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windbreak

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  • o123david
    Ed asked... can you offer a better description of your polyethylene rings w/ duct tape? This sounds interesting, but I can t envision it. Does the poly
    Message 1 of 2 , Aug 25, 2003
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      Ed asked... "can you offer a better description of your polyethylene
      rings w/ duct tape? This sounds interesting, but I can't envision it.
      Does the poly sheeting go completely under the hammock? Do you have
      any photos?"

      It seems to me that the reason we often can't keep warm in a hammock
      is the wind that blows through the hammock. It blows cold air into
      the insulation making the insulation less effective.
      One solution tried is a radiant heat barrier. If I understand the
      physics correctly this method is only meaningful if you don't have
      the right amount of thermal insulation. In other words it is only
      effective if you don't have enough normal insulation or, more
      commonly, if the wind has caused much of the normal insulation to be
      ineffective. It also creates a problem with condensation. A much
      better solution is to block the wind before it reaches the insulation
      and to have the right amount of insulation.
      Another method tried is a vapor barrier used inside most of the
      insulation. In my experience this is somewhat effective when it isn't
      too cold out and it works better when the humidity is low, situations
      where you normally lose a somewhat significant amount of heat due to
      evaporation from your skin. You may find it of some value. I find the
      weight and discomfort not worth the trouble. Anyway, it is not an
      effective way to prevent loss of heat to the wind.
      A third method is to wrap yourself in windproof material. You might
      make the hammock out of windproof material or spray it with something
      that makes it windproof. Since the material will also be waterproof
      (Gore-tex and similar materials don't work here because you don't
      have the necessary large difference in vapor pressures) you will find
      that condensation collects and decreases the effectiveness of your
      insulation. You might instead try to block the wind with a tarp
      pulled down almost vertically along the sides of the hammock. With
      the Hennessy diamond-shaped tarp I have learned that this doesn't
      work because of gaps in coverage. With the large tarp that comes with
      the Speer hammock this apparently does work as long as the wind
      continues to come only from the sides.

      The solution I use is to suspend windproof material around the
      hammock.
      Cool dry air comes from below, moves through the hammock, and what
      has become warmer more-moist air exits above. From what I have read
      this is part of the design of all good shelters and is the only way
      to both block the wind and rain and prevent the buildup of
      condensation.
      Taking the typical hammock which is 5' wide, if you suspend a 2'6"
      wide strip of material from the top edge of the hammock going all the
      way around then you will have effectively blocked the wind from all
      directions. When the wind blows from one direction the windproof
      material is blown against the hammock and blocks the wind from that
      direction.

      I will attempt to describe the how I do this. A picture would be
      better but, unfortunately, no camera.
      1. Take (or imagine taking) a piece of cord twice as long as a side
      of the hammock. Tie it in a loop. Suspended it from each end of the
      hammock. Set up the hammock. You will see that the cord hangs down
      just like the sides of the hammock. The cord continues to follow the
      top edge of the hammock.
      2. Now take some polyethylene. Cut it in a strip 2'6" wide. Use duct
      tape to tape the polyethylene in a loop just as long as the cord.
      Reinforce the top edge of the loop of polyethylene with more duct
      tape. Tie the reinforced edge of the polyethylene to each end of the
      hammock. You now have a removable windbreak.

      The windbreak does not block access to either the Hennessy or Speer
      hammocks.
      When used even in very little wind it adds a significant amount of
      warmth.
      It does not create a problem with condensation, but it does make it
      feel clammy in the hammock. I intend to switch to sleeping on an
      angle and hope that with a larger portion of the hammock body no
      longer being covered with a pad there will be more movement of air
      and the clamminess will go away.

      It is time for a confession. This is the first year since 1997 that I
      have not hiked over 2500 miles of trail. I have hiked very little
      this year and used the windbreak on only one week-long trip. It never
      got windy. I don't know that the windbreak will work - I only THINK
      that it will. And I know that something like it is needed.
      I used polyethylene because it is cheap, windproof, and easy to work
      with. Strength does not appear to be needed because the material is
      only blown against the hammock. The 2 mil poly that I used was
      probably excessive. The strip of full-width duct tape along the top
      edge of the poly was definitely excessive. With the Speer hammock I
      tended to put stress on the top edge of the poly as I left the
      hammock so it would be best to put a thin line of Spectra cord (that
      doesn't stretch) inside the duct tape along the top edge to prevent
      stretching. The stress points are at the ends of the hammock where
      the windbreak is attached, a problem that I hope will be resolved by
      adding the Spectra cord inside the duct tape that follows the top
      edge of the poly. When I cut the poly I made most of the windbreak
      2.5' wide but tapered it to only 1' wide near the ends.

      The windbreak is cheap and simple to both make and use, lightweight,
      and will hopefully make hammocks warm in windy conditions without
      creating a problem with condensation. Please let me know if it really
      does work. --David
    • Ed Speer
      Thanks for the details Dave--I m considered trying the same thing, but haven t gotten around to it yet. I even considered lowering the side walls all the
      Message 2 of 2 , Aug 25, 2003
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        Message
        Thanks for the details Dave--I'm considered trying the same thing, but haven't gotten around to it yet.  I even considered lowering the 'side walls' all the way to the ground--sort of like skirting around the bottom of a house trailer.  You're way ahead of me on this and maybe have tried this as well.  Nothing works like actual field performance--maybe this winter you'll get the chance to refine this some more.  It is an intriguing idea and may be the regal solution we're all searchng for....Ed
         
        From: o123david [mailto:o123david@...]
        Sent: Monday, August 25, 2003 3:05 PM
        To: hammockcamping@yahoogroups.com
        Subject: Hammock Camping windbreak

        Ed asked... "can you offer a better description of your polyethylene
        rings w/ duct tape? This sounds interesting, but I can't envision it.
        Does the poly sheeting go completely under the hammock? Do you have
        any photos?"

        It seems to me that the reason we often can't keep warm in a hammock
        is the wind that blows through the hammock. It blows cold air into
        the insulation making the insulation less effective.
        One solution tried is a radiant heat barrier. If I understand the
        physics correctly this method is only meaningful if you don't have
        the right amount of thermal insulation. In other words it is only
        effective if you don't have enough normal insulation or, more
        commonly, if the wind has caused much of the normal insulation to be
        ineffective. It also creates a problem with condensation. A much
        better solution is to block the wind before it reaches the insulation
        and to have the right amount of insulation.
        Another method tried is a vapor barrier used inside most of the
        insulation. In my experience this is somewhat effective when it isn't
        too cold out and it works better when the humidity is low, situations
        where you normally lose a somewhat significant amount of heat due to
        evaporation from your skin. You may find it of some value. I find the
        weight and discomfort not worth the trouble. Anyway, it is not an
        effective way to prevent loss of heat to the wind.
        A third method is to wrap yourself in windproof material. You might
        make the hammock out of windproof material or spray it with something
        that makes it windproof. Since the material will also be waterproof
        (Gore-tex and similar materials don't work here because you don't
        have the necessary large difference in vapor pressures) you will find
        that condensation collects and decreases the effectiveness of your
        insulation. You might instead try to block the wind with a tarp
        pulled down almost vertically along the sides of the hammock. With
        the Hennessy diamond-shaped tarp I have learned that this doesn't
        work because of gaps in coverage. With the large tarp that comes with
        the Speer hammock this apparently does work as long as the wind
        continues to come only from the sides.

        The solution I use is to suspend windproof material around the
        hammock.
        Cool dry air comes from below, moves through the hammock, and what
        has become warmer more-moist air exits above. From what I have read
        this is part of the design of all good shelters and is the only way
        to both block the wind and rain and prevent the buildup of
        condensation.
        Taking the typical hammock which is 5' wide, if you suspend a 2'6"
        wide strip of material from the top edge of the hammock going all the
        way around then you will have effectively blocked the wind from all
        directions. When the wind blows from one direction the windproof
        material is blown against the hammock and blocks the wind from that
        direction.

        I will attempt to describe the how I do this. A picture would be
        better but, unfortunately, no camera.
        1. Take (or imagine taking) a piece of cord twice as long as a side
        of the hammock. Tie it in a loop. Suspended it from each end of the
        hammock. Set up the hammock. You will see that the cord hangs down
        just like the sides of the hammock. The cord continues to follow the
        top edge of the hammock.
        2. Now take some polyethylene. Cut it in a strip 2'6" wide. Use duct
        tape to tape the polyethylene in a loop just as long as the cord.
        Reinforce the top edge of the loop of polyethylene with more duct
        tape. Tie the reinforced edge of the polyethylene to each end of the
        hammock. You now have a removable windbreak.

        The windbreak does not block access to either the Hennessy or Speer
        hammocks.
        When used even in very little wind it adds a significant amount of
        warmth.
        It does not create a problem with condensation, but it does make it
        feel clammy in the hammock. I intend to switch to sleeping on an
        angle and hope that with a larger portion of the hammock body no
        longer being covered with a pad there will be more movement of air
        and the clamminess will go away.

        It is time for a confession. This is the first year since 1997 that I
        have not hiked over 2500 miles of trail. I have hiked very little
        this year and used the windbreak on only one week-long trip. It never
        got windy. I don't know that the windbreak will work - I only THINK
        that it will. And I know that something like it is needed.
        I used polyethylene because it is cheap, windproof, and easy to work
        with. Strength does not appear to be needed because the material is
        only blown against the hammock. The 2 mil poly that I used was
        probably excessive. The strip of full-width duct tape along the top
        edge of the poly was definitely excessive. With the Speer hammock I
        tended to put stress on the top edge of the poly as I left the
        hammock so it would be best to put a thin line of Spectra cord (that
        doesn't stretch) inside the duct tape along the top edge to prevent
        stretching. The stress points are at the ends of the hammock where
        the windbreak is attached, a problem that I hope will be resolved by
        adding the Spectra cord inside the duct tape that follows the top
        edge of the poly. When I cut the poly I made most of the windbreak
        2.5' wide but tapered it to only 1' wide near the ends.

        The windbreak is cheap and simple to both make and use, lightweight,
        and will hopefully make hammocks warm in windy conditions without
        creating a problem with condensation. Please let me know if it really
        does work. --David



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