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12-22-2007, 22:00   #24

Join Date: Apr 2007
Location: Illinois
Hammock: DIY Bridge, v0.n, where n is large
Tarp: depends on season
Insulation: DIY UQ
Posts: 4,684
Quote:
 Originally Posted by TiredFeet Grizz - trying to understand what you have here. The ridge line is 10' - that must be the tarp ridge line of the JRB 11'x10' tarp.
You can hang this tarp either with an 11' length and 10' width,
or 10' length and 11' width. The sewn ridgeline is 11', as you'd expect
(because rolls of fabric tend to be closer to 5' wide than 5.5' wide). There are a number of tie-out lines along the 11' long edges.

Quote:
 what is the distance from the top of one suspension triangle to the top of the opposite triangle?
Have to approximate using some trig here, because the rig is down right now. Lemme see....

OK, just under 13.5' . You can work it out for yourself knowing that my rings are spread 36" apart, that the length of one side of a suspension triangle is 48", and typically the angle of ascent of the suspension triangle is about 30 degrees.

Quote:
 Looking at the picture, if the tarp is 10', it looks like the distance from triangle top to triangle top must be at least 15' or more.
Considering that you're look at pictures, that's not a bad guess, within about 10% error.

Quote:
 Reading TeeDee's articles - I figure from his directions that his hammock ridge line is about 10'. Yours looks like it would have to be much longer if you had one.
I'd be surprised if his was only 10'. You'll see why in a minute.

later edit: did what I should have done the first time...went back and looked at TeeDees article. Yep. 10' is the longest ridgeline length he describes... you'll see why in a minute.

Quote:
 Could you shorten and keep the triangles within the tarp?
So this is all about compression force on the spreader bar. My hammock is 7' long. To fit under a 10' ridgeline means the horizontal distance from spreader bar to apex of the suspension triangle is 18 inches. At a 30 degree angle that means a height of the suspension triangle is 20.8 inches. With a 36" spreader bar that makes the cotangent of the base angle 18/20.8 = 0.86. With the suspension lengths I have the cotangent is 18/44.5 = 0.4. So, all other things being equal, shrinking the suspension triangle "to fit" more than doubles the compression.

For another set of poles that might be fine. It might be fine with my poles. I've got funky handles though on them; frankly I continue to baby them.

TeeDee spreads his hammock out 39", and it is also 7' long I think. With a 10' ridgeline he'd have to have a suspension side length of 28.5". Pretty sure he used to run to 36" or more.

later edit: his article says 27.5" length for the side of the suspension triangle. He recommends a spreader bar no longer than 0.75 of the width of the fabric under the spreader, which for the hammock dimensions he gives is about 42". Spread out that wide, with a 27.5" suspension side, gives the cotangent of the base angle to be 1.18, so the compression force on the pole is just under x3 more than what I've pictured.

Quote:
 That looks to be one huge distance from triangle end to triangle end. What is the minimum tree separation you could use to hang. Also, it looks like you are hanging pretty high on the trees. How high do you have to hang on those trees and how far apart are they?
With a bit of trickery to get a biner (on the webbing) up flush to the tree, the minimum distance is about 14'. The trees you see in the pictures are 21 or 22 feet apart. I typically attach the webbing about chin level on me, so that's about 5.5 feet up.
Quote:
 Trying to get an idea of the sizes involved here. Also, are you using the grip clips on the bottom of the tarp? Looking at the JRB site, it doesn't look like they have tie outs at the bottom positions you are using for tie outs. Thanks.
yep, grip clips. cool little do-dads.

later edit : in light of paying attention to these dimensions, perhaps I'll try tightening up the suspension triangle...using a different set of poles first!

Grizz

Last edited by GrizzlyAdams; 12-23-2007 at 07:00..