tunnel clearance

Discussion in 'Multihulls' started by brendan gardam, Sep 2, 2020.

  1. brendan gardam
    Joined: Feb 2020
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    Location: east gippsland australia

    brendan gardam Senior Member

    hi everyone. can anyone tell me what the minimum tunnel clearance should be on a 23 foot sailing cat.
     
  2. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    There is a formula(e) applied to this, but it is probably more a rule of thumb, and not "hard science". I guess it depends where you are using the boat, as well. What clearance do you have at present ?
     
  3. brendan gardam
    Joined: Feb 2020
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    Location: east gippsland australia

    brendan gardam Senior Member

    Thanks Mr e. I am not at home to measure it. But I am looking at building a shallow cockpit with center cabin next winter.
    Will measure it on the weekend.
     
  4. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    Bdeck clearance 5-6% loa

    you can google bridgedeck clearance

    32 feet
    1.6 feet
    Mine is 17" or 1.42, but the bridgedeck is pretty short for that dimension..

    23'feet @ 6% is 1.26 feet
     
  5. brendan gardam
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    Location: east gippsland australia

    brendan gardam Senior Member

    Excellent. Thank you.
     
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  6. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    5-6% allows a bit of leeway for other factors I guess, but erring on the side of "more" might be appreciated under bad conditions. Of course, high clearance on a small boat, can easily spoil the "beauty" of the boat.
     
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  7. catsketcher
    Joined: Mar 2006
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    catsketcher Senior Member

    An International 23 does not have a heap of bridgedeck clearance to the beams. I would not recommend lowering anything under the beam bottom edges, especially as any added weight will reduce the clearance due to the boat floating lower.
     
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  8. brendan gardam
    Joined: Feb 2020
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    Location: east gippsland australia

    brendan gardam Senior Member

    I went for my 1st sail on the cat yesterday and I see what you mean. There is not a lot of clearance. I would not want to reduce it any further.
     

  9. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    5% of the Lwl at midships as a min.
     
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