MML--The Man, The Myth, and the Legend
"I am the eagle, I live in high country, in rocky cathedrals that reach to the sky;
I am the hawk and there's blood on my feathers, but time is still turning they soon will be dry;
All those who see me, and all who believe in me, share in the freedom I feel when I fly.”
Thank you, HappyHiker and BillyBob58 for those real-world examinations of specific gear. I agree; lab conditions rarely obtain outside the lab.
I'll just keep my contribution short by noting that below freezing, drafts (and, by extension, humidity control) become a huge problem compared to warmer temperatures. Once you reach freezing, even small drafts will cool the moisture on your skin much more quickly than above that temperature. Hence the disproportionate perceived warmth of hammock socks and overcovers compared to their actual insulative value.
I'd go so far as to argue that, once you reach the sub-30 regime of temperatures, draft control becomes as big, if not a bigger, issue as straight insulation--at least, it has been for me. Which applies regardless of whether the insulation is down or polyester/polyethylene/olefin.
Great to know that calc is roughly accurate - I haven't tried any synth for a long time.
Actually, the 48F there is probably exactly per my real world testing. I am not stopping to find the thread, but it was somewhere mid to hi 40s with high humidity, right next to a lake. I remember we all agreed it felt like a really cold hi 40s when we were cooking breakfast that morning. But, I'm also thinking I had nothing else for base layers, just cotton jeans/tee shirt. Not even a hat until near dawn, when I remembered I had one in the WBBB shelf, and put it on. A 40-50F semi-rectangular bag as quilt( 30 year old synthetic liner bag).70 -38.58(rating from the down method)= 31.42 (degrees from 70)
Not quite following here, can you say some more about this? 31.42? From above, I see you have about a ~ 40F rating for down ( 70- 29.52= 40.48) and a 48.58 for the CS( .86*2.5*10= 21.5. )
29.52/21.5= 1.37 So not a big dif, but is it 31.42 or 29.52?
70 - 48.58(rating from the CS/clo method)=21.42 (degrees from 70)
As you say, however you choose to look at it, a small difference.
Do you have the dimensions of the Yeti?No matter, it looks like the 850 down will be between 1.3 and 1.4 times as warm as an equal weight of CS, so that is enough to be worth considering. But not near as much as I would have thought, considering it is 850 down. I used your calculation for 750 down, and the dif was only ~ 1.2.
Though those figures for the down don't quite match extrapolating from the 3 season Yeti rating with 6.5 oz of down, which would give more like a 50F rating for 2.5 oz of down. But I will assume that your method is more accurate and that Brandon's rating is a bit conservative, which I find easy to believe. And of course, in both cases, those ratings are with both being bone dry. IMO, let some moisture enter the mix, and the warmth to weight advantage might actually switch to the CS.
It's really apples to oranges (my comparison) IMO, and likely off to some degree. Synthetics use a weight of material to ascertain the warmth of that given material, where down is commonly rated by loft (and density to some degree). I was just attempting to compare a given area with an equivalent weight of down vs. CS to supply food for thought in the theoretical discussion. Thats where knowing what the actual clo value for a given loft of down would be great to have. The earlier stated clo value of down gives no indication whether that oz of down is 1/4" or 2" thick given the area would be different for each value. If it is truly just a weight to area comparison, then my last example which gave down (800 fp) almost a 2x advantage would display a huge difference between down and synth. (I hope that makes sense ).
In the end, a comparison of the weight of bags given the same EN rating (with roughly the same dimensions) would probably be a far more accurate indicator of weight to warmth. But I can't resist playing
Thank YOU for working through that jumble!
I'm also going with your 1st figures, resulting in a 40F rating starting from 70. Why? Because until someone tells me dif, it is hard for me to think that folks are really getting more than about mid 40s out of torso UQs with only 2.5 oz of down. Unless maybe 900 down?
Thanks for the work, that was fun!
Experience is the worst teacher - it presents the exam first and the lesson later. - Unknown
I use down. It's lighter for warmth, takes less pack space for warmth and lasts longer.
I saw an Andrew Skurka talk last month. He says that down gets wet and looses loft when you're in high humidity weather, not from accidents.
I've had my down Peapod in very bad conditions twice.
Once the condensation was so bad that when I got up to try to adjust my tarp, I couldn't see because so much water was condensing in my face and running in my eyes. Not rain, condensation. There was water condensing on the inside of my tarp and on my Peapod. Water was running through the Velcro closure, dripping on me, running off of me, onto my hammock and dripping on the inside of the Peapod for several hours.
I thought that I was going to have to abort the trip because my sleeping insulation would be soaked. I was wrong. In the morning light, it didn't look too bad, so I decided to continue. At lunch, I spread my Peapod out in the sun to dry but it wasn't necessary.
Another time, I was camped in a high wind during a storm. I'd pitched my tarp too high above above my hammock and rain was blowing under the tarp and onto my Peapod. It was pushing me around too. My tent stakes were pulling out and it was hard to hold the tarp in the wind. I eventually lost a tent stake while fiddling with the tarp and decided to retreat to the car where the rest of my tent stakes were. So, I wrapped my soaked tarp around my wet Peapod, tied it with my guylines. In the morning, I stuffed the whole wet mess into a stuff sack.
When I got home, probably 12 hours later, there was a minor loss of loft. The Peapod wasn't quite as poofy as it usually is.
Then there was the time that I was in an incredible condensation situation like the first story. This time I was expecting it, so I pitched my tarp with the foot very low, upwind, and as closed as I could make it.
During the night, I woke up with trouble breathing. My tarp had sagged, and there was so much condensation on my tarp and my Peapod, that the tarp had sealed to the Peapod from the surface tension! The Peapod was fine.
If you've ever tried to wash a down bag, you know that it's not easy to get the down completely wet.
Also, I think the other current thread about some folks having severe problems from fog is worth reading.
I also want to repeat this question in case I have missed the answer:
I am asking this because I have done mid to hi 40s with 2.5 oz of Climashield in my torso UQ, wearing only cotton tee shirt, and was adequately warm. So does any one use a torso UQ with only ~ 2.5 oz of down fill for temps colder than that? If someone is doing 20 or 30 or even 35 with such an UQ, then that will clearly show a very significant warmth to weight advantage for down.What do Y'all think? How low do you think you could go with a torso or Yeti style UQ with 2.5 oz of 850 down in it?
Apparently, signature that I used from 2006 no longer tolerated so now deleted.
Ok. Now that the "balance" part of the discussion has been worked over, and the merits of both touted to a reasonable excess.
Which one goes in the BOB, and why? You can't have both, and you don't have time to allow the forecast to make the decision for you?
Will the few ounces you might save allow you to carry more, water? amo? food?
Will the volume/weight penalty prevent you from carrying sufficient amounts of the above?
Lots more variables. Can't hardly think of one w/o having to consider others, sometimes nearly everything, in one aspect or another.
Has anyone considered the vapor barrier option, long used by mountaineers as so forth for decades? I use them and consider them essential for adding [I]practically[I] no bulk insulation. They also keep one's bags drier and cleaner from the inside.
They are not "clammy" either. I wear woolies inside mine.
Transportation for Hiram Farm
Two Wheels Good, Four Wheels Bad