Idea: Modular Synthetic+Down UQ
I got this idea just yesterday and I would like to know if anyone has tried it. I am thinking of a modular UQ with two layers, basically two UQs which would attach to each other with zippers on the long seams. Inner layer would be stuffed with Primaloft and the outer with down.
I know this isn't ideal if you want to go (s)ul because you would basically use around 50% more fabric for the UQ. The catch is that in the summer we usually have temps around +20-30C (68-86F), averaging at 25C (77F) and in the winter -20-30C (-4-22F) (it can go down to -35-40 depending on the location + wind there is still the wind effect). So there can be over 60C changes in the temperature during the year. You could probably use the down UQ in the spring/autumn, the synthetic in the summer and synthetic+down in the winter. You could also just use down in both layers, I am just curious how well Primaloft and down would work together.
Layering insulation like this is done a lot. There is another thread about layering UQs that has gotten a good bit of responses.
In regards to how well synthetic insulation and down work together, they work very well together. The only adjustment I would make to your idea would be to switch the layers, down on the inside and synthetic on the outside. The reason being that when your body produces water vapor it will travel through the insulation and condense the most in whatever layer is coolest (readutside layer) If you have the synthetic insulation on the outside then you will not lose any loft/insulating properties because it is not effected by moisture like down is. This is more of an issue for long trips but still something to think about.
Skip the zipper. It will add bulk and weight. And you'll need a beefy heavy duty suspension to support the combined quilt.
Rely on each individual quilts independent suspension. It will allow for more adjustable system, reducing chances of overcompressing either layer.
Stacking insulation items works well for varying temps, these items can be pads of varying thicknesses, down or synthetic underquilts.
I see the possibility of an exponential increase in fiddle-factor with two underquilts adjusted separately. If the zipper is used and the quilts are properly sized, the bottom quilt would be less likely to compress the insulation in the top one. You're right that a strong suspension would be needed. Two separate suspension systems might be just as heavy, maybe heavier.
Originally Posted by gargoyle
I suggest making the down (inner) UQ first and perfecting () its suspension before adding edge zippers and starting the outer primaloft quilt.
Virkkte, I think Gargoyle hit on the most important consideration when he said the weight would make suspending it difficult. Much depends on how your hammock is suspended and whether the UQ pulls on the sides of the hammock or is entirely supported by the ridgeline. Double underquilts use twice as much fabric, not 50% more.
It's sure hard to think clearly in the morning, yep twice as much Thank you for the information about weight, suspension and that the down should go to the inner layer. With the zipper I was thinking the same thing as WV. If you would make the outer layer large enough so it wouldn't ruin the loft of the inner one. With the zipper, the layers would be always at the same distance of each other. You wouldn't have to fiddle as much with the suspension. How about this with the zippers, hammock, down layer, air gap between layers(maybe 1-2in?) and primaloft layer. If you had all of the sides of the UQs firmly pressed again each other and wouldn't the air gap give you more insulation? (in a perfect world this would work... probably...).
For suspension I am thinking about triangle thingies which go over my hammocks ridgeline maybe you could add two triangle pieces to the middle of the ridgeline (and have something to keep them from sliding). The suspension would support the outer layer, is the zipper enought to support the inner?
I added a professionally made illustration about this. The pink blob is the uq, yellow triangles well triangle thingies (four of them). Orange line some line to hold all of the triangle thingies in place. Pink lines are shock cord. Material wise cuben would be light This sounds so heavy.
If you have a strong enough suspension then you can just attach the second UQ to the first one with snaps. That will save you the weight of the zippers and make the adjustments easier. Maybe you could run two strands of 1/8" shock cord on each side for suspension. I would imagine that would be sufficient unless your UQs are unusually heavy.
I don't know if an air gap between the quilts helps or hurts. Anybody know?
Another consideration is air leaks, especially at the ends. DemostiX has pointed out that using a draw cord in a channel at the end of a quilt creates pleats, which can function as air ducts, defeating the seal. One strategy to deal with this is making a buffer around the edges that compresses to close the gaps, but adding buffers makes the whole thing heavier.
Maybe one could make baffles (or buffer as WV suggested) of some sort in the ends just to keep the air in. One on the inner layer and one on the outer, these would interlock when the ends are tightened with shock cord. It would still leave small gaps, but probably helps to keep the air in. (After writing this I realised I wrote the same thing as WV, so what he said).
ClockWork, sounds like a good idea to shave some weight off, this would still leave the same problem with air. I think the idea using air as an insulation would be more plausible with one piece quilts. Silnylon + seam sealer + down + air gap = ???, there would be condensation problems of sorts.
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