Crack in centre board case.

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Michael4
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Crack in centre board case.

Post by Michael4 »

Opinions sought...

Our Merlin has a crack in the centreboard case presumably caused by over tightening of the centreboard bolt. It runs a few inches either side of the bolt hole, the case is mahogany.
During the course of last summer I taped it with Gorilla tape which stopped the leak. I'm doing some work on the inside of the boat at the moment and thought it a good idea to effect a rather more elegant repair.
Regarding the repair my thoughts are:

Put the boat on its side, try and open up the crack a bit and flood with epoxy?
To do this I might need to open the crack up somehow with pressure from behind but there is obviously the danger that I might just make it bigger.
Not sure about this, chances are it will crack again if the bolt is overtightened and I doubt the epoxy would go into the crack that far.

Make some sort of 'tingle' from copper/aluminium/hardwood or similar which is thin enough to run behind the bolt?
Will be noticeable.

Cut the crack into the shape of a small seam and fill it with something flexible like one would a proper seam?
Tidy but no great structural strength.

Use Gorilla tape again, it works.

What would you do?
Tideway 206
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Obscured by clouds
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Re: Crack in centre board case.

Post by Obscured by clouds »

without more detail/photos it's difficult to give a definitive answer, but my approach would be to get the boat on it's side and try and clean out/slightly enlarge the crack, with a multitool cutter if you have access to one, then pack with thickenned epoxy,
I would also see to the bolt, changing it for one that cannot be overtightened without thought - screw end finishing short of the casing - any extra snugness can be applied with a spacer
Tony



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Michael4
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Re: Crack in centre board case.

Post by Michael4 »

Well, having just got many layers of varnish off it looks like someone has been there before...

ImageIMG_2224 by dralowid, on Flickr

...from what I can tell the crack was opened and filled many, many years ago, so time to get the boat onto her side, scrape the old filler out, clean the crack up and epoxy.

As to the bolt, it is not strictly a bolt being threaded at both ends with a nut on each.

ImageIMG_2228 by dralowid, on Flickr

It looks as if at one time one end has been punched to prevent movement but now they both move allowing over tightening. The solution to prevent this happening again is obvious!

A wee bit chilly in the garage this afternoon, tempted to play the hot air gun over my feet!
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Rupert
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Re: Crack in centre board case.

Post by Rupert »

The way I've also seen it done is to enlarge the hole right through case and board so you can push through a piece of brass tube cut to the exact width of the case on the outside of the bolt. The tube stops it tightening too far.
Rupert
Mikey
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Re: Crack in centre board case.

Post by Mikey »

Not often I disagree with Rupert but on this occasion I do! If you put a brass tube through C/B case you will clearly need to enlarge hole you will also need to drift out tube when you need to remove C/B possibly damaging wood around the hole. I would suggest you get proper brass C/B bolt for a start. As you suggest re epoxy crack. You could strengthen area around the hole by epoxying a small piece of ply/solid mahogany (the latter better) over the hole (suitably drilled!) both sides. This is frequently seen in Merlins and 12's. However it is essential that this has a close bond with the case - suggest screwing at corners. When board fitted ensure bolt has large brass washers and a rubber washer against case. A smear of frame sealant can also be applied (not silicone) around hole.

Mike Liggett (various Merlins)
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Ed
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Re: Crack in centre board case.

Post by Ed »

All seems like good advice to me....

Have to say and without close looking, so hard to be sure, but are you sure the leak is from crack and not just from the bolt in the hole? The crack looks pretty well fixed to me and unless there was evidence that the leak was from the crack, I would leave it alone.

I can see any of these methods working, even Ruperts brass tube, although I would be tempted to solder or superglue it to the bolt, so it comes out with the bolt, rather than needing to be drifted out separately. I think it depends on how much you want to spend and how well you want it done. A bit of brass tube and some sealant, I reckon would work and cost pence. Two nice mahogany cheeks, with a beveled arris (mmm...can you have a beveled arris or would it instantly become 'arrises' ) and four screws, capped off by a lovely brass centreboard bolt, would of course be a much nicer fix, but cost a wee bit more.

eib
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Michael4
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Re: Crack in centre board case.

Post by Michael4 »

Now that it is a bit warmer in the garage...

The filler in the crack was loose(ish) which happily explains the leak. All done now, a quick bit of rootling with a multi tool, then boat on it's side and epoxy.

Thanks for the advice.

Michael
Tideway 206
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Sold the 'Something bigger and plastic', it never got used.
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