Why waste money, weight, and space on down...or ANY fill for and UQ?

**Mystery Oneal** · 03-29-2016, 23:46

I have been hand sewing my down TQ, I'll try to get some pics up when she's finished. Since it is being hand sewn, I have had lots of time to meditate on the design for my UQ...which i will also be hand sewing...after I finish the winter tarp.

During my meditations I realized that the down in an UQ doesn't really do all that much to improve the efficiency of an UQ. On a TQ it is pushing the 2 layers of fabric apart to maintain the 1-3 inches of trapped airspace, and the trapped air is what is keeping us warm. But, on an UQ we have gravity working for us. In theory, with slight modifications, one could easily make an UQ shell that hangs with a relatively uniform space between the 2 layers of fabric and works just as a down filled one. The only real catch is that the shoulder area might need some help staying at optimal fluff.

My idea was to have the two layers of argon 90 with a 2 inch strip of webbing sewn between them around the perimeter (similar to the way baffles are generally sewn across the middle). Argon might work as the 2 inch strip, but I figure the stiffness will help it keep the 2 layers apart in the corners. Also, I would add a baffle (of any material) down the center (lengthwise) to keep the bottom layer from sagging too much. Everything else would be pretty standard, cinch cords on the head and foot, shock cord along the length for suspension, etc. I have also played around with the idea of having the top bit of fabric a few inches narrower than the lower fabric. The idea is that it would be easier to sew than darts, and should minimize compression (this is something I will mock-up once the rest of my fabric arrives).

For those that have months and years of UQ R&D experience under their belt, I challenge you to give me one good reason why I should put down in my UQ....other than the fact that I'll have 7 oz of the stuff left after I stuff my TQ. Thanks for the feed back.

**SilvrSurfr** · 03-29-2016, 23:53

So your idea is no insulation whatsoever? Just air? Good luck with that!

**Mystery Oneal** · 03-30-2016, 00:11

thanks for the encouragement... if the down actually did any of the insulation, we would find noticeable differences in the efficiency of , say, 950fp and 500fp. the 950 would weight half as much, but would also insulate half as well (per volume, not per weight) . So I say again, what good is the down actually doing?

**SilvrSurfr** · 03-30-2016, 00:21

I think you're gonna have to experiment to determine why air is not the best insulation. That sounds like a pretty boring exercise, but I guess you'll get to discover it yourself!

**Jeff Myers** · 03-30-2016, 00:40

It is not the total amount of air but the frequency of the individually trapped pockets. Heat becomes stored there. Even put a down jacket back on after being too hot. It is still warm. Sure a large air gaps means the heat has to travel farther, but unless we are talking a vacuum sealed chamber , air is not the insulation.

**kev138** · 03-30-2016, 01:12

Air filled baffles would be inadequate insulation because there is nothing to trap your bodies radiated heat. Down, synthetics, wool, etc., trap the heat you give off and warm up the air in between the fibers ( or feathers ) allowing you to stay warm. An undequilt with no insulation wouldvbe like running the heat in your house with all the windows and doors open.

Mylar ( space blankets ) and sleeping pads work ny trapping your heat because they are impermeable and do not allow the heat to pass through. The dowside being in really cold weather they also trap moisture generated by the temprature difference between your body and the air ( think a cold glass of ice tea on hot day and picture the beads of water. Same principle).

What you describe sounds like a very complicated wind sock. It may block some of the oustide winds on your bottom but it's not going to trap any of your heat. Air is a good thermal conductor but a poor thermal insulator.

But i am no expert, i just read alot. My understanding or attempt to convey it may be imperfect. It may be safe to say that if it were a bang up idea somebody would be doing it, and selling it.

**Levi Tate** · 03-30-2016, 01:20

Hey MO, according to your theory, we wouldn't need any insulation in the exterior walls of our homes either, but that is not the case.

**Theguywitheyebrows** · 03-30-2016, 01:50

Kev138 explains it very well, and levi tate explains it very simply. Countless millions of individualized heatpockets > empty baggy sacks dangling under you.

**Sunndog** · 03-30-2016, 03:46

Op, have you ever slept on one of those huge car camping air beds in cold weather?......they are 5 inches thick and bloody freezing, a 1 inch thick thermarest is waaay warmer because it has insulation inside it