Finishing/reinforcing seams on a pack

[J C]

Hi all. I've been working on my first MYOG project, a small Dyneema X summit-style pack inspired by the 2013 MLD Newt. I've done all of the seams with a basic flat seam (with roughly 1/2-inch seam allowances) and I'm now wondering what's the best way for me to finish and seal my seams? Is it necessary to do a flat-felled seam, or could I just do a top-stitch (which I understand does add some strength to a flat seam, but not as much as a felled seam would) and then apply seam-tape/seam grip.

I initially did flat seams because the pictures of the MLD Newt make it look like it has flat seams, but then the description on MLD's site says that "all seams are double stitched". In the absence of a second line of stitches I thought this meant that they simply go over the original stitching with another line of sewing but from what I've read this could actually make the seam weaker because it introduces a new set of needle holes. Are more needle holes likely to significantly compromise the material's strength? If so, what does this mean for areas where I've unpicked and re-sewn?

Finally, I've got one seam that has about 8 pieces of fabric going into it (shoulder straps, zipper tape, etc.), making it really fat and stiff. Any ideas on how to best to seal it? I think I should be able to sew it flat and tape it but any other suggestions would be appreciated.

Many thanks in advance!

[Michael Duke]

A flat felled seam is great when it can be used. If the seam is to stiff to fell, use a straight stitch, then bind the seam with bias tape or grosgrain ribbon. That is two lines of stitching. Unless I am mistaken, the four rows that mld refers to comes from running a Bar tack (zigzag) over the second line of stitching at stress points (webbing, compression straps, any sewn in connection point really. If you look at a pair of jeans, there is generally a bar tack on the pockets.

[J C]

Hi Michael,

MLD actually say "all seams are double stitched", however perhaps you are right and they are just binding flat seams which I guess does result in double stitches, but through 2 and then 4 pieces of fabric which I imagine adds strength. That would be the way to do it if I didn't want to seal the pack, but my thinking is that it's hard to seal a non-flattened seam which is why I'm considering a top-stitch to make the allowances lie flat…

[David Chenault]

I'd imagine MLD means a second line of stitching on top of the first. Flat felling pack seams is a pain, if not impossible in many occasions. Top stitching is fine, but exposes the exterior stitches to abrasion. If you seam grip the exterior seams that would obviate the abrasion problem, but look less clean. Interior binding tape/grosgrain is fine, but IMO is merely cosmetic and doesn't add strength. Otherwise just have an adequate seam allowance (1/2" is the minimum) and melt all the fabric edges. Plain double stitched seams are more than adequate for most packs, provided the seams are straight.

With gripstop fabric you don't need to worry about overperforating fabrics, or at least you'd need to have 6+ layers of stitching for it to become an issue.

[J C]

Thanks Dave! That's exactly the insight I was after. So what would be the best method for seam sealing straight seams with seam allowance sticking out? Would you glue/seal the two pieces of seam allowance fabric together, and then also seam grip the threads?

[David Chenault]

By far the simplest way is to run a bead along the outside. If you want to seal inside only for aesthetic reasons, you'll need to seal both sides of the stitch and between the fabric layers.

[Jerry Adams]

I put flat felled seam on the outside and seal inside. The seam sealer may rub off if it's on the outside. But, maybe the seam sealer actually gets more stress inside?

There is a strip of seam grip that covers the threads and the junction between the two pieces of fabric, and overlaps on both sides.

McNett Seam Grip works good on non silnylon material. Make sure you let it dry for 24 hours, then rub surface with powdery substance like talc or dry clay or just dirt from outside. Otherwise, the seam grip will stick to itself, then you'll have a mess – it will not release but it will peel off the fabric.

I think if you seal, then sew, the needle may get messy. You have to seal after the last stitch, so there's no reason to do any sealing before.

[K C]

You don't want raw edges of fabric exposed. I cover all raw edges inside the pack with cross grain, this also adds another seam, this will prevent fraying.

[Jerry Adams]

gros grain to finish seam? bad, bad, bad,… extra weight, no need for it, just fold over twice to hide raw edges, put in an extra row of stitches for strength if needed

[K C]

2 yards of cross grain weighs 8g, how would you fold where the waist and shoulder harness attaches with 1/2 seam allowance? I learned the technique from Chris Zimmer.

[Jerry Adams]

Isn't Chris a professional? I'm just an amateur

I'm just saying that to protect raw edge, fold over is sufficient

If you're attaching waist or shoulder harness then yeah, you need some more reinforcement

[J C]

"2 yards of cross grain weighs 8g, how would you fold where the waist and shoulder harness attaches with 1/2 seam allowance?"

This is my problem. I have a chunky seam with like 8 pieces of fabric running through it (I added a WR zippered pocket just above the shoulder straps). Folding the seam just won't work. Then again I do like the idea of not adding grosgrain, not so much because of the weight but because it'd be hard to waterproof properly (unless you did it before you put the grosgrain on, but then what's the point of the grosgrain if protecting edges isn't a big deal?)

I was actually thinking about the possibility of having a waterproof binding fabric, and then I noticed just today that One Planet packs use a piece of waterproof-ish canvas to bind their seams. I wonder if there is a waterproof binding material I could easily source and use…?

[Jerry Adams]

"but then what's the point of the grosgrain if protecting edges isn't a big deal?"

for reinforcing a shoulder strap attachment

sew a patch of thick fabric, a little bigger than the grosgrain, around the perimeter, to the pack fabric. Then sew the grosgrain to the pack fabric/thicker fabric, around the grosgrain perimeter. Then sew shoulder strap to grosgrain/thicker fabric/pack fabric with bar tack.

[David Scheidt]

Even a light weight seam binding (like nylon grosgrain) will increase the stiffness of a seam. That means you can build shapes that are a little bit more likely to stay in that shape, which makes pack openings easier to load.

[J C]

I'm still not convinced by the grosgrain/nylon option. Seems to me (and this has been backed up by what I've read on a few manufacturers sites) that having a grosgrain style binding could actually end up leeching/wicking moisture into itself from an unsealed seam. If I were going to use grosgrain I would want to seal the seams first… and I don't particularly care if there are raw edges on my Dyneema X.

[K C]

Keep in mind that the PU coating on Dyneema X will eventually wear off after a few years of use and it won't be waterproof anymore, if you are looking for waterproof backpack you should use xpac or cuben.

[J C]

That's true, K C, and I do plan on making one out of cuben, which I will glue rather than sew. But for now I am just trying to learn how best to seal and finish a small sewn pack.

[Mark Fowler]

One of the reasons for covering the seam with grosgrain, apart from making things look tidy, is to prevent rubbing on the cut edges of the fabric. This is to prevent fraying. If you take the time to hot cut the fabric it is properly sealed against fraying and so the binding is unnecessary weight.

[David Olsen]

I have a 35 year old lowe pack that has seen 70+ lb loads and slot canyon granite, still going strong that wasn't double stitched, sealed, bound etc. After 20 years I had to take a lighter to the edges that had started to fray.

Most seams are overbuilt on commercial packs. They can be a bear to patch if damaged (by say a bear) and you need to take out a seam in the process of repair.

I would sear the edges, stitch with heavy thread, say 69 nylon, stitch a second time 1/8" away as a backup to the first seam and as a backup fray stopper. For more waterproofness and more durability add a silnylon pack liner or plastic garbage sack that can be removed when not needed. A bright color for the lining makes things easier to see in the bottom of the pack.

[Sam Farrington]

For the one I'm finishing now, it will just be SeamGrip, put on very sparingly on the inside with a very small, stiff brush. Maybe a second coat if the first dries very thin.

Don't know what a 'basic flat seam' is, but the more stuff you sew over it, the more needle holes get made. Not progress if water resistance is a priority.

It's too bad we don't have accepted seam definitions with diagrams to work with on this site. There was a post with a link to dozens of seams – it might have been from Judy Gross. But all we need to work with is maybe ten or so. Without that, I decided to avoid seam threads (hah!) unless diagrams were provided. Too much "whose on first" miscommunication was happening.

P.S. Not so fast with the mylar stuff, like D-P and Cuben. The needle holes don't self-repair as on woven fabrics. That is not progress, either; and I'm doubtful about bonding mylar after it has left the factory that needs an autoclave to hold it together.

[Jim Colten]

David said: Most seams are overbuilt on commercial packs. They can be a bear to patch if damaged (by say a bear) and you need to take out a seam in the process of repair.

You can say that again!

Samuel said: It's too bad we don't have accepted seam definitions with diagrams to work with on this site.

Wwwweeeeelllll … if the "BPL Community" had put enough effort into the WIKI to keep it alive then we'd have such a place. But we didn't.

[Jerry Adams]

"It's too bad we don't have accepted seam definitions with diagrams to work with on this site"

I agree. I don't think there's 100% consistent definitions anywhere

thru-hiker.com has some good description under "projects"

French Seam

Under basic seams it describes simple seam and what he calls "felled seam" but is more commonly called "flat felled seam"

Those are about the only seams you need

You can do a flat felled seam with just one fold, leaving raw edges exposed, if you want it not so thick in case several seams overlap and it's difficult to sew through all of them. I forget what that's called.

[David Scheidt]

I've posted this before:
http://www.amefird.com/wp-content/uploads/2009/10/Seam-Type.pdf

But there's a problem: getting people to agree to use the same language. No one says 'an LSc seam', they'll call it a felled seam or a lapped seam.

[J C]

Samuel: "Don't know what a 'basic flat seam' is"

Yeah I don't really know what to call it either I guess. I just mean the easiest type of seam where you put the two pieces of fabric wrong side out and sew with a seam allowance, and then invert the seam to finish. My whole pack is sewn this way with Rasant 75 thread. I don't really mind about more or less needle holes since the seam grip should take care of those.

Edit: on Thru-hiker they just call it a "simple seam" http://thru-hiker.com/projects/basic_seams.php

What sort of seams does your current project have?

[Sam Farrington]

"Wwwweeeeelllll … if the "BPL Community" had put enough effort into the WIKI to keep it alive then we'd have such a place. But we didn't."

A bit of blaming the victims, perhaps?

BTW, when the WIKI started, I couldn't get into it, put time into making inquiries (have you ever tried to contact BPL on this site?-reminds me of the IT people at work), and got no comprehensible or workable answer.

Jeremy, now I think I know what you meant by 'basic flat seam,' but still not sure, because what you describe would be anything but flat, unless you rolled it over at stitched it down. But that probably makes no sense to most readers, either; which is why we need a simple standard reference.

I've put diagrams up before, but a few months later have seen the same confusion repeated on new threads. When I get time, I'll do up a set of diagrams with their common names, put it in a small jpeg form, and just keep posting it until rockets start coming into the back yard. In the meantime, it's hiking season, and getting out there is priority one. The bugs are just starting up and should peak in a few weeks, but I'd rather spend indoor time during bug peak modding a tent down to lighter weight to use this summer.

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