Sewing through foam for shoulder straps

[Myles S]

I’m new to sewing and I’m working on prototyping a simple frameless pack. I’ve started construction of various elements of the pack, and I’d like to nail down the construction method of the more complicated parts before I go ahead and make a full prototype. I’m using a Singer 301 that I bought used on Craigslist and cleaned, greased and oiled. Thread is Gutermann Mara 70 with a size 90/14 universal needle.

I’ve spent the most time (and had the most trouble) with the shoulder straps. The materials I’m using for the straps are 400d packcloth, 3/8” mini cell foam from Quest, and 4mm 3D spacer mesh. I’ve also tried sandwiching the foam between 70d coated ripstop nylon. To make the straps, I’ve been sewing together the right sides of the mesh and packcloth (or 2 layers of ripstop) to make a sleeve, inverting it, and then stuffing it with foam. I’d like to sew through all the layers of the strap in order to (1) attach webbing for the ladderloc at the bottom of the strap and for a sternum strap, and (2) secure the foam in the sleeve so it doesn’t roll around. So far I’ve been unable to successfully sew through all these layers.

Given my lack of experience, I don’t understand sewing machine mechanics all that well, but I’ll try to diagnose the problem anyway. It seems that the problem is not that the machine doesn’t power through the material but that the stitches don’t hold. The motor has been able to push through the layers, but I mostly use the hand wheel because I’m dealing with very short sections and I want to be precise. Sometimes when I try to sew, all the stitches fall out; other times the stitches appear long and irregular because only some of the stitches are skipped. I’m thinking that this means that the top thread isn’t locking with the thread from the bobbin.

Now onto some things I’ve tried to fix the problem:
– Switching to a new needle
– Adjusting the top tension from ~3 which seems to work well for sewing a couple layers of fabric (including pack cloth and 3D mesh or 70d ripstop) up to ~8 or higher
– Adjusting presser foot pressure
– Pushing/pulling strap along. I’ve read that this can break or bend the needle but is it okay/desirable to do this if you go slowly with hand wheel and push/pull only when needle isn’t in the material? Still, I don’t think the problem is with the feeding. Sometimes the material doesn’t feed well, but it usually does. The local sewing machine repair shop recommended a walking foot, but I’ve read that 3rd party walking “foots” like the one I’d get are not that effective (and wouldn’t make sense if the problem isn’t with feeding).
– Terminating the foam before the ladderloc attachment point at the bottom of the strap so that I only need to sew through the webbing, fabric and 3D mesh. Sewing through this material works pretty well, but o don’t think it looks as clean and I’d rather secure the foam by sewing through it.
– Working around sewing through the foam for webbing attachment points higher on strap (for sternum strap attachment) by cutting out ~1/4” x ~1” rectangles of foam. Also doing this for simply sewing reinforcements through the strap without attaching webbing. I tried this with a ripstop – foam – ripstop strap but there was a large air gap between the layers of fabric where I had cut out foam and all the stitches pulled out. Maybe this method would work better on a strap with 3D mesh on one side since it stretches more.
– Attaching webbing first to outside of strap (packcloth) and then sewing that piece to 3D mesh, right side to right side. I don’t love this method because the foam still isn’t anchored and the stress from the shoulder strap is (exclusively?) on the outer layer of the strap.

I’ve thought about experimenting with these solutions:
– Using a bigger, size 16 or 18 needle with appropriate thread and/or a (stiffer?) denim needle
– Hand sewing or using a sewing awl
– Using thinner foam – I’d like to avoid this if possible

Thank you to any and all MYOG gurus for your insight. I’ve looked at other related threads but I thought it would be good to get a take on my specific circumstances, especially from anyone with experience with the same machine.

[Lester Moore]

I had some of the same problems with shoulder straps at first. Switching from a Microtek needle to a universal needle helped. Adjusting the upper tension helped even more. And going really slow and manually assisting the hand wheel to rotate with my hand helped the most.

Make a test square of fabric (material-foam-material-webbing all layered) and play around with different settings/needles to get the best results. While I’ve heard that some machines (like the Juki 1181n) can sew through shoulder straps like they’re nothing, it seems like people often have trouble with thick stuff on home machines.

Also, while it may seem obvious, be sure to double check that the presser foot is lowered before sewing. With thick stuff, the presser foot may look lowered (it’s in contact with the fabric) even when it’s not. You’ll get a messy birds nest of thread if it’s up while sewing.

[Jerry Adams]

I’ve had similar problems and eventually got it to work along the lines of what you’re doing

Do all the sewing except the foam, put the foam in the sleeve, and do just one row of stitches through everything including the foam

If I pull or push it has more problems like you had.  If I let it feed through with my hands off, it works better

I use 200D fabric which is a little thinner which helps

Maybe let the machine do it’s thing, maybe fairly slow, don’t manually rotate

[Craig B]

I mostly concur with the above comments, especially Lesters about getting it correct on a test piece first.  This is absolutely the best way of figuring out how to do something that’s not obvious the first time.  It generally takes me several iterations on a test piece before I’m happy with something new, and I’m ready to apply it to the real thing.

My thought would be to try a larger needle.  It sounds like the machine is not forming the stitch underneath, possibly because it is somehow getting caught in all that material when the needle punches through.  The larger needle might make a better passageway for the thread.

I actually saw a bit of this problem recently when I was trying to sew through a hip belt assembly that had 1.5″ thick foam in it.  My presser foot only lifts about .5″, so I had to compress the foam a lot with my fingers and shove it under the presser foot.  When I lowered the presser foot, it basically did not move as the foam was already pushing up underneath it with a fair amount of pressure.  I let the machine have a go at sewing for about 5 or 6 stitches, and the stitches failed to form.  I have an Industrial Juki needle feed machine with a servo motor so it didn’t have any problems going through the material, but it had trouble feeding.  Definitely not quite the right tool for such a thick sandwich.  I then tried to compress the foam with my fingers right in front of the presser foot and help the feed a bit, and the machine was able to create stitches.  I was able to make about a 1″ seam in one spot.  I then came back the next day and tried to do it again in another spot, but promptly broke the needle because I was assisting the feed to much and the needle deflected out of the hole.

So try compressing the foam a bit as it goes under the presser foot, taking care not to interfere with the feed motion as much as you can.

I’ll be curious to hear which if any of these tips helps.  Keep us posted!

[Daryl and Daryl]

I avoid sewing through the foam by using adhesive backed insignia cloth.

They have worked well for many years.

 

Here’s a link to an old post:

https://backpackinglight.com/forums/topic/41336/

 

[Sam Farrington]

Must confess that have collected a number of used shoulder straps that looked good, and keep them on hand for pack projects. A lot of shops sell such items cheaply in boxes of assorted pack parts. Some of the straps even have seams sewn across the foam that can be oversewn to attach lift straps etc. The last resort is a bootmaker friend. Getting out of the workshop and enjoying the fresh air keeps me from becoming a purist. A life full of shortcuts ain’t so bad.

[Myles S]

Thanks all for the advice! Hope this thread proves useful for others with similar issues.

Today I bought size 16 and 18 universal needles and size 16 denim needles. Again, I had been using size 14 universal needles previously. The size 16 universal needle worked a little bit better than the 14, but still skipped most stitches. The size 18 universal has only skipped a few stitches – I’m very happy with the result so I have not yet tried the size 16 denim needles.

Thus far, I’ve mostly been testing the new needles on a test strap of 70d ripstop – 3/8″ foam – 70d ripstop. I’ve gotten the best results with this combination of settings/methods:

• Size 18 universal needle
• Top tension at 5
• Presser foot tension at maximum
• Primarily using the hand wheel, with some motor assistance to make it a bit faster
• Holding the strap with my left hand and *very gently* pushing/encouraging it along with the feed dogs. The strap does not feed so well/at all without a little encouragement, especially if the presser foot is on the edge of the strap and slanted.

I’ve also tried applying these same settings/methods to sewing through webbing – packcloth – 3/8″ foam – 3D mesh and it seems to work nearly as well, but there are a few more skipped stitches.

Craig, it seems that it was (mostly) as simple as using a larger needle. I think I will return the size 16 denim needles, but might it be worth experimenting with size 18 denim needles or maybe size 20 universal or denim? I would have bought them today but they were not available. I tried to compress the foam with my fingers ahead of the presser foot, but it didn’t do much with the relatively thin and dense foam I’m using.

Lester, I really like the test piece strategy. You can see (a sample of) my test lines in the image below. Very helpful for dialing in settings. And keeping the presser foot down… I’m embarrassed by the number of times I’ve forgotten to do this.

Jerry, interesting that you’ve found manually assisting with the feeding counterproductive. I have some 200d oxford that I will experiment with, hopefully that will produce better results than the thicker packcloth.

Sam and Daryl, luckily it seems that I won’t have to rely on your workarounds – though they are clever.

A few remaining questions:

• Would a different thread be more appropriate for the larger needles? Maybe something like Mara 50 from RBTR. I’ve exclusively been using Mara 70 so far.
• To help with the feeding, should I try the 3rd party walking foot attachment that the local sewing store recommended?

 

 

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