Is this progress in composite construction?

Discussion in 'Fiberglass and Composite Boat Building' started by Mark Peiffer, Dec 8, 2004.

  1. tschienque
    Joined: Feb 2004
    Posts: 33
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: rotterdam,netherlands

    tschienque Junior Member

    Hi Guys,

    Any details on what specifically you didn't like about Parabeam?

    In both cases I detect a reluctance in attitude to the "type" of product. In Tja's case, he specifically states he prefers solid glass and Herman doesn't like "the idea of a hollow core", ruling out NIDACORE etc.

    I'll be visiting the Parabeam factory in the next week or two to evaluate, so any all questions would be greatly appreciated.

    Caio
     

  2. brian eiland
    Joined: Jun 2002
    Posts: 4,964
    Likes: 188, Points: 73, Legacy Rep: 1903
    Location: St Augustine Fl, Thailand

    brian eiland Senior Member

    Core-Skin Bond Line

    One of the biggest problems in cored boat construction is bonding the dissimilar skin and core materials together, both their dissimilar properties and that property of the bonding adhesive itself. Failure occurs in shear, and then the two dissociated skins are not able to carry the load.

    Witness the problems with the ORMA 60 tri's:
    http://www.yachting-world.com/auto/newsdesk/20031004130431ywnews.html
    Nigel Irens comments
    "Last year there was a bulge in new boats being built and a wholesale move towards building in pre-preg carbon and Nomex core. Everybody had drifted towards this technology and although the stuff's been around for a long time, what went wrong was the result of that. There may be a big learning curve now underway and it may be that some people won't use these materials again. We certainly haven't used them on Ellen's boat [her new 75ft trimaran, currently building in Australia]. We've gone back to more traditional core material."

    "Basically, what it's all about is the materials have very adequate static strength and there's no problem in terms of sheer pressure head. But in reality what's appears to be happening is that there is not enough capacity to absorb the loads that the skin sees. These are much, much higher than was the case with a softer, more forgiving material."


    And now have a look at this latest failure....granted under extreme conditions and in a very large piece:
    ANALYZING SYDNEY HOBART DAMAGE
    (The designer of Konica Minolta, Brett Bakewell-White gave his view on what
    happened in a story posted on The Daily Sail subscription website. Here are
    a couple of excerpts.)

    "The damage to the boat was relatively minor. It consisted of a core shear
    failure across the cabin top from window to window - approx. 1.8m long -
    the skins remained intact. The transverse crease in the cabin top was about
    150mm in front of the keel tower and behind the mast. Essentially it was
    caused by the keel's momentum compressing the cabin top as the boat crashed
    out of the back of a very large wave. This part of the cabin top had
    received a significant design effort when the boat was designed and was
    capable of exceeding ABS grounding requirements, so it is rather surprising
    that sailing loads have managed to exceed these quite stringent requirements.

    "Whilst we tried to shore up the damage by bolting through the cabin top
    with bunk tops above and below, we found that the continuous movement of
    the keel began to slowly tear the carbon skins with the inevitable result
    being a gaping gash across the cabin top and the possibility of water
    entering the cabin. Once we turned and ran with the seas the cabin top was
    fine. Over the next few days the cabin top was through bolted with plywood
    either side (as we had attempted at sea) and she was motored down the coast
    to Hobart. Had we had some substantial material such as plywood we could
    have affected the same repair and won the race." -
    The Daily Sail,
    www.thedailysail.com
     
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