Camping quilt vs catsplat's UQ calc

[outdoor]

Aye, the calculator was intended to be set up for a certain design and then output what amount of down you would need to fill it - starting with a set down weight and then back-designing is a bit unusual, haha. Nothing I'm sure you couldn't achieve with some guess-and check!

Bumping an old thread..

The temp rating system works pretty well for the more common lofts and fills, but it breaks down when you get really extreme with the design.

I'm not an expert, but i feel the temp rating is very liberal. I have a 78 x 44 long quilt with 900fp 2.5"loft and it is rated for 20 deg F. if i reproduce these your temp calc is 2 deg F.

Now I get cold butt syndrome in mine at about 5-7 deg Celcius 41 to 44 F. I was thinking of adding about 6 oz of 800 fp to a total down weight of say 18.6 oz approx. According to the calc i should be good to -27 degrees F.

If i understand it, i should not necessarily expect much warmer overstuffing my existing quilt roughly 88% ???. I feel like when i look at my quilt there are a lot of empty spaces, that the extra down should fill in. So even if it has a given loft due to baffle heights, i should be able to get it warmer. Probably not to -27 F though.

I was hoping to maybe be able to get it to go to 32 F. I guess i will find out.

[Cruiser51]

Will make the assumption you are using a differential design.

With2.5" baffles, the lower limit is -6.7C ... assuming the chambers are filled. Once the baffles are filled no amount of additional down should change the temp rating until you start over compressing down and it starts to go down.
So 2.5" will give a specific insulation depth ... resulting in a specific temp rating ...... period

I use the latest version of the calculator and this is the exact issue I have with the temp calculator part. It bases the temp rating on the down used and not the calculated down thickness. If you design the quilt and put in in 0% overfill you get a bit of an inflated temp value, if you add overfill it gets to be wildly inflated inflated temp value (IMO). People love numbers, put a number on something and it becomes gospel .... the heading on my worksheet says "Temperature Rating (Experimental)" ... but it was a number and I pushed ahead confident in the "number" ...

The baffles don't give the loft. they just give a shape for the down to expand into, creating the depth of insulation you designed. If it doesn't fill the void, you won't get the insulation value you think you should have and you will get cold at a much higher temp than you planned. If you have spaces that are empty or don't seem "lofted" (they don't need to be tight, just filled) then you likely don't have sufficient down inside. In that case you can add some down and it should help.

I have a similar quilt using 2.5" baffles and i am fine to -1C ... the original design was for -15C and I used the Worksheet Temp number as a guide, i have replaced that temp guide with my own and recalculated the temp rating to the stated -6C and that better matches the actual performance (for me), so you should be getting better low end performance than you currently have ( I think).

The thing to remember about down FP is that it is a lab generated number, done with very specific conditions and after the down has been carefully handled and fluffed. Users don't tend to tread as carefully as that, we stuff it in a bag, compress it, use it outdoors etc and then expect it to match it's FP rating .... never going to happen IMO. I routinely use a 30%-40% overfill on any quilts simply to compensate for "FP wander" and " Sewing Wander" and this is just to make sure the baffles get filled, don't expect the baffle volume to be perfect and don't expect purchased Down FP to perform to advertised value, in the field. Overstuff is not there to increase the temperature rating, it is there to make sure the baffle cavity gets filled, so that the quilt performs to its design parameters.

The other thing that can really get you here is the quilt suspension and you don't mention that, but you really need to get some one to check that when you are in the hammock, checking there are no voids under you or obvious open areas. I thought i had that covered and the inspection yielded a couple open spots and a void that needed attention, so make sure you have it installed perfect before you start modifying.

I assembled this table of Temp vs Loft from 4 Cottage vendor sites, it is what I use for design now, you may find it useful

Down Information Table
Imperial		Metric
Degrees F	Loft Height (in)	Loft Height (cm)	Degrees C
40	1.5	3.81	4.44
30	2	5.08	-1.11
20	2.5	6.35	-6.67
10	3	7.62	-12.22
0	3.5	8.89	-17.78
-10	4	10.16	-23.33
-20	4.5	11.43	-28.89

Brian