head end-cap

[ceiliazul]

I know some folks (including Grizz) addressed shoulder squeeze by moving the head-end spreader bar down so it's directly above the head.

I'm having a hard time searching for people's info about that kind of bridge because I don't know if it has a name.

I'm interested in making a hammock using this concept. In particular, I'm trying to find how much taper does the head-end of the hammock body need (above the spreader bar) to keep the head as a flat lay?

Grizz posted this pic in the gallery that looks promising:

Anyone got more info?

[GrizzlyAdams]

my method...
a) when I scope the width of the fabric under the spreader bar I assume the shape of a parabola. I wrote a simple program that, given the spreader bar width and depth d of the parabola at the center, computes the arc length of that curve between spreader bar ends.

b) I compute the distance w between the ends of the fabric that stretch up the suspension sides, as a function of the length of those sides relative to the spreader bar width, and the length of the fabric. This is trigonometry.

c) I compute how far the suspension sides have risen from the level of the spreader bar, at the point where the fabric ends, assuming a 30 degree angle. Call that r.

d) I go back to my arc length program and find the arc length of a parabola with width w (from above) and depth d+r (also from above).

The answer to d) tells me how much fabric should be at end of the hammock. To make the taper I put in a dart from directly under the spreader bar to the edge, wide enough so that when finished the length at the end is the answer from d)

hope this makes sense....

[ceiliazul]

Thanks Grizz, lets see if I understand you right:



The goal is to find the dimensions of fabric to cut for the overhang portion of the head end (the end that goes past the spreader bar. If I do this right, my head should be level.

W1 and Arc1 are known, and are specified by the design.
L is also known by spec
D1 is observed with the hammock hung.
W2 is found using similar triangles
D2 = D1 + L * Tan(angle of suspension rise)

So Arc2 is to D2 and W2 as Arc1 is to D1 and W1

Even without an arc length program, that would let me estimate Arc2 pretty well.

However, I had an epiphany. I could cut the whole hammock body with the overhang not tapered or darted, (just a rectangle hanging past the spreader bar,) and sew only the main body to the suspension. I could then hang the hammock with the overhang unattached, and use pins to temporarily try different head fabric widths. This has the benefit of avoiding math, and also I could give the head overhang a small positive lift (like a pillow) if desired.

Yeah, that sounds like a better plan. This is not my first bridge, and will have a couple of "interesting" ideas. Wish me luck!

[GrizzlyAdams]

I have made already a couple of hammocks using this approach you see too, leaving a rectangle of fabric above where the pole connects. Fitting with pins to suit is entirely sensible.

I have found it convenient to cut a piece of fabric from the body to allow the roll of the webbing to not "creep" up into the entended path. Figured a 1.5" cut oriented 90 degrees to the tangent to the curve at the end, then curve that up to form a sort of semi-circle. Pictures below, showing also
a bit of dyneema I fitted there to cover the pole tip and protect the tarp.

tip.jpg tip cover.jpg