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RE: [Dragonflylist] Re: Hoop Gear Layup & Cloth Orientation

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  • Letempt, Jeffrey A CIV USA
    You open a big can of worms here. If you are not going to use a proven method of constructing the hoop landing gear, then you are designing your own landing
    Message 1 of 4 , Dec 1, 2008
      You open a big can of worms here. If you are not going to use a proven
      method of constructing the hoop landing gear, then you are designing
      your own landing gear. If you are qualified to do so, great...if not,
      you have to be willing to accept the risk of failure. Why do you want
      the gear to have more tension strength? Have you ever heard of a hoop
      gear failure?



      I am not an engineer, but CF and fiberglass have different properties.
      Important for this application is that CF is more rigid than the
      fiberglass. If 6-8 layers of CF is insufficient to handle the entire
      landing load, it will fail and the load will need to be carried by the
      fiberglass. If the fiberglass (because it is thinner when you replaced
      it with CF) is unable to accept the entire load, it will also fail. My
      suggestion would be to stick with either CF or fiberglass for this
      application. If you build the entire gear from CF, it will be lighter,
      but much stiffer and more costly (and you once again on your own because
      this has not been done on the Dragonfly before).



      All Dragonfly hoop landing gears are made from 3" wide unidirectional
      roving E fiberglass that is 22 ounces per yard (Aircraft Spruce part
      number 01-06800 or Wicks part number 1600-3). It is very thick glass
      that comes on a spool.



      Jeff



      From: Dragonflylist@yahoogroups.com
      [mailto:Dragonflylist@yahoogroups.com] On Behalf Of shaffer.jessie
      Sent: Sunday, November 30, 2008 11:30 PM
      To: Dragonflylist@yahoogroups.com
      Subject: [Dragonflylist] Re: Hoop Gear Layup & Cloth Orientation



      Thanks Dave......I see what what your saying. Although I have one
      more question. Does it matter which cloth (BID or UNI) is used? As
      long as the major fibers run the length of the gear? I have also
      been considering using some unidirectional carbon fiber on the first
      6 or 8 layers layed into the form to give it some extra tension
      strength.

      --- In Dragonflylist@yahoogroups.com
      <mailto:Dragonflylist%40yahoogroups.com> , "Dave Morris" <BigD@...>
      wrote:
      >
      > No, he used unidirectional "tape", which is sold in 3 inch width
      and ALL the
      > fibers run the length of the gear. He slit the tape in half to
      produce some
      > 1.5 inch widths that could be laid next to the 3 inch width to
      produce a
      > total 4.5 inch width, and alternated overlapping those. The
      unidirectional
      > nature of the tape is what gives it strength.
      >
      > When I did mine, I finished it up by wrapping several additional
      layers of
      > bidirectional over the top, to give it a smoother finish mostly,
      and because
      > I felt that the gear should have some strength across the span of
      the gear
      > to resist torsional loads caused by FOD on the runway, etc.,
      however that
      > was done entirely without any engineering calculations.
      >
      > Dave Morris
      >
      >
      > -----Original Message-----
      > From: Dragonflylist@yahoogroups.com
      <mailto:Dragonflylist%40yahoogroups.com>
      [mailto:Dragonflylist@yahoogroups.com
      <mailto:Dragonflylist%40yahoogroups.com> ]
      > On Behalf Of shaffer.jessie
      > Sent: Sunday, November 30, 2008 7:50 PM
      > To: Dragonflylist@yahoogroups.com
      <mailto:Dragonflylist%40yahoogroups.com>
      > Subject: [Dragonflylist] Hoop Gear Layup & Cloth Orientation
      >
      > To All,
      > I've searched all the past messages for any information on the
      > cloth fiber orientation for Gene Divincenzo's hoop gear design.
      > Unfortunately I didn't have much luck. According to Gene's notes
      > (published in DBFN #43), it appears (for the first part of the
      layup)
      > that he used continuous strips of cloth (i.e. from one end to the
      > other) for the layup until he reached a thickness of 5/8". This
      great
      > information, however nowhere have I been able to find any
      information
      > on the fiber orientation of these layups discussed. Does anyone
      have
      > any information they would be willing to share? As near as I can
      tell,
      > he used 10 oz. BID cloth with one set of fibers running with the
      span
      > of the gear and of course, the other set is 90 degrees to this.
      > However, I don't know if there is a whole lot of torsional strength
      > generated in this configuration. Undoubtedly, there will be some
      > torsion on this gear. Any information from anyone would be helpful.
      >
      > Thanks,
      >
      > Jessie
      >
      >
      > ------------------------------------
      >
      > Yahoo! Groups Links
      >





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