# tunnel clearance

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

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### brendan gardamSenior Member

hi everyone. can anyone tell me what the minimum tunnel clearance should be on a 23 foot sailing cat.

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### Mr EfficiencySenior 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 ?

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### brendan gardamSenior 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.

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### fallguySenior 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

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### brendan gardamSenior Member

Excellent. Thank you.

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### Mr EfficiencySenior 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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### catsketcherSenior 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. Joined: Feb 2020
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### brendan gardamSenior 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.

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### Ad HocNaval Architect

5% of the Lwl at midships as a min.

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