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RE: [Dragonflylist] Fw: Header Tank Integrity (escape tool)

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  • Letempt, Jeffrey A CIV
    Why fix something that isn t broke? If you are concerned about the header tank leaking in a crash, just eliminate the tank all together. This will generally
    Message 1 of 4 , Nov 1, 2007
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      Why fix something that isn't broke? If you are concerned about the
      header tank leaking in a crash, just eliminate the tank all together.
      This will generally mean adding complexity or more failure points into
      the fuel system, but it is all about making compromises.

      The Dragonfly has been flying for nearly 30 years and the composite
      construction has proven to be very crashworthy. I know accidents that
      have happened that are not in the NTSB database, but if you look at the
      accident history for the Dragonfly you will find that main fuel tank
      leaks are not a problem after a crash sequence. I have seen pictures of
      crashed Dragonfly's and could not believe the crew was able to walk
      away. Rich Goldman's off-field landing a few years ago was hard enough
      that it broke the wing and canard attachment bulkheads free from the
      fuselage, but the fuel tank remained intact. After his accident he
      recommended applying a couple plies of Kevlar to the underside of the
      fuselage under the fuel tank.

      Jeff


      -----Original Message-----
      From: Dragonflylist@yahoogroups.com
      [mailto:Dragonflylist@yahoogroups.com] On Behalf Of Charles W. Smith
      Sent: Wednesday, October 31, 2007 8:26 PM
      To: Dragonflylist@yahoogroups.com
      Subject: [Dragonflylist] Fw: Header Tank Integrity (escape tool)



      I would think the ideal place for a header tank would be outside under
      the cowling where it could tear away in a crash. However, the fuel tank
      is the seat in the plane, and any crash severe enough to tear away the
      header tank would likely also rupture the seat, especially since the
      seat is part of the main structure of the plane. I once drove a truck
      that had the gas tank under the drivers seat (a '53 Ford) and a friend
      of mine got barbecued in a similar truck after a crash. I consider this
      fuel tank to be a severe problem with both the Dragonfly and Q2 and have
      pondered for many hours about how to overcome it without being a
      high-tech aeronautical engineer. The closest probable solution is to
      abandon the canard configuration and convert it to a bi-plane using the
      existing airfoils and put the gas into tip tanks, or to build a larger
      wing, mount it at the gas tank position and configure the plane as a
      conventional LSA. All the other solutions I can imagine involves a
      computer controlled fuel management system for 4 tanks mounted in the
      tips of the canard and wing.
      ----------------------------------------

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    • DraagunFly@aol.com
      Bob Walters put the fuel tank(s) where it is for C.G. reasons. The C.G. does not change with fuel burn (except slightly with the header tank. Those who move
      Message 2 of 4 , Nov 1, 2007
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        Bob Walters put the fuel tank(s) where it is for C.G. reasons. The C.G. does
        not change with fuel burn (except slightly with the header tank. Those who
        move the tank forward pay a greater C.G. change price). Again, all airplanes
        are compromises. If you plot the C.G. on a Dragonfly, you'll find it falls
        right near the center of the fuel tank. Remember the John Denver crash? the
        original builder was highly concerned about the fuel entering the cockpit via the
        fuel selector switch, so he moved it back to the rear bulkhead to have the
        fuel line behind the firewall. The resultant twisting around to reach the
        selector switch resulted in Dener losing control at low airspeed, low
        altitude....dead! Like I said a few posts ago, we must think every change thru carefully,
        even seemingly insignificant ones. The safest course is stick to the plans,
        but since we are truely experimental builders, we rarely do that. Just think
        things thru to possiible concenquences and then decide on the compromises
        acceptable to you. My 2 cents worth.
        Richard in Chino



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