Down Hammock Design

[Youngblood]

But when looking at a separate UQ vs. a down hammock, another factor might be versatility. You would save several oz of weight for one layer of fabric. But then- at least with that hammock, you would always be stuck with the full weight of an UQ, and maybe a winter weight one. Though I suppose that would only be a concern in the actual summer heat, since many people carry an UQ at least most of the year, if not always.

If you assume all things are equal and all the design issues are resolved, then there are 2 sides to this. A truly insulated hammock isn't capable of being vented during times where you might want to do that... but it won't vent on you during times where you don't want it to do that. There are no issues of sealing it around the edges.

[BillyBob58]

If you assume all things are equal and all the design issues are resolved, then there are 2 sides to this. A truly insulated hammock isn't capable of being vented during times where you might want to do that... but it won't vent on you during times where you don't want it to do that. There are no issues of sealing it around the edges.

Now that brings up an additional question. What about being sealed on the sides? How much of a factor is that?

Please see new thread on this subject.

http://www.hammockforums.net/forum/s...1078#post91078

[Just Jeff]

Hammocks are easy to make. I don't use my insulated one in the summer, just like I don't take a winter quilt in the summer. Gotta pick the right tool for the job.

Bridge hammocks require more effort than a normal gathered end hammock, but still - if the weight savings and convenience are worth the effort of making another hammock more suitable for warmer temps (i.e., able to be vented as Youngblood says), then go for it!

Just realize its limitations and make sure you're not expecting this to be a year-round piece of gear.

[warbonnetguy]

i'd think a 3 season thickness would be a good choice. one option, don't know if dbl hammock was talking about this or not as i read quick, but it go me thinking. if you wanted to do baffles, you could do a double layer bridge out of lighter fabric, say 2 layers of 1.1, that would give you 2.2oz of fabric which would be close to your 2.5 oz supplex or whatever you were planning on using. baffles would be on the outside layer, so you wouldn't be laying on their seams, and you'd have a pad pocket for supplementing in colder temps, which might even make it reasonable to use less down thickness.

[Just Jeff]

I tried adding a second layer to my first version, so it was basically two layers of 1.1 with the undercover sewn to the layer I wasn't laying on. I got gaps between the layers along the sides of my legs. I didn't bother trouble-shooting it since I was already planning to make v2.

[I Splice]

...

While this is interesting and different and in no way would I discourage you from trying it out if you like, I'll just point out that extra effort doesn't save you a great deal of weight. With a bridge hammock a full length UQ needn't be more than 36-38 inches wide. Let's say 72 inches long. That's 2.11 sq yards. If you used DWR 30 denier ripstop, at say a real 1.2 oz/sq yd, the piece of fabric you're saving is 2.5 oz. Half that if you were to go the 1/2 UQ route.

The advantages of a built-in quilt include no shifting around...but hanging a separated UQ from the corners has been quite stable in my experience. In fact, in one model I suspended the quilt from the sides of the hammock from a seam; this actually is the preferred method for tensioning the UQ (and is something you get for free from the built-in approach).

You know the drill around here..if you build it, you gotta show us pictures! Good luck.

Grizz

If this ever gets built, I'll definitely provide pictures. That's a good point about the weight savings. Though saving 2.5 ounces is still 71 grams that I don't have to carry. A gram here and a gram there a pretty soon you're carrying an extra pound.

I suppose that I could use momentum or even noseeum mesh to trim the weight difference even more. (Has anyone built a down-filled article with exposed noseeum mesh?)

I was surprised by your suggestion of only needing 36 to 38 inches of width for an underquilt but I measured my shoulders and 36 inches will go around my back and will stick up about 2 inches on each side. I'll have to think about the implications of that.

I think I'll want at least my height plus 2 inches for the length, that gives me at least 76 inches for the length. The partial underquilts just look cold to me. If I were to add down filled bulkheads (end caps), I'd probably want a little more length.

BTW, most of my camping is during the spring and fall with just a little during summer and winter. It doesn't get very cold for my spring and fall trips, 30° F is cold for us.

The hopefully reduced fiddle factor in setting up an insulated hammock would be a plus. OTOH, the lack of flexibility would be a negative.

[I Splice]

...

On the other hand, that extra layer of fabric when used on the hammock body would allow a lighter fabric to be used on the under-quilt (if that quilt were sepparate). Then our net weight savings may be closer to 4 ounces. The extra layer also gives the option of using different insulations in different weather conditions.

That layer also adds strength. I would have also some concerns about forces when entering or exiting the hammock causing tears in the baffle material, if the hammock body was also the quilt shell. But this is only a guess.

I can tell you what has worked for me. Bridge hammocks with inflated pads can virtually eliminate contact with the hammock walls above the pad. They do it by widening the bottom and lifting the occupant, and giving the most comfortable hammock experience imaginable. At least this is true with my 26" wide WarmLite DAM. My POE AO-Lite (at 19 ounces and 20" width) gives the flattest lay with pad fully inflated. Although, in cold weather, a CCF pad needs to be added to it wide enough to insulate the shoulders. Anyway, that is how I see the alternative to a down quilt, for bottom insulation on a bridge hammock.

But to answer your question, in my own humble opinion, I would say make the hammock and quilt sepparate.

I haven't used my inflatable pad, a Big Agnes insulated, in a hammock for quite a while. I don't remember why I don't use it anymore, but I use a closed cell foam pad all of the time. It sounds like you're using your DAM as a bottom spreader.

I don't understand what you mean when you say ".. would allow a lighter fabric to be used ..." and the part about adding strength. It's hard to get lighter than a zero oz per yard (i.e. no fabric).

That's an interesting point about the baffles having to be strong enough or resilient enough. Does anyone have a data point on baffles that are too weak? The only thing that I can think of is some cautions to be careful not to overstress the baffles when washing a down sleeping bag but most of the instructions I've seen just ignore the issue.

It might be that a separate quilt is just better ... but a down insulated sleeping bag is just so cool

[I Splice]

Your torso will stretch the hammock body differently than your legs, so you'll need to shape the undercover to account for this or else you'll have less loft there. This would mean having a head and foot end.

I chose to not sew baffles directly to the hammock body for two reasons. First, I didn't like laying on the baffles...with the friction of moving around I thought I'd wear thru them quickly. Second, it minimized the number of holes I had to put into the hammock body...a seam is just like a perforated line...the kind designed to rip stuff! It can work, and my second version hasn't shown signs of failure, but it's definitely something to minimize.

So...if you want baffles, and they may be needed for a full-length version, I'd sew them only to the undercover and not to the hammock body. Basically, make a tube on all for edges with a big compartment in the middle. The tubes will keep the down up near the edges, and the big compartment doesn't need a baffle b/c the down will settle to that area anyway. BUT...this further decreases the weight you're saving.

I'm a fan of the down hammock and it saved me quite a bit of weight for the gathered end version. Not sure the weight savings would be worth it for a bridge hammock, though..it's worth doing the math on, though!

Be sure to post pics of whatever you choose!

So, if I understand correctly, you're suggesting that the baffles need to be decoupled from the hammock body so that the hammock body can stretch independently of the insulated volume. One approach would be to use noseeum or (maybe mosquito mesh if it's lighter) to cover the hammock body and then attach the baffles to the mesh. Effectively, it would be a permanently attached underquilt with one side made mesh. If that's necessary, maybe a quilt made of momentum would be better. I could also us "U" shaped or "L" shaped (i.e. "LLLLL") baffles to get the same effect.

You mentioned another idea, that I may not understand. That is to use some down-filled baffles (say down-filled noseeum mesh tubes) at fairly wide intervals to hold the bottom layer of fabric the right distance from the top layer. The top of each tube would be stitched to the hammock body and the bottom of the tube would be stitched to the bottom cover. That might make the baffles resilient enough to handle the stretching of hammock body.

I wonder if baffles on an angle other than straight down would provide a loose enough connection?

I saw your comment about not lying directly on the baffles but I can't quite visualize the problem. Why are the baffles different. If the stitching looked like it was under stress, I could use some seam sealer to reinforce it.

I appreciate everyone's comments on my crazy ideas. If we can come up with a design that makes sense, I'll be really happy.

[I Splice]

I tried adding a second layer to my first version, so it was basically two layers of 1.1 with the undercover sewn to the layer I wasn't laying on. I got gaps between the layers along the sides of my legs. I didn't bother trouble-shooting it since I was already planning to make v2.

It seems to me that with my lack of precision sewing skills, it would be hard to get both layers of fabric to lay so that each layer was taking some load. Maybe a temporary glue (starch?) to hold them together during fabrication?

[dblhmmck]

It might be that a separate quilt is just better ... but a down insulated sleeping bag is just so cool

Yes! I hope you do it.

I haven't used my inflatable pad, a Big Agnes insulated, in a hammock for quite a while. I don't remember why I don't use it anymore, but I use a closed cell foam pad all of the time. It sounds like you're using your DAM as a bottom spreader.

You probably don't use the inflatable pad because it doesn't stay put in most gathered end hammocks. But yes, I use the DAM as a bottom spreader. I have only spent two nights with this configuration, so I don't know about durability/longevity. However, on the Cuban hammock thread Gardenville was recently talking about his long time use of the WarmLite. And the company says they can be used for emergency flotation devices, they appear very durable.


My hiking temp ranges are usually not much colder than what you state. Inflatable pads in a bridge seem to go a long way in reducing the cold spots that come with gathered end hammocks that drape around more of the body. I don't inflate the DAM all the way. So it's not as firm as the POE, but the DAM presses out as the body sinks in. It conforms to any hollows brings the insulation up around the occupant in a very efficient way. I should mention the bridge hammocks that I make have wider head spreader bars than manufactured bridge hammocks such as the BMBH. I also use a DIY hammock with a JRB BMBH head spreader bar, but it has a wider spread than other bridges due to reattaching panels and cords at the side (shown here)

But regardless of all of that, you may want to think more about the width of the bottom insulation (as I see you are from another reply).

I don't understand what you mean when you say ".. would allow a lighter fabric to be used ..." and the part about adding strength. It's hard to get lighter than a zero oz per yard (i.e. no fabric).

Sorry to be vague. I meant using 2 lighter layers of fabric giving you the strength of your one heavier layer, and in that way still meeting your wieght requirements for the hammock. Warbonnet does this with his hammocks.