seams; but I think two rows of stitching are better, if only for the reason you mentioned; to hold things together if one seam fails.

It is probably just as important to have some seams that show only internally, as the exterior of the pack is where the abrasion occurs that can shred a seam.  I seem to remember there are articles, or at least links to articles, on BPL about seams.  I get the impression from the forums that many are joining dyneema fabrics with tapes these days.  I think it is a matter of ‘do what you know’ to get the best results.

I have had french seams fail.  Two rows of stitches.  The first row ripped out, then the second row took the load.

It’s at least good until I get back home.  Then I can sew the first row back again.

But I use flat felled seam on pack (that is, faux flat felled)

As pack fabric gets lighter perhaps it becomes more important to use some for of felled or top sewn seam? I have had canoe portage packs that use a standard seam still fine after twenty years but they use a combination 500D/1000D Cordura. Many years ago I made a pack from 30D silnylon, sticthing was fine, fabric failed around the stitches.

yeah, lighter fabric must make seams more critical.  And other techniques.

back in the bad old days, they used heavy fabric, heavy thread, problem solved