Question about possible Minima vest insulation
Posted: 14 September 2007 03:00 AM   [ Ignore ]  
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Hello.  This is my first post here.  I’m kind of new to MYOG, but I completed a bug bivy last summer with nanoseeum from Thru-hiker.com, and have aspirations for many more projects now that I have some confidence in my sewing ability.

For a variety of reasons, I’m looking to make a synthetic-fill vest (using the Minima vest kit) that has 1.5-1.75” of single layer loft.  Exactly which insulation, or insualtion combo I would be using for this is what I’m having a hard time figuring out.  The one criteria I have that I don’t want to change is the amount of loft I want the vest to have.  I’m not trying to replace a down vest, so I don’t care how it’s weight or compressed volume compares to a down vest of equal warmth, and I’m not trying to make a vest that will keep me warm down to a specific temperature.  I’m trying to make a synthetic-fill vest with 1.5-1.75” single layer loft.  Whatever insulation I use, I’d like it to be as compressible as possible and as warm as possible, for synthetic, to optimize the packability and functionality of just such a vest. 

  I think, maybe, my criteria boil down to the following sentence: I’d like to use the insulation that’s warmest per unit of volume—when compressed.  I’ve come up with a couple questions I can’t figure out the answers to on my own, but feel free to just cut through the multiple rambling questions with a single recommendation for the insulation you think I should use, given what I’m looking for.
-I see that the clo/oz is somewhat higher in Primaloft One vs Primaloft Sport and ditto for the clo/oz between Climashield XP and Climashield Combat.  What this means to me is that I should choose either Primaloft One (in multiple layers) or Climashield XP for my vest.  Is there any reason I should be considering PL Sport or CS Combat?
...as I’m typing this, I did a little math and figured that *assuming the loft of PL One is comparable to the loft of PL Sport* then the cost of using four layers of PL One instead of one layer of each 1.8 and 5.0 PL Sport to attain 1.6” of loft might be prohibitive.  But let’s say that cost isn’t a factor and I wanted to use a Primaloft.  Which of the two combos I mentioned would you prefer?
-What are the main differences between Primaloft One and Primaloft Sport?
-I should also ask about now, what’s the actual loft of 1.8 Primaloft One, if it’s different from 1.8 Primaloft Sport?
-In general, how does the compressibility of Climashield compare to that of Primaloft?
-A last question, if you can recommend an insulation or insulation combo, can you also give an estimated weight for a vest made with that insulation?

I intend to use the vest for backpacking, as part of my winter clothing and sleep system.  I have a roomy down jacket that would work great layered over just such a vest for the more frigid winter trips.  I just hope that a synthetic-fill vest with so much loft won’t be so ungainly and uncompressible that it wouldn’t be practical for backpaking…

Thanks for any help,
FT

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Posted: 14 September 2007 12:20 PM   [ Ignore ]   [ # 1 ]  
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I don’t stock any synthetics greater than about an inch and a quarter of loft in a single layer.  This is a lot of insulation.  The minima was designed for a 1.8 oz (@ .4”) layer of insulation.  You’re talking about cramming in around 8 oz per square yard of insulation.  This is going to be awkward and require modifications that you’d be on your own for.

The closest option to what you want to do that I think would work reasonably well and be sewable without too much trouble would be to go for either a layer of 6 oz Primaloft Sport (softer, more compressible) or a layer of 5 oz Climashield XP (a little stiffer, continuous filament).  This gets you a clo of greater than 4 for both insulations, which is a below-freezing type temperature rating about the same as 1.5 to 1.75” of good quality down.

If you want to shoot for that 1.75”, you’d add a 1.8 oz layer of sport or a 2.5 oz layer of XP to the main layer. 

The 1.8 oz PL1 prequilt would be a poor choice for this project.  You’d need some four layers of the stuff which would be 8 layers of scrim, adding @ 3 oz per square yard to the finished product. 

My recommendation would be to make a Minima with 1.8 oz or 3 oz of insulation, learn the pattern and the techniques that go into making a shell/insulation/liner item, and then when you’re more accomplished and have foresight for a project like you describe you’ll be able to modify the pattern for best results.

Trying to match the physical loft of a down item with a synthetic is going to produce an end product significantly warmer and heavier than the down item you’re trying to copy. But, it’s worth it if only to learn first hand the way these things work.  You might also look at user reviews & temp ratings for a respected commercial product such as the integral designs Dolomitti which uses a single layer of 5 oz PL Sport.

AYCE

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Posted: 14 September 2007 02:39 PM   [ Ignore ]   [ # 2 ]  
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FT,

Your focus on loft tells me you are thinking like I used to think ... that all inches of insulation are equal.  More recently I’ve given up and am learning to trust that CLO is a reliable measure of insulation value based on real measurements.

At another forum, someone posted a chart of insulation requirements based on ISO TR 11079, which also is backed up by real research.  If at first the chart makes no sense (my first reaction was “huh?”), read his later explanation.  That standard (any standard) must be based on the mythical average person so your mileage may vary (I get by with quite a bit less insulation that it suggests) but it is a start and once you “calibrate” yourself to the chart it could be extremely useful.

I have just one remaining frustration in this area, I have not seen CLO values for different qualities of down filled to a couple different densities (not that I’ve looked all that hard) .... that could be useful and fill a gap in comparing clothing options.

I think you might find that 1.75” of any of Thru-hiker’s synthetic insulation products will be somewhat warmer that the same thickness of down (based on my somewhat limited experience using both down and synthetic sleeping bags in temps in the 20-40 degree F range).

Good luck with your project, you might find MYOG to be very satisfying (but you’ll know Real Soon if it isn’t).  Be sure to let us know how it turns out.

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Posted: 14 September 2007 06:25 PM   [ Ignore ]   [ # 3 ]  
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I agree completely with the main thrust of what Richard Nisley is saying: that insulation requirements are a function of metabolic rate and temperature.

The place where he starts to lose me is in his contention that a physical measurement of loft, subjective assessment of fit and function, and the appropriate formula will produce a clo value that is representative of the standardized direct-measurement (copper mannequin) testing of clo. 

These home calculations of clo based on physical measurement of loft have in the past produced results significantly different from the direct-measurement of clo from the standardized method. His calculated value  of 1.467 for the clo/oz of polarguard delta overestimated the direct measurement value of 0.68 clo/oz by 116%.

Richard points out and I agree that it would be impractical to test all the different clothing and gear items at a cost of $600 a pop. However, given the past inaccuracies in the calculated value it would be helpful to be able to verify the method with one or two tests.  There should be more than enough interested people that raising the money for a test or two should not be too big a hurdle.  I’m willing to get the ball rolling with a donation of $100 towards the validation of the calculation method.

I think it’s great that folks like Richard are taking the time to advance more objective assessments of insulating gear. 

AYCE

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Posted: 14 September 2007 08:07 PM   [ Ignore ]   [ # 4 ]  
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I get what you are saying, and I’m familar to a certain extent with the fact that synthetic insulation is warmer per inches of loft than down is, but I’m not trying to make a replacement to a down vest.  I’m trying to make the warmest synthetic vest that would be practical for backpacking.  Since I could conceivably layer such a vest under a down jacket in extremely cold conditions, and considering how much a garment without arm insulation really can insulate on its own before I’d start needing the insulated arms, there’s a limit on both the loft and how much insulation is ideal without having too much.  This seems like an important point.  I’ve used insulated vests in the past in conjunction with a light fleece/midweight baselayer and windshirt.  I was thinking that 1.5-1.75” would be a good loft range for the vest I have in mind, but now I’m starting to scale it back a bit.  I looked at the weight specs for the Integral Designs vest that uses 5oz Primaloft Sport which has something like 0.8 or 1” of loft, and realized that the weight, and probably the bulk of this vest I have in mind is going to get up there.

Well thanks for the suggestions so far.  I had seen that post on Backpacking Light, but didn’t really care to understand much of it until now.  My view on backpacking clothing has been much like the guy who replied to the thread a page or two into it saying that he arrived at the same conclusions for ideal clothing but through years of experience and not through painstaking calculations.

Any input on how much a Minima vest made with either 6oz Primaloft Sport or 5oz Climashield XP would weigh?

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Posted: 14 September 2007 08:45 PM   [ Ignore ]   [ # 5 ]  
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My view on backpacking clothing has been much like the guy who replied to the thread a page or two into it saying that he arrived at the same conclusions for ideal clothing but through years of experience and not through painstaking calculations.

Any input on how much a Minima vest made with either 6oz Primaloft Sport or 5oz Climashield XP would weigh?

I hear you.  My main interest in clo values is in the design stage of making gear for doing exactly what you’re trying to do: compare and contrast synthetic insulations to match up the best insulation for the project at hand. I believe the best results for determining the warmth of already manufactured/homemade gear will be obtained through use. 

Since I could conceivably layer such a vest under a down jacket in extremely cold conditions, and considering how much a garment without arm insulation really can insulate on its own before I’d start needing the insulated arms, there’s a limit on both the loft and how much insulation is ideal without having too much.  This seems like an important point.

I agree- very relevant point.

Any input on how much a Minima vest made with either 6oz Primaloft Sport or 5oz Climashield XP would weigh?

What size are you planning to make?

AYCE

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Posted: 14 September 2007 08:54 PM   [ Ignore ]   [ # 6 ]  
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I’m planning on making a size medium.  No need for lots of specifics, but I’m not sure the actual square yardage of each fabric that goes into a vest project.

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Posted: 15 September 2007 12:02 AM   [ Ignore ]   [ # 7 ]  
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The area of the back, left and right front, and collar pattern in size medium is 1312 square inches.  This is almost the same as a square yard which is 1296 square inches.  You can calculate the expected weight based on the materials you choose for the fabric and insulation.

Exclusive of the insulation, I would expect a medium vest in 1.1 or Momentum to weigh a little less than 3 oz, so a medium with 5 oz XP would come in around 8 oz and with 6 oz around 9 oz.

AYCE

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Posted: 15 September 2007 02:26 AM   [ Ignore ]   [ # 8 ]  
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Thanks AYCE.  That’s very much appreciated info.

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