Curved vs Flat Baffles on a quilt?

[jordo_99]

For this specific example, a quilt using a 2" baffle height that lofts out to 3" in the center of each baffle...why not just make the height 2.5" and the loft remain 2.5"? It would have the same amount of volume/down/etc (no, it wouldn't because that's not how the area of parabolas work, but to keep things simple let's say it does--a more accurate height would be around 2.6" without me trying to recall how calculus works)

So, the big question here is...Why are the outer shells curved at that baffles but the inner shell is flat? Specifically, why not make the outer shell flat too?

I understand that the inner is flat to allow the quilt to contour to the body/hammock/etc for better warmth but I haven't come across the advantage of the outside shell being larger to accommodate a curved baffle.

Racking my brain came up with a few possibilities but also reasons why they might not work out:

* Better wind/draft resistance
-- This advantage would be negated by using a tarp/tent or even just choosing a windproof fabric.

* Retain heat better
-- I'm not sure how this is possible since it's leaving you with uneven insulation; The strips where the loft is lower should be colder than if it were an "even loft" quilt.
-- On top of that, it also seems reasonable that this would actually reduce warmth because of the added surface area to the outside temperature (adding the curve, adds more area for heat to escape).
-- The only way I can think of that this would work is if the "valleys" on the quilt could trap air and essentially add a theoretical volume to the size of the quilt without adding weight...essentially having a 2"/3" curved baffle could perform similar to a 3" flat baffle because the trapped air would heat up.


I hope that I'm not confusing anybody here. Hopefully some people have thought this through before...I realize that if there has to be an advantage for curved baffles or else the "big names" wouldn't be making gear that way and I'm sure they've got lots of engineers researching this...I"m just curious if it's going to make a huge difference just to use a flat baffle for the slight advantage in weight/packing/cost that results from it.


EDIT: This was quite helpful to me, still didn't address my question though.
http://www.downbags.co.uk/info/sleep...g-construction

[MAD777]

The baffles are shorter than the average thickness of the quilt in order to compress the down just a bit. The shorter baffles (thats those vertical pieces that divide the chambers which you cannot see) make the chamber volume a little less than the volume of down contained within. If you didn't do this, the down would shift around inside the quilt and you would have cold spots.

[gmcttr]

Also the outer shell flattens out somewhat as the quilt is wrapped around a cylinder (you). The smaller the cylinder diameter, the more flattening. It's the differential cut of the shells that lets the outer shell "puff" and this is exaggerated when the quilt is laying flat.

[jordo_99]

Also the outer shell flattens out somewhat as the quilt is wrapped around a cylinder (you). The smaller the cylinder diameter, the more flattening. It's the differential cut of the shells that lets the outer shell "puff" and this is exaggerated when the quilt is laying flat.

That makes a lot of sense. For whatever reason I had completely missed that it was a differential cut calculator and that's definitely what was throwing me off.

Thanks