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Farr 11.6 (Farr 38)
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Received the following estimate for repairing the keel on my 2006 Beneteau 423 after anticipating new anti fouling. Anyone confirm if this is appropriate? Thx


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If they are really going to grind the entire keel down to bare metal, apply two coats of thickened epoxy sealer, fair the keel, and then apply three coats of barrier coat, that is a real bargain.

If they are only spot grinding and spot repairing, you can expect to spend the same amount or more next time, and then its not a particularly cheap price.

In addition, looking at the photo of the top leading edge of the keel, it looks like you may need keel bolts., You should probably remove a few and check their condition.

Jeff
 

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Emmalina
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I would buy an angle grinder and do it myself ;) Cleaning that up would be a days work check the bolts from above to see if any infiltration has occurred ! Cast iron is always going to have rust spots where the paint has been scrapped.
 

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Since the quote reads "grind keel rust to bare metal", it makes me think this is a spot repair and a complete waste of money. Once an iron keel starts to have that many issues, I think it's best to do it over.

First, it should be soda blasted down to bare metal, then immediately primed with an etching primer of some sort. The mold imperfections will then need to be refaired, then epoxy barrier coat. Then, of course, antifoulant. I had all the above done on a 54ft Jeanneau for about $5k and RI is well known to be high cost. Cure temperatures and times are critical!! Be sure the yard follows them. I needed a warranty repair done the following year on a 4sqft area.

The rust at the keel joint is what would get my attention the most. The keel flexes against the flat bottom, so rust on the outer surface of the joint is common. You want to know if sea water has breached the bedding adhesive and reached the keel bolts. Hoepfully not. As Jeff said, I'd check a few, if not all of them. You might make this a project to replace them, as you check them. I did that too, from the inside of the boat. They are a wear item.

Then, I would fair that cleaned up keel joint with 3M 5200 and don't be stingy. I good inch wide. I tried several other things over the years and this was the only one that worked.
 

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Since the quote reads "grind keel rust to bare metal", it makes me think this is a spot repair and a complete waste of money. Once an iron keel starts to have that many issues, I think it's best to do it over.

First, it should be soda blasted down to bare metal, then immediately primed with an etching primer of some sort. The mold imperfections will then need to be refaired, then epoxy barrier coat. Then, of course, antifoulant. I had all the above done on a 54ft Jeanneau for about $5k and RI is well known to be high cost. Cure temperatures and times are critical!! Be sure the yard follows them. I needed a warranty repair done the following year on a 4sqft area.

The rust at the keel joint is what would get my attention the most. The keel flexes against the flat bottom, so rust on the outer surface of the joint is common. You want to know if sea water has breached the bedding adhesive and reached the keel bolts. Hoepfully not. As Jeff said, I'd check a few, if not all of them. You might make this a project to replace them, as you check them. I did that too, from the inside of the boat. They are a wear item.

Then, I would fair that cleaned up keel joint with 3M 5200 and don't be stingy. I good inch wide. I tried several other things over the years and this was the only one that worked.
Did you find corrosion on the keel bolts? How long after the rust appeared at the top edge of the keel did you inspect the bolts?
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Why does the keel joint flex? I would think it being bolted to thousands of pounds of torque it's not a flexible connection, rather a stiff one.
I do suspect that the top of the keel and the bottom of the hull... bearing surfaces are not smooth and gaps are filled by bedding. If the bedding fails it offers a pathway for water to the bolts... and if the keel has "exposed" iron on its top, this too is a where rust will manifest.
When you replaced the bolts did you do anything to the hull to keel joint/mating surfaces? If not...ie no new bedding was installed... water will find the same paths to the bolts
I suspect it's very important to have a watertight bedding on top of the keel... otherwise both the top of the keel and the bolts will corrode.
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My keel is iron as well. However the keel has an integral cast flange which is about 1 or more inches thick and extends forward, aft and to the sides of the keel forming a very large plate for load distributing and bearing. The flange fits into a hull recess and the hull down there is around 3" thick. There are 14 - 25mm bolts and 80mm wide steel belts which the bolts pass through and go up the sides of the hull. This is quite stiff. However I do get rust at the edge if the flange because the caulking used is not effective. Caulking appears to be the problem because it behaves differently than GRP or the iron of the keel.
 

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Did you find corrosion on the keel bolts?
Not below the bilge. Part of my motivation was notable corrosion on the studs and nuts that were above the bilge. I was pleasantly surprised to see the threads actually hold the keel on were sound. Although, felt better to replace the rusting nuts and backing plates too.

How long after the rust appeared at the top edge of the keel did you inspect the bolts?
Quite a number of years. Rust at the top edge of an iron keel is too normal to rush to judgement, unless it's really bad.

Why does the keel joint flex?
It wouldn't take much more than a microscopic crack to allow ingress of salt water, which is also under pressure a couple feet below the surface.

Our iron keel weighed 11,000 pounds and had an athwartship section of maybe a foot? 18 inches max, by memory. When heeling to one side, that kind of lever against a flat hull is just going to open an unprotected seam. It needs to be faired and sealed. I don't know why they don't come that way from Jeanneau, as their instructions for rebedding the keel include them. Could be that local yards bed the keel and do it wrong. Perhaps to your point, you don't need to allow for super flexible sealant, as it's shouldn't move much.

My keel is iron as well. However the keel has an integral cast flange which is about 1 or more inches thick and extends forward, aft and to the sides of the keel forming a very large plate for load distributing and bearing.
I'm not really following what you have. Maybe it's like what I now have. We have a keel stub that extends below the hull. The keel is bolted to the stub and their is a groove between the two, which is designed to be filled with a flexible caulking/adhesive to take up an movement. This is different from the 90 deg seem in the OPs pic. It's a parallel seam/groove.
 

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Does antifouling adhere to the 5200? Any special treatment required?
Yes, I was using Petit Vivid, at the time, and it did adhere. No treatment, other than allowing for a long cure. As we know, 5200 can take days. In this case, simply due to when the work was done, it probably cured for weeks.
 
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