Core cell or Balsa??

Discussion in 'Fiberglass and Composite Boat Building' started by SOB, Jan 8, 2005.

  1. SOB
    Joined: Sep 2004
    Posts: 13
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    Location: Georgia

    SOB Junior Member

    What are the pros and cons of the two for high performance boat applications. Would like to use for coring, bulkheads.
     
  2. lakerunner
    Joined: Oct 2004
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    Location: ohio

    lakerunner Junior Member

    When you say HP I assume you mean under power,Or HP sailing?
    Either way The properties of a solid class lay-up may always be the best bet for HP
    due to a single matrix as to a mutiple one . Simply due to impact, shear, and flexing.
    Although Balsa is my choice for Bulkheads , Stringers and deck. But comes with weight penalties. As does the hull with solid fiberglass lay-up. This ? arises quite often .. Although there is no one correct way , The pros and cons would most always be strength to weight or visa versa .and the dirty word (ROT) and extreme stiffness that comes with a balsa core. Core-cell , athough with better flexing properties has the inherent problems of adhesion inturn causing seperation in the matrix due to the flex which can cause catastrophic falure at high speeds. These are a few pros and cons
    but each have there own, I am sure others will help out with your ?. And hope this may help you . Good luck
     
  3. lakerunner
    Joined: Oct 2004
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    Location: ohio

    lakerunner Junior Member

    It is Ironic, That just this evening I was watching the History channel where they where talking about the history of the cigarrette boats, And finally showed how it is built. I was a little surprised to see that it is all mat Hand laid hull and deck.. At least that is all they showed . 15 layers if I remember correctly. with duratec balsa bulkheads and stringers .And she tops out at 90 to 130 mph. with approx. 1200 to 1500 hp. Again note the solid glass lay-up with just mat. Woven and bi axials are stiffer and stronger than mat , but again note the flexing abilities at high speed with the less stiffer hull . another thing they noted is that the deck and hull , once mounted were also glassed together to achieve in effect a single shelled craft.
    Become. one unit in whole.
     
  4. SOB
    Joined: Sep 2004
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    Location: Georgia

    SOB Junior Member

    If using all glass lay up and say a 3oz skin how many layers of 1708 would be adequate. By the way this is for hulls similar to Cigarette.
     
  5. lakerunner
    Joined: Oct 2004
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    Location: ohio

    lakerunner Junior Member

    This is a ? that can not be answered without engineering calculations. each boat is going to be different based on a multitude of design specs. ie: Size, type, power,
    use, etc. etc. etc. it is impossible to give you an exact lay-up schedule. and it would be irresponsible to even assume or guess. Although , If you are looking for a good basic
    approach to calculating several of these questions. I suggest you look into purchasing
    Dave Gerr 's book on ''The Elements of Boat Strength '' This book covers the /'s you ask. I believe you can find this book on this web sight or order from barns and noble.
     

  6. mmd
    Joined: Mar 2002
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    Location: Bridgewater NS Canada

    mmd Senior Member

    Structural foams are prone to compress when impacted (e.g., a hard bump against a piling) and not spring back to shape. Sometimes this leads to seperation from the 'glass skin, leaving a void that will eventually fill with water. In my area of winter freeze, this can be a big problem.

    Balsa is more resistant to bruising and tends to rebound to it's pre-impact shape. It's Achilles heel is that if any moisture gets through the fiberglass skins, the balsa turns to the structural equivalent of wet carboard in an amazingly short time. Production details like proper methods of mounting hardware on balsa-cored surfaces are very important.

    It is well worth the money spent to have your preliminary design vetted by a skilled and experienced naval architect/marine engineer. Bruce Pfund Special Projects LLC comes to mind.
     
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