Yacht loses keel

Discussion in 'Boat Design' started by jdworld, Mar 2, 2010.

  1. jdworld
    Joined: Nov 2009
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    jdworld Junior Member

  2. Guest625101138

    Guest625101138 Previous Member

  3. Paul Kotzebue

    Paul Kotzebue Previous Member

  4. troy2000
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    troy2000 Senior Member

    Well, I'm not going to wade through all the stuff. But offhand, I would be suspicious of any results of a University investigation that directly contradicts the Coast Guard. Obviously, the University had a vested interest in blaming someone else.
     
  5. jdworld
    Joined: Nov 2009
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    jdworld Junior Member

    hmmm......ok, i didn't have to read too much beyond page 18 of that final report. A little over 1/2" of plywood and FG, and narrow backing plates supporting 2.5 tons of keel. No wonder. But still, the thing had been run aground 5 times and sent to the repair place for keel work. You would think the repair place would have brought that weakness to someone's attention and recommended beefing it up somewhere along the line.
     
  6. foxy
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    foxy Junior Member

    I've read the reports on this boat along with several other reports on keel failures. Dobroth raises some good points and then looses credibility by backing into a required hull thickness of 3 inches from the size of the backing plates. He might have simply said the hull thickness required by ABS was 1 inch, the CF 38 was substantially under that and the backing plates were too small.

    The Coast Guard report was critical of not having a proper engineering survey when repairing the grounding damage. Dobroth makes a statement that the yard should not have to call in anyone, but simply re-build what was there. He goes out of his way to point out necessary ABS complience to enter the race. But he fails to include that the ISAF Special Regs (formerly ORC regulations) required an engineering evaluation to ABS if the structure is changed or undergoes a major repair. Oops, I think the school and Dobroth neglected that part.

    I sympathize with Bruce Marek whose original engineering appears to have been in accordance with ABS. It would appear that a different keel design (with more righting moment) was fitted by Cape Fear and the structure reduced. It is never stated who designed the new keel.

    I have been in the position of a builder making changes to our engineering without consulting with me. About the only thing you can do, assuming you find out about it before it becomes a disaster, is send certified letters to all the affected parties that you can identify notifying them of the problem.
     
  7. TeddyDiver
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    TeddyDiver Gollywobbler

  8. idkfa
    Joined: Sep 2005
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    idkfa Senior Member

    Think there is a general failure of engineering here. Keels fail on new racing boat too that have never had a grounding or repairs at a yard.

    Keels fail at the hull join, and not that they snap in two. (Correct me if I'm wrong.)

    A yard should be able to replace what was there, and without the involvement of an engineer.

    A family on vacation to a secluded island should be able to have a severe grounding at their deserted island getaway, and survive the trip back. (Don't know if this has happen either.)

    Keels should be stuck with 4200/5200 in a box; that will survive grounding. There is a top plate bolted on that allows detailed inspection, removal and attachment of keel. A single bolt, that gives indication to severity of grounding and will hold the keel in case of adhesive failure.

    Diagram was done in MS Paint, sorry, the hull and box sides has a thickness.

    Don't expect you guys will adopt this but give it some thought. The cost the bolts normally used to bolt on the keel and cost of embedding them the keel top or making T flange should cover the cost of the top plate. The frames and hull thickness (which will be thinner) is a given.
     

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  9. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    That is too simplistic. The keel is part of a whole structure and there are many ways of designing a keel that won't fall off.
     
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