Help re:leak between deck/hull.

rays

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Bought new(to us at least) boat back from Hamble to Orwell a couple of weeks ago (Jeanneau 40DS). Encountered v rough water rounding Selsey bill (The Owers??). Nasty spot that with wind over tide.Found water had come into forward cabin s/board side only. After thorough look around we concluded that it was coming in through the join between hull and deck. Once back in port I walked around the bow feeling beneath toe rail and found that someone had previously filled the gap with sealent, some of which had fallen out. Two questions:
1) Does my analysis of the problem seem reasonable or can anyone come up with an alternative one? 2) If I am right what product would be best to use to plug the leak?

Hope you fellows can help.

Cd
 

Aja

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If you had a pre-purchase survey, I would contact the surveyor and ask him to comment.

Donald
 

vyv_cox

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I suggest you need far more than to plug the visible gap with a bit of goo. The potential for serious problems here is very high. I suggest you get a surveyor who knows these boats and is highly competent to have a look. A friend of my son took to the liferaft when a similar boat sank withing two minutes in mid-Atlantic when the deck and hull parted. It was brand new, being delivered.

In case of confusion, I am not saying it was a Jeanneau. It was French and about 40 ft but I don't remember any more detail. Happened about 5 years ago.
 
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Different manufacturers use different ways of joining hull & deck. It is, possibly, the "Achilles' Heel" of the mass production boat building process. Basically, give the structure a whack against a hard object and the forces trying to part the two halves are enormous. Notice what happens when you bash an easter egg on the join between the two halves.

Unfortunately, with boats it is this join's location at the widest part that makes it vulnerable to knocks from quaysides, locks and other boats (& I don't mean unfendered knocks alone). Because of this, the join needs to be immensly mechanically strong.

The strongest is where both the hull and the "lid" are moulded with a flange sticking out all around and this flange is through bolted at small intervals, a tough sealant having been inserted between the two halves first. This is then glassed over both on the inside and by wrapping extra layers of impregnated rovings or tape over the edge of the flange which also has the effect of sealing and protecting the screws and nuts. Unfortunately, this method leaves an unsightly knobbly flange visible on the outside which can he hidden by a fubber moulding to act as a fendering on workboats and other chunky motor craft but which would just look too unsightly on a "Fine Yacht"

So, with yachts, other methods are used, like butt joining the two halves and relying upon the glassing over to provide strength. NOT the best choice by any means. Others use some sort of jointing medium like a plywood jointing strip to which a smaller flange or, better an interlocking flange from each half is screwed and then this too is glassed over leaving a much neater outside appearancewhich is easily disguised with an aluminium or wooden toe rail. Again though, this isn't assembled "dry" but some sort of sealant is incorporated.

Anyway, going a long way around it, I admit, but what I am trying to say is that this is a serious fault that will be needing a professional thorough approach to remedy. If there is wood involved in your joint, leaving it with water getting in will soon lead to that wood progressively rotting which could leave you with at best an unsaleable yacht and at wqorst a dangerous one, liable to come apart around the join. If Janneau's jointing method uses only resin and sealants, it is much easier to put right in a localised way. Sealant = Sikaflex 291. It really needs professional attention though by someone who knows and appreciates the problems.

Steve Cronin
 

hairbox

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Hi I know how you feel, had same problem when delivering a 40ft yacht a few years ago, still after much worrying and lost sleep the problem was solved relatively easily.
PM me for more details
 

Victorious

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The joint is often glassed over on the inside of the boat.
a leaky deck fitting can let water into the INSIDE face of the hull deck joint,
The water then tracks along the glassed over joint and finds its way into the boat (sometimes a considerable distance from the offending deck fitting)
Thus appearing to be a deck joint leak but no amount of sealant in the joint will cure it.
I have no idea if this may be applicable to your boat.
Some westerles were very prone to this problem and i encountered one that the prev owner had resealed the entire joint all around the boat and could not understand why NO improvment whatsoever was achieved !
 

AndersGu

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I had exactly that problem on my boat. Water would end up inside when sailing heeled over, but only to one side. Removed the U-shaped rubber thing that ran around the boat and found that deck and hull were riveted together, with goo in between and then glassed over on the inside.

Solution was to remove as much hardened goo as possible. Then used an angle-grinder to deepen/widen the crack, clean out and seal with sikaflex and replace rubber thingy (what do you call it?). That was approx 8 year ago. Never had a leak since.
 
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