Baffle size and down fill temps.

[RE8ELD0G]

Hey folks
Just to start by saying thank to the guys who have done the spreadsheets etc for filling things with down.
But i can get my head around it.......with thing being in Inch's instead of CM and OZ instead of Gramms.

Can someone please simplify it for me and tell me how to do the Math

How to calculate quantity of down per baffle.
and then how that equates to temp rating.

I got people asking me " Can you make me one for 'x' temperatures"
so need to be able to do the math myself to work out what i will need.

Thanks

[boulderv7]

Temp rating is subjective but generally corresponds to a number of inches of loft, Here is a pic from Dream Hammock showing this.
As for the actual math of determining amount of down per baffle, you can just use calculate the volume of the quilt, (LxWxH, height should be the intended loft), and then figure the total amount of down needed, which = [(Volume of Quilt) / (Down Fill Power)] x (Percentage of Overstuff). Overstuff is up to you. Then take the total amount of down needed and divide by how many baffle chambers you are planning on the quilt. This will give you amount of down per baffle chamber.
Dream Hammock also has a Down fill Calculator that will give you the total amount of down needed for the quilt.
Things get more complicated when using a differential cut such as on an underquilt. That is when I use the aforementioned spreadsheets.

[genixia]

Multiply the inches by 2.54 to get the sizes in cm
Multiple the oz by 28.35 to get the weight in grams.

Someone should make that spreadsheet handle both metric units too.

[RE8ELD0G]

Thanks guys.
that been a great help especially the loft vs temp chart.

[BillyBob58]

Thanks guys.
that been a great help especially the loft vs temp chart.

That chart seems a bit optimistic to me particularly for hammock hangers using quilts and even more so for UQs. But, I'm sure it would be fine for warm sleepers and depending on what layers you are wearing. And with plenty of good head protection like a thick hood.

For one thing, seems to me the traditional rating for many years was 2.5" for 20F. But this chart shows 2.2. Maybe the 2.5 has more slack built into it for colder sleepers.

Also, JRB rates their TQ with 2.5" loft(2" baffles) for 25-30F, and their 3" loft(still 2" baffles) UQ 20-25F. On that chart, 3" loft would get you to zero! I'd say that is a huge difference in expectations. But, the variation between individuals is huge, even from one day to the next when on the trail. And maybe JRB is just being extra conservative considering these are quilts rather than zip up bags.
http://www.jacksrbetter.com/quilt-comparison-chart/