===> Great video! Love the set-up! I love the idea of expanding the limits of hammock sleeping, from rock ledges to treetops. It all works for me! Of course, I jump out of airplanes for fun, so heights kind of appeal to me! LOL! Keep on climbing and hanging, and take us along again occasionally!
~ SkyPainter
Live Purposefully; Dare Greatly; Land Gently
If you're going to do something wrong, go for it! - Beryl G.
"Never knock on Death's door - just ring the bell and run. He hates that!"
SkyPainter, I am jealous that you have so many skydives under your belt. I went skydiving once (greatest valentines day present in the entire history of presents!) but my ears didn't pop and about half way down I couldn't even think because of the pain. I think we started at 14,000 feet. It was higher than most other beginners jumps because the plane was filled with a bunch of skydiving veterans like yourself.
Personally, I would do some testing with it. What I'm thinking is just taking a straight piece about 6" long and slipping it over the two pieces being connected. From there you'd have a couple pins on each side of the connection. EMT is what I would start with. It's the lightest, common material that I think would take the stress. If that didn't work I'd move to "rigid conduit." Just remember to get a snug fit.Originally Posted by Refreshing
The better option would be to find some aluminum tubing that's like what you have, just the next size up. At least, it looks like aluminum in the pictures. But aluminum tubing can get expensive.
I am a bit confused with how the fitting bent just because of how your straps are set up. Do you have a pic?
Last edited by Truehart; 09-22-2014 at 22:11.
~We all start at the bottom~
It bent inwards. Imagine looking from the top down at the frame and it formed an hour glass shape. No pics.
I have found an aluminum store online that I might purchase from with pretty good prices but I am not too worried about it yet.
OK. I think I understand how the forces are acting. Your weight and the straps both have force components pulling the frame towards the center. I missed that. You might be able to get the rigid conduit pipe to work, but realizing that those forces are there, I think you're going to have to have something there that counter acts them. That's why having the center leg in there works.
Right now, I believe making your straight piece out of aluminum, probably, won't work. I would at least try the rigid pipe in your "testing lab" and see if it holds up. It's pretty strong, but the forces pulling it toward the center are significant, obviously. If you can give me some dimensions and the total weight that's going in this thing I can calculate the forces. I'd need the length of the straps and the dims of the cot.
[edit] I also had the idea of putting the spreader bar above you. This would have your straps coming straight down to your cot. The forces pulling it inward would be lessened by doing this.
Last edited by Truehart; 09-25-2014 at 13:32.
~We all start at the bottom~
"spreader bar above you"
Now that is truly thinking outside of the box! I have done a lot of research over the past two weeks in preparation for the double ledge that I plan to build and have read many posts from other engineers but haven't heard that one. Although it might get in the way of certain tasks I like the idea.
I will be building a spreader-bar-less double ledge as soon as materials arrive and I have a feeling that I will be dealing with some major hour-glassing. Two portaledge manufactures use a spreader bar, two do not. The ones that do not use one are of course much smaller and state that due to the size they don't have the hour-glass problem. I will be using 4130 chromoly steel 1" OD tubes with a .035 wall based on recommendations from other portaledge builders and the corner pieces I was able to find (I would have liked to use 1.25 OD aluminum tubes instead).
Truehart, do you think that lengthening the long side by three inches (from 75" to 78") will significantly impact the amount of hourglassing that happens? Or do you think that a small change in length will equal a small change in hourglassing? I hope that question makes sense.
OK. Before answering here's the madatory disclaimer: DO NOT HANG HIGHER THAN YOU'RE WILLING TO FALL. DO NOT TRY ANYTHING I'M ABOUT TO TELL YOU. That should about cover me.
I am an engineer, but we're dealing with something I haven't tried or tested personally. The other thing to note is that the protaledge you have made, thus far, does not present a simple force diagram. You have forces that are acting in all three planes and multiple angles on those planes.
That said, I believe that changing the long side will not affect the hourglassing very much, if at all. The hourglassing is a result of the forces that are acting parallel to the width of the portaledge. Think about hanging a gathered end hammock. When you hang at a 30* angle the horizontal forces are pointed away from the hammock. In your case, if you're looking down the length of your portaledge your center straps make a triangle and the horizontal forces are pointed toward the center. I'll see if I can draw a pic and attach it.
Bare bones: make your portaledge narrower and you'll begin to lessen the hourglassing. Make it wider and those forces increase.
As for the length of your bed, if you make it longer you are increasing the compression force that runs along your long side.
~We all start at the bottom~
Hammock side view.
hammock.PNG
Portaledge end view. (looking down the length)
poraledge.PNG
~We all start at the bottom~
Truehart. I appreciate your help! I decided to trust your experience and added a few inches of length which will make life a lot more confortable for me.
Your advice was just in time as the materials arrived yesterday and I already have the frame built.
Thanks!
I, certainly, want to know how it turns out.
~We all start at the bottom~
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