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  1. #11
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    I've use a prolite (R2.2) down to 35. It worked but I was on an island and if any part came off the pad instant cold. I did shove extra gear and clothes around the sides. Part of the problem with the R value not standing true in a hammock is that the pad is to be fully inflated to reach full potential heat retention.
    Last edited by threadlessclimber; 04-26-2017 at 16:48. Reason: spelling

  2. #12
    OlTrailDog's Avatar
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    Quote Originally Posted by threadlessclimber View Post
    I've use a prolite (R2.2) down to 35. It worked but I was on an island and if any part came off the pad instant cold. I did shove extra gear and clothes around the sides. Part of the problem with the R value not standing true in a hammock is that the pad is to be fully inflated to reach full potential heat retention.
    I find that a lightly inflated exped downmat or synmat is much more comfortable than a "fully inflated" pad. The same for the TR Trekker torso. I try and mimic an underquilt, i.e. lofted but not rigid. This works exceptionally well in the hammocktent 90 degree because the pad pocket is differentially cut so that it doesn't squeeze the pad like my WBRR did. It may loose some loft, but the gain in comfort is worth it to me.

  3. #13

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    A section of reflectix added under your pad boosts the insulating factor quite a bit. I sleep with my feet tucked up and on my side, so a short piece under my torso does the trick.

    Charlotte

  4. #14
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    A little late to the thread here, but I did a quick calculation based on the thermal resistance of down feathers. Looks like a 20 degree underquilt (with 2.5 inches of 800 fill down) has an R-value of about 5.9875.

  5. #15
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    Quote Originally Posted by Runner497 View Post
    A little late to the thread here, but I did a quick calculation based on the thermal resistance of down feathers. Looks like a 20 degree underquilt (with 2.5 inches of 800 fill down) has an R-value of about 5.9875.
    Could you post the formulas you used? That would be interesting.

  6. #16
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    Certainly. I started by finding the clo value of down. Interestingly, the thermal conductivity of down is expressed in Clos/oz/yrd^2 instead of the standard units of W/m*K (or btu/ft*R for imperial). See this source for information on Clo value: http://www.adventurepoet.com/adventu...ngs-explained/. 800 fill is 1.68 clo/oz/yd^2.

    Since Clo and thermal resistance are analogous, the equations became relatively simple. Keep in mind that thermal resistance and R-value are not the same. The R-value that is quoted by sleeping pad manufacturers is actually the thermal resistance per yd^2 (that way it is independent on if you get the longer pad or shorter one).

    With that in mind, the clo-value (clo/yd^2) can be found by simply multiplying the clo/oz/yd^2 found at the link by mass of the down in a volume which has dimensions of 36 in *36 in * height (the loft of the down in the sleeping bag). Then multiply this value by 0.88 to get the equivalent R-value.

    The equation broke down to: R-value = density of down (oz/in^3) * loft (in) * 36^2 (in^2) * clo-value/oz (clo/oz/yd^2) * 0.88.

    In this case it is: 1/800 (oz/in^3) * 2.5 (in) * 36^2 (in^2) * 1.68 (clo/oz/yd^2) * 0.88 = 5.9875 (R-value)
    Last edited by Runner497; 10-07-2017 at 14:07.

  7. #17
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    It would be fantastic if this caught on with UQ manufacturers. Being able to directly compare R-values between pads and quilts (or between various quiltmakers) would be useful.

  8. #18
    Two Speed's Avatar
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    Quote Originally Posted by Runner497 View Post
    Certainly. I started by finding the clo value of down. Interestingly, the thermal conductivity of down is expressed in Clos/oz/yrd^2 instead of the standard units of W/m*K (or btu/ft*R for imperial). See this source for information on Clo value: http://www.adventurepoet.com/adventu...ngs-explained/. 800 fill is 1.68 clo/oz/yd^2.

    Since Clo and thermal resistance are analogous, the equations became relatively simple. Keep in mind that thermal resistance and R-value are not the same. The R-value that is quoted by sleeping pad manufacturers is actually the thermal resistance per yd^2 (that way it is independent on if you get the longer pad or shorter one).

    With that in mind, the clo-value (clo/yd^2) can be found by simply multiplying the clo/oz/yd^2 found at the link by mass of the down in a volume which has dimensions of 36 in *36 in * height (the loft of the down in the sleeping bag). Then multiply this value by 0.88 to get the equivalent R-value.

    The equation broke down to: R-value = density of down (oz/in^3) * loft (in) * 36^2 (in^2) * clo-value/oz (clo/oz/yd^2) * 0.88.

    In this case it is: 1/800 (oz/in^3) * 2.5 (in) * 36^2 (in^2) * 1.68 (clo/oz/yd^2) * 0.88 = 5.9875 (R-value)
    This whole explanation made the engineer in me smile. I dont know of many folks that went to search for an under-quilt with their pads R value in mind but its a good reference if you have the connection above.

    In regards to your question I would go for the under quilt for overall comfort. Now that prices are coming down and some manufactures have econ lines its time to try one.

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