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Thread: reflects 90% body heat

  1. #11
    Join Date
    Oct 2018
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    Not going to do any E or E, I can leave confined spaces, vehicles or structures. Like I said, hard to imagine.

    The only thing there I'd worry about is fuel, and here in Seattle, I wouldn't worry about it too much.
    "When I have your wounded." -- Major Charles L. Kelly, callsign "Dustoff", refusing to acknowledge that an L.Z. was too hot, moments before being killed by a single shot, July 1st, 1964.

    Black Lives Matter. All confederate symbols and monuments need to go.
    Proud to live in a sanctuary city.

  2. #12
    Join Date
    Dec 2013
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    2 (100%)
    They are not technically wrong from a scientific standpoint, yet I can see why real world users have deemed them "shit".

    Heat works in three ways:

    Radiative- How these blankets "reflect"

    Conductive- think cooking bacon in the pan

    Convective- boiling eggs or noodles in water

    In space suits (my shit) mylar is the main insulation because there is no air or ground to steal your heat. Only the sun or shadow. Here on earth though conductive andd convetive heat flow are exponetially larger than any radiative heat flow, especially at night. Now if you managed to roll yourself in the mylar like a burrito it might reflect some of your radiated heat (again not very much) but the main benefit would be it would block convective (airflow) heat loss. Just trapping the little poclets of air around your body and allowing them to heat up would be the "warmth" if any you would get from this device. A real sleeping bag would be SUBSTANtially more comfortable. But a smart person in a survival situation shouldnt deem these completely worthless.
    "Just throw Krylon on it"

  3. #13
    Join Date
    May 2009
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    10 (100%)
    There are several vids on the use of those mylar sheets. I think they are like a knife or gun to some extent. It's how you use it and what other things are around you.


    I saw Cody Lundin put one across a slanting rock face, then put clear mylar as a front face and a fire outside that. Supposedly the fire heated that living space.
    It was an episode of him and Dave C.

    this guy shows some closeups of the mylar after one nights use... He's doing a "I got lost unprepared" type deal.
    https://www.youtube.com/watch?v=xdOCuGb4108 42:00 he shows the damage of his mylar sheet.

    He also has a pretty cool jacket I have never seen before. You stuff it with leaves and brush as insulation. He claims it was really dry the next day so useful for tender.

    There are many more vids. If you watch enough of those hiking vids all the most experienced people have the mindset that every piece of gear they travel with has to have two or more uses.

    Not sure if you have seen those sleeping mats by thermarest but the Thru Hikers swear by them. Very light and also made to reflect heat internally. They make a yellow one and gray one. The gray is a little more robust I believe.


    While a good sleeping bag might run you $350 and pack into a space the size not much larger than a softball I have heard people say the REI stuff is very good too at 1/3 the price and only slightly heavier.

    ETA: Here's that shelter Cody made.... https://www.youtube.com/watch?v=EvKLOMgtM1Q
    Last edited by tb-av; 11-09-18 at 13:05.

  4. #14
    Join Date
    Mar 2019
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    Been curious about these. Since they reflect heat, do they cover your IR signature from IR detection technology?

  5. #15
    Join Date
    Oct 2007
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    I don't know about covering up you IR signature, but I tried my idea out last winter and it did work. Somewhat.

    Temperature was in the 20s, moderate to light wind. I removed my jacket to simulate getting caught without a coat, and found a somewhat sheltered spot in my yard. Used old cardboard and evergreen branches for a makeshift ground pad. Sat down with my knees up and lit my candle lantern.

    It did work. The temperature did go up to a level that I felt would definately aid in surviving the night. If it was 20 below with strong winds, maybe not, but the concept is sound.

    I did find a few problems though. The Emergency Bivvy I used was too narrow to allow for comfortable sitting with my knees drawn up. It's designed to lay down in as if it were a sleeping bag, but that won't work with my candle lantern. The heat from the candle melts the bivvy. I next tried the Escape Bivvy, which is stronger and breathable (being made of an almost Tyvek-like material), but it's even narrower than the Emergency Bivvy.

    I finally tried the Two Person Emergency Bivvy and this is just the right size to allow for any seated position while keeping enough space between the candle lantern and the bivvy material.

    I'm now trying to put together something that will let me fall asleep but support the candle lantern to keep it from tipping over and at the same time support the bivvy and keep it from colapsing on top of the lantern and melting. All this while being small enough and light enough to fit within my GHB (511 Rush 12).

    As it is, the two person bivvy and the candle lantern take up almost no room in the pack and are very light. I keep them, a dry pair of socks and an insect hood all together in the small mesh pocket of my pack. I think they are a sound addition to my pack for a situation where I need to spend the night outside, in the cold, and without my prefered MSS sleeping bag.

  6. #16
    Join Date
    Sep 2010
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    I was rock climbing in the North Cascades and when we got to the peak we found we couldn't cross over the back wall to rappel down due to an unexpected ice wall. We were forced to rappel back down the face 12 pitches. It was getting late so we ended up hunkering down in a small open area rather than attempt to rappel in the dark. We flaked out our ropes to cover the ground, put on all of our clothing, put our legs into our backpacks and covered ourselves with the off brand space blanket I carried. The blanket cut the wind off us and kept us warmer than without. We did get condensation on the underside. It was definitely warmer using the Mylar blanket. It earned a place in my kit.

  7. #17
    Join Date
    Apr 2010
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    For what little it's worth, I took a wilderness first aid class this last spring. When it came time for scenario training and using only what's in your bag to treat "casualties", everyone in the class seemed to pull out one of those Mylar emergency blankets to treat the "patient"; myself included. When it was my turn to be the patient, the main benefit I found from the Mylar was as a wind break/ sunscreen. You're laying there starring up at the sky while the other students are working on you, and the stuff actually helped to cut down on the glare and the wind chill effect. Most of my actual warmth on what was an early spring day laying outside was in getting off the ground and the other materials the students were using to turn me into a burrito with.

    I still have one or two of the Mylar sheets I got as freebies somewhere, but right after the class I went to an outdoor store and bought something a little more robust to carry. I never had high expectations about the stuff in the first place, but it was an interesting experiment to be able to see what the stuff was actually capable of.
    * My views discussed on this forum are personal opinion only and do not constitute information released in an official capacity*

  8. #18
    Join Date
    Oct 2008
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    1 (100%)
    Having spent some time in the woods overnight without shelter I found here in the PNW the things that chill you the fastest is rain and wind. Anything that protects you from wet and wind is good. The emergency nubby bags can be sliced open for more room and/or ventilation.

    It is just plastic so not fire friendly. If no fire then I keep it wrapped around me and try to air it out occasionally to prevent too much condensation. If I have a fire then the Mylar goes behind me as a wind break and reflector.

    No way will it replace a proper tent or sleeping bag. But it can make the difference between bone chilling death in a few hours or staying mostly dry, and warm enough to see the sun tomorrow.

    If you can add a fire to your situation then you might even be somewhat comfortable. Your emergency candle is a decent last resort.

    Mylar = wind and wet protection, and even then not great but sufficient. Mylar has zero insulation value.
    It is in vain, sir, to extenuate the matter. Gentlemen may cry, Peace, Peace but there is no peace. The war is actually begun! ... Is life so dear, or peace so sweet, as to be purchased at the price of chains and slavery? Forbid it, Almighty God! I know not what course others may take; but as for me, give me liberty or give me death!" - Patrick Henry in an address at St. Johnís Church, Richmond, Virginia, on March 23, 1775.

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