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Re: [Hammock Camping] Zigzag stitch - good or not?

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  • Rick
    ... I tried the zigzag stitch after I saw that it was used along the length of some elastic in a piece of clothing. It allows the elastic to stretch. I am
    Message 1 of 6 , May 9, 2006
      jwj32542 wrote:
      > In an email a while back, Youngblood questioned the usefulness of
      > the zigzag stitch in an insulated hammock. He said that as it
      > stretches in one direction, it necessarily contracts in the
      > orthogonal direction. So if you stretch it vertically, it will
      > contract horizontally and therefore stress the material.
      > Admitting that this is how the zigzag stitch works, I've been trying
      > to apply it to insulated hammocks. I have two ideas on how it
      > should work...here's what I came up with:
      > - Start with an insulated hammock just like Risk described in the
      > recent post - basically, a large rectangle with a smaller rectangle
      > sewn to its center...whip it into a hammock.
      > - That means you have four seams _inside the hammock body_ that
      > might cause structural failure. I'll call the ones running across
      > the width of the hammock near the user's head and
      > foot "perpendicular seams" and the ones running down the length of
      > the hammock "parallel seams".
      > - When you lay in the hammock, most of the stress is along the
      > centerline, or the ridgeline, as evidenced by the hammock stretching
      > in length more than it stretches in width (actually, that's an
      > assumption I'm making b/c it seems to makes sense). That's why I
      > chose parallel seams - the seams are parallel to the force vector.
      > Why zigzag seams work better than straight seams:
      > - If most of the force is along the centerline, the seam will
      > stretch along the hammock's length and compress along the width.
      > - However, since the hammock's ends are whipped, the material at the
      > perpendicular seam is already bunched up. That means that the seam
      > compressing perpendicularly to the force WON'T stress the material
      > in that direction.
      > - That means that zigzag seams do indeed reduce the stress on an
      > insulated hammock better than a straight seam.
      > Why zigzag seams are no better than straight seams:
      > - Just use a longer stitch length
      > - Then, for the perpendicular seam at least, it won't matter if the
      > hammock stretches - the seam can't expand in the parallel direction,
      > and the material isn't stressed in the perpendicular direction.
      > - Using a longer stitch length means fewer holes per inch...to about
      > the same number of holes as a zigzag stitch...which reduces the
      > impact of the seam whether it's straight or zigzag.
      > - One problem I see with this is that the hammock's material will be
      > stretched in the middle of the perpendicular seam more than at the
      > ends of that seam - which may pull the thread tighter, which will
      > stress the fabric.
      > - It also doesn't address the stretch in the parallel seams, but
      > since these are near the hammock's sides they don't get a lot of
      > stress, either.
      > So which one is right? I'm leaning more towards the "zigzags are
      > useful" side because of the problems I noted with the straight
      > seams. Anyone see anything wrong with this analysis? Any other
      > issues I didn't include? Dave? Bueller? Anyone? :)
      > Jeff
      I tried the zigzag stitch after I saw that it was used along the length
      of some elastic in a piece of clothing. It allows the elastic to stretch.

      I am generally only interested in the stress imposed by the material
      stretching along a line of stitching and the stitches not stretching as
      much, pulling into the occupied hammock and away from the plane of the

      I am going into my second year of testing this sort of stitch. It
      should still be considered experimental.

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