Overstuff question

**Mike210** · 01-09-2011, 21:50

I just got a hammock and am already planning on DIYing top and under quilts for myself and my son. However I have a question about overstuff. I know it is good to overstuff a down quilt as it keeps the down from shifting. However how much is appropriate?

Looking at the quilts from Hammock Gear on the 3 season icubator it looks like the dimensions are 78x44x2. 12oz of 800 fill down seems to work out to almost a 40% overstuff whch seems high. Am I not doing the math right or is there some other factor I am not figuring. I want to make sure I am ordering the correct amount of down for my DIY projects and this is causing me some concern.

**jbo_c** · 01-09-2011, 22:11

I recently finished an UQ with about 16% overstuff. It is ok but I'm going to go up to a little over 25% for the TQ I'm working on now. Not saying either of those is right just saying what I saw and decided. I'd say 20-35% depending on how much fudge factor you want to build in.

Jbo

**traftonm** · 01-10-2011, 09:12

If you overstuff more then about 10% it adds nothing but weight does not add much insulation. The idea is air space and if you reduce the air space with down you may loose a little insulation value. At least in insulation to weight.

**Lonely Raven** · 01-10-2011, 10:40

Originally Posted by traftonm

If you overstuff more then about 10% it adds nothing but weight does not add much insulation. The idea is air space and if you reduce the air space with down you may loose a little insulation value. At least in insulation to weight.

While I agree with this, I also feel that too many down products have barely enough down in them (usually commercial stuff).

This weekend I slept at -14F with a Winter Incubator and Winter Mamba. Both were properly stuffed with no dead spaces (hold your quilt up to a light, can you see through it!?!) and I was comfy.

There is a point of diminishing returns, but it's difficult to judge/measure where that is. So if you can handle the weight, I'd error on the side of over-stuff.

**angrysparrow** · 01-10-2011, 10:49

Originally Posted by traftonm

If you overstuff more then about 10% it adds nothing but weight does not add much insulation. The idea is air space and if you reduce the air space with down you may loose a little insulation value. At least in insulation to weight.

It's about more than dead air space. Down actually does provide insulating properties.

Overstuffing diminishes heat loss through convection from breezes. Many hammockers have felt how a cold wind blowing in can rob a down UQ of it's warmth from the outside. If you have two quilts with equal loft but one is more densely stuffed, then it will be more resistant to that.

**Mike210** · 01-10-2011, 10:52

I'm not overly worried about the weight as most of my camping is car camping. Mainly worried about how much down to order as I only want to order once to minimize the shipping charges. While having too much is not bad, I guess, at some % of overstuff don't you hit a point of diminishing returns? Just trying to figure out where that point is.

**Lonely Raven** · 01-10-2011, 10:58

Originally Posted by Mike210

I'm not overly worried about the weight as most of my camping is car camping. Mainly worried about how much down to order as I only want to order once to minimize the shipping charges. While having too much is not bad, I guess, at some % of overstuff don't you hit a point of diminishing returns? Just trying to figure out where that point is.

I wouldn't hesitate to overstuff 10-20%. If I was expecting colder/windy weather camping or I was a cold sleeper, I'd lean towards 20%.

I read something on Backpacking Light about some studies done about down and the point of diminishing returns...but even after pouring over the info for hours, I still don't see any hard and fast numbers. So like I said, error on the side of overstuff.

**jbo_c** · 01-10-2011, 12:41

Going from 10% to 20% with 12oz of down is only an ounce of weight - cheap insurance for me, though I realize not for some.

Jbo

**Mike210** · 01-10-2011, 14:57

Originally Posted by jbo_c

Going from 10% to 20% with 12oz of down is only an ounce of weight - cheap insurance for me, though I realize not for some.

Jbo

I guess that's true...when you do the math its only a couple of ounces. However, I plan to order it premeasured from Stormcrow and would like to get it right the first time.

Maybe I'll just order the difference from 10 to 20% in a seperate packet and then I can add it if I think its needed.

**TiredFeet** · 01-10-2011, 20:32

Compute the ideal amount of down using the fill power, then over stuff. The amount of over stuff depends on personal preference, 10%, 15%, 20% ...

One reason to over stuff: With time down degrades due to moisture buildup when used and just plain breakdown of the down fibers. Thus 900 fill power down becomes something less, 800 maybe?? and 800 fill power becomes something less, 700 maybe?? Never seen any measurements made, but it does happen.

So by over stuffing initially you compensate for the degradation over time of the loft of the down.

Also, fill power is based on ideal laboratory conditions which are never matched in actual experience and considerable preparation of the down to obtain the ultimate loft possible. Thus, the real fill power of down is less than the number quoted.

So by over stuffing you also compensate for the real fill power of the down.