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Old 08-09-2012, 08:50   #1
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Concave Hull by Keel on Beneteau

We are at the inspection stage with a 1996 Beneteau Oceanis 400 and have found the typical issues for a boat that age except for one item. On the hull immediately behind the keel there is a rounded indentation that is approximately a half inch concave inward over a roughly two foot section. We are concerned about whether this means anything for the hull integrity and are not sure how to proceed or how to tell if this is a serious or minor issue. Any insights or thoughts would be helpful and appreciated. Thank you.
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Old 08-09-2012, 09:28   #2
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Re: Concave hull by keel on Beneteau

Looks like the boat has run aground hard, the keel pushing the hull up at the trailing edge resulting in the concave bit. I would think the glass has been compromised and would need reinforcing or rebuilding. I'd pass on the boat.
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Old 08-09-2012, 10:29   #3
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Re: Concave hull by keel on Beneteau

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Looks like the boat has run aground hard, the keel pushing the hull up at the trailing edge resulting in the concave bit. I would think the glass has been compromised and would need reinforcing or rebuilding. I'd pass on the boat.
Sounds like it. Good call.
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Old 08-09-2012, 10:43   #4
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Re: Concave hull by keel on Beneteau

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Originally Posted by Vasco View Post
Looks like the boat has run aground hard, the keel pushing the hull up at the trailing edge resulting in the concave bit. I would think the glass has been compromised and would need reinforcing or rebuilding. I'd pass on the boat.

If this is the case, there will be a corresponding "smile" crack at the front edge of the keel/hull joint as well. A half inch concave depression would require a massive impact which would result in a lot of obvious damage. Look for failed bulkhead tabbing, engine alignment off, etc. etc.
I have seen a very similar result with Beneteau's which have had major blister repairs done, drying out with infrared radiant. If a heater is left in one spot for too long it can cause the hull to deform, usually right around the keel or jackstands. I have seen several severe cases, with close to an inch of deflection. If have only ever seen this on a Beneteau, it's why they're often derisively called a "Bendy-Tow". I think it has something to do with their resin formulation....
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Old 08-09-2012, 10:58   #5
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Re: Concave hull by keel on Beneteau

Yep, Real surprised it would stay up rather than buckle and pop back though. Fiberglass Yield strength is close to the breaking ultimate strength. How do you "bend" fiberglass layup? Sounds like Minaret has the answer. I would stay on this until you get a satifactory answer for sure, then again.... you likely should just walk away....
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Old 08-09-2012, 11:29   #6
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As a Travelift operator I have seen brand new fresh from the factory, never seen water do this . Have the yard pick up the boat. Too much weight on the keel. Ben. Have very thin fiberglass compared to later 70's and 80's boats older boat were built to wood spec. Thinking that much glass was needed. Later boats have less for several reasons. Cost saving etc. when you lift it it should disappear. Oil canning is not usual for new production boats.
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Old 08-09-2012, 12:45   #7
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Re: Concave Hull by Keel on Beneteau

We are rebuilding a Ben 50 this past months here in St Marteen , inded if the keel dont have any impact damage or the smile at the forward section probably the boat is bad suported in the keel and the jackstands , we have also oil canning in the keel area and in the chainplates area around the hull , dont surprise me , laminate thicknes is thin , you can check for bad cracks inside around keel bolts , many new production boats flex at the keel with the boat resting in the keel, Good Luck.
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Old 08-09-2012, 12:49   #8
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Re: Concave Hull by Keel on Beneteau

I have a 1995 Beneteau, 400, and while doing the bottom paint this last time I noticed a small version of what you have described. There was a lot of weight on the keel, maybe most of it. The deflection that I had was maybe a 1/4 of an inch which went away when lifted. I checked the honey comb structure under the floor and everything looked fine, so I am not worrying about it. I would have someone who knows more than me look at it, but I wouldn't automaticly run from it.
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Old 08-09-2012, 13:09   #9
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Re: Concave Hull by Keel on Beneteau

Given the comments about it being a non sturctural problem I would use it as a negotiating item to decrease the price. ;-)
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Old 08-09-2012, 14:13   #10
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Re: Concave Hull by Keel on Beneteau

A little oil canning is one thing, but 1/2" of deflection is a whole lot and would have me looking for other reasons. If it's just oil canning you'll know as soon as they lift it, but I personally wouldn't own a boat that oil cans 1/2" right next to the keel. This boat is a '96 model, I wouldn't expect it oil can that much.
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