So why do 2oz (or more) overstuff? why not just order the next lower temp rated quilt?..
So why do 2oz (or more) overstuff? why not just order the next lower temp rated quilt?..
Some people like their down packed in a little tighter I guess...
Theory is that extra down holds the loft better, stops the air in the baffle from moving better, and doesn't increase conductivity too much.
CMFSAT
ok, first, thanks to the two previous answers.Originally Posted by kitsapcowboy
now you say it's mainly as insurance to maintain the rated temp in harsh conditions and after ravages of time, correct?
talking about a 20* TQ, what would you say would be minimum/sufficient to do this - 1oz? 2oz? is there a limit where it would simply be better to buy a warmer quilt?..
We had some good discussions here in the past on this topic.
A few items from that discussion if you wanted to kill yourself with numbers:
Here is my insulation comparison chart for MYOG across multiple fills (down and synthetic). https://1drv.ms/b/s!Apygyt54yYPwt0gfDXlK3vFZg1AL
This is also the chart that I used to conclude/prove that Primaloft Gold was a superior insulation (in terms of warmth to weight) for summer conditions (45* plus).
Here is the document specifically related to overfill/overstuff. https://1drv.ms/b/s!Apygyt54yYPwrnwpJrIVOByjm3B7
We had a lively debate about overstuff vs overfill and this was my contribution here and at BPL.
Finally- here is my 2017 temperature chart- https://1drv.ms/b/s!Apygyt54yYPwg40vo1VSor5A3Tm47w
The goal here was to update the original APEX ratings that I provided here and other places (used by a few vendors here).
It was also an effort to quantify and create a SEPERATE chart for TQ vs UQ ratings. It is clear they are not the same formulas.
It is also clear that synthetic (especially APEX) does not perform as well when used as an UQ as it does as a TQ insulation. To be fair, neither does down.
So...
To answer the original question... it comes down to an educated consumer and the individual vendor.
I don't disagree with Sailor or Kitsap's line of logic. Nor do I disagree that it plays out that way in real life (especially in damp conditions)
However for the products I make or am familiar with... (mainly UL backpacking gear) I would probably just spend my ounces (and money) on bumping up the 10* on the rating for a TQ.
An extra ten degrees often weighs less than a 10* bump.
For an UQ... my suspicion and theory is that gravity is working against you so if you ran into the multiday "slump" in performance there is a possibility you could have the down settling away from you and a small layer of convective dead air build up which would magnify the losses to a much greater degree. So in this case... some overstuff may make good sense. That said- it is important to talk to the vendor to find out how well filled the UQ is to begin with and what numbers they used to fill it to begin with. It is possible they have already compensated for this... especially in the case of the hammock vendors who tend to err on the side of caution over absolute minimum weight (specs).
That said, if properly sealed up then this minor gravity slump shouldn't be as big a factor.
https://support.enlightenedequipment...2284868-Revolt
http://www.undergroundquilts.com/uq/...0-%20sale.html
These are two vendors that are a bit hard to compare... but you may note that the EE quilt rarely if ever comes close to 2 oz difference between sizes, where this is much more common in the Zepplin. So when talking brand A... the temp jump may be a lighter choice, talking brand B... maybe the extra overstuff is. All of these are ignoring the absence or presence of treated downs too... which when talking DownTek specifically may have drastically reduced or eliminated the slump issue with their current formulation/process.
If you're looking for a current bottom line (my opinon evolves):
I would say that your biggest bang for the buck, best budgeting of grams and highest point of failure- is the UQ. By a large margin.
Thankfully, from an UL perspective, it is relatively small in area. So counting grams... It "costs" you little to jump your UQ by 10* or even 20*... generally in the 2-4 ounce range.
In a GE hammock... you've covered the bulk of your insulation there and in my opinion and experience we can likely then "push" the TQ much further, or easily cover any condition based slump in performance on a multi-day trip.
So back to the TQ then... I would not buy the overstuff, and I would not buy the next temp up. I would size it "just right".
Looking at the system as a whole I would dump my gram budget on the UQ.
Given Kitsap's scenario above... I think my wallet, my scale, and my butt would be satisfied using a 30* UQ and a 45* TQ in those conditions of roughly 40* or so.
You are much less likely to overheat when things are good, as you TQ is easy to vent and manage. And you are much less likely to bottom out as your UQ is taking up any slack in the TQ.
So if you're dumping a few ounces into the system, or looking at the total insulation system as a whole... discretionary $ and grams pay the highest return on investment in the UQ.
This isn't really a plug for it- but here is a pricing and info packet for my PLG TQ. The reason I share it is it has a good page in there that shows the relationship of TQ/UQ visually compared to the ground.
https://1drv.ms/b/s!Apygyt54yYPwg5BPmq22GYZ1SR9sNQ
Skip to page 3 on the right hand side to see what I'm talking about.
ok, thanks. I admit a lot of the math went over my head but it did get me to look at previous discussions on this very topic.
as I see it, there's an issue of defining, "fill vs overfill vs overstuff?"
leaving out manufacturer's design, I realize there is a formula they use to determine the "proper" amount of down fill but then, for whatever reason, some add a certain percent more (15%, 20%, 30%) to their bags. It makes sense to me to call this overFILL...
this may be based on their testing, customer feedback, philosophy, confidence, etc., but I'm coming to believe it's mostly marketing. as Just Bill said elsewhere, "At the end of the day they slap a rating on it that either matches or doesn't."...
OTOH, it's easier for me to think of "overSTUFF" as that amount the customer can order to be added to the bag at time of purchase. this can be to increase the warmth to address their personal physiology (cold sleeper), as insurance to maintain temp rating in wet/humid/dirty conditions, or to "bridge" a temp rating (making a 20* into a 15* or whatever), or simply their lack of confidence in the manufacturers' rating.
so, TWO QUESTIONS THAT COME TO MIND 1) how much overstuff is necessary to achieve a 5* change in say, a 20*TQ - 1oz? 2oz? more?..
and 2) what is the "sweet spot" in function, weight, and cost between overstuff, and simply going to the next lower temp rating? ...
other justifications are to extend the product life after loft degrades over time. I have a couple down bags/quilts (1 new, 1 old) that even after being fully lofted and fluffed, show voids or areas where there is no down.
is this correct fill? is it underfilled? should I have gotten overstuff?..
I don't get into the science of it all but I always order +1oz of overstuff on my quilts from HG. It just seems to keep them looking that extra bit puffy and makes me more comfortable to push the lower limit of the rating.
Yar- this is mainly super nerd gear maker stuff. It was discussed mainly for those of looking to build SUL bags or better understand MYOG.
But you did get to the root of the discussions:
FILL-is calculated by volume (Cubic Inches) which should be as simple length, width, depth (loft) of your project.
However trying to get it exact doesn't work- but mainly because our geometry/modeling of the actual shape is a bit flawed as we aren't building cardboard boxes but fabric shells that move.
OVERFILL- then is the % you add to the base calculation to correct for this margin of error. 30% is a pretty standard number... but each designer/vendor may modify this "fudge factor" based upon their experience and feedback.
Assuming this is all done correctly- you should be done and ready to rate your bag.
Also- real life is not a laboratory. We do not fluff our down and let it rest for 24 hours prior to using it. So some of this overfill is math slop in calculating the volume of the shell, some of it is the reality that XXX Fill power down will never achieve that fill power in real life.
OVERSTUFF- is basically "an extra pinch". To be blunt; I hadn't really seen that option coming from anyone but HF vendors when I first got interested in hammocks. I'm not sure where it came from and seemed to be more a customer driven thing. If the bag has been properly designed and filled to it's rating... as that charming fella you quoted mentioned... the bag should perform.
In logic land one might argue for overstuff-
1- non-treated downs "slump" after several days exposed to humidity and the real world. So the more often you encounter this problem.. and if you had a chance to correct for it via the custom options offered here... guess it makes sense to ask for some overstuff to combat this issue. In theory treated down solves this issue.
2-Everything wears out/breaks down. We can talk about a down bag lasting a long time but just because you use your bag 20 nights a year, store it well, care for it, and it lasts 10 years doesn't really mean it lasts forever. It lasted 200 nights. So overfill as a preventive measure to extend the life of a heavily used bag makes sense. I believe there are a few established companies (western mountaineering, etc.) that have offered reconditioning services to effectively add that extra pinch to an older bag.
3-You may be a compression victim... just because you can get a 6 strap 18 way 3:1 mechanically advantaged compression sack to demolish a down bag to the point that each atom of down is touching... doesn't mean you should. If you frequently pack like this (which good organized backpackers were once taught to do) then you didn't wreck your down per say; but it will take some time to recover. So if your bag looks listless in camp compared to how it came out of the drier you may be inclined to overstuff it so that it rebounds faster. Or you could just leave the 6-8 ounce compression sack at home and give it a good half hour to fluff up before bed and avoid the overstuff too.
In science land-
I have absolutely no idea where the concept of overfilling a down product somehow equates to an increase in performance measured in degrees.
Items 1-3 in logic land would see measurable increases in performance from overstuff.
However there is no evidence I am aware of that would involve overstuffing down leading to a gain in temp rating. I'd be happy to see some.
This topic was debated here and at BPL a bit.
In short- insulation has no value on it's own other than it's ability to trap air.
If you pack in more and more down... don't you displace more and more air? The answer is yes. So in theory you have displaced the very thing you are insulating and decrease the temp rating of the piece of gear.
In reality; it seems there was some testing to determine if this principal would work and the basic gist was that (in reasonable amounts) that down did not LOOSE performance from being overfilled 10-20% beyond ideal.
SO the scientific moral of the story- it didn't hurt. But there was no thermal advantage. If there was you'd have nut-job gram weenies like me sewing up 1" baffles stuffed to 200% to save a little weight on shell materials. Simplest way to put it- down temp rating goes up when loft increases. In theory- if you overfill a properly filled shell- it just gets denser, not taller.
So again... I have no idea how you could possibly make any statement on; oz of overfill = *F. You would basically have to run the full set of numbers and specs the designer did to create the bag in the first place.
Back to logic land and real life:
If you don't care about an ounce or two.... and now that down is currently cheap as dirt... toss in an extra ounce or two for safety. It can't hurt and your gear will do well.
If you're watching your grams- buy a good product from a good vendor and use just what you need.
To answer question 2 (question 1 answered by the statement I know of no way to quantify or correlate over fill to temp rating increases):
The sweet spot depends on the vendor and the piece in question IMO.
Normally I think I would have answered this simply and said the same as above. UL minded folks will find bumping up 10* the sweeter spot. Value minded folks will find overfill a nice option to protect their investment.
As my knowledge and experience grows with UQ's though... I believe a different set of rules applies.
It may be worth putting overfill in these products compared to TQ or apparel. However... that is a question for the vendor to answer as you have no idea if they have not done this already.
The bottom line remains the same... if you buy something you should expect to get what you bought... within reason.
If you know for a fact that you sleep colder or warmer than the average customer; you should adjust your purchase accordingly. Not expect the vendor to magically correct it. If you frequently go out in heavy humidity or deep winter trips lasting more than 3-4 nights then you should expect some environmental degradation. But on night 1 of your trip- the product should work fine.
So assuming you have bought from a quality vendor with ratings that have been field tested and accepted by the community at large: then I still feel you should jump temp ratings up or down if you are looking to fine tune your experience. I don't think overfill has any bearing on temperature regulation unless you are experiencing the logical issues in the field that would cause the bag not to perform as intended.
I think my bottom line... overfill was a customer service or marketing offering for bend over backwards cottage vendors.
I don't think it has any real value for any of us and has become confusing and misleading especially when many vendors are now within 2-4 oz per temp jump anyway.
I think both vendor and customer would be better served with the tried and true advice of simply shopping by the temp rating.
It is simpler to say... I have (whatever need or condition) and I will buy a bag X* warmer or cooler than average to compensate for my specific use.
This would free both vendor and customer up to better discuss and understand those individual items.
To be blunt- realize it or not- most of those not making their own gear are buying a down product that is already overfilled, overstuffed, and over rated.
Average rating... well even if 70% of customers are happy with your rating. If 10% complain vocally then you will need to meet their below average demands to maintain your reputation and customer satisfaction.
When you hear about SUL backpackers "pushing" gear 10-30* past it's rating... they aren't. They are simply using gear closer to where science dictates it be used.
Down is light... so a handful of ounces truly is 10-20* more in some gear... the truth is simply that your average gear is rated for your slightly below average user so nobody complains.
And sleep is sleep... nobody wants to be cold and for your best gram and dollar nothing works as well as a warmer than needed piece of sleeping gear... so it's a good lie we all agree to tell.
Other than a rare guy like me- nobody ever returns a bag for being too warm. (Yes I have)
Your average customer happily posts "I was toasty right down to the rating... best quilt ever!" That's what we all like to see. So that's what we get.
one other quick thought-
"Ounces of overfill" is a meaningless concept regardless.
If I add an ounce to a Yeti sized UQ... I might have added 10-20% more down.
If I add an ounce to a long wide TQ... I might have added 5% more down.
This doesn't even discus the temp rating... simply the size of the product. You need to very specifically know the product, dimensions, loft, temp rating, and perhaps the formulas the vendor uses to even debate it.
Even if we are saying and ABC brand XYZ Top quilt... one ounce to a 50* is not one ounce added to a 0*.
So again- without running the numbers of the entire piece of gear (Fill and overfill) you have no context to meaningfully add overstuff. Or more accurately stated- to increase the Overfill % of the total bag.
The very final thought-
One of those papers I posted discussed how down deforms the shape of every baffle... which is one reason for overfill %.
If you keep stuffing down in, you keep deforming the baffles. At some point your 42" wide UQ can easily become a 38" wide UQ that looks like an air mattress because the down will keep pushing to find equilibrium and a cloth box eventually turns into a cloth circle if you push hard enough.
Totally agree! I don't want to sound dismissive of all the in-depth conversation, but I feel like this is all you need to know.
If I'm already spending $200-300 on something, an extra $8 for 1oz peace of mind is priceless. Especially considering how much life you will (can) get out of a quilt. I'll never miss that $8 years down the road, wondering if I should have added a little extra. After 5 years and 8 quilts (or more?) I never second-guessed myself on the overfill. I can't imagine 1oz hurting anything. More? Possibly.
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