Bridge Hammock

**lvleph** · 09-04-2007, 14:04

Well, I decided that with all this bridge hammock stuff, someone may like a catenary cut generator. I essentially just modified the one for the BlackCat.

I had to zip, otherwise the forum wouldn't allow me to upload.

**funbun** · 09-04-2007, 14:18

One of the problems with tie-outs I described earlier (in the post linked to above)---that there is less force on the lines when you're inside the hammock than when it is empty. This suggests that what one wants to do is to apply only enough force on the lines to allow you to get into the hammock, and then tighten up the lines while you're inside. The angles for this aren't so good if you're laying down, so some help is needed.

I don't understand. Less force on the tie outs? Why?

**funbun** · 09-04-2007, 14:49

Originally Posted by GrizzlyAdams

After a good night's sleep I saw that there's a trivial solution to the spreader-free bridge hammock flatness issue. Tie a length of Spyderline between the hammock corners at an end, with a length equal to the desired equivalent spreader bar separation. As the tie-outs are tightened, the pulling of the corners is limited by this length.

Ahh, i get it. So it serves as a ridgeline of sorts.

**GrizzlyAdams** · 09-04-2007, 14:49

Originally Posted by funbun

I don't understand. Less force on the tie outs? Why?

It's geometry. Think of the compression force like a big spring between the ends of the hammock. The farther apart are the ends, the more elongated the spring, and the larger the force it is pulling on the ends. Since the corners of the hammock aren't moving, the force on the tie-outs have to be pulling by exactly the same amount as the spring (as measured horizontally---this now gets into trigonometry).

So, when you are in the hammock the ends are closer together because your weight has pulled the center down; the "spring" is less compressed than when you aren't in the hammock.

If we had trees adjacent to the hammock to which we could attach the tie-outs higher than the hammock, the situation would be reversed. The force on the lines would increase, and this time come from your weight. It would be a bit problematic with the rain fly though...

Grizz

**GrizzlyAdams** · 09-04-2007, 14:50

Originally Posted by funbun

Ahh, i get it. So it serves as a ridgeline of sorts.

exactly.

I should add though that I mispoke. The length of the line will limit the distance between corners when you are not in the hammock. Get in and the corners will come together....how far?....depends on how much tension you've put on the lines. So tightening up from inside is still desirable. You could also tighten up the "ridgeline" to prevent the hammock rising as far when you get out.

Grizz

**schrochem** · 09-04-2007, 20:58

I mentioned it earlier in this thread (post #131

) about making a double hammock with a silk liner. I'm seriously considering this for a future version.
It would add a nice soft sleeping layer (like the claytor did with polyster) and another layer of protection from skeeters (so I might not have to use permithrin.

**GrizzlyAdams** · 09-04-2007, 21:26

Originally Posted by schrochem

I mentioned it earlier in this thread (post #131

) about making a double hammock with a silk liner. I'm seriously considering this for a future version.
It would add a nice soft sleeping layer (like the claytor did with polyster) and another layer of protection from skeeters (so I might not have to use permithrin.

Not sure if I'd joined the forums yet so far in the past as #131.

There's a 86" x 35" silk travel sheet for $58 at backcountry.com You could sew that into the inside of an existing hammock, it's the right size basically for your new rig (or my v0.1) and you don't spend $$ on silk up on the tall head and foot sides where it doesn't do any good.

I have a silk sleeping bag liner that I like. I've used it, a pad, a quilt and a bivy bag under a tarp back in my ground-huddling days.

Grizz

**dblhmmck** · 09-04-2007, 22:02

I mentioned it earlier in this thread (post #131 ) about making a double hammock with a silk liner. I'm seriously considering this for a future version.

Cool idea about the silk liner. In my suspension hammock that I posted pictures of a couple days ago, I used the "Fuzzy Stuff " from Stephensen's the makers of the down air mattresses. I t has an incredible feel to it- just kike a Marmot jacket that I had in the early 90's. The trouble with it as a liner was that it didn't stretch as much as the nylon under it. I sewed in billow expansion panels, but at a weight cost of around 7 ounces total. I thought about silk too, but I was advised against it due to lack of durability. However, I think the "Cool Max" type synthetic liner would be excellent.

What I am currently using for my "hammock in progres"s is from owfinc.com it's a wickaway fabric that feels like my UnderArmour T-shirt. It is much more stretchy, lighter weight, but not windproof like the "Fuzzy Stuff". So I will still use the latter on the hood area/ head box closure.

I am very interested in your double hammock ideas, it is something I am trying to figure out also (my unpronouncable online name actually hints at this).

**warbonnetguy** · 09-04-2007, 22:03

hey guys, finally made one yesterday.

i decided to make the head and foot different lengths. i gave the head end a curve cut too to better facilitate a end pocket.

i wanted to use 1/2 flat weave nylon.(the lightest webbing used so far i think). i only had enough for one side so i used 1" strapworks poly on the other side. the nylon seems strong enough, but that side stretched signifigantly more than the poly side and i had to compensate by tightening the suspension ropes on the nylon side.

i did not even use the ridgeline. i had lots of sag at first, then tightened the suspension alot to decrease the sag, but still could not get an inverse banna without the ridgeline no matter how hard i tried. i could only get flat if i used short spreaders, creating too much squeeze.

i found i had to really spread the head end alot to get the shoulder squeeze to an acceptable point. i even spread the head end as far as the fabric would allow. this made it quite comfy. when in full spread mode, the webbing seemed like it was under no more force than with a shorter spread, the spreader bar however is under lots more force under full spread. i could see the pole bend quite alot, this is a pretty beefy segmented aluminum pole (15/16" diameter)

i also noticed that with the head end spread far enough to reduce shoulder squeeze to an acceptable point, it simultaneously raised the head end up making a flat lay impossible.

i am thinking a sharper curve cut would raise my lower torso more in relation to the ends?

the slits in the fabric are an idea that was touched on a few weeks ago about how side to side cuts will be structurally sound. the idea was to use slits for my knees to poke out in the fetal position, but the webbing is too low, and i can barely get one knee under it, much less both. if the sides were higher it might work fine. seems structurally sound though, although there is enough end to end force to pull them open a bit when weighted.