I went through agonizing about this last year when I was considering which boat to buy. I'd always had external lead on prior boats and didn't realize just how many boat were made with either external or encapsulated lead or iron. Many of these are considered to be very high quality boats with good reputations. My first reaction was just like the OP, what a stupid thing to do, putting something that reacts (rusts) with
salt water and surrounding it with
salt water. But after talking to many people who had worked on these boats, I overcame my initial fears and ended up
buying our Tayana 47 with an encapsulated iron keel.
First, I couldn't find a
single boatyard where anyone could remember dealing with a solid encapsulated keel that had been damaged by
salt water intrusion. If it were really a big problem, it seems like there would be lots of boats sitting in yards with keels cracked open and rust stains oozing out of the crack, but you just don't see that and there are a whole lot of boats with encapsulated iron keels around. I have heard of the kind of ballast where smaller pieces of iron are embedded in some medium being more problematic but it seems even that is quite rare. Most high quality boats with encapsulated iron have one big chunk of iron lowered into into a hollow keel shape and then resin poured around the iron to fill any voids. Also, the solid fiberglass that surrounds the iron, especially on the bottom, is thicker than anywhere else in the
hull. So, in order for water to come in contact with that solid hunk of iron, the water would have to make it all the way through thick layers of fiberglass and then through the resin that was poured in to fill the voids. If it does, then the supply of oxygen that would be required for damaging extensive corrosion to take place would be severely limited due the fact that the iron has resin adhered to its entire surface.
So, I came to the conclusion that I was worrying about something that seems to just not hardly ever happen unless I hit a rock or
coral head pretty hard. In that case, I would want to have the boat hauled for
inspection no matter what the keel was made of. With an encapsulated iron or even lead keel, I would want it dried out, any exposed iron recoated with
epoxy, and the fiberglass repaired. With a bolted on lead keel, I'd either just fair the dent in the lead, or drop the keel so the bolts could be inspected, depending on how hard I had hit. I would have more urgency to get hauled out sooner with encapsulated ballast than external ballast though.
I think my first choice of ballast would be encapsulated lead because fiberglass is a lot easier to keep
paint stuck to than lead, and it eliminates any chance of a catastrophic loss of keel resulting from corroded
keel bolts that can't be seen unless keel is lowered and inspected. Next would be a bolted on lead keel. Third, but by a very, very small margin would be a solid iron encapsulated keel built by a reputable yard with a good track
record. Fourth would be smaller chunks of iron or scrap iron or
steel embedded in
epoxy or some other medium because there is so much more surface area of iron involved, thus possibly increasing the risk of corrosion problems, though some reputable boats are built this way and have few problems. For me, my last choice would be a solid iron keel that is not encapsulated because it represents just one more task to knock the rust off and repaint during each haulout. But even external iron has been used successfully for a very long time and if the worst happens, it can be removed/replaced.
The problem with ruling out any boat with either encapsulated or external iron keels is that SO many good boats were made this way that your job of finding what you want is going to be made much harder. If the iron in encapsulated keels is a problem for a particular model boat, by going on their owners group forum or website, you'll see plenty of evidence of it. But, when I was looking, I did that and used the search functions of their sites and you find boat owners discussing how to fix just about everything aboard, but very rarely do you find even any mention of repairing or replacing encapsulated iron keels. Either there's a HUGE and successful conspiracy of silence by thousands of encapsulated iron keel owners, or the problems I'd envisioned of unstoppable corrosion causing the iron ballast to corrode and expand to the point of cracking the fiberglass shell is just not happening.
Good luck with your search and have fun!
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