Ultra Heavyweight Winter Down Quilt Set

I've aquired two down pillows with 39 oz. of 600+ fill down each (78 oz total) and am starting on design of an ultra heavyweight winter top and bottom quilt set for my hammock. Because this will be used only for winter camping only the overall weight of the final product is not as much of a concern, but I am wondering just how much of the down I should use. Thanks to the great calculators developed by forum members (Meteor and gt7599a quilt spreadsheets) I am able to calculate just about any weight quilts, but I don't really know how that will translate to warmth.

Has anyone had experience with either DIY or custom made down quilts targeting sub-zero temperatures? And how much down and and at what fill power have you used?

I haven't made any sub zero quilts..however I have made quite a few quilts for different temp ranges. The amount of warmth the quilt provides is a product of the amount of loft. The more loft you are seeking equals the amount of down that will be required. The amount of down is then related to the fill power of the down. With that said most quilts that are in the 0° range are around the 4ish inches of loft range. I'm not on my computer now but there is a great thread in the under quilt sub forum that discusses the relationship of loft and warmth quite well. I hope that is of some help.

I can get a fairly good estimate of the loft required for various temps down to 0 degrees, based on the nice variety of quilts from the various cottage makers. However, I'm guessing there probably isn't a larget market for sub-zero quilts as I haven't seen any commercially availible.

I can calculate the amount of down required based on fill power, but I guess what I really need to know is how much loft will get me the a given temperature? E.g. What temperature range would a 5 inch or 6 inch loft achieve with a 15-20% overfill? :confused: Are there any commercially availible quilts with sub-zero ranges?

I'm no expert with this in any way and there are a number of folks here who hang in sub zero temps and hopefully they'll chime in. One thing you might want to keep in mind is the fill power your using and what that will weigh in the end to achieve sub zero, not so much for the TQ but the UQ. You might need to have extra suspension just to keep it directly under/against you.
Good luck with your project.

bill

Have recently overstuffed my TTTG Polar Pod. Stock polar pod measures 10.5'x7.5' w/30 oz. of 900fp down. I added 20oz. of 850fp. 10 channels,2 oz.over stuff per/channel. This gives me a total of 54 oz.of down:boggle:,I forgot I ordered the pod with a 2 oz. over stuff. I did this based on Fourdog's 16 oz. overstuff of a Speer Pea Pod. I also added a suspension system to carry the extra weight. I've personally have gone down to a -20 F, using different combinations of 0deg f UQ's, pad's. sleeping bags and TQ's. What I'm working towards is the least fiddle factor necessary. Everything takes longer in the winter.

Just a slightly different thought. Would using 2 UQs be a more flexible option? You should be able to attach a second one to the same points on the hammock. Most UQs give you a range below what you could comfortably sleep. But adding 2 together may not be exactly 1+1=2 it may work out to a 0 degree plus a (I'm assuming Fahrenheit) say 10 degree may get to to minus 10 to 15F. I read some survival guy talking about buying 2 sleeping bags for maximum use, a warmer one and a cooler one, combined they'll keep you warm to very low temps and be a lot cheaper than a single low temp bag.

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Originally Posted by mbiraman

One thing you might want to keep in mind is the fill power your using and what that will weigh in the end to achieve sub zero, not so much for the TQ but the UQ. You might need to have extra suspension just to keep it directly under/against you.

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Very good point. I had planned on using heavier shock cord, and an additional ridge line support in the middle, but given the weight, I may start with two additional supports. If I start from scratch, I should still have amble time for testing and modification before the temperatures really drop.

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Originally Posted by stairguy

Have recently overstuffed my TTTG Polar Pod. Stock polar pod measures 10.5'x7.5' w/30 oz. of 900fp down. I added 20oz. of 850fp. 10 channels,2 oz.over stuff per/channel. This gives me a total of 54 oz.of down:boggle:

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This is good information. For this pod, the equivalent volume of down in only 600 FP would be about 74 oz. I had my eye on better quality down, but since I was able to get 78 oz. of new 600 FP down for only $50, I couldn't resist. For my summer and fall gear, I plan on using smaller amounts of the good stuff.

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Originally Posted by yaddayaddajoe

Just a slightly different thought. Would using 2 UQs be a more flexible option? You should be able to attach a second one to the same points on the hammock.

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I'd like to have this be just a dedicated winter set, all in one package for convenience and consistency in use. Also, that way I still get to shop for lighter weight gear for backpacking, and everyone knows more is better. :rolleyes:

I made it back to my computer and did some rough temp calculations based on using 600fp down..I am no math whiz, but from the quilts iv'e made i have been pretty accurate..
So for a quilt that is 72L X 52W with 9 baffles and 10% overstuff with 4 inch baffle height with a maximum hight of 4.5 inches.

The amount of down per chamber would be approximately 3.35 oz per for a total of 30.15 oz of down. This would produce an average loft of around 4.25 inches and approximately -10 to -15ish degree rating based on my calculations.

As always YMMV, and these calculations are just some quick math based on down density and average loft that would be achieved to calculate the temp rating. I hope that makes sense :)

Thank you for the information, that is helpful, and gets me in the right range. Has anyone made a calculator or chart that approximates temperature ranges for various loft heights? You indicated 4.5 inches of loft with the 10% overstuff might get to -10 or -15. Any experience with loft sizes over that?

What temp range are you looking for? I will be happy to run a few numbers for you :) Like others mentioned thought your suspension set up will be very important when your talking about these kind of weights for a quilt to keep it snug or you will loose the benefit of the hight amount of loft. I can calculate approximately any loft to temp ratio..how it will perform in the real word however may be another matter. I will be happy to run some more numbers for you like a said, and they you should just go for it :) that the only way to find out if it's going to work for you. Here in the Middle Ga area and most of my hiking grounds in N GA even in the dead of winter if it gets in the teens it's cold ;)

I am reading some quantities here that remind me of a severely DIY overstuffed quilt here that I find unpleasant. It is too much to compress, and too much to fight with in the hammock. (That said with due respect for those who willingly share twin beds with others.)

I'd suggest you do a trial with carefully measured quantities of down and a sample chamber, such as a pillow case.

You shouldn't start sewing without tests with your thread and fabric for tensions etc. No different with down of unknown quantity.

Average nightly temps in the areas I camp are single digits throughout the winter, and often vary significantly below zero. Planning would depend on forecast weather (with a margin of safety). Before I start testing, I'd like to get an idea of what loft it would theoretically take to get to -20 or -25 as a bottom temp.

I ran a few more numbers for you based on my previous calculations. With a 5 inch baffle height and a 5.25 max chamber height. With 9 baffles it equals out to 3.96 oz per baffle w/ 600 fp for a total of 35.67 oz of down. That would work out to be about 5.13 inches of total loft. I come up with a temp rating of around -25 to -30 give or take a few degrees. That would be one heck of an underquilt for sure! It would be a monster :D. I will say that DX makes a good point about some single baffle experimentation, and testing before going all in. I know you said weight is not a major concern but a quilt of that size using 1.1 ripstop for the shell and .9 or 1oz no see um for baffles your looking at around 50 oz for the completed quit with out suspension. I say run some experiments and get a solid plan/diagram together and see what happens. In those kinds of temps you can never be too careful! If you need anything else please let me know :D

When I go to see how Western Mountaineering does it for their deep cold SBs, I see two layers, which limits the variation in heat flow. Other steps to stop air leaks, too. Severe temps are associated with wind, and convection currents matter a lot more.

Even if this were not going to be heavy, fit matters more than it does at higher temps. I wonder if more attention needs to be paid to controlling air and water vapor with fabric selection, as against brute force of lots of down.

I completely agree with fit being very important to the effectiveness of the quilt as well as fabric selection. With that much heat being generated there would be moisture accumulation for sure. The use of a wind block on the head and foot end would be a must to prevent heat escape and cold seeping in. I have never had the need to make a quilt for that temp range. I also wonder if making a double layer of baffles that were slightly offset would be effective..but then that would be up to the OP and there sewing skills. Yall have me intrigued to the point of wanting to make one just to see if it would work. I also wonder if there is a certain point where the amount of loft that is wanted becomes unobtainable via traditional baffle construction...hmm something to look into.

I am also constructing a canvas sock, to help with the wind while maintaining breathability. I'm currently testing various designs, though the weather has only been in the mid to upper 30s so far. I had also planned on adding draft collars at the head and foot ends to help prevent air leaks. I was considering a double offset baffle, but was unsure how much benefit it would gain over the the standard baffling.

I'm interested in your thoughts on managing vapor permeability of the UQ/TQ with material selection. My initial thought was to use a vapor barrier liner to help prevent condensation in the down. The liner would also allow me to potentially pair its use with other quilt sets. Do you see additional benefit in using coated materials in part of quilt construction?

Because you are thinking "special purpose", consider custom design for your hammock.

Draft stoppers and collars may be inefficient use of materials. Traditionally, on SBs, they fill and insulate a space along zippers, or are smaller-circumference collars, applied full length. In contrast, when used at the ends of hammock UQs they are expected to be scrunched, stuffed like backing for caulk to fill furrows.

I'd suggest instead a short trapezoidal skirt of low permeability fabric sewn to the end and up the side seams of the UQ, just long enough so the inner hem overlaps and encloses the last few inches of the UQ. That hem has a channel and is threaded with a light shock cord and a cord lock. Total weight for both skirts, head and foot ends? An ounce?

The full length UQ gets mounted and the skirt hem gets pulled just snug against the loft. The seal here,of a few inches of skirt overlapping a few inches of UQ is excellent, with the minimal compliance of the U. Air passing up and down the furrows beneath the UQ, such as when feet shift and those furrows re-form inside the hammock, cannot escape the skirt because the skirt is sewn on three sides, and cinched on the fourth. Airr cannot get in from the outside either.

Wow, I like that line of thought. Basically a hammock custom fit for the UQ to address the heat seal, rather than trying to modify the UQ fit to seal to the hammock in extreme conditions. With materials for the hammock generally being a fraction of the cost of the UQ, that is a really interesting suggestion.

What started as a relatively rudimentary project may just turn into something much more interesting...

I as well really like that thought, and it gets the gear making juices flowing for sure! Its amazing how a simple question can take us down the proverbial rabbit hole. DX thank you for your gracious input and OP I hope you haven't been dragged in over your head...or at least to deep anyways ;)

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Originally Posted by vampiresmiley

Wow, I like that line of thought. Basically a hammock custom fit for the UQ to address the heat seal, rather than trying to modify the UQ fit to seal to the hammock in extreme conditions. With materials for the hammock generally being a fraction of the cost of the UQ, that is a really interesting suggestion.

What started as a relatively rudimentary project may just turn into something much more interesting...

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Every time I get into a Clark hammock, I see the stitching across the bed of the hammock. The company is still in business, and still stitching those pockets.

So, I suggest to you that this can be easily tried with just about any hammock

You can even keep all of the stitching in the side hems on the sides and within the channel, if you insist on not putting any stitches across the bed of the hammock, That will make the skirts longer than necessary. Assuming a 10 ft hammock an 80" UQ, and 5" over overlap/ adjustability, it is a 2' swath of fabric for each skirt.

With the anticipated weight of the quilt, and the expected additional suspension, the skirt is puzzling me a bit. The ability to run the suspension lines out of the skirt would need to be built into the design, possibly just reinforced button hole type openings at the necessary points.

Did your vision of this skirt include any ideas for suspension?

Also, I'm considering a double layer of 2.5 inch baffles on the UQ with a different channel count so the baffles would offset from one another - e.g. 10 on the outer and 9 on the inner, so the center baffles would be evenly offset, moving closer towards the edge. It would be challenging, but is intriguing to me.

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Originally Posted by vampiresmiley

With the anticipated weight of the quilt, and the expected additional suspension, the skirt is puzzling me a bit. The ability to run the suspension lines out of the skirt would need to be built into the design, possibly just reinforced button hole type openings at the necessary points.

Did your vision of this skirt include any ideas for suspension?

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No problem running the lines out. They just are run through gaps in the non-continuous seams of the skirt to the gunwales of the hammock.

"Non-continuous?" Sure, the gaps between series of tacks will all seal up under tension.

Come winter, and even well in advance of that, Shug has occasion to show again one of his pics with his down-filled parka wrapped around the tail end of the hammock, enclosing the tail end of his UQ (and all the nasty furrows and gaps, stable and transient). eg http://www.hammockforums.net/forum/s...0&postcount=10

(Well, not so in that pic, because a parital UQ is in use.......)

That's all I'm proposing with the skirt. It even seems to me there's better use to made of the parka----maybe inside the hammock wrapped around the foot box of the UQ, closer to where scant heat is flowing?