balsa divinny combo

Discussion in 'Fiberglass and Composite Boat Building' started by rturbett, Oct 8, 2008.

  1. rturbett
    Joined: Aug 2005
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    Location: FINGER LAKES, NY

    rturbett Senior Member

    Before I place my balsa order, I am still considering divinycell. Does anyone have thoughts about using diviny below the waterline and balsa above?


    This boat would only be in the water for a couple of hours per week for racing. I am more concerned with water possible collecting in the hull and sitting.

    what consideration would you give to the joint line where the two different materials meet?
    Thanks,
    Rob
     
  2. CTMD
    Joined: Dec 2007
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    Location: Melbourne, Aus

    CTMD Naval Architect

    While I understand your logic, structurally you would be better off placing the balsa below the waterline and divinycell above.
     
  3. rturbett
    Joined: Aug 2005
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    Location: FINGER LAKES, NY

    rturbett Senior Member

    I love balsa core- for strength and ease of use. I know I can come in at weight with just standard density as well.
    My only nagging thought is what if... - since we dont have access to the insid of these hulls, how can I ensure its long term survival?
    I may paint the inside layer of glaas/ epoxy just for peace of mind.
     
  4. rwatson
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    rwatson Senior Member

    As GRP allows water to seep through, I agree a layer of epoxy over the GRP should be a good addition, and as it will be covered, will not degrade due to UV, so will not need to be painted.
     
  5. Herman
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    Location: The Netherlands

    Herman Senior Member

    Always coat the inside, and drain the boat after use. Also chasing leaks is not a bad idea. A well built boat can be made completely watertight. When that is the case, no need to worry about water entrapment.

    I always kept my boats leaning backwards on the trailer, and have the drain plug and inspection covers open.

    About balsa and foam: Much guessing here, as I have no idea of the boat at all, but you mention it is a racing boat. Generally balsa generates more stiffness, so that should be in the bottom. However, it would be a good idea to calculate stiffness beforehand, to make a well founded decision.
     
  6. rturbett
    Joined: Aug 2005
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    rturbett Senior Member

    I am very happy with the all balsa hull I made. I am only considering divinycell because I am making it for someone else, and I can't garuntee they would take care of it as good as I would.
     

  7. Herman
    Joined: Oct 2004
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    Location: The Netherlands

    Herman Senior Member

    Indeed that is the problem with balsa. Especially in decks. Properly bonded and encapsulated it lasts a lifetime, but what if an enthousiastic owner starts drilling holes, and not re-encapsulate the balsa?

    Or leave the boat flooded?

    anyhow, a good inner laminate should be able to cope with the latter problem.

    But indeed, you must convince your client that these hulls are thoroughbred racing hulls, and should be treated that way...
     
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