When selecting a sleeping bag for hammock use, do you generally go for a lower temperature rating? My understanding is that temperature ratings are based on use with a fully enclosed tent on the ground.
What is a good rule of thumb in determining ratings for hammock use, ie. 10 degrees lower etc.
Many (Most?) hangers use a quilt or use their sleeping bag as a quilt. I used my OLD, 35 degree bag as a quilt, & I stayed warm down to 28 in the hammock, but in my tent, 35 was pushing it.
I now use a hammock sock so have a "enclosed tent" like shelter. The sock does add at least 10 degrees to my R-factor. YMMV
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Doctari, what do you attribute that to? People are often warmer on top than when they are using the same bag on the ground, at least if their under insulation is plenty adequate.Originally Posted by Doctari
A few of us have reported difficulty using our bags as quilts, and have been cold well above the rating until we got inside and mummied up. I at first attributed this to inability to stop drafts around the shoulders, due to the way a mummy tends to narrow around the neck/ head, and loss of hood use. But recently I have figured out how to get a better "seal" around the shoulders/neck, and even use the hood when laying on my side with the bag quilt style. So I think I might have better luck now, we will see.
But today I tried out a 56" wide ( at the shoulders) quilt ( 21 ozs, about 2.5" single layer loft average, maybe a tad less). I don't seem to have any draft problems with this unit, with it's neck draw cord. Plus it is long enough that I can make a passable hood if on my side, shaping a breathing hole. Preliminary results look pretty good. Taking a 30 minute test as the sun was setting, at 39*F with just a cotton under shirt and jeans ( I did have a hat though), in a NoNet with WB UQ and pad under my legs, I was quickly a bit too warm and had to ventilate. Which was easy to do. So this shows promise and should be good for deep winter in a PeaPod, or with very lofty clothing or both.
But to what do you attribute your 35*F baf being good to 20s in a hammock, whe 35 in a tent is pushing it? Considering how much colder hammocks tend to be, compared to on the ground in a tent for most folks, unless you really have things worked out.
the drawcorded head end is key for me.
I would guess it's because hammocks tend to have REALLY good ventilation when compared with tents. All the moisture from your breath can hang out inside a tent, pushing the relative humidity up and up. Then it gets cold. It touches your body and soaks up heat from you.
In a hammock, that moist air can be exchanged or dispersed more easily. So there's a tradeoff between continually-refreshed air and cold-but-static air. I can't tell you where the tipping point is, but I'd guess that it's partly about humidity.
The other piece is that cold air sinks, and tents are on the ground. Hammocks are often several feet above the ground. NOAA/NWS standards allegedly require measuring temperature at exactly six feet off the ground, which seems like the difference of a few feet really can matter when it's that close to the ground.
I imagine that the humidity piece would be easily tested: try sleeping with the same gear, one night in a tent, one night under a tarp. See which one's warmer.
Anyone done this?
Good theories. Either or both might be factors.
Interesting. On the one hand, most folks ( like me ), who start hammocking without thorough tutorials from a place like HF, tend to freeze their asses off during their first cold weather hammock experience, using the same bags they used on the ground with great success.
OTOH, other folks report being warm in a 35*F mummy bag, used as a quilt, at 25*F or even 20*F. Warmer than they were in a tent.
Interesting! I've never thought about it much, but have never really fealt frozen in my hammock and remember lots of nights freezing in my tent before I went to hanging. I've had cold nights in my hammock, but never dangerously so. Except in the beginning, before I knew better, most of the time I've used a JRB No Sniveller, which should be colder than the 20 degree bags I use to use. What I've learned is what I have under me seems to be slightly more important than what I have above me.
But, a question - I always thought high humidity made things feel warmer, not colder? Think about how people always say it's the humidity, not the temperature, when things get too warm outside.
My experience is cold and low humidity is "crisp" Cold and high humidity is "raw". Crisp is far more comfortable and seems warmer to me. Raw is just plain and simple nasty.
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Humidity enhances the temperature, hot or cold. It makes cold seem colder because of the dampness, and hot feel hotter because of the dampness. the air is actually thicker with the water molecules hanging in it, so heating and/or cooling is actually enhanced, traveling through a thicker medium.
Sometimes we get fooled on what is actually going. We get locked in thinking there is only one variable and we look to see what happens in different conditions. But many times things are more complex than we realize and our conclusions are not based on all the relevant facts.
Bottom side insulation, wind, humidity, when we ate, what we ate, how tired we were, how long we were sleeping, what we wore, how we used something, how much space we were enclosed in, etc can all be factors that we overlook. For instance, if I use a bugnet I sleep a few degrees warmer (on the top side) in my hammock and if I replaced that with a less breathable cover I might sleep even warmer. Of course many times things are as simple as they seem-- it takes experience, wisdom, and often another pair of eyes to know when that is and when it isn't.
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