MYOG backpack # 2 – and lessons learned from # 1
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Backpack # 2 took a different approach than backpack # 1, adding 5 additional ounces for more stoutness and added storage space. Pack # 2 is the same size (22 L) as the first pack, but weighs 8.5 ounces stripped – a workable upper limit for an SUL pack. Pack # 2 also took advantage of some lessons learned after making the first pack (see below).
Design Changes
Pack # 2 has simplified panel shapes that were easier to sew (mostly). The back/bottom/front panel was a single right rectangle 10 x 48”, sewed together with different fabrics at different locations. The bottom curve of the side panels and the flat-bottomed side pockets still took extra time to sew. This pack has a front pocket, which added 1.25 ounces to the weight. The height of the pack was increased a few inches to add to the torso length and to add a little space between the shoulder strap seams and the roll-top collar (easier to sew). Several high stress and abrasion area were reinforced with thicker fabric while lighter fabric was used for the main panels.Pack # 1 concentrated all the pull from the top of the shoulder straps toward the outside of the seams attaching the shoulder straps to the back panel. For pack # 2, the angle of the shoulder straps coming off the back panel was adjusted slightly to better distribute force along the entire attachment seams. Specifically, at a distance of 4 inches away from the attachment seams, the inside edges of the shoulder straps were 7 inches apart (see diagram below). This combined with 3.25” between the insides of the shoulder straps at the attachment seams provided a nearly ideal shoulder strap angle coming off the back panel. For the next pack, 6.75 inches should be about perfect.
The thickness of the foam in the shoulder straps tended to push the presser foot sideways while sewing the straps to the back panel, making it difficult to maintain proper strap angle and to sew the straps on with a straight line. The straps and back panel were taped to a paper form in the precise orientation prior to sewing, which helped hold the straps and back panel at the correct angles while sewing the attachment seam (image below).
Fabrics
Pack # 1 was 100% 1.1 oz 30D MNT Silnylon 6.6 XL, with no heavier fabric for reinforcement areas. This pack used three different DP X-Pac fabrics: Lite Skin LS-07, VX-07 and VX-21. The LS-07 was used for the main panels, middle front of shoulder straps and the roll-top collar (the majority of the backpack). VX-07 was used for medium wear and moderate stress areas (side pockets, front pocket top and bottom, underside of shoulder straps and bottom 5 inches of both side panels). For high wear and stress areas, VX-21 was used (pack bottom, top and bottom portions of the shoulder straps, the top of the back panel where shoulder straps attach, and the small wings where the shoulder strap webbing attaches to the bottom of the pack). The front pocket mesh is 5 osy Lycra mesh from Quest Outfitters.Sewing
One big improvement for pack # 2 was stitching. This pack used a 2.7 mm stitch length (9 stitches per inch) for most straight stitches. Especially with the Lite Skin fabric, this longer stitch length should minimize the risk of seam perforation and weakening by the thread holes. For the most part, the X-pac fabric was MUCH easier to sew than the 30d MNT silnylon 6.6 XL used for pack # 1. However, tight corners were more challenging to access because of the stiffness of the X-pac fabric. Guttermann Mara 70 thread was used throughout.Instead of pins, masking tape was used to hold multiple layers of fabric in place for sewing. This was faster and worked reasonably well, especially on the tightly curved pack bottom seams.
A Microtex needle was used (size 90/14) for all straight stitches. The extra sharp Microtex tip bit through the X-pac fabrics quite well. However, a LOT more top tension was needed for the machine to sew good stiches with this needle for some reason. For bar tacking or zig zag stiches, the Microtex needle jammed the machine, so a standard 100/16 needle and a more “neutral” top tension were used for these two stitch types.
Most seams were flat felled except for the main panel seams, which were simply double stitched and the edges torched to reduce fraying. We’ll see how the X-pac fraying is over time.
Lessons Learned for the Next Pack (# 3)
- Simplified (flat-bottomed) side panel shapes will be used. Also, the entire bottom panel will be sewn together first, before the other panels are attached to it (for easier sewing).
- Is there a smaller profile presser foot for sewing tight, 3-D inside box corners on stiff fabric? If so, that would make the pack bottom easier to sew.
- The seam closing the roll top collar into a tube will be sewn AFTER most of the collar has already been attached to the main pack. This will ensure no fabric overlap on the collar due to differential fabric speed through the machine while sewing the entire circumference of the collar to the pack.
- A zipper foot may be used while sewing the main backpack panels so that the plastic hardware on the side tie out points does not push the presser foot sideways while sewing, resulting in a wavy seam in the vicinity of the tie out points. Alternatively, a temporary spacer may be used under the other side of the presser food to alleviate sideways presser on the foot while passing tie out point hardware.
- Any sewn channels for shock chord will be made AT LEAST 1/2” wide, so it doesn’t take a half hour to insert 10 inches of chord.
- A different kind of needle will be tried for the Lycra mesh pocket to avoid skipped stitches, or a tough mesh will be used instead.
More Photos
Pack #2 looks great!
I noticed that you have your sternum strap mounted much lower than most packs will accommodate. It’s so low that it almost forms a continuous line coming off of the webbing that attaches the shoulder strap to the bottom of the pack (I don’t know what to call this!). I’m not sure if this is significant but I suspect this keeps the sternum strap from twisting the shoulder straps. I also wonder if this gives more of a solid harness/vest feel enveloping the rib cage… Any thoughts?
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