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Stiffening the hull

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Gepke IV View Drop Down
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Post Options Post Options   Quote Gepke IV Quote  Post ReplyReply Direct Link To This Post Topic: Stiffening the hull
    Posted: 15 Nov 2015 at 9:29pm
Hello there,

My 1976 contessa is one without stringers in the heads section. In heavy seas you can feel the hull flexing. Last summer the bonding with the bulkheads broke sailing upwind in +30knots in Scotland. Now i am thinking of stiffening the hull behind the toilet to lead the forces the proper way. Has anyone done this before and can give me an example? 

Cheers Robin
co489 Gepke IV
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moongirl View Drop Down
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Post Options Post Options   Quote moongirl Quote  Post ReplyReply Direct Link To This Post Posted: 17 Nov 2015 at 9:36pm
Bonding of Bulkheads failing & hull flex are common problems. Nearly all of the older boats have had to be repaired at some stage.
An e-mail to Kit Rogers might help if nobody else responds to your Post but my past experience has been limited to additional stringers in the bows and not the heads.

COLIN
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Galatea View Drop Down
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Post Options Post Options   Quote Galatea Quote  Post ReplyReply Direct Link To This Post Posted: 18 Nov 2015 at 2:01am
I'm thinking that if you properly re-bond the bulkheads, the hull  in the head area will be sufficiently stiffened to eliminate the flexing.
Mark
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Post Options Post Options   Quote Brigitte Quote  Post ReplyReply Direct Link To This Post Posted: 18 Nov 2015 at 1:49pm
Brigitte is a 1977 boat and the hull has been stiffened either side of the mast foot, up to the bulkhead. All that can be seen is a substantial layering of extra fibreglass, hidden by raising the saloon floor in a step around the base of the mast, the same level as the forepeak sole. Unfortunately I don't have any pictures but I can take some next time we go down if you like.

It wasn't done by us so I can't offer any advice but, FWIW, the surveyor nodded approval when he saw it.
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George Isted View Drop Down
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Post Options Post Options   Quote George Isted Quote  Post ReplyReply Direct Link To This Post Posted: 18 Nov 2015 at 4:51pm
I had new stringers fitted in the heads area (behind the GRP Moulding) by Rogers a few years back, the same on the opposite side in the hanging/wet locker and can share some pics with you if you email me. The stringer "formers" are simply lengths of plywood (probably 20mm or so)bonded to the hull with CSM over. Your best option is to take advice from the Rogers Yard.
George Isted
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Richard Ritchie View Drop Down
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Post Options Post Options   Quote Richard Ritchie Quote  Post ReplyReply Direct Link To This Post Posted: 18 Nov 2015 at 5:25pm
My 1974 boat was reinforced in a  similar way to Concerto (before I bought her)  :  a strip (In my case D shaped) laminated onto inside of hull horizontally at about the level of the forepeak bunk .  The boats all flexed here without it.   I believe the other side was done originally for some reason. 
Richard Ritchie
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doug View Drop Down
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Post Options Post Options   Quote doug Quote  Post ReplyReply Direct Link To This Post Posted: 22 Dec 2015 at 4:12pm
Does anyone know when/if the port side stringers were incorporated into the original build? My 1979 boat seems to be the same port and starboard and seems, to my eye, to have a mid height stringer in place. Would be interested to know if anyone knows anything about dates.

Anyway.

I had some minor delamination and refurbished it with more extensive layers of GRP, both sides of the bulkhead.

I also beefed it up a lot at the foot of the bulkhead - that area that you see if you kneel alongside the mast and stick your head into the grating void; in effect looking back aft.
I re-laminated it, fitted a new ply backing piece front and back (ie in the cabin and under the heads floor), screwing this through from the cabin side before counterboring and adding cosmetic plugs. Finally I laminated again on the underfloor area.
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