Hooray!

[GreatDivide14]

The Hennessy underquilt is complete, and it seems to work pretty well. I based the design largely on <A HREF=http://www.thru-hiker.com/workshop.asp?subcat=5&cid=72>Dennis Klinsky's original.</A> I made a few changes, most notably that I used P3D instead of down. The quilt uses two layers of 3-ounce insulation for a total thickness of about 2 inches, quite a bit thicker than Klinsky's, albeit considerably heavier. (Lacking access to a scale, I don't know how much it weighs, but I'm estimating that it's close to a pound, and not a whole lot heavier than my 3/4 length Thermarest.) Pictures and more details follow.

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Here's the whole thing in action. The odd green thing along the ridgeline is a line level that helps angle the thing on steep ground.

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The liner is 1.1 oz white silnylon, waterproof for wind and sweat, white for reflectivity. Some of that might actually be useful, but I'm not sure. The shell is 1.1 oz breatheable black ripstop, black to absorb solar heat for fast drying.

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Detail of the end attachments. The guylines are 1/8" shock cord, secured to the hammock ropes with a piece of parachute cord.

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The entire perimeter has an elastic drawcord to tension it. They can be adjusted with 4 cordlocks.

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Detail of side attachment. The Delrin mitten hooks attach to the side elastics on the hammock body. Note the reinforcing circle. The tab is set an inch or two inward from the edge of the quilt to cheaply take tension off the shell to preserve the loft. A more talented person would have made the shell larger to accomodate the differential.

[GreatDivide14]

Quality craftsmanship, man. If you can tell, the stitching is all over the place. I'm not too good at this.

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I don't know at this point exactly how warm it is, but I'm planning to head over to the national forest and sleep in it tonight. I'll let you know how that goes. Coverage seems to be quite adequate. Plenty of material at the foot, a bit narrow at the head, but nothing a wadded up rainjacket under my head can't fix. I do that anyway. To get in and out, you push the quilt out of the way-- the elastic attachments stretch easily-- and get in normally. The hammock and fly (Expedition 2.5) is two and a half pounds, and supposing the quilt is a pound and a half (which seems a bit much), I've got about the same total weight as a Hilleberg Akto and a full-length Ensolite pad, but it's more comfortable than any sleeping pad, so it feels lighter in the morning. Of course, the lighter hammocks knock off another half pound or more. If I sleep warmly tonight (forecast says lows around 30), my love for my Hennessy will be unconditional.

[GreatDivide14]

The night's low stayed around the forecasted 30* F. I wore typical backwoods pj's-- midweight bottoms, midweight zip turtleneck, light fleece zip turtleneck, fleece socks-- and slept in my Marmot Sawtooth (rated 15*, generally considered an accurate value). I was certainly warmer than I would have been without the quilt, but I still got kind of chilled. It always started with the hip of whichever side I was lying on, then slowly spread until my whole body was uncomfortable. I noticed that some of the sides were slack, so I tightened them up, and I think it was marginally warmer that way. After getting cold again, I wondered if the shell was under enough tension to flatten out the insulation under my hips. I loosened the end attachment cords, to little or no effect. I noticed that there was a bit of an air gap between the bottom of the hammock and the quilt, which led to my working theory: I suspect that by warming this low-lying patch of air, I'm creating a convective current that consistently drags 30* air under my hip. I tightened up the end cords to reduce the air gap and think I stayed warm longer as a result, but I still got cold. The only thing that made a major difference was giving up and shoving a fleece vest under my rear end. In any case, I was somewhere between glowing warm and slightly uncomfortable that way.

An insulated jacket is only as warm as its collar and hem are snug, and the problem here appears to be much the same. It fits closely, but it still unloads too much warm air. Klinsky's used longitudinal elastic bands to snug the quilt against the hammock body, and I'm wondering if that was more important than the insulation. Even so, I think it should be adequate above freezing, and I wasn't expecting miracles below that. Perhaps I'd acclimate to the cold enough on a long trip to sleep well-- I'm used to central heating right now. In any case, in its present form, it's not enough for serious fall-winter-spring mountain weather, but it's good for summer just about anywhere, and by the time I get the opportunity to do anything interesting with subfreezing nights, I'll probably be rich enough for that Beta Light.

[walt walkabout]

Very cool looking, and a good field report.
Have you thought about using a Space Blanket or other type reflector underneath you? Me and everybody I hike with carries a Blanket and while I use mine as a ground cloth they use them inside the tents not only to reflect heat but as a barrier if we get water inside the tent on the floor.
The Space Blanket is wind proof and I know that wrapped around a person it does reflect body heat so it might be a good addition to some one sleeping in a hammock where heat loss is greater than in a tent.
Just an idea.
Walt

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When the Hennessy first came out, that was what they recommended. They offered directions on how to hang one underneath it, but consensus was that it wasn't enough on its own. Of course, that's on its own, and it might do a lot of good with the insulation. I might throw one in on top of the quilt. It would be truly outstanding to line it with the aluminized silnylon used in the Western Mountaineering Hot Sac VBL. Maybe if I make another...David.

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Nice that the shootout a few forums down has let up. Anyway, I set up the hammock with quilt in the backyard yesterday, and I was actually warm this time, in the high 20's. The only changes I made were tightening the end attachments pretty much to the limits of the elastic and, more importantly, laying my down jacket inside it. And, like I said, I was warm. Now, the caveats. I think I'm stretching the shock cord of the end attachments farther than it can reasonably go, so I plan to replace them with parachute cord, perhaps with a doubled loop of shock cord on each side of the foot end to allow it to stretch when I get in and out. The down jacket is to fill up the airspace under my hip, and it seems to do that just fine. However, for whatever reason, after a late-night call of nature, I couldn't get as warm again. Also, even though my sleeping bag is a 15* and the quilt is 2 inches thick, I took off my fleece pullover in the name of science and wasn't quite warm. Finally, for reasons that are utterly beyond me, it doesn't seem to work as well when I'm on my left side.

As near as I can figure, the best thing you can do to make one of these warm is not to make it thicker, but to eliminate airspace under it. I'm guessing that the second layer of Polarguard was wasted, and I should have spent that much on elastic ribbon to sew into the liner. Eliminating airspace requires that the end attachments be under a ludicrous amount of tension, so don't bother elasticizing them. I think the drawcord around the perimeter affords enough stretch. I don't think it's possible to be completely warm in low temps without wearing some form of noncompressible insulation, at least under you. Still, it *can* be warm below freezing, and from here on, it's about eliminating variables.

[walt walkabout]

Yea, if you find out where to get that silnylon let us know. I wouldn't put the blanket on top of the quilt but underneath it as the space blanket is crinkley and noisy and not very comfortable next to the body when laying down.
Walt