Across hull strengthener

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purejoy
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Across hull strengthener

Post by purejoy » Tue Mar 17, 2015 9:12 pm

I have uncovered a split in the keel stub of my Berwick. It extends toward the centre of the boat. The split was there when I bought the boat 5 years ago but had been bodged up and not discovered by the surveyor. (No blame on him as it was craftily covered up). The crack has been ground out and prepared for a proper repair.
My question is having removed the badly done lay up and stripped back the original I discovered that the cross hull strengthener does not touch the hull.There is a gap of about 1cm between the bottom of the stringer to the hull. It would appear that it has always been like this. Is this correct? If not what action should I take?
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Re: Across hull strengthener

Post by Jolly Roger » Tue Mar 17, 2015 10:03 pm

What exactly are you using for the rebuild of the crack? Hopefully you will be using epoxy with a powder bound chopped strand mat, rather than a polyester resin. The reason is the epoxy gives a stronger bond.

With regard to the cross hull strengthener, is this a bulkhead or a floor stiffener? You also mention a stringer, this should be a horizontal stiffener bonded to the hull. Are you mixing terms? If you are unhappy with what you have found I would call the surveyor back in for professional advice, he may not even charge as he missed this in his survey.

When the Berwick was designed the hull was greatly over engineered by modern standards, so the stiffening would not be as essential as today. As long as it has been bonded to the hull then it should be fine. If you want to strengthen it, then it would be sensible to combine it with the other work. If I was in your position, I would strengthen it to be safe.
Roger
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Re: Across hull strengthener

Post by purejoy » Wed Mar 18, 2015 7:49 pm

Thanks for your thoughts Roger. I was going to use polyester, in fact I have already bought it, but since you recommend epoxy I will swallow the cost and re order.

The strengthener runs right across the boat, from just towards the stern of the second keel bolts, and is to firm up the hull. The original lay up on it allowed the gap of about 1cm from bottom of the stiffener to the hull with contact of stiffener at the side of the hull. Fibreglass lay up over the stiffener and down to the hull makes it look as if it is touching all along. By the shaping of this stiffener it looks as if it was designed to have that gap. Either way the boat has done well over the past 5 years. if the original repair to the crack was done properly at that time none of this would have come to light.
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Re: Across hull strengthener

Post by rhumlady » Thu Mar 19, 2015 5:38 pm

I have to say that I don't understand what that 'strengthener' is doing as to achieve anything - it needs to be attached to the hull right along its length. It may be to support the cabin sole.
Derek
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Re: Across hull strengthener

Post by purejoy » Thu Mar 19, 2015 9:14 pm

My thoughts exactly. Which is why I asked the question. When the repair is being done (Monday) I will have an extra length of ply bolted to the original and taken down to the hull before glassing it all in again. That should cover all the bases.
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Re: Across hull strengthener

Post by rhumlady » Thu Mar 19, 2015 9:32 pm

Excuse me saying this but it looks even worse than it sounded. Not certain it wouldn't be better removed and replaced completely then the hull could be completely cleaned back for re-glassing.
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Re: Across hull strengthener

Post by rhumlady » Thu Mar 19, 2015 9:36 pm

Having said that I remember going there and ending up with nothing left in the hull due to taking out iffy bit after iffy bit [CONFOUNDED FACE]. There lies madness down that road.
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Re: Across hull strengthener

Post by purejoy » Thu Mar 19, 2015 9:49 pm

Thanks for all your input into this.

This is how it looked after stripping off the original glassing in which was NOT cracked?? Like you I am puzzled as to why there is a gap. I can assure you that it does contact by the keel stub and up the side of the hull. Very confusing. If it was not fixed at those points and the original lay up was cracked I would assume it had moved due to flexing or collision damage. Without cutting out the cabin sole there is no access to replace the whole piece but, by using a mirror, I can see the original is all intact. How far do I go with this when the boat appears to be coping. (Apart from the bodged repair, not found by surveyors, from before I purchased her?).
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Re: Across hull strengthener

Post by rhumlady » Fri Mar 20, 2015 4:58 pm

That's a big question. It is very easy to do as I did and end up with an empty shell. The floors and stringers were in a very poor state with the top of a number of them having been removed I assume to level the cabin sole. There had also been very large holes cut in some of them to pass the pipe for the bilge pump. The problem was none of the cut edges had been sealed and so oily waster had penetrated into the ply which had rotted. The whole thing was a mess. I also had two bulkheads that had broken away so I really had to gut the boat. With the benefit of hindsight I went too far but at the time I wanted to get out palace that would mean me not going there again. I don't know if you have seen Roger Ball's blog, A Gentleman's Yacht, but it is worth a look for Anyone and especially Centaur owners.
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Re: Across hull strengthener

Post by Jolly Roger » Fri Mar 20, 2015 5:27 pm

That does look worse than you stated. I would be reluctant to cut it out. There is no reason why you just cannot glass over the top. The fibreglass is the strength, not the plywood inside. If you filled the gap between the hull and the strengthener with a 2 part car body filler, then laminated over this, it would certainly give to the required strength you should have. Many stringers are only a paper covered rope or foam, so the fibreglass is certainly providing the strength. This should save a lot of time and additional expense.
Roger
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Re: Across hull strengthener

Post by purejoy » Tue Mar 24, 2015 9:53 am

Thanks to all for your input into this problem. I am delighted to say that the repair has now been successfully completed. After careful discussions and consideration a great deal of grinding out was done. The new lay up was done using several layers of heavy CSM and Woven with polyester resin as used on the original hull. The strengthener or stringer was re-bonded to the hull, again using several layers of CSM and Woven. When the keel bolts were drawn they were found to be bent, which indicated that the cause of the crack was an underwater collision at some point in the distant past. Shame her owner, at that time, did not have a proper job done. Or was the repairer a yard that bodged the job for a quick profit?
Externally new gel coat has been applied and faired. "Purejoy" will have a new survey before launch, hopefully in late April, as there are many more jobs to be done including replacing the engine mounts.
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Re: Across hull strengthener

Post by rhumlady » Tue Mar 24, 2015 5:37 pm

Bent keelbolt don't necessarily indicate an underwater collision I am afraid to say. More likely the guys trying to get the bolts into the hull when lowering it onto the keels. My Konsort has the same thing.
Derek
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