Loading ...
Sorry, an error occurred while loading the content.

Re: [EOSS] Heat shields on hotwire cutdowns

Expand Messages
  • K. Mark Caviezel
    for most of my cutdowns I rig the flight string, then the cutter nichrome, then I give it a wrap with silica cloth tape. Then I use a normal desk stapler to
    Message 1 of 2 , May 7, 2005
    • 0 Attachment
      for most of my cutdowns I rig the flight string, then
      the cutter nichrome, then I give it a wrap with silica
      cloth tape. Then I use a normal desk stapler to keep
      it in place. Very lightweight, and very heat/flame
      proof, too.
      I've often run commanded and timed 'watchdog'
      timers, and having a 'watchdog' go off on the ground
      in the most often bone dry Colorado area has always
      been a concern.

      - KMC



      --- Zack Clobes <zclobes@...> wrote:
      > Those of you using NiChrome for cutdown devices,
      > what are you guys using
      > as heat shields and insulation?
      >
      > My experience is that the blue/pink Styrofoam will
      > ignite under the
      > right conditions (unlikely but possible). I've
      > tried epoxy to keep it
      > from burning through, but enough heat will melt the
      > epoxy away.
      >
      > Zack Clobes, W0ZC
      > Project: Traveler
      >
    • Mike Manes
      Hi Zack, We mitigate the risk of fire by hitting the burner for just 10 seconds after receipt of a valid cutdown command. It takes jut 2 - 4 sec to
      Message 2 of 2 , May 8, 2005
      • 0 Attachment
        Hi Zack,

        We mitigate the risk of fire by hitting the burner for just 10 seconds
        after receipt of a valid cutdown command. It takes jut 2 - 4 sec to
        effectively melt the nylon lift line, but there must be some tension on
        it to achieve sepataration. Once or twice, the line has melted w/o
        tension,
        and it came back simply welded back together.

        We wrap the burner in some refractory ceramic insulation fabric to
        about 1/4" thickness and then enclose the whole shebang in a 1/2" thick
        styrofoam clamshell covered with Al foil duct tape. I keep the 2" of
        burner feed wires closest the the burner inside the clamshell to avoid
        cooling to the slipstream. The clamshell is then closed with several
        wraps of common PVC electrical tape and secured to an anti-rotation yoke
        attached to the 'chute apex.

        The inside surface of the styrofoam does melt back a bit, but it's never
        ignited.

        73 de Mike W5VSI

        Zack Clobes wrote:
        >
        > Those of you using NiChrome for cutdown devices, what are you guys using
        > as heat shields and insulation?
        >
        > My experience is that the blue/pink Styrofoam will ignite under the
        > right conditions (unlikely but possible). I've tried epoxy to keep it
        > from burning through, but enough heat will melt the epoxy away.
        >
        > Zack Clobes, W0ZC
        > Project: Traveler
        >
        >
        >
        > Yahoo! Groups Links
        >
        >
        >
        >

        --
        Mike Manes manes@... Tel: 303-979-4899
        "Things should be made as simple as possible, but not more so." A.
        Einstein
      Your message has been successfully submitted and would be delivered to recipients shortly.