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  1. #1
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    Portable Hammock Stand (PHS) with Amsteel?

    I've been researching DIY stands as my yard is treeless and I had been planning to do TrailH4x's Portable Hammock Stand as designed, but came across some other ideas today that made me wonder if the upright braces could be eliminated. It stems from this design:

    http://www.anchorhammock.com/pd2.html


    and this post by WonderMonkey:

    http://www.hammockforums.net/forum/s...ad.php?t=20361


    What if you extended the base of the PHS 2' past the upright, keeping the uprights in the same place. You could then attach some Amsteel whoopies to the ends of the base up to the uprights through an eye bolt like WonderMonkey's design shows? What kind of forces would we be looking at on the whoopies? I'm going to try and go through the math exercise to see what the tension would be, but someone whose statics skills aren't 10 years old might get it faster.

    You'd need some sort of light line between the uprights just to keep them from falling down until the hammock is loaded, but the line would not be under tension in use.

    ~Dan
    Last edited by DannyBoy2k; 10-05-2010 at 07:09.

  2. #2
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    Created what I think is a force diagram at the top of the left upright.



    115 lb should be 230 lb (my weight) as I mistakenly thought a 30 degree hang halved the force on each upright till I looked at the "Hang Force Diagram" someone here so kindly put together.

    a = force on whoopie

    b = compressive load on the upright? I wasn't entirely sure about this one as I think there will be bending moment in the equation here somewhere. Like I said, I'm 10 years rusty on my statics.

    Any mechanical engineers in the house?

    ~Dan
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    Last edited by DannyBoy2k; 10-04-2010 at 21:33.

  3. #3
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    Think I figured it out. Just a simple balance of forces problem.

    ax - bx + 230 cos 30 = 0
    -ay + by - 230 sin 30 = 0

    a = 351 lb
    b = 531 lb

    So, 351 lb should be no problem for the amsteel whoopies. I was surprised by the force on the upright at 531 lb, but it should be compressive and inline with the board (I think).

    So, then it's a question of whether the additional weight of the longer base offsets any gain by eliminating the upright braces. We'd have 8' more board in the base, which is exactly what the upright braces would consist of. However, you would eliminate the two hinges for the uprights and the small 1x that attach the braces to the uprights. So... maybe?

    ~Dan

  4. #4
    in it for the naps oldgringo's Avatar
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    You're on the right track, methinks.

    Totally diggin' the Aussie design...sweet!
    Dave

    http://www.uark.edu/misc/xtimber/rna/pattonsbluff.html

    It has always been my private conviction that any man who pits his intelligence against a fish and loses has it coming.
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  5. #5
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    Thanks, oldgringo. I thought the Aussie Anchor Hammock was pretty cool too! Not sure I want to shell out that much for it, but pretty neat nonetheless!

    I realized this morning that you only need 4 more board feet since you only need to extend one base board on each side. So, you eliminate the cost of one upright brace, the upright brace hinges, and the 1x pieces that connect the braces to the uprights. Perhaps enough of a weight savings to make it worth it?

    I do wonder if the 2" offset from the whoopie anchor at the base to the top of the upright is significant enough to need to take into account. It would put a small sideways force component on the base board. However, the distance from the base board connection point to the upright connection point is long enough (5.2') that it probably is not that big of a bending moment to need to worry about.

    Also just realized that, if you shorten the uprights by 4", you can fold everything inline with the base, making the PHS even more compact than it already is.

    ~Dan
    Last edited by DannyBoy2k; 10-05-2010 at 07:33.

  6. #6
    Senior Member KayakCarl's Avatar
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    I'm in the prosess of making one out of plywood, and 1" pipe. I was at work last nite on temp light, and power. I came across four 3 3/4"x8' strips of 3/4" plywood. I took two of the strips for the base. I cut them at 4'6", and screwed one short to one long. Creating a step at one end. This step will be where the hing goes on the bottom. This will allow the base to fold almost in half. I took another strip, and cut that one into 8) 1' pieces. 4 for each side will be stacked and screwed together to the base. In each stack I drilled a 1 3/8" hole on a 45* angle( or so "free hand") threw the 4 1' pieces, and the first layer of the base. I think the plywood will not crack like the 4x4 because the grain runs in 25 different directions not just one. I will run a piece of amsteel from the top of the pipe to the outter edge of the base to take the flex out of the pipes when weight is added to the hammock. I will post some picks later.

  7. #7
    RootCause's Avatar
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    Quote Originally Posted by oldgringo View Post
    Totally diggin' the Aussie design...sweet!
    This "Aussie Anchor" is really an elegant solution- now I'm waiting for some of the engineering-minded HF folks to take the next step of DIY'ing it and saving me the time, failures, and wifely abuse as I extend my hammock addiction....

  8. #8
    in it for the naps oldgringo's Avatar
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    Quote Originally Posted by RootCause View Post
    This "Aussie Anchor" is really an elegant solution- now I'm waiting for some of the engineering-minded HF folks to take the next step of DIY'ing it and saving me the time, failures, and wifely abuse as I extend my hammock addiction....
    Imagine the base as a diamond, instead of a cross...

    Also, they show a baseless version of this thing that can simply be staked out.
    Dave

    http://www.uark.edu/misc/xtimber/rna/pattonsbluff.html

    It has always been my private conviction that any man who pits his intelligence against a fish and loses has it coming.
    John Steinbeck

  9. #9
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    Is there anything like the aussie anchor available on this side of the pond? That seems like a really elegant solution but shipping kills it for me.

    What would weight on that be if you used carbon fiber poles and amsteel?

    The instructions show how to use just one anchor point. Now that is cool! How many of us couldn't find at least one anchor point?

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