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  1. #1
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    Howdy! And, here's my attempt at a bridge hammock for your critique!

    Hi all! I'm Scott from North Carolina.

    A couple of weeks ago I decided to go down the bridge hammock rabbit hole and some googlin led me here.

    I've been a backpacker and maker forever and a gathered hammock lounger for years, but I'm a side and stomach sleeper so, while I've hammock camped quite a bit, I've never slept great in a gathered end hammock. A few years ago, I made a hammock with RBTR XL fabric, full width, and a short ridgeline and it's great for naps, but not full nights. Ergo, most of my camping has been on the ground.

    Being a hermit and (mostly) solo backpacker, I've never been within 15 feet of a bridge hammock, but the idea that one could give a flat lay for stomach sleeping is intriguing. I decided I'd buy one and try it out. I looked around at the models out there for sale, compared photos I could find of the hang position and weight and whatnot. I was really surprised that there seem to be so few commercially available models that look to give a really flay lay and don't weigh a ton. Most of them just seem like an alternative for back sleepers with an occasional roll to the side. When I did find one that looked really promising, it's sold out. :-(

    So, I guess I'll just have to make one. I had collected some pictures from the web of promising ideas, so I commenced to building models.

    Proto Model 1.3.jpg

    After 6 or 8 scale models models led me through bad ideas, worse ideas and a couple good ones, I decided it was time for a full scale prototype.

    IMG_0750.jpg

    Results, I think, are pretty good. Though, admittedly, I have no experience with other bridges to compare. I haven't had a chance to sleep in it, but it seems to lay pretty flat and comfy. 1.6 HyperD from RBTR, 1/2" MuleTape, 3/4 wood dowels from Ace Hdwr.

    Whaddaya think?

  2. #2
    Senior Member WV's Avatar
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    I think it looks great, Scott. I like that side profile. What are the fabric dimensions? Hope you'll find it comfortable all night long. Even if the first night's not perfect, practice and tweak. Nice model, too.

  3. #3
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    Thanks, WV! I didn't read much on the forum before I did this build, but I've seen your name pop up a lot in my reading since. Appreciate the feedback.

    The hammock body is 8.5' long, 4.5' wide at the bars, 3' wide in the middle. The spreaders are 36". Through the models, I came up with a shape that isn't like anything I've seen in my research before or since. The side curves aren't catenary or parabolic or hyperbolic or any of those other big words. They're just somethin I drawed freehand for a model and it worked, so scaled it up for for proto. Seems to lay pretty well, though. I've seen a little extra fabric stress I'm going to address with the next prototype, but its ok I think.
    Last edited by justaboutso; 10-13-2020 at 12:35.

  4. #4
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    Update: Got a pretty darn good night's sleep in the thing last night, about half on my side and half on my stomach, I figure. The fabric may be a bit wide over all. There was a little bit of squeeze flat on my stomach and when I rolled onto my back for a bit. And it really is longer than it needs to be. So, I think I'll shrink the next one a few inches in all dimensions. I don't want to go too much smaller in width, because I also think I'm going to try lighter fabric and I don't want to increase stresses too much. I got my easton spreader bars from Quest and was a little dismayed to find they're over an ounce heavier than my wood dowels. :-(

    Test hang video from the other day:

    Laying on my back, then side, then stomach

    IMG_4510.jpg
    IMG_4511.jpg
    IMG_4512.jpg

  5. #5
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    Hi all!

    I've finished and tested my second prototype for a few nights and, while it's super comfy, I think there might be long-term durability issues. :-)

    Specs-
    1.0oz HyperD from RBTR
    DynaGlide in channel suspension
    Spiced-in eyes for bar end spikes
    Body is 96" x 50" at the widest point and reshaped a bit from Proto 1 to take out a couple of stress points
    131 grams - hammock body and suspension out to and including the dog bones


    IMG_4521.jpg

    IMG_4525.jpg



    The issue I'm having isn't surprising - stitch elongation on the edge channels near the center of the span. While failure of the fabric doesn't seem imminent, I also wouldn't be surprised if it dumped me on the ground. And I'm not going to be bouncing around in it or inviting a companion. I'm 180lbs or so. OK, maybe 185.

    Can anyone tell me if there's a fabric in the 1.0-1.3 oz category that's significantly more resistant to stitch elongation than the HyperD? Hexon? MTN Hybrid?

    Additional note - while I'm not a seasoned seamstress, I have made several things with light fabric. But, geez, this was NOT easy. Sewing 3/8" rolled hems around curves, on 1 ounce fabric, is for the birds.
    Last edited by justaboutso; 11-30-2020 at 13:31. Reason: Edited to add my weight

  6. #6
    Senior Member WV's Avatar
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    Video looks good. Back level, legs elevated, but knees not hyperextended. I predict you'll find it most comfortable with a pillow for your head and neck - try different sizes. About the stitch elongation - the dynaglide should be taking all the lengthwise force, rather than the fabric. I make the channels up to an inch longer than the tendons inside them for that reason. There's still transverse tension and diagonal tension on the fabric, so you may be right about 1.0 oz. fabric being too light. I've had 1.6 oz suddenly fail after 50+ nights. (I probably leaned on one elbow when starting to get up.) I reinforce the stress points in the channel with polyester blanket binding. On my PBHs, that's the four corners (about 8" along the side from the corner) and at the knee angle (about 4"). With your curved edges you could gauge where to reinforce the edges by looking at the stitch elongation. Keep up the good work!

  7. #7
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    Quote Originally Posted by justaboutso View Post
    Hi all!

    I've finished and tested my second prototype for a few nights and, while it's super comfy, I think there might be long-term durability issues. :-)

    Specs-
    1.0oz HyperD from RBTR
    DynaGlide in channel suspension
    Spiced-in eyes for bar end spikes
    Body is 96" x 50" at the widest point and reshaped a bit from Proto 1 to take out a couple of stress points
    131 grams - hammock body and suspension out to and including the dog bones


    IMG_4521.jpg

    IMG_4525.jpg



    The issue I'm having isn't surprising - stitch elongation on the edge channels near the center of the span. While failure of the fabric doesn't seem imminent, I also wouldn't be surprised if it dumped me on the ground. And I'm not going to be bouncing around in it or inviting a companion. I'm 180lbs or so. OK, maybe 185.

    Can anyone tell me if there's a fabric in the 1.0-1.3 oz category that's significantly more resistant to stitch elongation than the HyperD? Hexon? MTN Hybrid?

    Additional note - while I'm not a seasoned seamstress, I have made several things with light fabric. But, geez, this was NOT easy. Sewing 3/8" rolled hems around curves, on 1 ounce fabric, is for the birds.
    Great Start!

    On your issues:
    Mountain Hybrid 1.2 is your next step up, and the fabric I use for my lighter bridges. I have worked with 1 ounce fabrics but will no longer do so (for now). The 1/4 ounce or so difference isn't worth it as you can easily 'spend' that savings on reinforcement to the lighter fabric and end up heavier than you would have simply bumping up.

    Hyper D 1.6 or Hexon 1.6 work fine, but I prefer the hybrid 1.7 in that weight. This is probably a better fabric to use to work out your design as it will forgive some issues/weaknesses.

    Finally- the Hybrid is much easier to work with/sew than the softer Hyper D. The Hexon doesn't quite split the difference on workability. More like a third better than HyperD to sew, with the Hybrid being 100% better.

    On your design:
    In the pictures there is a clear 'flat spot' in the center. While this is potentially comfy for you, by not having a smoother curve you are creating high stress at those points and the fabric in between.
    Likely your end fabric width is too large (wide) and you hand smoothed the curve out to compensate.


    It is very obvious in your unloaded pictures, but still visible in your loaded picture.
    While the mathemagical name of the curve isn't that important or even always accurate (unless you're Grizz)- what does matter is clean lines.

    Basically- you've got too much 'pickup' in the butt area. This portion of the hammock is taking load differently than the rest of the fabric and it's not transferring your weight smoothly along the curve.

    All that said- if you like the lay- simply rebuild with Hybrid 1.7 and see where you are at.
    The extra weight capacity of the fabric may be enough to overcome the design shortcoming and balance out on the durability.

    Don't be too discouraged... if you don't screw up your first five then you aren't trying something new, lol!

  8. #8
    Senior Member kayak4water's Avatar
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    Rather late to this party, but I've been curious about how others have designed their bridges. Mine was modeled after a DIY pattern on this forum (Hikingdad might have been former pen name--not sure of current name)

    Your design is beautiful and simple and the second version weighted seems to be a truly flat lay. Very nice. Pat yourself on the back. Thank you for the DIY inspiration to modify my own.

    Cheers

  9. #9
    Senior Member stevebo's Avatar
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    Nice job on your hammock!
    FYI: If you want to know what type a certain bear is, sneak up behind it and kick it. Then,
    run like crazy and climb up a tree. If the bear climbs the tree and eats you, it's a black
    bear. If the bear just pushes the tree over and eats you, it's a grizzly bear : )


    Do not walk behind me, for I may not lead. Do not walk ahead of me, for I may not follow. Do not walk beside me, either, just leave me alone.
    --unknown

  10. #10
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    Thanks, everybody for looking and giving your feedback.

    WV- Yeah, after a couple of more nights on the 1.0 HyperD proto, the stitch elongation is getting worrisome.

    Exhibit A:
    Stitch Elongation.JPG

    All 4.6 ounces of that one is getting ready to be retired to the "stupid-light" archives. I will miss it, it sleeps gooood. Surprisingly, I don't have any signs of wear/stress in any of my reinforced areas (pole insert points and corners where the dynaglide exits). I reinforced those the way I do all "ultra" light fabric reinforcements, 1 additional layer of the same fabric, bonded with seamgrip or similar and pressed. No stitching.


    Just Bill - Thanks for chiming in with your first hand info on the fabrics and how they work in a bridge hammock. And how they sew. I'm definitely gonna go with the Hybrid on the next attempt, don't know for sure 1.2 or 1.7. I'm really glad to hear the Hybrid sews a lot easier, too. What a pain was that 1.0!

    I am gonna smooth out the midsection curves some to reduce the stresses near the middle. I really don't want to reduce the butt lift, because it lays so well, but I would like to take a bit of the stress out. Observation of the fabric when weighted doesn't show the direct high stress vectors there like you can get around the rigid structural element provided by the poles, but it is increased somewhat in those spots, although spread out a little by conformation of the dynaglide.

    Thanks, too, for the pics, videos and other content you have available. Your designs provided inspiration. If they'd been available before I started down this rabbit hole, I would've just bought one of yours.

    kayak4water - both these are simple designs and the first one was dead-simple to make. I could probably make another in 1 hour if I had to. But, the muletape (while I think it's perfect for this application) rolled into the hem is heavy, adding nearly 4 ounces over the dynaglide. The second doesn't really lay any flatter than the first (that's just a heavy blanket laying in it, not an actual person) but when in them they both *feel* as flat as I could ever ask for. Very comfy on my stomach. But, I'm thinking the reduced stretch of the Hybrid fabric will flatten things out even more.

    I'm close to ready to build #3, which I hope will be Goldilocks. I've written a spreadsheet to compare weights of different fabrics and poles as they would apply to this design, in order to decide my exact course of action, and I've got 3 scenarios I'm kicking around:

    1) Completely bomb-proof, can loan it to my hefty friends or just use it into the next decade without ever worrying about an issue - 1.7 Hybrid, Amsteel in channel, Easton Alum poles - should work out to 475 grams or 16.7 ounces

    2) Maybe not bomb-proof, but certainly strong enough to last with my 185lbs, used with respect and not abused - 1.7 Hybrid, Dynaglide in channel, DIY Carbon poles (thanks cmoulder!) 18mmOD/16mmID - 390g or 13.8oz

    3) SHOULD be strong enough, handled with care, but who really knows until I build it - 1.2 Hybrid, Dynaglide, DIY Carbon poles 15mmOD/13mmID - 318 g or 11.2oz


    These DIY pole calculations are based on the 16mm OD poles cmoulder built to 3.6 ounce spec, but with double the wall thickness, so the 15mm should be strong enough for me, and the 18mm should be overkill.

    Thanks again for the encouragement, and I'll follow up with progress as it comes.



    Scott


    Gonna miss this little guy. . .

    IMG_4642.jpg
    Last edited by justaboutso; 12-16-2020 at 12:52.

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