Iron v. Lead Keel - SailNet Community
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post #1 of 17 Old 05-18-2006 Thread Starter
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Iron v. Lead Keel

I have a heard people express a strong preference for lead keels over iron keels. What are the differences and is it a big deal if you encapsulate it? I'm talking about a big fin keel on a 40 + foot boat.
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post #2 of 17 Old 05-18-2006
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Lead is favorable because it weighs more in the same volume (alot more) than iron. The result is getting the weight lower in the keel for a better righting moment.
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post #3 of 17 Old 05-18-2006
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It is a big deal. All other things being relatively equal, there is a major impact on stability vs drag. Iron is roughly 2/3 the density of lead (490 vs 708 lbs per cu ft) If you have two keels of equal external shape the center of gravity of the iron will be roughly 1/6th of the height ballast casting above the cg of the lead. That is very significant.

So much so, that what normally happens when a boat goes from a lead to iron keel is that the designers will often increase the weight of the iron ballast 20% or so above the weight of the lead, or else increase the length and width of the keel so that the cg of the iron is roughly the same as the lead, or some combination of a larger keel external dimension and increased weight with iron. Either can really damage performance and harm seaworthiness. The increase in ballast weight means additional structural loads and decreased carrying capacity. The extra keel area means greater drag and so brings the risk that comes from the need to carry more sail longer in heavy conditions.

Also it is generally considered very bad practice to encapsulate an iron keel. If moisture enters the encapsulation envelope, as happens more often than not, it is able to cause small amounts of corrosion which progressively destroys the bond between the ballast casting and the encapsulation envelope. Since that bond is an important part of the keel structure in most production boats, this is the beginning of the end for that boat. Iron works better for a bolt on keel where it can be maintained with a sacrificial barrier coat.

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Last edited by Jeff_H; 05-18-2006 at 04:53 PM.
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post #4 of 17 Old 05-18-2006
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Also, Jeff H probably should have mentioned that iron tends to expand as it rusts, and the pressure caused by the expansion of iron corroding can do an awful lot of damage to the nearby fiberglass.
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post #5 of 17 Old 05-18-2006
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While I would agree that lead is much preferred (for a number of reasons, previously stated) I would not consider a bolt-on iron keel a deal-breaker if the boat was otherwise suitable and had been reasonably and properly maintained. We have owned, over the years, 5 sailboats of various sizes (24 - 40') three of which had iron keels. The maintenance routines are more onerous, more frequent haulouts and careful maintenance of antifouling and whatever other rust protection coatings are used is a definite must. Repairing a neglected iron keel is a rather big job, especially if it has been left a long time. But if the boat was designed around the keel material in the first place, it could still be a decent boat.

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post #6 of 17 Old 05-25-2006
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I have an iron ballasted fiberglass encased boat (Alacrity, 1960s), and the years of moisture has caused the iron to expand and explode the fiberglass keels. So, yeah, lead would have been a much better idea (actually, they used both, 50/50). The boat is reparable, but only at considerable time and expense, which it may not get. As I shop for a new boat, lead or iron keel is my first question.
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post #7 of 17 Old 05-25-2006
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One compromise that is common now and works pretty well is to bolt on an iron keel and use a lead bulb. The iron needs to be epoxy coated but if done correctly will last as long as you don't sand through it. The iron provides the strength and the lead bulb provides the weight in the best place. I think it is a very workable solution. I had an iron keel on a long (full) keel boat once that had not been epoxy coated and it required extra work each time it was hauled, but not a huge problem. I would not own a boat that did not have a bolted on keel.
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post #8 of 17 Old 05-25-2006
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deal breaker

For me the lead vs iron was a dealbreaker. I was looking at new Catalinas vs new Beneteaus. The Catalinas have lead keels, and the Beneteaus I considered had iron. I went with the Catalina and that was a very important consideration for me. Rob
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post #9 of 17 Old 05-31-2006 Thread Starter
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I appreciate the input. Many thanks to all.
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post #10 of 17 Old 08-19-2006
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Quote:
Originally Posted by CBinRI
I have a heard people express a strong preference for lead keels over iron keels. What are the differences and is it a big deal if you encapsulate it? I'm talking about a big fin keel on a 40 + foot boat.
Am looking at a Jeaunneau 42 DS with cast iron keel and bronze bolts that are electrically insulated. Sail Net Artical a good one......I attached just part of Don Casey's fine explanation.
george
Bronze Keel Bolts Bronze cannot be used in a cast-iron keel (unless the bolts are electrically insulated from the iron) but it is a superior choice for attaching a lead keel. Unlike stainless, bronze likes stagnant seawater. A good marine bronze can lose less than one thousandth of an inch to corrosion in 40 years of immersion. Bronze keel bolts generally succumb to overtightening rather than to corrosion. Under normal circumstances they are good for the life of the boat.
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