Calculating Down

[SGT Rock]

I am replacing the 550 down in a quilt with 800 down. the quilt weighs 19.5 ounces and there is supposed to be about 11.25 ounces of 550 down in it (I haven't pulled it out yet). I assume this is a straight math question since 11.25 x 550 = 6187.5 total fill. I also assume that if I do the math in reverse I will need 6187.5 / 800 = 7.73 ounces of 800 fill down. Since I am not that educated in engineering I hope I am computing this right, but if any of you engineering types could confirm or deny this for me I would be obliged.

[snuffleupagus73]

I believe the math you've done is correct. Then again I get confused with weight conversions. I think the question you ask yourself when doing this math problem is x(6187.5) is still eqivalent to x(6187.5) There's not really any conversion. So it looks correct to me. Two uneducated guesses equals one educated guess (either that or one great big mess). LOL

[JAK]

I never knew what 550 vs 800 fill was. Now I know. Thanks.

Here is an interesting site that explains why 700+ fill is so rare:
http://www.foundmark.com/pers/gallery/parkas/designer/insulation.html
( Another reason to raise your own big fat goose for Christmas. )

p.s.
You math is correct Sarge. When doing math like that I like to carry my units. i.e.
11.25 oz x 550 ci/oz = 6187.5 ci
6187.5 ci / 800 ci/oz = 6187.5/800 ci/(ci/oz) = 7.75 oz
(Oops - Corrected - Thank Joe.)

oz x ci/oz = ci x (oz/oz) = ci
ci/(ci/oz) = oz x (ci/ci) = oz

6187.5 in^3 /(12 in/ft)^3 = 6187.5/1728 ft^3 x (in^3/in^3)
= 3.58 ft^3 ~ 3.6 cubic feet

If 30 in x 80 in, how thick is that ?
6187.5 in^3 /(30x80 in^2) = (6187.5/2400)(in^3/in^2)
= 2.58 in ~ 2.6 inches ( that's a nice quilt )

[txulrich]

All real kewl, but a minor math error!

6187.5/800 ci/(ci/oz) = 7.75oz

Sarge had it right in his post.

Peace

[SGT Rock]

My math was right, and so was the guy that reccomended how much to use - Peter Pan. His "No Sniveling" underquilt he sent me was a prototype that had 550 down instead of 800 down, So to make it closer to the end product, I went ahead and got down from www.thru-hiker.com

The removal of the old down was actually the worst part, it made a real mess. After that, I took the total down weight of 7.73 and divided that by the 8 baffles. Since this came up to be .97 and my scales don't go that accurate, I converted it to grams and figured 27 grams per baffle. During transfer, there is some loss, so I measured out 28 grams for each baffle and I ended up having less transfer loss than anticipated since my quilt noqw weighs 18.2 ounces, which means I got about 7.9 ounces of down in there - about a .17 ounce overfill.

The quilt is pretty cool. I twill make a good vest, underquilt, and summer top quilt.