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  1. #21
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    My two bits is that diamond tarps were a good choice back when materials were heavier and hammocks were shorter. Now with lighter fabrics and 11' hammocks rectangles (or hexes with doors) seem to be the best all around choice.
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  2. #22
    Senior Member Brancher's Avatar
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    Quote Originally Posted by sargevining View Post
    I did a quick sketch in Autocad using your dimensions. Assuming that the ridgeline is place at 7'-0" above the ground, and the pitch of the tarp is ~30* a 6'-0" tall person laying at 15* to the ridgeline in the center of the hammock and the hammock centered on the tarp would be well under the overhead coverage of the tarp. However, if the lowest point of the hammock is ~30" above the ground, the ends are exposed at the sides. This is mitigated by lowering the ridgeline of the tarp. If the ridgeline of the tarp is at the same height as the ridgeline of the hammock (and at around 5'-0" from the ground), you will get adequate coverage from sideways blowing rain, but just barely. As mentioned, a UQP can and will provide more protection from rain. That's what its for. Its why its made of a water-resistant material. This should allow you to protect your hammock from sideways blowing rain if the tarp ridgeline is between 6'-0" and 5'-0" above the ground. What effect that may have on your personal weight preferences is up to you, but if you're going to carry a UQP anyway, the point is moot.

    This all assumes that wind and rain will be coming in parallel to the ground. IMHO, if the wind and rain are doing that, you've got more problems than just staying dry.

    I personally find that a tarp that low is uncomfortable to get around in. (But at 62 years old, any kind of bending over is uncomfortable.) But I think its safe to say that if you have experience in ground tarps, you'd likely find a tarp ridgeline 5 feet off the ground to be liberating.

    I should say that the geometric variations are almost infinite, and its difficult to get the assumed curvature of the hammock and the effects that a diagonal lay will have on its shape. Site selection is also going to have a lot to do with effectiveness and pitch.
    Sarge,

    This is what I was looking for! Thanks (and no offense to the peanut gallery).
    Yes, I already have a 10X10 tarp (actually about 9.8 X 9.8) - I love this tarp as a very versatile piece of kit, and I'd like to have one made in CF to the same (or smaller, if it can retain its versatility) shape, with copious tie-outs, so that I can maximize my flexibiity while minimizing weight (and of course, $$ output). It's a dl hammock (ccf under), and I use a JRB quilt for all outings including ground.

    So anyway, I was wondering about a diamond config for hanging, keeping the sq shape for going to ground. I think the 10X10, with a 14-foot diagonal, may be way too much ridgeline for an effective 9.x foot hammock, so maybe 9.5 - or just a small hop to an 8.5 (std width for HG tarps) square. That's where the 8.5 came from.

    So - assuming a 9' tarp, the ridgeline is just under 13'..... and ridgeline to corner is 6.5 feet (thereabouts). Hmmm....okay, divide 13 by 6.5, and you get 2. So, for every foot the hammock is away from ridgeline, I lose 2 feet of length coverage. Make sense? Okay, if that makes sense, then what's the hammock sag? Maybe 18 inches? Not quite? (I am not that heavy and don't use stretchy suspensions). So at 18 inches I lose 3 feet of horizontal coverage. So, losing 3 ft of horizontal coverage means my effective horizontal coverage is about 10 feet when I am in my hammock.

    Same Same for a 10' tarp. Sqrt 200 is about 14, which means 7' ridgeline to corner, and I still lose about 2 feet for every foot away from the ridgeline, but since I have a longer ridge, I have more room to sag, and an 18-inch sag will result in an effective horizontal coverage of 11 feet (!).

    So where's the flaw? Well, the flaw is the height of tarp hang (not really a flaw as such). If the tarp hangs at 5', and a 7' ridgeline to corner, then I will have a hang width of about 10' feet otal corner to corner. If I raise that to 6' hang, then I will have about a 6.x ' width hang.

    ......which leads me to believe a 10X10 square tarp will work well.


    ..... or not.

    Okay start firing your shots!
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  3. #23
    Senior Member Brancher's Avatar
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    Quote Originally Posted by nothermark View Post
    You might want to bear in mind that Hennessy gets away with a small tarp by attaching it to the hammock not a separate ridge line. That way it sags with you instead of letting you sag out from under it. All it takes is a couple of prussic loops on the tarp lines. ;-)
    Yeah, I did notice that. I used to have one (in a former life).
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  4. #24
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    Quote Originally Posted by Brancher View Post
    Sarge,

    This is what I was looking for! Thanks (and no offense to the peanut gallery).
    Yes, I already have a 10X10 tarp (actually about 9.8 X 9.8) - I love this tarp as a very versatile piece of kit, and I'd like to have one made in CF to the same (or smaller, if it can retain its versatility) shape, with copious tie-outs, so that I can maximize my flexibiity while minimizing weight (and of course, $$ output). It's a dl hammock (ccf under), and I use a JRB quilt for all outings including ground.

    So anyway, I was wondering about a diamond config for hanging, keeping the sq shape for going to ground. I think the 10X10, with a 14-foot diagonal, may be way too much ridgeline for an effective 9.x foot hammock, so maybe 9.5 - or just a small hop to an 8.5 (std width for HG tarps) square. That's where the 8.5 came from.

    So - assuming a 9' tarp, the ridgeline is just under 13'..... and ridgeline to corner is 6.5 feet (thereabouts). Hmmm....okay, divide 13 by 6.5, and you get 2. So, for every foot the hammock is away from ridgeline, I lose 2 feet of length coverage. Make sense? Okay, if that makes sense, then what's the hammock sag? Maybe 18 inches? Not quite? (I am not that heavy and don't use stretchy suspensions). So at 18 inches I lose 3 feet of horizontal coverage. So, losing 3 ft of horizontal coverage means my effective horizontal coverage is about 10 feet when I am in my hammock.

    Same Same for a 10' tarp. Sqrt 200 is about 14, which means 7' ridgeline to corner, and I still lose about 2 feet for every foot away from the ridgeline, but since I have a longer ridge, I have more room to sag, and an 18-inch sag will result in an effective horizontal coverage of 11 feet (!).

    So where's the flaw? Well, the flaw is the height of tarp hang (not really a flaw as such). If the tarp hangs at 5', and a 7' ridgeline to corner, then I will have a hang width of about 10' feet otal corner to corner. If I raise that to 6' hang, then I will have about a 6.x ' width hang.

    ......which leads me to believe a 10X10 square tarp will work well.


    ..... or not.

    Okay start firing your shots!
    I used your 8'-6" square dims and got a ridgeline of 12'-0 1/4" and used a +/- 33* pitch. This yielded a base dimension of 6'-7 1/2" point to point. I set the ridgeline ht at 7'-0" for the first go round, then reduced the RL height to 6'-0" then 5'-0". I don't have the ability to print to .jpeg on this system, otherwise I'd post the pics. At 5'-0" and a 33* pitch, the points of the tarp are on the ground.

    EDIT TO ADD:

    At lot will be affected by the distance between supports and the resulting deflection of the ridgelines which, given the elasticity of the materials used, can be considerable.

    Bottom line is that it can be done, but its not optimal for all conditions.

    There's a reason why everybody went to hex and rectangular tarps.

  5. #25
    Senior Member Brancher's Avatar
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    So if we substitute 9.5 in place of 8.5, we get about a 13.5 ridge - given sag characteristics, etc, that'probably as small as I'd want to go for this config. Of course, I also like the Hennessey idea of putting the tarp on the hammock ridgeline.....maximizes coverage and maintains same.
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  6. #26
    Senior Member lostagain's Avatar
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    I read this thread early enough in the morning that all this math gave me a headache.
    Remember...no matter where you go...there you are.

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  7. #27
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    Quote Originally Posted by lostagain View Post
    I read this thread early enough in the morning that all this math gave me a headache.
    Math?

    Heh.

    That's what Autocad is for.

    We do it with pitchers these days.

    Quote Originally Posted by Brancher View Post
    So if we substitute 9.5 in place of 8.5, we get about a 13.5 ridge - given sag characteristics, etc, that'probably as small as I'd want to go for this config. Of course, I also like the Hennessey idea of putting the tarp on the hammock ridgeline.....maximizes coverage and maintains same.
    Keep in mind that the longer you go, the higher the ridgeline or the shallower the pitch to keep the points off the ground. You'll reach a point of diminishing returns.

    I haven''t done a sketch using these new dims, but intuitively it would seem that you would get better coverage on the sides. If I get to a point where I can spare more time from drawing the steel for the new HEB in SE Houston, I'll sketch it out and get back.

  8. #28
    Member NM_Leo's Avatar
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    you know, anywhere else but here....you would be picked on for this tarp conversation, but here you are covered. ;-) Its always good to see there are others out there with my same affliction.

  9. #29
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    Quote Originally Posted by NM_Leo View Post
    you know, anywhere else but here....you would be picked on for this tarp conversation, but here you are covered. ;-) Its always good to see there are others out there with my same affliction.
    Yah, and it beats the heck out of "That sounds stupid, I wouldn't try it and you should do what I do." kind of post that shows up now and again.

    But as I said before, there's a reason why everybody went to hex or rectangular tarps. And there's a reason why UQP's have become popular in the past couple of years.

    No tarp gives 100% coverage (unless all sides go all the way to the ground) , and no tarp is adequate under all conditions. The UQP is designed to bridge those gaps where the inevitable will happen. Relying on it to insure coverage should not be used as a rationale to minimize your tarp coverage, IMO, but it can be factored in.

  10. #30
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    Quote Originally Posted by JasonACraft View Post
    I was, so tired. Last night. I missed this, last line. I was not mocking. Merely stating, there's some weight to your, point of view, that one must, take into consideration.

    Please read that in your best Shatner.
    That's a pretty good, imitation, of the Shatner cadence!
    "A foolish consistency is the hobgoblin of little minds." Ralph Waldo Emerson

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