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-   -   Engineers, start your engines!! (https://www.hammockforums.net/forum/showthread.php?t=67280)

 Timberrr 01-29-2013 18:36

Engineers, start your engines!!

1 Attachment(s)
I need a horizontal bar that is strong enough to a hammock from each end. Basically, you have two of these bars, each attached to, or suspended from a tree (somehow). Then you would hang two hammocks between them.
One of the possible materials for the bars is carbon fiber. Which I know close to absolutely nothing about. Here's a spec sheet. Does this say it could withstand the various dynamic forces? What do you think?

http://www.rockwestcomposites.com/ck...pdf?1340058755

I tried to insert a pdf but it didn't work. Sorry. :(
How 'bout now?
Nope, still didn't work. :cursing:

 ahhhgladius 01-29-2013 18:51

illustration please?

 GrizzlyAdams 01-29-2013 18:52

I are kind of an engineer, but there's a verb missing or something in your description, so I'm not entirely sure I grok your problem.

I'm gonna guess...you want to hang two hammocks side-by-side, off the same pair of trees, but separate them. So you're thinking some kind of spreader bars that would push the suspension lines of the two hammocks apart.

I'm thinking maybe somebody has done this already. I think you need only separate the two hammocks at the head, the two hammock occupants can play footsies with each other OK. The compression forces on that bar would be a function of the weights, the length of the suspension triangle from the bar to the tree. Thumbnail sketch, twice the compression force you have on spreader bars for a bridge hammock, since there is twice the weight.

 Timberrr 01-29-2013 19:03

@Grizz

Yes. Your thinking is correct. Mostly.
Here's what I'm still going after.
http://www.hammockforums.net/forum/s...ad.php?t=35582
As you can tell from the date of the thread, this is a work in progress.

Thanks for your insights.
I know from previous failures that there is much more than compression on the bar. I had a bar of 1.25" dia. poplar give way slowly and finally break on the third night.

 streamline 01-29-2013 22:15

People use trekking poles for this. Don't put the pole at the tree though, put it at the ends of the hammocks.

 TFC Rick 01-29-2013 23:19

Tim is this hiking based or for your boat trips? Would pipe work? Obviously heavy as sin but stout enough to accomplish the deed?

 Dustb2000 01-29-2013 23:54

If your goal is to hang two hammocks just using two trees I've had success using the following method:

http://www.hammockforums.net/gallery..._143_thumb.jpg

Basically just took a 1" x 2" x 18" board and drilled a hole in each end to run the suspension to for one end.

 Jayson 01-29-2013 23:57

I have used my hiking poles to do this many times with my wife. They are cheapy twist lok poles and they held just fine. As was said just put them as close to the ends of the hammock as you can.
No worries.

 Detail Man 01-30-2013 05:53

Timberr, I'm assuming you want to use the spreader bars with your Chrysallis bridge hammocks. The spreader bars will function best at the end of each hammock, rather than at the tree. The forces on the spreader bar will be less at the hammock ends. If you try to put them at the tree, as in your diagram, the forces will be much greater, hence the poplar dowels failing.

The downside to having the bars at the hammock ends is that one occupant transfers his/her motion to the other hammock. Once both occupants are settled in, it's no big deal in my experience.

To place the spreader bar at the tree, the bar will need to be able to withstand lateral stress more so than compression. Tubing tends to withstand these forces better than solid material The thicker the wall thickness of the tubing, the stiffer the tubing will be.

Carbon fiber withstands compression quite well, but I'm not sure it would hold up to the lateral forces involved if placed at the tree.

 jordo_99 01-30-2013 11:23

I'd probably go with titanium as it's much more forgiving to torque yet still very light.
When torque is applied to Aluminum poles they bend and carbon shatters but titanium will revert back into it's original shape afterward.

Ti poles will likely run you about the same as carbon would.

If you use trekking poles that's definitely the way to go though.

Another consideration would be to use 4 guy lines and stakes to pull the hammocks apart. Would be lighter and cheaper but some people like to swing so maybe that's not ideal for you.

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