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andy59 said..
Someone told me Finestere had a plywood fin keel. Does anyone know if this is true?

Hi Andy,
Carbon fibre over wood yes, I don't know what type of wood though. The lifting keel mod was done in 2009, then a new keel was fitted in 2012.
Weird construction for a keel to me, I don't understand the use of carbon in a keel when it's an Ior hull design.

Yep Shaggy that's seems a real weird choice of materials for a keel. Kind of foreseeable that it would fail.
It might have gone something like
hairline cracks in the carbon at the load point where the keel exits the hull, watered ingress, rot, failure.
I get that it would be easier to shape a foil with layers of ply or even laminated timber but it just seems mad to hang a lump of lead on it and go offshore sailing.
It almost like it would be better just to varnish it so you could check for rot regularly. Wouldn't the carbon laminate just make it stiffer without adding much overall strength?

Yep Shaggy that's seems a real weird choice of materials for a keel. Kind of foreseeable that it would fail.
It might have gone something like
hairline cracks in the carbon at the load point where the keel exits the hull, watered ingress, rot, failure.
I get that it would be easier to shape a foil with layers of ply or even laminated timber but it just seems mad to hang a lump of lead on it and go offshore sailing.
It almost like it would be better just to varnish it so you could check for rot regularly. Wouldn't the carbon laminate just make it stiffer without adding much overall strength?

Yachting World Diamond class keel boats have a plywood keel with a heavy metal shoe attached to the bottom. I imagine that over time some of those have possibly fallen off as well, but unless there is a loss of life then in most instances we would not hear about it via the media as it would be deemed an inconsequential event.

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LooseChange said..
Yachting World Diamond class keel boats have a plywood keel with a heavy metal shoe attached to the bottom. I imagine that over time some of those have possibly fallen off as well, but unless there is a loss of life then in most instances we would not hear about it via the media as it would be deemed an inconsequential event.

In the 25' and under range I have seen timber encased with glass/carbon keels, but never come across it in large boats. My understanding is that once you get above about 30' the sheer strength of the plywood layers become a limitation and you are better off going for laminated solid timber.

A

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andy59 said..
Yep Shaggy that's seems a real weird choice of materials for a keel. Kind of foreseeable that it would fail.
It might have gone something like
hairline cracks in the carbon at the load point where the keel exits the hull, watered ingress, rot, failure.
I get that it would be easier to shape a foil with layers of ply or even laminated timber but it just seems mad to hang a lump of lead on it and go offshore sailing.
It almost like it would be better just to varnish it so you could check for rot regularly. Wouldn't the carbon laminate just make it stiffer without adding much overall strength?

Hi Andy,
Good point on the inspection aspect, I'm wondering how you can check for delamination or a rotted core? I thought its not correct to drill holes in a carbon skin without effecting the integrity, so what options are left? XRay? Finistere had a 3.5mtr draft with a bulb on the end, on a 8-9 ton boat that's a pretty massive load for wood I would have thought, so one would assume the carbon layup was hence structural and not just form. This is the part I don't understand, I get carbon as a material is weight saving, but in the keel? Weight there isn't really a major design/performance factor.

I'm interested as the Pogo's swing keel, like any lift mechanism, means a part of the keel is buried in the keel box and is not easy/a mongrel to inspect. My keel box is built like the proverbial brick *&^%house, its not a trivial exercise to even gain entry.
So how does one inspect the encapsulated section of the keel? Its not usually antifouled, is this demarkation between the antifouled section a possible weak spot for rot?
I used vinylester in my keel and hull layup for this reason, to offset water absorption, but I don't know how you waterproof carbon. Can you use vinylester in a carbon epoxy resin? Boty?

Its sounds like Finistere was a well run seasoned campaigner, my questions/ponderings are not intended to cast aspersions on the boat/crew. If we learn from it though, that's one small positive out of a tragic affair.

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Andrew68 said..

LooseChange said..
Yachting World Diamond class keel boats have a plywood keel with a heavy metal shoe attached to the bottom. I imagine that over time some of those have possibly fallen off as well, but unless there is a loss of life then in most instances we would not hear about it via the media as it would be deemed an inconsequential event.

In the 25' and under range I have seen timber encased with glass/carbon keels, but never come across it in large boats. My understanding is that once you get above about 30' the sheer strength of the plywood layers become a limitation and you are better off going for laminated solid timber.

A

Andrew, this makes sense, the static pressure from the water would provide a measure of resistance against sheer loads on a keel with not much weight combined with a small/er sail plan. A 3 ton bulb (guessing at these numbers) on a 3.5mtr cord with say a 17mtr rig fully powered up would be an order of magnitude difference.

I finally got down to my boat yesterday and took these pics of my keel bolt arrangement.
Does it look OK ???.

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samsturdy said..
I finally got down to my boat yesterday and took these pics of my keel bolt arrangement.
Does it look OK ???.

Speaking from a perspective as a corrosion engineer they look like prime candidates for crevice corrosion failure. I would investigate further.

Thanks for the reply Frant. I had never taken up the sole before and I should have cleaned up BEFORE I took
the pic. It looks like rust but it's 30 years of grime, but I had someone waiting for me so I hurried. Once cleaned
up I had a real good look and I could not find anything untoward, but I didn't try tightening the bolts. Should they
be tightened to a torque setting or just get them as tight as you can (assuming they're loose) ??.

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frant said..

samsturdy said..
I finally got down to my boat yesterday and took these pics of my keel bolt arrangement.
Does it look OK ???.

Speaking from a perspective as a corrosion engineer they look like prime candidates for crevice corrosion failure. I would investigate further.

At least they are dry - there are a lot of boats out there where the keel bolts are sitting in a pool of bilge water !