Second forestay chainplate on A-cat hull

Discussion in 'Multihulls' started by revintage, Jun 25, 2019.

  1. revintage
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    revintage Senior Member

    TTLF please make a sketch to show your idea. Sounds interesting, but I am not sure how you want it to be done. Dyneema fiber is slippery as hell and will not adhere to epoxy, is the braid ment to hold it?
     
  2. trip the light fandango
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    trip the light fandango Senior Member

    I tried to make a sketch but struggle with the software sorry. You will have to ask the person who posted that epoxy takes to Dyneema, I assume you spread it like splicing using a fid, then glass over it. Or just undo the braid. The drawing would look much the same as your diagrams but with chain plates made of dyneema with 2 or 3 arms to spread the load, with a loop protruding out through the reinforced gunwhale[dyneema again], deck/hull join glassed internally and a transverse plate/spreader, which perhaps could also be made of dyneema and glass. If glueing Dyneema with epoxy works I'll be using it to edge the bottom of my dagger board cases I think.
     
    Last edited: Jul 6, 2019
  3. Doug Halsey
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    Doug Halsey Senior Member

    That thread on "SA" is currently 45 posts long. I've gone through it once, but didn't find anything about epoxying Dyneema. I'm assuming it's there somewhere though.

    If you can find it, I would appreciate knowing the post #.
     
  4. trip the light fandango
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    trip the light fandango Senior Member

    Hi, it's mentioned by Bottman just before halfway down the page, ...so Ultra High Molecular Weight Polyethylene (UHMWPE) is able to absorb epoxy... I suppose the next issue is how to anchor it, ultimately it still boils down to the strength of epoxy and its ability to bond and spreading the load . I'd be really interested to find out more about this, Bottman could be onto something it could be a bit of a game changer.[am I hyperventilating]., what do you think? It could be used to localise shearing forces ,like the bottom of a dagger board case to protect the hull I was thinking. Or using it as a web or cage to carry load.
     
  5. revintage
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    revintage Senior Member

    Even if the Dyneema fibers do not adhere to epoxy, they will be fixed in the resin if you use a 12-strand line, as the epoxy will lock around the woven structure. I could think of using it for deck eyes if one could arranged for it not to be bent where the the line comes out of the epoxy.
     
  6. trip the light fandango
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    trip the light fandango Senior Member

    If the dyneema absorbs epoxy it would be better, we'll have to do some tests. You could make a simple internal frame out of dyneema, standard stainless thimbles would work fine, epoxy could be used to lock simple dyneema splices, like a swage if it doesn't absorb. O rings and dyneema used as pad eyes plus another O ring on a stay could be a really tidy strong and cheap and light way of rigging . It could be used as stringers and to strengthen bulkheads if it absorbs epoxy.
     
    Last edited: Jul 8, 2019
  7. revintage
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    revintage Senior Member

    A single dyneema fiber as a single carbon fiber does not absorb epoxy. The difference is that epoxy adheres to carbon but not to dyneema. As I mentioned a 12-strand dyneema drenched in epoxy will act like hundreds of small knots. No doubt it will lock the line. But better to do some tests. Will glue two 3mm dyneema loops to G10 and load with 250kg.
     
  8. trip the light fandango
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    trip the light fandango Senior Member

    I wont be using epoxy for a while "dyneema is compatible with epoxy resin so it can be used just like glass cloth/cf " to quote Bottman , so your test will be very interesting.
     
  9. TeddyDiver
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    TeddyDiver Gollywobbler

    :D no ripping. There's holes allready which are quite adequate for the work..
     
  10. revintage
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    revintage Senior Member

    That one is a little dated, so you’ll have to catch up! The guys at SA Multihulls carried the discussion further to an acceptable solution. Still not decided which way to go. Found a block of 10mm G10 in my workshop that might be used. Will anyway start cleaning up the right inside with the Dremel tomorrow, if weather allows.
     
  11. revintage
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    revintage Senior Member

    The forestay fitting design went into a completely different direction. This is the bulkhead to be fitted inside the hull with the help of epoxy and carbon fiber. A pair of wooden dowels are temporally fitted to guide the bulkhead. The chainplate will be anchored to the bulkhead with 6 layers of 220gr carbon fiber. The 118gr bulkhead is made from plates of 1mm G10 on each side of 10mm Divinycell.

    F4E9787A-07FD-4432-BED8-E5B9268F71B7.jpeg 1B2BEB9E-E791-4318-AE5A-0D0C07A423D6.jpeg
     
    Last edited: Jul 14, 2019
  12. trip the light fandango
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    trip the light fandango Senior Member

    That looks good, I'll be interested to see how you go about spreading the shearing force-load,the bulkhead looks like it could act as a guillotine.

    You could glass in Stringers, let them cure, say 600mm long, cut notches in the bulkhead in its corners to take the stringers , then glue the bulkhead to them. I'm guessing this is your intention.
    It's going well, any results from trying to saturate dyneema with epoxy?
     

  13. revintage
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    revintage Senior Member

    The bulkhead will be epoxied to the hull sides with three layers of 220gr carbon fiber to transfer the load. Will not load the deck very much that way.
    Have not experimented with dyneema and epoxy yet, but will do.
     
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