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Re: Hammock Camping Franken pad and bride of Frankenpad

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  • starnescr <starnescr@yahoo.com>
    That s why I said slightly warmer. I would be interested if anyone has tested how warm a space blanket is compared to say a waterproof silnylon space
    Message 1 of 18 , Feb 2, 2003
      That's why I said slightly warmer. I would be interested if anyone
      has tested how warm a space blanket is compared to say a waterproof
      silnylon "space" blanket.

      I'll have to admit I'm not as smart as NASA engeniers except for
      maybe Gordo.

      Coy Boy

      --- In hammockcamping@yahoogroups.com, "Ernest Engman"
      <ebengman@h...> wrote:
      > If reflective pads are so good, then why not a sleeping bag that
      is made
      > from them? They aren't. Can a space blanket really work? Somewhat,
      but
      > I've never bet my life on one and will never do so because the
      theory
      > that tells you they will is very flawed. But people buy them, so
      people
      > will sell them.
      >
      > My position that radiant heat reflectors are snake oil has grown
      over
      > time, and after a couple of debates with some people smarter than
      I, I'm
      > sure of it.
      >
      > The science is this, and don't take it is as just me, this is from
      an
      > aerospace engineer working for NASA and another engineer that have
      both
      > convinced me of this:
      >
      > Heat isn't as simple as saying 25% of your body heat is lost thru
      > radiant heat loss. It is much more complicated than that. On a
      night
      > with high humidity but low temperature, you will be a lot colder
      than on
      > a night with the same temp with lower humidity. Why? Because the
      > moisture in the air is conductive, same principle as sleeping in a
      wet
      > bag in a way, but you are loosing more of a percent of heat this
      way and
      > less thru radiant heat. Same thing in high winds. How can higher
      winds
      > make that big a difference if more is lost thru radiant heat loss?
      It
      > couldn't but the real problem is demonstrated by this is
      convective heat
      > loss. I hope this isn't too much of a tangent for the discussion,
      but it
      > just shows how one factor can change the percentages.
      >
      > Radiant heat reflectors (actually insulators) were made to work in
      > space. In space there isn't any air flow at all to worry about, so
      > absolutely no convective heat loss to worry about. In space they
      not
      > only have to protect the person from heat loss, but excessive heat
      gain
      > from solar radiant heat. Ever hear that in space one side will
      freeze
      > while the side facing the sun would burn up?
      >
      > So what is heat? Heat is energy, cold isn't the opposite, it is the
      > absence of heat. Heat energy, by its nature, will try to equalize
      the
      > energy from places of higher energy to places of lower energy. If
      your
      > body is the point of higher energy (which it normally is at night)
      then
      > your heat energy will attempt to displace outward.
      >
      > There are about 4 means of heat loss that you must worry about.
      >
      > 1. Evaporation. When you sweat or breathe, the water loss from
      your body
      > carries heat energy with it. To prevent this you can wrap yourself
      in a
      > vapor barrier. But to make this work, you will most likely want to
      be
      > totally undressed or you will end up in soggy clothing which is
      also
      > bad. Ed talks about always allowing your breath a way to get out -
      very
      > important!
      >
      > 2. Radiant heat loss (the main topic) which is heat transfer based
      on
      > how IR opaque or transparent barriers between you and the object
      are. If
      > you were to stand naked in a freezer, you would loose a great deal
      of
      > body heat thru radiant heat loss. Wrap yourself in a space
      blanket, and
      > you would reflect about 50% of your heat loss back at yourself
      because
      > the air will still carry away some through convection. But to
      reduce
      > this loss, you can wear clothing. Since the clothing is
      essentially IR
      > opaque, you can reduce this loss of you radiant heat energy down to
      > about 5% of your original loss. So if you have a given (which I
      disagree
      > with) of 25% heat loss thru radiant heat, and reduce that to 5% of
      the
      > original loss by wearing clothing, then you are down to less than
      2% of
      > your total body heat loss. Now use a radiant heat reflector to
      capture
      > 50% of that, and it is returning less than 1% of your total body
      heat
      > lost. This 95% (give or take) heat loss prevention occurs for every
      > layer of IR opaque material between you, and the colder objects
      around
      > you. So if you wear clothing, then a sleeping bag (inside layer)
      then
      > you already have reduced your IR heat loss to less than 1%.
      >
      > For a radiant heat reflector to work (in the atmosphere) you would
      need
      > to be inside it without clothing and not touch it (which is where
      I'm
      > going next) for it to be of any help. Interestingly Stephensons
      > Warmlight sleeping bags understands this and explains it quite
      well for
      > someone looking at their bags.
      >
      > To prove this, feel free to make a shower curtain of mylar then
      turn
      > your heat off. Stand inside the shower with the curtain nude and
      see if
      > it (the curtain) gets warm. It won't. You are not a big enough an
      > emitter of IR to make it work. The sun is a huge IR heat emitter
      and
      > does this quite well, unfortunately our bodies don't come with a
      huge
      > supply of self heating hydrogen.
      >
      > 3. Convective heat loss. When air passes around your body, it
      carries
      > away heat; this is the biggest problem keeping warm in an
      atmosphere.
      > The trick is to stop air from passing around you and create
      pockets of
      > still air that can be warmed and kept into place. Sleeping bags
      and pads
      > are designed to do this. Again, if radiant heat reflectors were
      truly
      > beneficial, then that is how we should have been staying warm for
      the
      > last 50 years in the hiking world, but so far we all still use
      sleeping
      > bags and pads. Ed has done a great job of figuring out how to make
      this
      > happen with a pea pod. And to make it even better would be to
      surround
      > the pod with a waterproof material that totally stopped any air
      from
      > getting out and totally stopped any moisture from getting out.
      Foil wrap
      > does a great job of this, by the way - that is what a space
      blanket is
      > made from. But it also has a drawback that it traps moisture that
      > destroys loft in a down bag. The best solution would be some
      material
      > that could surround your pea pot and prevent air flow in, strip
      heat on
      > the way out for moisture, and wouldn't suffocate you.
      >
      > 4. Conductive heat loss. This is a problem because some people try
      > laying directly on the reflective surfaces which are also excellent
      > conductors. Some spots under these conductors are warm because they
      > prevent evaporation or convection, but they also conduct heat
      away. This
      > is also how the moisture carries away your body heat.
      >
      > So to conclude this lengthy post and spark the debate I don't mean
      to.
      > Radiant heat reflectors are not that inside the atmosphere, they
      are
      > serving as barriers to convective heat and if used right,
      evaporative
      > heat. I've never said that people using a system that involves
      a "Heat
      > Rflector" aren't staying warm (heck I have one) I'm just saying
      they
      > should get smart about why they work and figure the best
      applications
      > for these materials. Aluminized plastic (mylar) is very good at
      blocking
      > moisture, and it is what all really long shelf life packet foods
      are now
      > packed in.
      >
      > Ernest Engman
      > AKA SGT Rock
      > sgtrock@h...
      > http://hikinghq.net
      >
      >
      >
      > -----Original Message-----
      > From: starnescr <starnescr@y...> [mailto:starnescr@y...]
      > Sent: Sunday, February 02, 2003 1:37 PM
      > To: hammockcamping@yahoogroups.com
      > Subject: Re: Hammock Camping Franken pad and bride of Frankenpad
      >
      > If a reflectic pad is snake oil then why are "emergency blankets
      > made of reflective material. Of course you wrap a space blanket
      > around you and are not laying on it only. Would a reflective pad
      be
      > more effective (no mater how unpracticle) if it went all the way
      > around you. I think the reflective pad is somewhat usefull if you
      > are not laying directly on it. From what Tom Hennessy and others
      > have said there needs to be a little space between the heat source
      > and the reflective surface. Hence my fleece covered reflectic
      pad.
      > A 1/2 inch closed cell foam pad the same size as mine would be
      > heavier but I'm not sure how much. I'm not saying a reflective
      pad
      > is the answer either. I just believe given the same R value a
      > reflective pad would be slightly warmer.
      >
      > Coy Boy
      >
      > --- In hammockcamping@yahoogroups.com, "Ernest Engman"
      > <ebengman@h...> wrote:
      > > The pad I use serves a couple of purposes.
      > >
      > > 1. Wind/air barrier. It is made of aluminum coated close cell
      > foam
      > > pad. I can use it alone in cool but not cold temps by turning it
      > shiny
      > > side down and preventing air circulation.
      > > 2. Since it is also foam, it adds a light and small layer of
      > > insulation.
      > > 3. It serves as a ground pad under the hammock when I lay it on
      > the
      > > ground to stay warm. It is wide and long enough for that. Often
      > when
      > > having to do this, the ground isn't dry and no sense getting the
      > fabric
      > > wet.
      > > 4. Closed cell foam pads work better against a non-breathable
      > > barrier than against a breathable material like than hammock.
      See
      > this
      > > excellent post by youngblood:
      > > http://hikinghq.net/forum/showthread.php?
      > s=10900e520cfd29662ed8485b43feb
      > > ff2
      > > <http://hikinghq.net/forum/showthread.php?
      > s=10900e520cfd29662ed8485b43fe
      > > bff2&threadid=359> &threadid=359
      > >
      > > I say heat reflectors are snake oil, because the science that
      says
      > they
      > > are a radiant heat reflector for someone sleeping in a hammock
      is
      > highly
      > > flawed.
      > >
      > > Ernest Engman
      > > AKA SGT Rock
      > > sgtrock@h...
      > > <http://hikinghq.net/> http://hikinghq.net
      > >
      > >
      > > -----Original Message-----
      > > From: David Chinell [mailto:dchinell@m...]
      > > Sent: Thursday, January 30, 2003 9:25 AM
      > > To: hammockcamping@yahoogroups.com
      > > Subject: RE: Hammock Camping Franken pad and bride of Frankenpad
      > >
      > > Sarge: Thanks for the R&D work. I'm dreaming along the same
      lines.
      > > That's what the evazote "shawl" is about -- extra width between
      > the hips
      > > and shoulders.
      > >
      > > But I need to make a cloth casing to hold the wings so they're
      > > detachable, rather than permanent, so I can roll it all up in a
      > single,
      > > 24-inch wide roll. How do you pack the Frankenpad?
      > >
      > > And if, as you say, "heat reflectors are snake oil" why do you
      use
      > a
      > > windshield reflector? Why not just another pad?
      > >
      > > Bear
      > >
      > >
      > > To unsubscribe from this group, send an email to:
      > > hammockcamping-unsubscribe@yahoogroups.com
      > >
      > >
      > >
      > > Your use of Yahoo! Groups is subject to the Yahoo!
      > > <http://docs.yahoo.com/info/terms/> Terms of Service.
      >
      >
      > To unsubscribe from this group, send an email to:
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      >
      >
      >
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    • Ed Speer
      Good discussion on heat loss Ernest. I think we all agree that the major body heat loss is from conduction, convection, evaporation & respiration. So unless
      Message 2 of 18 , Feb 2, 2003
        Message
        Good discussion on heat loss Ernest.  I think we all agree that the major body heat loss is from conduction, convection, evaporation & respiration.  So unless one has conquered these, it's pretty pointless to worry about radiant heat loss.  I gather you feel that the warming benefit from reflective fabrics is due to their vapor-barrier properties, not their radiant properties; or at least the radiant advantages are overshadowed by the vapor-barrier advantages.  A good point indeed.  Maybe we like using the Aluminum-coated Mylar emergency blankets because they are so light weight--even lighter than plastic sheeting.  However, I often use my plastic sheet ground cloth as a vapor barrier on the bottom outside of my hammock--does it work as well as the emergency blanket?  Of course, I don't know--they both work well enough to keep using them!
         
        I'd be interested in seeing dependable numbers on actual body heat loss by the various processes.   I have found the following, but its' incomplete for our purposes:
         
        "The human body at rest losses 76% of it's heat due to conduction, convection and radiation; the remaining 24% is lost through evaporation, insensible perspiration and respiration".
         
        It would perhaps be useful if we knew exactly how much each process contributes.  Then again, nature is never a constant--like you said, things like wind and humidity greatly change the rules.  So maybe exact numbers are impossible to determine.
         
        Thanks for your reasoned discussion...Ed
         

         
      • Ernest Engman
        Thanks Ed. I think the two strongest sections of your book are the part on cold weather and building a hammock IMHO. And again, I hope everyone doesn t think
        Message 3 of 18 , Feb 2, 2003
          Message

          Thanks Ed. I think the two strongest sections of your book are the part on cold weather and building a hammock IMHO.

           

          And again, I hope everyone doesn’t think I’m putting them down for using a heat reflector or thinking the reason that they are staying warm is radiant heat reflection. I’m just certain now more than ever that there isn’t the science to support that. BUT, people using them are staying warm. If that is true, then how? If we can figure that out, then maybe more efficient systems can be found to make it work.

           

          Ernest Engman

          AKA SGT Rock

          sgtrock@...

          http://hikinghq.net

           

           

          -----Original Message-----
          From: Ed Speer [mailto:info@...]
          Sent:
          Sunday, February 02, 2003 6:31 PM
          To: hammockcamping@yahoogroups.com
          Subject: Hammock Camping RE: Radiant Heat Reflectors

           

          Good discussion on heat loss Ernest.  I think we all agree that the major body heat loss is from conduction, convection, evaporation & respiration.  So unless one has conquered these, it's pretty pointless to worry about radiant heat loss.  I gather you feel that the warming benefit from reflective fabrics is due to their vapor-barrier properties, not their radiant properties; or at least the radiant advantages are overshadowed by the vapor-barrier advantages.  A good point indeed.  Maybe we like using the Aluminum-coated Mylar emergency blankets because they are so light weight--even lighter than plastic sheeting.  However, I often use my plastic sheet ground cloth as a vapor barrier on the bottom outside of my hammock--does it work as well as the emergency blanket?  Of course, I don't know--they both work well enough to keep using them!

           

          I'd be interested in seeing dependable numbers on actual body heat loss by the various processes.   I have found the following, but its' incomplete for our purposes:

           

          "The human body at rest losses 76% of it's heat due to conduction, convection and radiation; the remaining 24% is lost through evaporation, insensible perspiration and respiration".

           

          It would perhaps be useful if we knew exactly how much each process contributes.  Then again, nature is never a constant--like you said, things like wind and humidity greatly change the rules.  So maybe exact numbers are impossible to determine.

           

          Thanks for your reasoned discussion...Ed

           


           


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        • David Chinell
          MessageSarge: Didn t mean to get you side-tracked on the reflective heat issue (though I am glad to have someone more credible than me weigh in on it). You
          Message 4 of 18 , Feb 3, 2003
            Message
            Sarge:
             
            Didn't mean to get you side-tracked on the reflective heat issue (though I am glad to have someone more credible than me weigh in on it). You didn't answer my other question... How do you pack your super-wide closed-cell foam pad?
             
            Bear
             
          • Ernest Engman <ebengman@hikinghq.net>
            Doh, Sorry. I use a Moonbow Gearskin, so I don t roll up my pad. Instead I put the two layer part against my back and pack it like a Taco, compression straps
            Message 5 of 18 , Feb 3, 2003
              Doh,

              Sorry. I use a Moonbow Gearskin, so I don't roll up my pad. Instead I
              put the two layer part against my back and pack it like a Taco,
              compression straps on the side close the wings like side panels. You
              can see the pics of my gearskin and get the idea at:
              http://hikinghq.net/gear/moonbow_gearskin.html

              SGT Rock

              --- In hammockcamping@yahoogroups.com, "David Chinell"
              <dchinell@m...> wrote:
              > MessageSarge:
              >
              > Didn't mean to get you side-tracked on the reflective heat issue
              (though I
              > am glad to have someone more credible than me weigh in on it). You
              didn't
              > answer my other question... How do you pack your super-wide closed-
              cell foam
              > pad?
              >
              > Bear
            • David Chinell
              Neeeeet. Bear ... From: Ernest Engman [mailto:ebengman@hikinghq.net] Sent: Monday, February 03, 2003 02:40 PM To:
              Message 6 of 18 , Feb 3, 2003
                Neeeeet.

                Bear


                -----Original Message-----
                From: Ernest Engman <ebengman@...>
                [mailto:ebengman@...]
                Sent: Monday, February 03, 2003 02:40 PM
                To: hammockcamping@yahoogroups.com
                Subject: Re: Hammock Camping Franken pad and bride of
                Frankenpad


                Doh,

                Sorry. I use a Moonbow Gearskin, so I don't roll up my pad.
                Instead I
                put the two layer part against my back and pack it like a
                Taco,
                compression straps on the side close the wings like side
                panels. You
                can see the pics of my gearskin and get the idea at:
                http://hikinghq.net/gear/moonbow_gearskin.html

                SGT Rock
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