Page 2 of 4 FirstFirst 1234 LastLast
Results 11 to 20 of 33
  1. #11
    Senior Member schrochem's Avatar
    Join Date
    Jun 2007
    Location
    Austin,Tx
    Posts
    796
    Images
    57
    Quote Originally Posted by GrizzlyAdams View Post
    I worked up another figure before you posted, will share anyway.

    I wondered if when you split the spreader after shortening the length of the line from spreader to suspension rings, you were trying to lower the ridgeline. The diagram in the attachment explains how you could control the length of the ridgeline independently of the suspension. This is looking at the hammock from above. Rather than have two ridgelines from spreader bar end to spreader bar end, you make those connections but then run them to a center line. The forces on the ridgeline (recall TeeDee's analysis) aren't that large. With strong cord you could tie knots and avoid the added weight of more rings. This in turn lets you extend the length of the lines from spreader to suspension rings all the way to the tree if you like, just using enough webbing around the tree to let you tighten things up comfortably. The long lines here reduce the compression force on your spreader----which might be of interest if that spreader is your hiking pole and you didn't remember to bring a spare

    of course, you guys have the real deals to play with, and all I've got is powerpoint. Have at it, and don't mind the peanut gallery.

    Grizz
    Oh that's interesting!
    No idea if it will work though. I 'll see if I can try it out.
    Scott

    "Man is a stream whose source is hidden."
    RWE

  2. #12
    GrizzlyAdams's Avatar
    Join Date
    Apr 2007
    Location
    Illinois
    Hammock
    DIY Bridge, v0.n, where n is large
    Tarp
    depends on season
    Insulation
    DIY UQ
    Posts
    4,628
    Images
    564

    no free lunch

    To the above I neglected to see that placing the ridgeline this way induces its own compression force on the spreader bar. I've been scribbling around with the formula to determine conditions under which the total compression can be less using long suspension lines and a lowered centered ridgeline, but it is more technical than interesting.

    Using a back of the envelope estimate, if the triangle formed on the interior with the centered ridgeline is identical to the triangle formed by the spreader and suspension lines, then we've added a compression force equal to that induced by the triangle formed by spreader and suspension lines.

    If the interior ridge line was just two triangles whose apex's meet in the middle, then the added compression is (assuming 36" spreader and 80" hammock length) is about 0.2*W for an occupant lying down, twice that for someone sitting on the end.

    You can still reduce the compression due to the suspension lines and rings by lengthening that edge. And you can get overall less compression if you are able to extend those lines a long ways, but that has its own problems.

    I should have coffee before trying to do analysis in the morning.

    Grizz
    Last edited by GrizzlyAdams; 07-05-2007 at 08:22.

  3. #13
    Senior Member
    Join Date
    Apr 2007
    Location
    Honduras
    Hammock
    Warbonnet Black Bird
    Tarp
    BWDD Winterdream
    Insulation
    Speer Snugfit
    Posts
    912
    Images
    14
    Even skipping every 3rd or so word, reading Griz makes my head hurt.

    Purdue AS/EET But it's been awhile. Engineers design on paper, us techs put it together and make it work. Now I remember why I'm a tech...
    Bad spellers of the world Untie!

  4. #14
    GrizzlyAdams's Avatar
    Join Date
    Apr 2007
    Location
    Illinois
    Hammock
    DIY Bridge, v0.n, where n is large
    Tarp
    depends on season
    Insulation
    DIY UQ
    Posts
    4,628
    Images
    564

    nothing to lose but your chains

    Quote Originally Posted by Shadowmoss View Post
    Even skipping every 3rd or so word, reading Griz makes my head hurt.

    Purdue AS/EET But it's been awhile. Engineers design on paper, us techs put it together and make it work. Now I remember why I'm a tech...
    A guy I know had an academic paper returned from review once, complaining about the wordiness, that recommended he remove every other word, then every other line. I tend to wordiness too, although I understand that isn't what you're talking about.

    But, I'll have you know I'm joining the tech union. I'm just back from Wally World where I scored 10 yards of ripstop nylon out of the $1 bin. Soon I'll be poking holes in my fingers with needles along with the rest of you.

    joining the proletariat,
    Grizz

  5. #15
    poncho's are sil. the outermost layer should protect from wind as well as windblown rain especially if there is down or synthetic under the hammock. it seems that loose sil under the hammock might not have the condensation problems you are affraid of. consider a sil shell that hangs so that there is a couple of inches of air gap between it and the bottom of the hammock. this provides more insul. like jeff said, but also gives room for body vapor to evaporate into, and assuming the thing is not sealed around the edges, that vapor wouldn't necesssairly be trapped. in fact when wind blows, it would even act as a bellows and force said air out of the system, but would still protect from direct wind gusts and windblown rain. just something to consider. also, for that matter, since it is open on top unlike the garlington insulator full hammock sac thing, any body vapor inside the loose sil undercover could just come back through the breathable hammock body anywhere there is not a bodypart laying there to stop it, and could escape through the breathable hammock fabric also, this is how heat escapes when there are large air pockets in an underquit, the air pockets don't have to go all the way to the side of the quilt, they just have to be large enough to lead out from under the edge of your body/sleeping bag and will then release air through the hammock itself and into the sleeping area where its gone forever. if the sil shell hangs loose what would keep body vapor from evaporating back through the breathable hammock?



    Quote Originally Posted by schrochem View Post
    I agree. I had just recalled my layering of clothes and thought....noone really uses silnylon as an outer shell.....

  6. #16
    Senior Member schrochem's Avatar
    Join Date
    Jun 2007
    Location
    Austin,Tx
    Posts
    796
    Images
    57
    Quote Originally Posted by GrizzlyAdams View Post
    But, I'll have you know I'm joining the tech union. I'm just back from Wally World where I scored 10 yards of ripstop nylon out of the $1 bin. Soon I'll be poking holes in my fingers with needles along with the rest of you.

    joining the proletariat,
    Grizz

    Cool, it will be interesting to see what you come up with.
    I still don't have a solution for the spreaders yet....
    Scott

    "Man is a stream whose source is hidden."
    RWE

  7. #17
    Senior Member schrochem's Avatar
    Join Date
    Jun 2007
    Location
    Austin,Tx
    Posts
    796
    Images
    57
    Quote Originally Posted by warbonnetguy View Post
    poncho's are sil. the outermost layer should protect from wind as well as windblown rain especially if there is down or synthetic under the hammock. it seems that loose sil under the hammock might not have the condensation problems you are affraid of. consider a sil shell that hangs so that there is a couple of inches of air gap between it and the bottom of the hammock. this provides more insul. like jeff said, but also gives room for body vapor to evaporate into, and assuming the thing is not sealed around the edges, that vapor wouldn't necesssairly be trapped. in fact when wind blows, it would even act as a bellows and force said air out of the system, but would still protect from direct wind gusts and windblown rain. just something to consider. also, for that matter, since it is open on top unlike the garlington insulator full hammock sac thing, any body vapor inside the loose sil undercover could just come back through the breathable hammock body anywhere there is not a bodypart laying there to stop it, and could escape through the breathable hammock fabric also, this is how heat escapes when there are large air pockets in an underquit, the air pockets don't have to go all the way to the side of the quilt, they just have to be large enough to lead out from under the edge of your body/sleeping bag and will then release air through the hammock itself and into the sleeping area where its gone forever. if the sil shell hangs loose what would keep body vapor from evaporating back through the breathable hammock?
    Good points. I was thinking about the packa also. With the large pit zips and roomy fit, air is allowed to move around.
    I'll admit I haven't a clue as to what combinations might be beneficial, so your thoughts were helpful.
    Scott

    "Man is a stream whose source is hidden."
    RWE

  8. #18
    Senior Member TeeDee's Avatar
    Join Date
    Jan 2007
    Location
    Maryland
    Hammock
    DIY Bridge
    Tarp
    DIY 10'x11'
    Suspension
    Whoopie Slings
    Posts
    1,631
    Images
    300
    Quote Originally Posted by GrizzlyAdams View Post
    Scott--that's clever.
    I've been looking at the pictures you and TeeDee posted, and I get the impression that the ridgeline is mighty high relative to the prone occupant. Doesn't look like lying on your back you can reach up and touch it.
    Grizz
    Grizz - with the suspension line lengths I have, the compression forces on the spreader bars can be handled by my treking poles and when I reach up, flat on my back, the ridge line touches my fingers right across the first knuckle. If I raise my torso even slightly, I can easily hook and unhook micro carabiners to/from the ridge line.

    So handling "controls" on the ridge line is really no problem.

  9. #19
    Senior Member TeeDee's Avatar
    Join Date
    Jan 2007
    Location
    Maryland
    Hammock
    DIY Bridge
    Tarp
    DIY 10'x11'
    Suspension
    Whoopie Slings
    Posts
    1,631
    Images
    300
    This is brilliant idea.

    I can already see where I could take some 1.1 oz DWR ripstop, shape it for an undercover in this manner, sew my GG thin light pads to the ripstop exactly where I want them. The pads can then be lowered or raised into position and they stay exactly where needed. Better than the Speer SPE.

    The same with under quilts.

    Brilliant.

  10. #20
    Senior Member TeeDee's Avatar
    Join Date
    Jan 2007
    Location
    Maryland
    Hammock
    DIY Bridge
    Tarp
    DIY 10'x11'
    Suspension
    Whoopie Slings
    Posts
    1,631
    Images
    300
    Quote Originally Posted by GrizzlyAdams View Post
    I worked up another figure before you posted, will share anyway.

    I wondered if when you split the spreader after shortening the length of the line from spreader to suspension rings, you were trying to lower the ridgeline. The diagram in the attachment explains how you could control the length of the ridgeline independently of the suspension. This is looking at the hammock from above. Rather than have two ridgelines from spreader bar end to spreader bar end, you make those connections but then run them to a center line. The forces on the ridgeline (recall TeeDee's analysis) aren't that large. With strong cord you could tie knots and avoid the added weight of more rings. This in turn lets you extend the length of the lines from spreader to suspension rings all the way to the tree if you like, just using enough webbing around the tree to let you tighten things up comfortably. The long lines here reduce the compression force on your spreader----which might be of interest if that spreader is your hiking pole and you didn't remember to bring a spare

    of course, you guys have the real deals to play with, and all I've got is powerpoint. Have at it, and don't mind the peanut gallery.

    Grizz
    I would not recommend running a ridge line connected to the spreader bars for te simple reason of convenience. One of the things I really didn't like about my HH ULBA was that the ridge line is ALWAYS in the way. I don't know how many times I have attempted to slice one of my ears off on that ridge line. That is one of the reasons the HH Safari is so much better - the ridge line is about finger tip height above me when laying in the Safari.

    That is also one of the things I really love about the Bridge Hammock - you can adjust the height of the ridge line.

    If you tie the ridge line to the spreader bars in any manner, then the ridge line is lowered to a position that you are going to be: (pick one or all) 1. slicing off an ear, 2. hanging yourself, 3. decapitating yourself, 4. always annoyed with the irritating string that always in your way.

    Ideally you want that ridge line fairly high and out of the way, but reachable. I've got that with my suspension line lengths.
    Last edited by TeeDee; 07-05-2007 at 19:50.

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •