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  1. #1
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    Inflatable spreader bars?

    Hi all,

    I'm just starting to read about bridge hammocks, so take this with a grain of salt.

    I don't hike with trekking poles, and I'm a gram counter, so I've been looking at ways to minimize the weight of the spreader bars. 4oz for carbon isn't bad, but what about an inflatable?

    Intuitively, I think a 6" diameter tube should be stable in compression at 36" length. At least that's a ball park we can base some numbers on. Sew a shell from, say, 1osy nylon, or what ever you have left over from your hammock build. That has a surface area of just over half a square yard, so a pair will come in at about an ounce. Stick-on valves can be found under a half ounce. A bladder heat-sealed from poly film will round that out to about two ounces for the pair. So half the weight of carbon spreaders.

    But that's not all there is to this.

    A 6" diameter means you kind of get two spreaders, 6" apart, vertically. Put differently, imagine your spreader bar was a 36"x6" sheet of plywood. It seems like this could help reduce shoulder squeeze for a given spreader length. Increasing the diameter to 8", lowering the virtual second spreader by another 2", adds about a half ounce to the pair. Having that lower spreader will likely let you reduce the length of the spreaders, saving weight on the spreaders, and by having less fabric in the hammock body.

    Two thinner poles in an X would have a similar effect. Not sure how the weight would work out on that.

    I know Grizz played w/ lowering the spreader and adding a second suspension triangle and didn't find it effective. But I don't think he played w/ double spreaders.

    Thoughts?

  2. #2
    SilvrSurfr's Avatar
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    I can't tell if you're joking, but inflatable spreader bars is pretty darned funny!
    "A foolish consistency is the hobgoblin of little minds." Ralph Waldo Emerson

  3. #3
    Senior Member jeff-oh's Avatar
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    Replies to new people on the forum do not have to make fun of them or belittle the question.

    To answer the OP. People through lung power can exert 1.3 PSI at the diameter you suggest that would only be 37 PSI in the structure you suggest. Even if that were enough the inflated column would likely collapse as there is no lateral stiffness in the material. The column would fold over on itself.

    Could you create a shape that would be stable as an inflatable column. Absolutely. Though I believe it would not be as simple as proposed not meet the weight requirement and simplicity of the carbon fiber pole.
    Last edited by jeff-oh; 02-10-2019 at 20:35.

  4. #4
    Phantom Grappler's Avatar
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    Inflatable spreader bars?

    A while back Kitsapcawboy was custom building a bridge hammock. He is really good at DIY and design. I threw in idea of inflatable spreader bars, into his post (hijack-bad Phantom). He said it was outside his current project, and if I had enough interest to start a new thread.
    I never did, as I’m an idea man and don’t usually DIY—also I didn’t have a bridge hammock.
    I did run it through my guessing machine mind.
    My best guess is that an inflatable spreader bar will bend (fail) if shaped like a regular spreader bar. I think inflatable spreader bar would have to be close to cubicle or spherical in shape to stop it from bending. Or shaped like a football—footballs don’t bend.Possibly this inflatable spreader bar could be trapped between end cap and a false end cap. The inflatable spreader bar could fit between two end caps while deflated and after inflation it would be stuck inside due to small openings.
    After all this guessing, I thought this new creation would weigh more than most spreader bars.
    It might work, but be too heavy—defeating original purpose.
    Another possibility, some ingenious ultralight campers have mentioned, is cutting spreader bars at campsite.
    Some problems with that
    Most Rangers do not allow cutting green wood
    Time consuming—sun is going down before set up is done
    Cut wood spreader bars will probably damage tarp when wind kicks up.

    I can be wrong—inflatable cylindrical spreader bars might work (without bending), best way to see is build it
    Last edited by Phantom Grappler; 02-10-2019 at 22:27.

  5. #5
    TrailSlug's Avatar
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    Seriously, let us know when you finish testing these

  6. #6
    Senior Member Karla "with a k"'s Avatar
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    Quote Originally Posted by jeff-oh View Post
    Replies to new people on the forum do not have to make fun of them or belittle the question.
    +1

    In fact, not treating people like how you'd like to be treated goes against what this forum is about. "This is a great community where the norm is to support others in their ideas and projects, and not assume offense where none is intended...and therefore not to flame, call names, or create friction in our threads. Respectful disagreement is ok; disrespectful comments are not."
    ◘ May 17-19: 3rd Annual BACONFEST @ Devil's Lake S.P. ◘ May 31- June 2: Kickapoo Valley Challenge @ Wildcat Mtn SP ◘ July 12-14: DaShack Hang @ Iola, WI ◘ July 18-21: 2nd Annual Boat in Hang @ Tommy Thompson S.P. ◘ YouTube: karlawithak216 ◘ Instagram: i.am.karla.with.a.k ◘ 40 months ◘

  7. #7
    Phantom Grappler's Avatar
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    I’ve enjoyed this thread and have enjoyed reading all posts—for different reasons.
    autox our original poster, for his creativity—if you’ll look back at his earlier post about new whoopie sling design—you will see he’s inventive and brave to try new ideas—without which we’d be freezing in a cave.
    SilvrSurfr for realizing that this idea won’t fly and having some fun by pointing to past threads about new ideas that mostly failed. SilvrSurfr, my favorite was when you described dryer lint as “belly button lint”
    And jeff-oh and Karla “with a k” for being brave enough to extend kindness to our new friend and ask our old friends to be kind and welcoming to all new friends.
    And TrailSlug for suggesting a test build

    autox welcome to Hammock Forums, you are among friends here. I commented on your earlier post about improved whoopie sling design.
    Also I think you will find over time SilvrSurfr to be one of our most fun posters, with his storytelling ability, quick humorous wit, and detailed knowledge of hammocks and how the world generally works.

  8. #8
    SilvrSurfr's Avatar
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    Sometimes things are intentionally funny, and sometimes things are unintentionally funny, but that doesn't mean that they aren't funny. I think the OP understood some people might find the notion of a 6" diameter inflatable tube (or two 6" tubes) might find that humorous, and I certainly do. So, no apologies from me for getting a chuckle. All honor and glory to thinking outside the box, but if you can't see the humor in this notion, then you can't see humor at all.
    "A foolish consistency is the hobgoblin of little minds." Ralph Waldo Emerson

  9. #9
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    It would be wiser to weld the seams instead of sewing them. You should ask ‘Ripstop by the Roll’ to see which fabric is most appropriate for the task. Your biggest hurdle is going to be keeping it from folding in the middle. It should be designed to handle an accidental bump as well. Would these spreader bars be permanently attached or separate removable components? I’m thinking it would be easier to pull off they were integrated and permanent. Or maybe the hammock body could have a sleeve for these to reside inside that would keep them from deforming and when the hammock is occupied it would possibly put this sleeve under tension and provide the lateral stability.

  10. #10
    GrizzlyAdams's Avatar
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    Anything inflatable by human breath would surely buckle under load. Compression force on the spreader bar is on the order of your weight. That's a lot of force.

    I did in fact toy with two spreader bars at the head end, thinking they could share the load. Each had its own suspension triangle. What I found with this architecture was that it was very hard to get them to split the load. Depending on the lengths of the suspensions from bars to tree and the angles either the top bar took the load leaving the lower one flapping, or vice versa.
    Grizz
    (alias ProfessorHammock on youtube)

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