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5oz XP rating of 20* with only 1.2” loft?
Posted: 05 July 2007 04:55 AM   [ Ignore ]  
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Hello All!,

I am playing with the idea of making my own quilt. Either down or Climashield. I see plans here for the down quilt, as well as a kit for same, but I don’t see any info on a XP or PL1 quilt. Does anybody know of directions for a synthetic fill quilt? Or even better, is there a kit?

Also, is warmth rating of synthetics based on something besides loft in comparison to down? I notice that the heaviest weight of Climashield is called appx. “20*”, (“5 oz/sq yd: @1.2 ” loft. clo=.82/oz… Total CLO : 5.0 oz * 0.82 clo/oz = 4.1 (approx temp rating 20 degrees)”. So a temp rating in the 20s can be achieved with 1.2” loft? A down bag rated at 20* would normally have about 5” total loft ( total both layers—2.5” single layer. )


Would the loft on this new Climashield be about the same as with PG Delta? The reason I ask is that I have a so called “15*” PG delta bag( Cat’s Meow) with an Endurance shell. Apparently they are lowering the rating about 5* due to the shell, since the regular Cat’s Meow was always a 20* bag. Now I realize there are almost infinite variables re: temp ratings and individuals. And I sleep a bit colder at 58 years than I did even at 48 years. However, for me this bag ( after some loft loss due to age/usage) is just barely good in the mid-high 20s under the stars, and that’s with light weight fleece top, bottom and hat with draft collar and hood cinched down.

But here is the thing: even after loft loss, this bag still measures appx. 2.2 to 2.4” of top layer loft. In all spots measured at least 2”. That is fairly close to the loft of down bags with similar temp ratings, though not quite as much.

So 1.2” of XP seems a good bit away from the 2+” used in these 20* bags loft, both PG and particularly down. I must say that I have always been a bit warmer in the similarly rated down bags( when dry!).
Bottom line to my questions: is the loft of PG Delta, even though with a lower “clo” per oz, greater than XP? So that 1.2” of XP could be expected to equal about 2” of Delta warmth wise? Or, more likely I suspect, does this mean that XP will have more loft and/or clo per unit weight, but loft wise I am going to need some amount of XP ( or PL1 or sport) that will give me about the same loft as my PG Delta bag, if I expect to be as warm as I am in that bag?


Sorry about rambling. What makes this a confusing comparison is that I have no “clo” or loft per weight specs for PGDelta, and I have no idea what weight of Delta was used in the bag I have available for comparisons. Experience has shown me that for hiking the Wind Rivers of Wyoming in September or early June, I don’t want a bag or quilt that is not at least as warm as my Cat’s Meow Endurance.

I just returned the Cocoon 180 quilt, though it was wonderfully light weight,  it didn’t seem to me that it’s appx. 1.2” to 1.3” single layer loft, even wearing warm clothes with it, would be warm enough for my needs.
Thanks in advance
Bill

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Posted: 05 July 2007 01:07 PM   [ Ignore ]   [ # 1 ]  
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Down is a loose insulation.  The quality of down and the density to which you stuff it is not standardized.  In contrast, synthetic insulation comes in sheets of uniform thickness.  This is why you can use the normalized weight per square yard of the insulation (basis weight) in your calculation of total clo (a measurement of thermal resistance).

The clo value of polarguard delta is 0.67 clo/oz.  The fill weight of the cat’s meow bag was 1 lb 12 oz of delta.  Based on my own patterns, a ballpark figure for a regular size bag’s area is 4.5 square yards.  This would give a basis weight of 28 oz/ 4.5 sq yds = 6.2 oz/sq yd polarguard delta.
The total clo for your cat’s meow delta bag would be somewhere in the neighborhood of 6.2 oz * 0.67 clo/oz = 4.2

RE clo of 4.2: this is about what I would expect for a bag with a rating around 20 degrees.  The rule of thumb for clo values is that 2 is good to around 40 degrees, 4 to 20 degrees, and 6 to 0.  But as with all of these ratings, the subjective part is where you peg a clo value to a comfort rating.  You’ve just gone to great length to tell me that you were cold in a cinched down full mummy bag with more than 4 clo, draft tubes, shingle construction, and internal draft collars.  You’re considering making a bottomless quilt with minimal air sealing.  So I agree with you: something like the cocoon 180 quilt or a single layer of 5 oz xp in a quilt of your own design will not be enough for you.  Maybe you should shoot for something in the 6 range for the total clo of your project quilt.  This would be around 7 oz/sq yd of XP, so something like a layer of 5 oz and a layer of 2.5 oz would be about a clo of 6.

The 180 quilt uses three layers of 2.0 osy delta:  (2.0 * 3) * 0.67 = 4.0.  Again, this is about what you would expect from something rated to 20*.  They’ve also specifically mentioned that it was designed for use with supplementary clothing which is good since it is, after all, a quilt and as such will be more vulnerable to heat loss from air infiltration than something like your cat’s meow mummy bag.

A quilt has large panels, so for ease of construction you would be best off to stick with continuous filament insulations.  You can stabilize them with simple yarn-loops quilting. 

XP has a clo value of 0.82 clo/oz.  The 5.0 oz basis weight XP has a clo value of 5.0 * 0.82 = 4.1.  Note that you get the same clo value for one less ounce of insulation basis weight by going with XP over delta.

AYCE

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Posted: 05 July 2007 01:55 PM   [ Ignore ]   [ # 2 ]  
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Thank you AYCE for your very helpful response. You have pretty much confirmed what I had been thinking/guessing. Which is that, for me, I’m probably going to need something a little thicker than one layer of 5 oz. XP to be comfortable at 20*, (particularly considering the increased draft problems with a quilt). And that this can be done by layering more than one sheet of XP. Now I just need some plans to guide me to do just that, or preferably a kit!
Bill

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Posted: 06 July 2007 05:27 AM   [ Ignore ]   [ # 3 ]  
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WindRiverMan - 05 July 2007 04:55 AM

So a temp rating in the 20s can be achieved with 1.2” loft? A down bag rated at 20* would normally have about 5” total loft ( total both layers—2.5” single layer. )

Clo rating notwithstanding, it seems unlikely that a 1.2” thick layer of any synthetic will be that warm.  That would mean that it would have to stabilize the air twice as well as down.

...is just barely good in the mid-high 20s under the stars…

Keep in mind that bag ratings assume sleeping in a tent.  Sleeping out is normally much more demanding.

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Posted: 06 July 2007 01:03 PM   [ Ignore ]   [ # 4 ]  
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BillK-

If you accept that two insulating materials sufficiently alike to be used in backpacking bags and apparel can have different thermal resistance, than what you’re disagreeing with is my subjective clo to warmth chart.  And I have no problem with people figuring out for themselves how to peg a clo number to a comfort rating. Reasonable people commonly disagree about comfort ratings because they are fundamentally subjective.

If in spite of the independent heat loss research done in places like Kansas State U and Natick Labs you still think that a ruler and direct measurement of loft gives better results, use the direct loft measurements given with every synthetic insulation product I sell rather than the clo values.  At its heart, this line of thinking believes that an inch of insulating loft is essentially equivalent among products.  And at the end of the measurement, you’re still left with the subjective step of pegging inches-of-loft to a comfort rating.

AYCE

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Posted: 09 July 2007 03:25 AM   [ Ignore ]   [ # 5 ]  
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Temperature ratings are, of course, very subjective; one person’s 0-degree bag may be another’s 30-degree bag. No problem there.

All of the insulating materials under discussion insulate by trapping air in tiny spaces between fibers, limiting convection currents. Some may do this slightly better than others, especially under laboratory conditions, but the largest single factor determining how warm a layer of insulation will be is thickness, or “loft,” in sleeping bag parlance. Since the thickness of a sleeping bag is easy to see and measure, it remains the best way to determine the likely warmth of the bag, or to compare two bags. To expect a given thickness of synthetic insulation to be warmer than a thicker layer of down is asking to spend a cold night. 

As an aside, here’s an interesting chart from 3M.  Note that they include a clo value for down (550fp). Also, their clo values use kg/sq. meter.

http://solutions.3m.com/wps/portal/3M/en_US/ThinsulateInsulation/Insulation/Thinsulate-Products/Thinsulate-Lite-Loft-Insulation/

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Posted: 09 July 2007 12:32 PM   [ Ignore ]   [ # 6 ]  
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Some may do this slightly better than others, especially under laboratory conditions, but the largest single factor determining how warm a layer of insulation will be is thickness, or “loft,” in sleeping bag parlance. Since the thickness of a sleeping bag is easy to see and measure, it remains the best way to determine the likely warmth of the bag, or to compare two bags. To expect a given thickness of synthetic insulation to be warmer than a thicker layer of down is asking to spend a cold night.

If all other things are equal, the thicker layer of insulation will be warmer.  There’s no disagreement on that basic fact. The problem is that all other things are not equal: different materials have different thermal resistance. 

If you have no other tools or information, using a ruler and measuring loft gives you a reasonable way of estimating warmth.  This remains unchanged with the discussion of clo values. It doesn’t take long, though, in working with these synthetic insulations to realize that there is something to these clo values: thermal resistance between products is not equivalent per unit of thickness, and as the amount of insulation gets larger this difference becomes more apparent. 

The problem of including down in these insulation discussions is that it’s a loose insulation of different qualities and can be stuffed to varying degrees.  But assuming a company with responsible temperature ratings, if you compared the loft of similar down and synthetic bags with equivalent temperature ratings the down bag will always be loftier.  This does not mean, as you suggest, that the synthetic bag will be colder.

Or compare two of my own kits: the Maxima and the Whitney.  These are equivalent jackets, the Maxima being the synthetic version of the Whitney.  They are both about the same warmth too: over three years use with the Whitney and two for the Maxima they’re comfortable for me in the 30’s just sitting around.  The Maxima has a 3.0 oz basis weight layer of PL Sport with a single layer loft of 0.6” (clo: 3.0 * 0.74=2.2) while the Whitney fully lofted has on average about 1.5” of single layer loft.  In other words, the synthetic jacket is as warm as the twice as lofty down jacket.  There’s no slight of hand going on here where the synthetic per unit weight is more efficient than down: the down Whitney weighs 32% less than the synthetic Maxima for the same temperature rating.  When you say things like “that would mean that it would have to stabilize the air twice as well as down”, it’s not really looking at the fill weight per unit volume.  The synthetic *does* insulate better than down per unit volume, but it *does not* insulate as well as down per unit weight.

Bill, you and I have had this discussion on more than just my own message board, and it’s clear to me that you’re a ruler guy.  If it gives you good results and you feel comfortable using a ruler, do so: I continue to list loft measurements on all the insulations I sell. I know that for many people warmth considerations end with inches of loft because, as you say, it’s easy and convenient.  But if you’re more interested in accuracy and precision, clo values are a better way to compare the thermal resistance of synthetic insulations.

AYCE

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Posted: 12 October 2007 02:05 PM   [ Ignore ]   [ # 7 ]  
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Go to the home improvement store and talk to someone about fiberglass insulation. They will tell you that you can buy a 3.5 inch bat of fiberglass insulation that will give you a R value of 11 when you put it in the wall of your house. However, if you were talking about blown in celulose insulation in that same 3.5 inch thick wall you could gain an r value of about 13.

The Celulose insulation is about 17 percent more efficent at blocking heat transfer than the spun fiberglass in a wall.

Take that same celulose insulation blown into your attic and you end up with exactly the same R value as the fiberglass.

Why? ... simple ... density of the material has a effect on the insulative value of a material. To say a different way, density has an effect on the thermal conductivity of a material.

If we look at a simplified equation for the flow of heat through any material we get:

Heat flow =  Delta * Area * conductivity / thickness

Delta is the temperature difference between one side of the material and the other side. In our case it’s skin temperature on one side and air temperature on the other. It would be the same for all our examples.

We’ll assume that the area is the same in all our examples

Thickness would be loft

Conductivity is a measure of how good a material is at passing heat. Steel, for example, would have a high conductivity.

So .... if the Delta and the Area do not change, then we’re left with the termal conductivity of the material and the thickness.

Conclusion .... thermal conductivity (clo) of the material is just as big a factor as thickness (loft).

(check out http://www.ux1.eiu.edu/~cfadd/1150/Hmwk/Ch13/Ch13.html for an example of the math)


So .... let’s look at an example from my own experience.

A Polarguard 3D quilt, with a clo of around .63, and a basis weight of around 2.7 oz per square yard (correct me if I’m wrong here AYCE). Two layers, or 5.4 oz per square yard, times .63, yields a clo of about 3.4 (and the loft is about 1.5 inches).

I sleep a bit on the warm side and I found that this was good down to around 36 without a bivy, and about 28 with a bivy.

My Montbell #3 has about 1.7 inches of single layer loft and is rated at 32 degrees. I’ve found the temp rating to be about 30 degrees for me. So far, so good. That would suggest that the termal efficency of 3D and Down, per unit volume, are similar.

So, if I were to use the same 3D quilt material I would need an extra layer to get to 20 degrees ... or 7.6 oz per square yard, yielding a clo of about 4.7. This would give me a loft of about 2.25 inches.

For the new XP material, I should yield a clo of 5 times .82 or 4.1 for the 5 oz basis weight material. That, based on what I’ve experienced, should take me to about 24 or 25 with no problem. Then, add a bivy to get to 20 and possibly even 15.

Thermal efficency of your system depends not only on your insulation and bag/quilt design, but also on appropriate use of a bivy or tent, or other technique to recapture heat lost through breathing.

Remember ... your talking about a system that either all works together, pad, quilt, bivy, tent, clothes, etc. or works against you. The best zero degree quilt or bag in the world would be worthless if your trying to sleep on snow without a insulated pad under you.

So ... take any 20 degree quilt or bag, toss it out in a 20 mile an hour wind, with too little insulation under you and no tent or Bivy to block the wind and you’re going to be cold.

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Posted: 29 November 2007 10:14 PM   [ Ignore ]   [ # 8 ]  
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There are two factors that will affect thermal conductivity: how well the material prevents convective air currents, how well the material itself conducts heat. All of the popular synthetics are made of the same basic material (polyester) and hence conductivity of the material is probably ultimately determined by how thick the strands of polyester are and whether they are hollow or not and what shape they are. Thin, hollow strands conduct heat more slowly than thick, solid strands of polyester. Also, for the same weight, thin hollow strands of polyester will stop convective air currents better and give bigger air spaces as well.

Bottom line: to boost the CLO values from vanilla Polarguard to Polarguard 3D to Polarguard Delta to Climashield XP, what has happened is changes in the thickness and shape of the same basic polyester fiber. This change in shape works quite nicely in the laboratory. But in the field, over a long period of time, what happens is that the thinner and hollower fibers tend to break and permanently deform more quickly than the sturdier fibers. This collapses the air spaces and increases thermal conductivity because the fibers are more closely pressed together (heat can move from fiber to fiber more easily rather than being forced to jump over dead air space). Bottom line is that all of these continuous fiber synthetics will tend to perform the same after extended use and loft degradation.

The manufacturer of Polarguard used to have a graph where they showed how much superior Polarguard Delta was to Polarguard 3D and then another graph where they showed how great Polarguard Delta and 3D were at retaining loft. But when you examined carefully, what you saw was that Polarguard Delta lost more loft than 3D, so that AFTER loft degradation, they performed essentially the same. Which confirms what I am saying here, at least with respect to Delta and 3D. I suspect you’d get the same results when comparing Delta or 3D to Climashield XP.

I would not go so far as to say that vanilla Polarguard or the cheaper continuous fiber insulations at Walmart are equivalent to the high-end insulations, but I would be very suspicious of statements to the effect that Climashield at 5 oz/sqyd really gives the same warmth as Polarguard 3D or Delta at 6 oz/sqyd, at least AFTER inevitable loft degradation. Maybe it does in the laboratory, when the insulation is still fully lofted, but if so, the loft of Climashield will surely degrade more than Polarguard on a long thru-hike (because the fibers are more fragile), unless you are super careful to avoid compressing the insulation at the bottom of your pack. Thus by the end of the thru-hike (when it is cold and you need the insulation more than ever) both insulations will be essentially equivalent.

The only way manufacturers will be able to get improvements over polyester continuous fiber insulation is to use something that is stronger than ordinary polyester, but otherwise has the same characteristics as polyester, in the way that kelvar is stronger than ordinary nylon for the same weight.

BTW, you need to be quite tough to sleep with just 6 oz/sqyd of Polarguard 3D or Delta (supposedly equivalent to 5 oz/sqyd of Climashield XP) at 20degF, assuming the insulation has lost some of its original loft, as is typical on a long thru-hike. Most people will probably feel bitterly cold with just this amount of insulation, unless they are wearing further insulation in the form of clothing.

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Posted: 30 November 2007 10:03 PM   [ Ignore ]   [ # 9 ]  
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If I have it right, you’re making one main point: as continuous filament insulations wear out, the newer ones and the older ones approach the same decreased efficiency.
Sure- what you’re saying is reasonable.  I think the rough time scale you mention of a thru-hiker hitting the cold weather again towards the end of their hike is about right too.  I figure we’re talking about somewhere between 90 and 120 uses (3-4 months daily compression). 

But is anyone really surprised by gear wearing out? 

It’s a problem that is easy to solve by either a) using more insulation and carrying the extra weight or b) retiring worn out insulation.  Solution A will probably appeal to those who don’t want to make (or buy) more than one, while B will appeal to those willing to pay a little money to drop a pound.

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Posted: 02 December 2007 01:31 PM   [ Ignore ]   [ # 10 ]  
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Springing for two quilts/bags for a 3 season long hike opens an additional possibility ... starting with a warmer quilt/bag, swapping to a lighter/less warm one for the summer months and then switching back to the warmer one when it cools again. 

For that matter, if quilts don’t do the job for you in cold weather you could go with a bag for the start/end and use a quilt through the summer.

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Posted: 02 December 2007 10:45 PM   [ Ignore ]   [ # 11 ]  
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My experience is that Polarguard 3D loses loft in something like 30 days, and then it doesn’t lose any further loft after that. That is, 6 oz/sqyd Polarguard 3D starts at about 1.8” of loft then degrades to 1.3” after about 30 days of use and then stays at 1.3” indefinitely. I suspect something similar would happen with Climashield. In other words, I suspect 5 oz/sqyd of Climashield to be warmer than 5 oz/sqyd of Polarguard 3D when new, but equally warm after 30 days, and both of them will be a lot less warm than when new. If 5 oz/sqyd of Climashield is equally warm as 6 oz/sqyd of Polarguard 3D when new, then it will be less warm after 30 days. Maybe I abuse my gear more than other people. I’ve never used a compression sack with Polarguard quilts nor have I used much force to push them into a small stuff sack. But the quilt does sit at the bottom of my pack. Then again, there isn’t that much on top of it, since I go fairly lightweight and the water bottles are on the sides of the pack and water is the only really heavy thing I carry.

My own recommendation is for thru-hikers is to expect 5 oz/sq Climashield to keep you warm down to maybe 35°F, same as 6 oz/sqyd Polarguard 3D, wearing just shorts and t-shirt, after loft degradation, which will occur rapidly. This is for a man who is fairly tolerant of cold (sleepign in 35°F with 1.3” of loft and little clothing implies quite tolerant of cold, according to the inches system). To handle colder temperatures comfortably, add an insulated top and hat. To get still lower, add still more insulated clothing, such as down pants and down vest to go under the insulated top.

As for switching to bags, my own experience is that a bag is no warmer than a hooded quilt with draft skirt. A hooded quilt, by the way, is very easy to make. Just make the quilt longer (about 86” for a man 72” tall), and about 52” wide at the head end (these are finished dimensions). Then fold together at the head end, but don’t stitch the entire 26” shut (26” = 52” / 2). Instead, just stitch about 16” shut, thus leaving 10” towards the middle unstitched, as a breathing hole. This breathing hole works very well for back and side sleepers, but not for stomach sleepers.  I’m mostly a side sleeper, but I like resting on my back while awake. The draft skirt is equally easy. Visit ray jardine’s web site for some illustrations. Basically, you add a skirt of shell fabric about 7” wide around most of the quilt. The main purpose of the draft skirt is to stop drafts, but you can also lie on it while side-sleeping to hold the quilt in place. And for God’s sake, make the quilt large enough to cover you completely with a little to spare on either side if you plan to use it below freezing. Saving an ounce or two is pointless if the thing doesn’t work properly.

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Posted: 03 December 2007 01:04 AM   [ Ignore ]   [ # 12 ]  
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My experience is that Polarguard 3D loses loft in something like 30 days, and then it doesn’t lose any further loft after that.

I realize that part of your argument is that all continuous filaments are fundamentally the same, but if you only get 30 days of use out of your insulation before it goes flat you’ll be surprised to find out that improvements have been made in the decade since Polarguard 3D was developed.

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Posted: 03 December 2007 05:42 AM   [ Ignore ]   [ # 13 ]  
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you’ll be surprised to find out that improvements have been made in the decade since Polarguard 3D was developed.

That was the same line the manufacturer gave when they came out with Polarguard Delta a few years ago. Then it turned out that Delta lost loft faster than 3D so that they ended up the same after a short period of time.

The Climashield website talks a lot about how continuous fiber has significant advantages over down and cut stape insulation, and I certainly agree with all that. Then I find a chart (click here) showing that Climashield is either 3% or 7% more efficient, in terms of weight, than “large diameter” continuous fiber insulation. (One chart shows 3.3 clo/kg versus 3.2 clo/kg, while another shows 41 ounces versus 44 ounces. What is the difference between “thermal efficiency” and “lighter weight”? When I see this sort of discrepancy in marketing material, my BS detector hits the red zone.) Let us assume that the competitor is Polarguard Delta and let us be generous and use the 7% improvement. How does that reconcile with your figures which show that 5 oz/sqyd of Climashield is equal to 6 oz/sqyd of Delta, which implies a 17% improvement?

In any case, if Climashield simply has thinner fibers as compared with Delta and 3D, then it will lose loft and thus warmth faster, which is the same problem with Delta versus 3D. Sounds like another rediscovery of the wheel…

Let me be clear that I’m not knocking any of these insulations. I’m a big fan of continuous fiber, including for winter bags/quilts. Simply supplement with down clothing in winter and you have the best of both worlds.

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Posted: 03 December 2007 11:28 AM   [ Ignore ]   [ # 14 ]  
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It was a longshot to think that someone who believes that the pinnacle of continuous filament technology was a dozen years ago with polarguard 3D could be persuaded to actually try one of the newer products, but there’s always hope.

If you’re satisfied with your flat 3D quilt, that’s good enough for me.

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Posted: 03 December 2007 05:01 PM   [ Ignore ]   [ # 15 ]  
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It was a longshot to think that someone who believes that the pinnacle of continuous filament technology was a dozen years ago with polarguard 3D could be persuaded to actually try one of the newer products, but there’s always hope.

This is certainly hope and I will be trying Climashield soon. But let me clarify the argument in case anyone is confused.

There is a tradeoff between fiber thickness and loft. Thicker fibers retain loft better, so you gain warmth by having more dead air space, but you also lose warmth with thicker fibers because the thicker the fiber, the better it conducts heat. And vice-versa for thinner fibers. The tradeoff is a fairly flat one, but there is no doubt an optimal point and perhaps Climashield has hit that optimal point better. That is, XP has thinner fibers and hence less loft but also less thermal conductivity along the fiber itself, and perhaps this gives a better overall result. But the manufacturer of Climashield does not allege that they have improved by 17%, they allege only 3% in the chart showing clo/kg (click here). 3%, AYCE, not 17%. I am perfectly willing to believe that a 3% improvement is possible from 3D or Delta to XP. Maybe even a 7% improvement. But not 17%.

Also, why do you say my 3D quilt is flat? I measure 1.3” loft after much use. It lost some loft since when it was new but it is still warm and still loftier than 5oz of XP when new. (Of course, loft isn’t everything, as noted in the preceding paragraph.) Clearly, my quilt is not “flat”. But this is an apples and oranges comparison. I am probably being overly conservative in my measurements, we are comparing different weights of insulation, and one of the insulations is new and the other has been abused for many months. The correct way is for someone to standardize the measurements. And I would assume Western Nonwovens did just that when they ran the test upon which their chart is based. And the chart shows that XP is 3% warmer than 3D or Delta for the same weight per unit area. 3%, AYCE, not 17%. That is what the manufacturer of XP themselves states on their website.

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