[Rhodes22-list] FRP strengthening/ slide hatch

[Lou Rosenberg]

  Roger,
   I saved this reply b/c it applies to my sliding hatch which 
definitely has a visible crack in the  leading edge ( fore) .   My 
seat was poor judgement and inexperienced eyes on FRP. I have since 
been corrected by ( God ) of all folks, and Don Casey helped too 
along with  yourself!
Would you advise doing the strengthening on the hatch  with thickened 
epoxy as you stated below a few wks ago?
  thanks
Lou



Lou

>
>If there are visible cracks or other flaws in the FRP composite underneath
>the cockpit seat; then, you will have to do something ASAP.  Failure of an
>FRP composite structure is a cumulative damage sort of phenomena.  Every
>time you step on the seat & hear a "crack", that is the sound of some glass
>fibers snapping or the bond between some of the glass fibers and the
>polyester resin substrate failing.  FRP composites do not "heal" themselves.
>Under moderate overload, they just progressively fail one fiber or one
>fiber/substrate bond at a time until the remaining structure is too weak to
>support the load.  Then these materials fail catastrophically in a sudden
>brittle manner.  If the cracks are visible on the surface; then, you may be
>able to reinforce the structure by injecting unthickened epoxy into the
>cracks with a syringe.  Have someone stand on the weak spot while you inject
>the epoxy as deeply into the opened surface cracks as possible.  Then, have
>your assistant get off the seat.  Repeating this several times will work the
>epoxy up into the FRP composite structure out to the tip of the developing
>crack.  After the epoxy hardens inside of the FRP composite structure, this
>should arrest the crack development.  However, you will still need to
>reinforce the cockpit seats or this sort of failure will start occuring
>again.
>
>Roger Pihlaja
>S/V Dynamic Equilibrium
>
>----- Original Message -----
>From: "Lou Rosenberg" <lsr3 at MAIL.nyu.edu>
>To: "The Rhodes 22 mail list" <rhodes22-list at rhodes22.org>