Overnight insulation test

I've been playing around with different combinations gear and last night I wanted to test the lightest combination I have.

My gear locker has a lot of ground camping pads and I wanted to get that in the mix. I have a Prolite extra small torso-length pad that is about 10oz and it stows smaller than anything else I have found. I have a Z-lite pad and a bunch of bulk 5mm EVA blue foam.

I have a Hennessy Expedition hammock and a Grand Trunk Ultralight that I have upgraded the suspension on. The GTUL is about 16 ounces with carabiners in the end channels, whoopie slings and Hennessy tree straps and a couple more carabiners. I could eliminate the biners, go with lighter straps and use toggles if I really wanted to get it light. But for testing, the suspension was fine. The GTUL is really comfortable for a such a cheap hammock, with a slick polyester fabric that is very breathable and soft. It is great for a nap on a hot summer day.

So I rigged the GTUL under the Hennessy Asym tarp and tried the pads. It was a wiggle fest. I'm just not impressed with the feel and fiddle-factor of foam pads on top of a hammock. The Prolite felt the best and I understood the size limitations. The shell on the Prolite was easy to move around on the slick GTUL fabric. I added a Z-seat foam sit pad for my feet. I used a Cocoon Ultralight inflatable pillow.

For my ultralight test, I used a Mont Bell Alpine #7 bag that is a 50F rated 16oz down bag with the "hugger" feature with elastic in the shell and a big drawstring opening at the top-- no zipper.

The low was 49F and about 80% humidity, with little or no wind. I was wearing light fleece pants and a long sleeve polyester base layer top. No socks.

I got in an wiggled the pad around, finding that the valve poked me in the shoulder. I finally got it up high enough to clear. The Z-seat pad on my feet was okay, although the open-topped hammock and slippery cloth could allow it to escape. Same with the pillow. Once in place, the Prolite felt pretty good. It is 20" wide maximum and I think the taper and rounded top and bottom edges helped keep it from buckling and making lumps. Of course, it only covered to the edges of my trunk and not my arms and outer shoulders or head. It made a minimal intrusion to the comfort of the bare GTUL.

I woke up about 5AM with the birds singing overhead. My sides were cool and there was some dampness on my back. My feet were a little cold, but I'm sure that just adding socks would have taken care of that. I wouldn't want to tackle anything colder and I wouldn't rate it as a good night's sleep or rave about comfort.

So I got up and had a cuppa coffee and got out my silnylon poncho/undercover and the space blanket/polyfil under quilt I made. The 104" long under cover was perfect for the GTUL and when I pulled in the side shock cords in the UC, the top came up and over the sides of the GTUL. I put the space blanket UQ between the hammock and UC and got in, using the pillow and Mont Bell bag.

Night and day difference. I could feel the warmth off the space blanket right way and the outer cover blocked the light breeze and kept the warm air below. I think the breathable fabric of the GTUL and the airtight silnylon UC worked well together. The UQ is an envelope, so there are two layers of HeatSheet space blanket with 1/2" of polyester batting inside. I spent another 3 hours in the rack. There was nothing to detract from the comfort of the hammock fabric and I was warm and dry. I could lie on either side and position my legs wherever it suited me. After 3 hours, I put my hand in between the hammock and the UQ. It was warm and I could feel moisture in the air, but there was no condensation on the space blanket or the hammock. I think I could take this system to 40F with socks, a foot pad, a fleece top and a beanie.

Weights:

GTUL with suspension: 16oz
Mont Bell bag: 16oz
Under cover: 10oz
Space blanket under quilt: 10oz
Hennessy Asym tarp: 10oz
Total: 62oz (3lb. 14oz).

This was my first night in an open hammock without a bug screen and the air contact above was noticeably different-- felt more like sleeping outdoors. No bugs, and nice with no wind and moderate temps.

Conclusion? IMHO, pads inside a hammock suck. I am just not impressed. I would like to try a double layer hammock with a pad between. I have fiddled with a segmented pad extender, and it takes care of the side insulation issues, but it still feels lumpy and detracts from the natural comfort of the hammock surface.

I'd like to see a good pad solution. Of course under quilts will solve the problem, but pads are readily available and most people own them already. They are light, waterproof, durable and can be very cheap to purchase. They are little bulky, but they roll up and we've been dealing with packing them for decades now.

You can good quality damaged/leaky self-inflating pads for a song, although most are too narrow. You might be able cut up and combine two, with sections used sideways. You can make your own self-inflating pad with open cell foam and heat-seal fabric. In fact, a pad on the outside wouldn't need an airtight valve, as it would only have to inflate against the outer cover, not your weight. A Velcro flap would keep internal moisture to a minimum. It would be easy enough to attach a suspension. I wonder of it is possible to make a self-inflating pad with a differential cut, so it would take a curve? What you want is something like a section of a cone, or two intersection cones-- a large one for the upper torso and a longer, thinner one for the legs. and butt.

CCF pads could be cut in sections to assemble to a cone shape and joined with fabric joints/hinges.

My $0.02 :)

Dale,
I'd forget two-layer hammocks for your tests. I find them uncomfortable with ccf pads between the layers. My attempts to use a 15" separating zippers to fasten an underquilt at the left shoulder and right foot points (with edge shock cords to hold the other edges against the hammock but permit the hammock material flexing under me) have been hampered by the fact that a dl hammock is a tube, and what I think is "the edge" can be pulled toward the center when the two layers slide past each other. On the left side of my hammock I don't have this problem because my bugnet is sewn to the edge on that side, stabilizing it somewhat. I'm going to "quilt" the two layers of the hammock together near the foot end to see if that prevents this slippage. I put "quilt" in quotes because there won't be any insulation between the layers, just hand-stitched spots spaced 8" or so apart in a grid to keep the layers together. Obviously, the next hammock I make to try this with will be a single layer 1.9 oz. ripstop.
Regardless of the insulating material, your experiments with the "'silnylon poncho/undercover and the space blanket/polyfil under quilt" (forget acronyms - don't want to go there) sound very encouraging. Are you tempted to make it lighter by making a smaller version? Then you get into the fiddle factor, trying to keep all spots insulated. Carry on. :)

WV, hey I am sure you know what you are doing, but...

I did just that, in a 1.9 oz DIY double layer in ripstop. I hand sewed pretty much like you did. Excessive movement (and possibly having the hammock hung too tight) caused the bottom layer to tear out in a line along the stitches. Could have been a few reasons, including poor alignment, stitches too tight, what have you, but it seemed fine till I tryed to get the sleeping bag comfortable and jerk it up towards my shoulders... now I am nervous about any stitching in the body of a hammock.

All my attempt to put a pad between layers simply don't work. I move around too much. I end up in the middle of the night not on the pad, but with the pad up on my side in my face. The only one the does work that is a bit bulky is the Gossamer 1/4 pad at 40 inches wide. I used this till i got an underquilt. I use to stuff some clothes around my shoulders for extra warmth.

I think it is better to go thinner to save weight rather than smaller-- less fill. You have get some gains by the amount of surface area as well as thickness, although thickness prevails in real cold. My thought is if you are insulating for say, 40F and raining, an over all cover and thin insulating layer will cut wind and convection over the majority of the hammock. With my poncho under cover, you get a "free" under cover weight wise, because I will always have some sort of rain gear. A middling light rain shell is 12oz, to the poncho is a weight bargain.

Then it is getting a light, compressible and effective layer of insulation. All I'm trying to do there is to isolate the bottom of the hammock from circulating cold air that absorbs the heat off my backside and cools the air I have heated inside the hammock. It needs to be of a material that doesn't transfer heat efficiently or in the case of the space blanket, might even reflect some back to me. The system needs to keep it close to the hammock, but I don't think it needs to be snug-- you get that nice dead air space between the hammock and the space blanket. I could be wrong. I'm counting on the fact that the outer cover is keeping the air inside fairly still too.

The space blanket is fairly fragile, so compressing it for travel is the weak part. It isn't hard to roll it up and with 1/2" of polyfill inside, it can be rolled to Nalgene size or close without really crunching on it. A rubber band keeps it rolled. That is where the AMK Thermal Bivy comes in-- it is windproof and it have some reflective properties, but less than the space blanket. It is more on the quick and dirty side, but it can be manhandled more than the space blanket and still provides a good thermal barrier so heat doesn't pass through the shell and the insulated dead air inside. You could knock out a whipped-end outer cover from ripstop nylon and quilt part of it or all of it. You could have Velcro strips inside and add "pillows" of insulation in light covers to change length/thickness and weight to your needs.

As to the double layer hammock problem, I think you need a differential cut, with the inner weight-bearing hammock just a little smaller. That outer layer just needs to hold the insulation and it's own weight. Quilting thought the works goes back to my "hanging sleeping bag" question. I think that is the way to really deal with the whole "mountain hammock" issue. It would be easy to alter the top insulation to suit the season. So take a typical gathered end hammock with a matching outer shell that is baggy, add a couple layers of Primaloft, sew the sides together and run a few lines of stitching across to lock the batting in place--- spaced what, 12" apart? You need to be able to launder it, so I would go with a separate bug net. I like carabiners in channels for suspension and that would make laundering easier too. The outer layer should be windproof and have some DWR properties. The inner layer needs to handle the weight and stress. It doesn't sound that hard :)

If you are dealing with sub-zero stuff, it isn't raining. Hopefully your shelter has more coverage, taking care of most of the wind issues. Then it is just raw insulating value and it's time for the lofty under quilts.

I have been playing around with all kinds of combinations of pads and fillers to use with an under cover. I took a space blanket and crumpled it up and stuffed it in a 45 gallon LDPE (low density polyethylene) trash can liner, and sealed the top with a rubber band. I made up a couple and put them in the bottom of my under cover, and then put another pace blanket between the bags and my hammock. You can use the cheapest space blankets in the bags, but I recommend an AMK HeatSheet for the one under your hammock -- they are MUCH quieter and hold up better too

It works :) The bags are 1.4oz each and the space blankets are 2.5oz each, so the whole works is 7.8oz, plus my 9.7oz under cover. You get at least 2" loft, maybe a bit more. That should be fine for anything over 32F-- I would want to test it for the cold limit. It doesn't take long to assemble and packs small. I would just take the rubber bands off and roll it all up in my hammock for travel. This is warm, light, cheap and easy to make. :thumbup:

You can use the lightest, cheapest trash can liners you can find. I like the clear LDPE ones as I can see what is happening inside, but any color would work.

I want some really big ones now. They make big tubes for covering stuff like carpet rolls. If you could get some really wide (48" or so), lightweight stock, you could make one big pad with several blankets stuffed inside. You could pull it off with painter's drop cloths and some tape too.

Might want to check out Ray Garlington's Insulator... :)

Quote:

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Originally Posted by Frawg

Might want to check out Ray Garlington's Insulator... :)

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Darned if I didn't re-invent the wheel! Thank you for pointing it out. I bow to Ray's genius :D Great minds do think alike, eh?:cool:

I know the under cover has been done before, although I haven't run across one like my poncho version.

It does work, if you have an under cover. You can make one by simply gathering the ends of a rectangle of cloth, making a non-weight-bearing hammock really. Make it long enough to cover your main hammock and suspend it with shock cords. Insert insulators and space blanket. Sleep... sleep...

Sounds like you are coming up with your owm DIY version of a HH SuperShelter. Which has always worked pretty darn good for me.

What kind of space blanket are you using at 10 oz? Mine all weigh 2-3 oz.

That HH OCF pad does a great job for me ( and Newt! ;) ) hanging under the hammock with an UC under it and a 3 oz space blanket on top of it. The HH UC is tensioned just right to hold the pad just snug enough against the hammock without really much depending on the suspension. But down or especially fleece jackets and many other things also work well down in that UC, either to boost the OCF pad or just by themselves. Just have to be careful with down, the UC tension tends to compress it in spots.

Quote:

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Originally Posted by BillyBob58

Sounds like you are coming up with your own DIY version of a HH SuperShelter. Which has always worked pretty darn good for me.

What kind of space blanket are you using at 10 oz? Mine all weigh 2-3 oz.

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Yes, I'm totally cloning the SuperShelter. And the Garlington Insulator too.

I had a space blanket/polyester fill insulator with 1/2" loft that was about 10oz-- I think that is what you saw. The cheapie single space blankets I've been fiddling with are 2.5oz and the AMK HeatSheet is about 3oz.

I'm revved up about the Insulators. I call using materials like this in new ways "Applied Junque." The space blanket/trash bag combo really does the trick. I think anyone with a Clark Hammock should try this, stuffing the side pockets with space blankets with or without the trash bags.

Now I want big mylar bags. AMK makes the HeatSheet bivy, but it is a little narrow and I'm a cheapskate. Another option might be to use the big bags made for storing and compressing clothing.

I see Garlington mentioned using alternate filler, even crumpled newspaper. Heheh-- take the paper with you camping, use part to start the campfire and the rest to insulate your bed :cool:

Update:

I went surfing for larger mylar bags and it dawned on me that I had already made one-- just fold a space blanket in half and seal the edges with double stick tape. All I was missing was using Garlington's method of crunching and folding space blankets to fill it. That will give a 48" wide insulating pad and much better side protection. Two pads would cover from head to toe and wrap around the sleeper. A little stick-on Velcro can hold the two pads together. You could make one long pad from two space blankets taped together-- even a double folded the long way is a little skinny--- 30"x96". I would leave at least a small hole so you can roll/fold it for travel. I would still use the AMK brand for the outer cover, for strength and quiet. We're talking 10-12oz for four space blankets. The single AMK HeatSheet folded would be 56"x42". I could see using the one on the head end with the 56" dimension athwart ships and the foot end with the 42" across. It could overlap under your butt and have plenty to cover your sides and even roll under. Full bore retail for four AMK single HeatSheets is $16. If you are on a budget for Scouts, etc, you can get generic ones on eBay super cheap.

So I was sitting at the computer thinking about insulation. I spend too much time thinking about insulation-- ask my wife.

I've been working on alternative insulation options to use with an under cover-- space blankets, foam pads, sandwiches of space blankets and polyester batts, yadda, yadda, yadda. And I was feeling sorry for myself because I don't have the Big Bucks for an underquilt. My computer is in the rec room and there is a card table nearby-- my project table. And laying on the table was my 16oz Mont Bell down mummy bag...... DOH!

I threw the bag in my under cover and tossed a space blanket on top--- vapor barrier and more coverage. Nice! The Mont Bell is a zipper-less design with a drawstring at the top, so I can't spread it out like a quilt. I'll have to try one of my other bags. :cool: