Uncomfortable shoulder straps on backpack – Suggestions?

looks like the comfortable straps have foam in them and the uncomfortable straps don't

1/8" inch or 1/4" (3 or 6 mm to you?) stiff foam, like used for sleeping pad. The lightest material possible so it's easier to sew through.

Make a tube of nylon, put the foam into it, you have to do at least one row of stitches through foam and nylon to prevent the foam from rotating around after you use it for a while,…

I can sew through nylon/foam/nylon with my cheap home machine, a Janome, but it's marginal

nice Rube Goldberg tee-shirt : )

The photos are very helpful — it looks to me as though the new pack's shoulder straps are angled too sharply outward (compared with the older pack) causing them to feel like they're slipping. If that's correct, it should be an easy fix [remove existing shoulder straps, then re-sew them at a slightly less acute angle].

But Jerry also has a point about the padding on the older pack… padding will usually feel more "comfy"; plus the mesh on the padded straps is inherently more "grippy" and therefore less likely to slip.

Hello Victor,

Some observations:
1) The straps seem to be coming out at too large an angle – almost 45 degrees from vertical. This will place most of the load on the outer edges of the shoulder strap and make them slip outwards and off your shoulder – just as what you're experiencing. From my experience in making packs, an angle of around 15-25 degrees off vertical should suit most people. Conversely, an angle of <15 degrees, or even vertical, can cause the load to be taken by the inner edge of the strap, and that could cause chafing near the neck area.

2) There seems to be very little padding to spread the load around a larger area. This might cause discomfort.

3) Have you considered using the sternum (chest) strap? Doing that would prevent the shoulder straps from slipping outwards, though you might still experience some discomfort because of the wrong angle.

Now, if you want to modify, you could do the following:

Items needed:
a) 1 sheet of 5mm EVA foam
b) 1 sheet of 5mm open-cell sponge foam
c) Adhesive (3M Super77 works really well)
d) Cloth of choice
e) Bias tape/grosgrain ribbon (3/4" or 1")

1) Layer 5mm of EVA foam and 5mm of open-cell foam to create a sheet of dual-density foam. Merge the two layers with a liberal application of 3M Super 77. If you only plan to use one kind of foam, get an open-cell, as the closed-cell might be too firm.

2) Trace the shape of the shoulder straps onto the foam. If the left/right sides are mirror images of each other, be sure to trace that, and not trace one side twice. This is because, for dual-density foam, the softer open-cell layer needs to be facing you.

3) Offset the drawing on the foam by about 10mm/12.7mm(1/2") inwards. This will help you avoid the existing bias tape on the shoulder strap. Cut the foam pieces out. At this thickness, a good pair of scissors will suffice, but a penknife works too.

4) Using the cut foam pieces, cut out pieces of cloth offset about 20mm (3/4") outwards. These pieces will serve as the cover.

4) Spray Super77 onto the EVA foam surface, and glue the foam piece down onto the underside of the shoulder strap. Let it set for a couple of minutes.

5) Spray Super77 onto the pieces of cloth, and place them onto the foam. Press the sides down and make sure they stick onto the original shoulder strap too. There should be little excess – trim any excess off.

6) Wrap and sew bias binding around the shoulder strap to finish the job.

Cheers
QX