Grizz phoning home.
Originally Posted by JerryW
I doubt very much an arrows shaft is going to do it. Compression strength increases with diameter significantly (something like diameter^2 or diameter^3, Rapt will know), something on the order of a hollow carbon hiking pole like gnome's or fatter is the way to go I think.
BER is taking one for the team, he ordered some hollow carbon poles over 0.5" in diameter. If we hear back in a couple of weeks or so we'll have data. If we never hear from him again, well then I guess it didn't work
A quick back-of-the-envelope calculation tells me that in general, for a bridge hammock, the compressive force in those members would be around half the hanger's weight, depending on load distribution and fabric angle.
Even my stiffer 7595 arrow shafts would likely (eventually) shatter under that kind of sustained compressive load. A cool idea indeed, but I would shy away from using the arrows.
Yes, as Grizz mentioned, I placed an order 2 days ago from Rockwest Composites for a couple 72" CF tubing with inner diameter of 0.5" and outer diameter of 0.56 with a wall thickness of 0.03" (item# 45166). I have received shipping info so should have them in a couple days. If my calculations are correct it should decrease the weight of my spreaders from ~9.9oz to 3-4oz.
Originally Posted by GrizzlyAdams
Rockwest has a lot of different tubes available. I chose the one I did because 1) they were fairly close to the size specs of 0.625" aluminum tubes from Quest that I use now and 2) at 72" length, I can cut the tube to get the desired length spreaders with minimal waste. It should be noted that these will not be collapsible, but have noted that the 0.625" aluminum poles fit into the backpad of my pack and could be used to replace the aluminum stays (albeit uncurved like stays). This might be one way to carry the longer CF tubes. It remains to be seen.
Shipping costs were rather high (almost as much as the tube itself), but I suppose that is to be expected with an oversized item.
I will make a separate thread to report once they arrive and have had a chance to test them with the next iteration of my DIY bridge hammock.
Last edited by BER; 10-12-2011 at 18:38.
What about bamboo as spreader bars?
As with any other man made fiber, if you decide to cut one up to try it, wear a respirator or atleast a face mask. You dont want to have those little splinters floating around in your lungs...just a thought on safety for what its worth.
One arrow shaft might not work, but 2 or 3 bound together maybe? Not sure what the point would be then.
rcfoam.com has a wide selection of carbon fiber tubes (all a meter long though and I'm not sure how wide they need to be a for bridge): http://www.rcfoam.com/index.php?cPat...5075a4978e5dd3
Something like an elliptical or flanged tube would be best for the weight (http://www.rcfoam.com/product_info.p...5075a4978e5dd3). That would get you a lot of material where on top where the compression force in the spreader bar is the highest and less material on the bottom where it doesn't matter as much.
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