Re: [Hammock Camping] Zigzag stitch - good or not?
- jwj32542 wrote:
> In an email a while back, Youngblood questioned the usefulness ofI tried the zigzag stitch after I saw that it was used along the length
> 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? :)
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.