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  1. #11
    Senior Member GrizzlyAdams's Avatar
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    +1 on Just Bill's analysis. We got us another bridge hammock engineer. We'll have to out shug shug and make up some T-shirts.

    Shortly (really!) I'll be pushing a video on the design of the 'Ariel'. w.r.t. this discussion here it is ballpack Just Bill's numbers.
    36" spreader bar, 46" hammock width at head and foot, 7" cut in the middle, which gives me 32" in the mid-section.
    The spreaders are recessed to be 5'6" apart, which helps both with making that 7" cut "do more" and flatten things out a bit more
    near the shoulders. The tricky bit, at least from a design point of view, is cutting the fabric beyond the spreader bars because that piece
    will be support some of the head (almost) and the feet.

    My earliest bridge hammocks were bathtubs, coffins almost. Narrower for flatness is the name of my game these days.


    Quote Originally Posted by Just Bill View Post
    Did I read that wrong? You are going 58" wide as the head and foot base width?

    If so, that is your problem, not your spreader bar. 90" long? Those are gathered end dims, not bridge dims.

    I hope I'm not giving any big secret away here- but in doing bridges myself I started looking for some common math and came up with a formula that roughly works/fits most bridges.

    As far as the body/spreader bar- a good ratio to start with is 4/3.
    So a 36" bar multiplied by 4/3= 48"
    If you look at the picture- you'll see that this results in a curve a bit over 10" deep. You'll also see if I put a 20" wide (1'8") person in there you are relatively close to the top. The shape will deform a bit in real life though so you are looking for a balance of shallow enough but still supportive. In a bit of an extreme example- I took the same fabric size and made a V (in yellow)
    If you look at the first curve (4/3 ratio) you'll see the two lines cross the 20" wide line about the same. In your 36 bar-58" fabric shape- you can see it's much too deep and the crossover point is much higher (more squeeze).

    In reality the shape is more of an ellipse but that gets a bit messy to express and is for Professors in hammocking to do. But your bar size to fabric is way too far out to be flat enough.

    As far as the cat cut- roughly speaking two things happen:

    If you stick with the roughly standard 80-84" length (plenty for 6' tall folks) then a good starter is to make the center of the bridge the same width as your spreader bar. (48" head/foot- 36" bar= 12"/2= 6" cat cuts)

    As you go longer with the bridge- the cat cuts need to get deeper and deeper to "pop" the center of the bridge up. So longer doesn't help you much- it actually hurts you in a bridge. You want to stick with the bare minimum length or you're cat cuts will need to be so deep that you lose too much width to be comfy in the middle. Or, if not made deeper, you'll fold up and feel like a banana.

    If you are heavier (say above 180ish) you may need an extra inch of cut vs somebody Grizz's size as well to help counteract your fat *** (I'm 220+). If you are lighter you may find the center has too much pop, so you might want to go with an 1" or so less cut.

    My personal opinion- if you go much past 36"- you have to go with the heavier (.75" vs .625" poles) if you are above 180 or so. Which adds a good bit of weight all around if you care.

    If your shoulders are extra wide- or you just want more hammock...
    Then go with the bigger bars- but keep the ratio about right and fine tune from there.
    42" bar= 56" of fabric and would probably give you a good 25" of fairly flatish sleep space (at the bottom of the ellipse.)

    That's a big bridge- I can pretty easily use my wife's monster car camping pad into a 36" bar/48" 7 ish foot long bridge-
    https://www.rei.com/product/870757/r...00873461&lsft=

    That said- next bridge I will work on is a 1.5 person for me and my kid using this pad- Pretty sure I can work it out with a 36" bar, but may have to bump to a 40"
    https://www.rei.com/product/896427/e...o-sleeping-pad


    Attachment 128051
    Grizz
    (alias ProfessorHammock on youtube)

  2. #12
    New Member NekroVirus's Avatar
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    Wow thanks for the analysis Bill, thats awesome! So looks like I can go with 36" spreaders but I need to cut my initial fabric width to 48" with a length of 84". This brings you up closer to the level of the spreader bars though, would this make the hammock feel tippier?

  3. #13
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    Quote Originally Posted by NekroVirus View Post
    Wow thanks for the analysis Bill, thats awesome! So looks like I can go with 36" spreaders but I need to cut my initial fabric width to 48" with a length of 84". This brings you up closer to the level of the spreader bars though, would this make the hammock feel tippier?
    Tippy is tricky- but at that size I wouldn't worry.
    To an extent it's a mental problem, not a physical one. While it might feel like you might roll out, in reality you are physically much lower than the center of rotation (a straight line from pole to pole) and also much lower than a line from apex to apex. That's not to say you couldn't force yourself to roll out, but you'd need to make an effort in a 36" spreader bar hammock. Your butt is a good 12" below the poles, and a good 24-30" below the apex of the suspension.

    That's not to say you might not feel tippy though until you learn to trust the bridge- the slight side to side rocking is either comforting or nauseating depending on your personal tolerance for the motion.

    Here is my 225 lb butt, side sleeping, rolled over, fetal position with all my weight on one suspension side.
    AND... this is my 26" bar micro bridge... the center is only about 24" wide.
    Tippy.jpg
    Last edited by Just Bill; 04-05-2016 at 09:45.

  4. #14
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    Quote Originally Posted by GrizzlyAdams View Post
    +1 on Just Bill's analysis. We got us another bridge hammock engineer. We'll have to out shug shug and make up some T-shirts.

    Shortly (really!) I'll be pushing a video on the design of the 'Ariel'. w.r.t. this discussion here it is ballpack Just Bill's numbers.
    36" spreader bar, 46" hammock width at head and foot, 7" cut in the middle, which gives me 32" in the mid-section.
    The spreaders are recessed to be 5'6" apart, which helps both with making that 7" cut "do more" and flatten things out a bit more
    near the shoulders. The tricky bit, at least from a design point of view, is cutting the fabric beyond the spreader bars because that piece
    will be support some of the head (almost) and the feet.

    My earliest bridge hammocks were bathtubs, coffins almost. Narrower for flatness is the name of my game these days.

    A compliment from the master- Makes my day!

    I've been keeping mine quiet but inspired by your gram counting efforts I came up with a Micro bridge using 26" bars and keeping the pole to pole distance about 4' apart and using some magic for the foot end.
    26" .451 poles, single layer Hyper D 1.0 and roughly 11 ounces (tree to tree- including the poles). These days I'm using a double layer Hyper D 1.6 version closer to 16oz all in so I can use my Neo-air's and go with the land and air attack as needed.

    Been slowly growing a bit from there and I think I am ending up closer to a version of the ariel these days as well as an ideal shape. Putting the head out a little, but not too much... and throwing the feet out there, but not as far as the original micro bridges.

    I went the webbing route rather than the channel route- but REALLY like your channels on the Ariel. I've been having some long term seam elongation on the webbing channels... so been rethinking your method again. I use a channel on the ends that extend past the webbing, thinking that a triangular (wedge) shaped channel from zero to x" will be the next addition at the foot side to make that part of it work... thinking that you are thinking the same on the Ariel...

    Another big fan waiting in anticipation to learn some more from the Professor.

    Come by the I&M canal hangs one of these times... good group and I try to bring a few creations out when I can.

    Here's a top secret photo of the micro bridge with some magic occluded by the tarp, but likely you can put it together. As a skinnier fella than me perhaps you might appreciate this set of curves- 30-26-36!!

    Towns-end Micro bridge.jpg
    Last edited by Just Bill; 04-05-2016 at 09:52.

  5. #15
    Senior Member WV's Avatar
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    Looks comfortable, Bill. Mind the drafts on your elbows and ankles! Grizz, we've been waiting for details on the sections beyond the spreaders at head and foot ends of the Arial. Lots of possibilities to copy and expand on from both of you. Thanks!

  6. #16
    New Member
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    Quote Originally Posted by Just Bill View Post
    Did I read that wrong? You are going 58" wide as the head and foot base width?

    If so, that is your problem, not your spreader bar. 90" long? Those are gathered end dims, not bridge dims.

    I hope I'm not giving any big secret away here- but in doing bridges myself I started looking for some common math and came up with a formula that roughly works/fits most bridges.

    As far as the body/spreader bar- a good ratio to start with is 4/3.
    So a 36" bar multiplied by 4/3= 48"
    If you look at the picture- you'll see that this results in a curve a bit over 10" deep. You'll also see if I put a 20" wide (1'8") person in there you are relatively close to the top. The shape will deform a bit in real life though so you are looking for a balance of shallow enough but still supportive. In a bit of an extreme example- I took the same fabric size and made a V (in yellow)
    If you look at the first curve (4/3 ratio) you'll see the two lines cross the 20" wide line about the same. In your 36 bar-58" fabric shape- you can see it's much too deep and the crossover point is much higher (more squeeze).

    In reality the shape is more of an ellipse but that gets a bit messy to express and is for Professors in hammocking to do. But your bar size to fabric is way too far out to be flat enough.

    As far as the cat cut- roughly speaking two things happen:

    If you stick with the roughly standard 80-84" length (plenty for 6' tall folks) then a good starter is to make the center of the bridge the same width as your spreader bar. (48" head/foot- 36" bar= 12"/2= 6" cat cuts)

    As you go longer with the bridge- the cat cuts need to get deeper and deeper to "pop" the center of the bridge up. So longer doesn't help you much- it actually hurts you in a bridge. You want to stick with the bare minimum length or you're cat cuts will need to be so deep that you lose too much width to be comfy in the middle. Or, if not made deeper, you'll fold up and feel like a banana.

    If you are heavier (say above 180ish) you may need an extra inch of cut vs somebody Grizz's size as well to help counteract your fat *** (I'm 220+). If you are lighter you may find the center has too much pop, so you might want to go with an 1" or so less cut.

    My personal opinion- if you go much past 36"- you have to go with the heavier (.75" vs .625" poles) if you are above 180 or so. Which adds a good bit of weight all around if you care.

    If your shoulders are extra wide- or you just want more hammock...
    Then go with the bigger bars- but keep the ratio about right and fine tune from there.
    42" bar= 56" of fabric and would probably give you a good 25" of fairly flatish sleep space (at the bottom of the ellipse.)

    That's a big bridge- I can pretty easily use my wife's monster car camping pad into a 36" bar/48" 7 ish foot long bridge-
    https://www.rei.com/product/870757/r...00873461&lsft=

    That said- next bridge I will work on is a 1.5 person for me and my kid using this pad- Pretty sure I can work it out with a 36" bar, but may have to bump to a 40"
    https://www.rei.com/product/896427/e...o-sleeping-pad


    Attachment 128051
    I am looking at building a bridge myself. If you or the professor want to tell me numbers I will take that and run with it cause I am shooting in the dark. I want to build one with a pad sleeve and my pad is a self-inflator and big at 25x72X3in. I am not really concerned with weight cause I am also a fat-a$$ at 6'0 / 280 so dropping lbs on me would be a better plan (in the works). Pretty much one like the "rhino-bridge" is perfect to the dimensions I need.

    Question about the spreader bars too...how much stress do they take? Could I have a 48in in 12in segments? What size tubing? Etc.
    “Being smart is what keeps some people from being intelligent” --- Thomas Sowell

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  7. #17
    New Member NekroVirus's Avatar
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    Thanks for all the info guys this is great. I just watched the Rhino vids grizz made, and now I'm not sure how to do the end caps. Should I do them like in those videos or is there another way of doing it?

    Thanks!

  8. #18
    Senior Member GrizzlyAdams's Avatar
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    Quote Originally Posted by Just Bill View Post
    Interesting lounger, or back-sleeper!
    Grizz
    (alias ProfessorHammock on youtube)

  9. #19
    New Member NekroVirus's Avatar
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    Hey Bill, how did you go about making the end caps? What shape do they need to be etc?

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