DIY Down underquilt questions

[Golden Bear]

whats up,

I'm in the process of making a underquilt and wondering how many ounces of 850 down to put in it. I'm planning on making it full length (6'L x 28"W x 2"D). Any plans and suggestions would be great thanks.

[WetRivrRat]

I don't have direct experience with down (just yet, that's last on my todo list - asthmatic family members.... :scared: ) - but here are some links that i've used as reference for myself:

http://www.whiteblaze.net/forum/showthread.php?5269-Inches-of-down-loft-for-a-32F-bag
http://www.trailspace.com/forums/gear-selection/topics/90935.html
http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=57158

This is a good idea - makes sense to me, I'll probably use the same technique -
JohnSawyer: I used a shop-vac to harvest down from a comforter... (http://www.hammockforums.net/forum/showpost.php?p=708132&postcount=10)

[WetRivrRat]

{...} (6'L x 28"W x 2"D). Any plans and suggestions would be great thanks.
These seem to be pretty big around here...
Red River Gorge Quilt Instructions (http://www.hammockforums.net/forum/showthread.php?t=26542)
My DIY winter under quilt with instructions (http://www.hammockforums.net/forum/showthread.php?t=1434)

Good luck

[wwk10]

Temperature ratings are subjective, but I rely on this chart originally posted on HF.
1.5" loft = 40 degrees
2.0" loft = 30 degrees
2.5" loft = 20 degrees

For your dimensions 72" x 28" x 2" = 4,368 square inches
Add 10-15% of overstuff = 5,000

5,000 / 850FP = 5.75 - 6.0 oz of down
Hard to believe, but less than 6 oz for 30degrees of comfort

BTW 28" seems narrow, but A) I am not an expert and B) I think I overcompensate the other way too much.

Calculates UQ differential http://www.hammockforums.net/forum/showthread.php?t=53701

Another UQ differential calculator https://docs.google.com/spreadsheet/lv?hl=en_US&key=0Aju4vJLH9dFcdDNkOHNsZlVnNVhOYm5kUUptbE5uV0E&hl=en_US&f=true&noheader=true&gid=0

Down/chamber TQ https://docs.google.com/a/kingknob.com/spreadsheet/lv?hl=en_US&key=0Aju4vJLH9dFcdDNkOHNsZlVnNVhOYm5kUUptbE5uV0E&hl=en_US&f=true&noheader=true&gid=6

[MAD777]

May I suggest that you reconsider the width. I make my underquilts 40" wide which is more narrow than many. I've seen them 50" wide. I weigh 200# am happy with my 40" but I could never make 28" work for me.

[wwk10]

SoCal,
MAD777 is a minimalist (gram weenie).
His suggestion to make it wider means even more than mine.

Math is the same Width x Length x Heigh (See Catsplat spread sheet. Height of chamber is higher than height of baffle) divided by Fill Power = total weight of down neeeded.