UQ Overstuffing

**dustinpn** · 01-20-2014, 23:24

What is the point? If I buy a 20F underquilt and overstuff with 2-3OZ what is that effectively making the temp rating? Is it just a crafty way of reaching a middle ground between ratings sold? Somewhere between 0F and 20F?

**nuttysquirrel** · 01-20-2014, 23:36

aside from making your UQ warmer, more down means better down stability.

**Storytellertn** · 01-21-2014, 00:16

Originally Posted by dustinpn

What is the point? If I buy a 20F underquilt and overstuff with 2-3OZ what is that effectively making the temp rating? Is it just a crafty way of reaching a middle ground between ratings sold? Somewhere between 0F and 20F?

If I understand correctly, the amount of loft (in inches) determines the degree of effectiveness. I'm not sure how many oz of down five 1 inch of loft?

**nuttysquirrel** · 01-21-2014, 00:29

the amount of overstuff only lowers the temp. rating to an extent, after a couple of oz. you dont gain much warmth. remember the baffle hight largely determines the warmth, stuffing 10 extra oz. into a 1'' baffled quilt wont realy make it much warmer.

**neo** · 01-21-2014, 00:31

Originally Posted by dustinpn

What is the point? If I buy a 20F underquilt and overstuff with 2-3OZ what is that effectively making the temp rating? Is it just a crafty way of reaching a middle ground between ratings sold? Somewhere between 0F and 20F?

in my experience it best just to get a lower degree under quilt

neo

**Storytellertn** · 01-21-2014, 00:34

I went with the Winter Yeti by WB. 0 degree.

**genixia** · 01-21-2014, 11:30

0% overstuff represents the theoretical mass of down needed to fill the baffle volume 100%. This mass depends on the fillpower of the down - as FP goes up, less mass of down is needed to fill that volume. Your quilt rating is calculated based upon filled baffle volumes.

That theoretical mass is just that - theoretical. Practically there are factors that can prevent 0% overstuff from behaving ideally.

Down can clump in storage and leave unevenly filled baffles.
The weight of the top fabric isn't accounted for in fillpower testing.
Condensation within the down reduces loft.
It takes time for down to fully loft. I recently read Testing sleeping bags according to EN 13537:2002: details that make the difference that studied the effectiveness of the EN13537:2002 rating system for sleeping bags. The research team varied each the control parameters and how they could impact testing. One of the most interesting results was that of time between unpacking a bag and testing, especially with down bags. The standard calls for 12 hours minimum, but doesn't specify a maximum. The insulation value after 106 hours of conditioning could be as much as 15% higher than that after 16 hours, which translated into 8C difference in the rating. This is interesting to us because the way that fillpower is calulated requires the down to be conditioned first. The US and EU methods are different, but they require a minimum of 48 or 72 hours of steam or tumble conditioning. From this I surmise that to get the theoretical maximum loft of your 0% overstuff bag you'd need to tumble dry it for 3 days or wait 106 hours, and if you don't do either than your insulation could be compromisd by as much as 15%. Obviously, neither is practical in the field.

Overstuffing helps compensate for all of these issues. That paper linked above is well worth a read btw.

**OutandBack** · 01-21-2014, 11:59

Originally Posted by nuttysquirrel

the amount of overstuff only lowers the temp. rating to an extent, after a couple of oz. you dont gain much warmth. remember the baffle hight largely determines the warmth, stuffing 10 extra oz. into a 1'' baffled quilt wont realy make it much warmer.

I respectfully disagree. OK not on the 1" baffle but in true winter quilts I disagree.
I recently had a 15F full UQ overstuffed with 1oz per channel. (7oz total)
Although I have only tested it to 8F this year I feel confident I can go below 0F with no trouble.
For me overstuffing prevents thin spots in areas where the down is not evenly distributed and the down tends to stay in place better.

Here is the exact same model of UQ not overstuffed, 3 years old with over 100 hangs
can you see a slight difference in loft?

**dustinpn** · 01-22-2014, 13:22

Originally Posted by genixia

0% overstuff represents the theoretical mass of down needed to fill the baffle volume 100%. This mass depends on the fillpower of the down - as FP goes up, less mass of down is needed to fill that volume. Your quilt rating is calculated based upon filled baffle volumes.

That theoretical mass is just that - theoretical. Practically there are factors that can prevent 0% overstuff from behaving ideally.

Down can clump in storage and leave unevenly filled baffles.
The weight of the top fabric isn't accounted for in fillpower testing.
Condensation within the down reduces loft.
It takes time for down to fully loft. I recently read Testing sleeping bags according to EN 13537:2002: details that make the difference that studied the effectiveness of the EN13537:2002 rating system for sleeping bags. The research team varied each the control parameters and how they could impact testing. One of the most interesting results was that of time between unpacking a bag and testing, especially with down bags. The standard calls for 12 hours minimum, but doesn't specify a maximum. The insulation value after 106 hours of conditioning could be as much as 15% higher than that after 16 hours, which translated into 8C difference in the rating. This is interesting to us because the way that fillpower is calulated requires the down to be conditioned first. The US and EU methods are different, but they require a minimum of 48 or 72 hours of steam or tumble conditioning. From this I surmise that to get the theoretical maximum loft of your 0% overstuff bag you'd need to tumble dry it for 3 days or wait 106 hours, and if you don't do either than your insulation could be compromisd by as much as 15%. Obviously, neither is practical in the field.

Overstuffing helps compensate for all of these issues. That paper linked above is well worth a read btw.

Very informative. Thanks a lot for all of that.

**Paul-Stefi** · 11-05-2014, 07:59

I realize this is an old thread but I have questions and rather than start a new thread I figured I would just comment on this one. I understand that overstuffing can aid in loft and warmth, however is there a point where the amount of overstuff becomes pointless. What I mean by that if I have a 20f UQ with 1oz of overstuff and a 20f UQ with 4oz of overstuff is the 4oz going to be 4x better or am I overthinking this. I am thinking 20f is about what I want to buy but I would like the option of going colder in emergency cases without having to buy a 0f UQ. FYI my tarp has doors which may help too.
Thanks
-Paul