PS Advisor January 2007 Issue

Iron vs. Lead Ballast

Lead has the upper hand in corrosion resistance.

I am shopping for an offshore-capable boat. Among others, I am considering a Cabo Rico 38. Looking through back issues of PS, I noticed that earlier models of this boat used iron for the internal ballast. (I confirmed this with Cabo Rico.) My instinct when confronted with iron ballast, particularly internal ballast, is to write that boat off the list and run away from it as fast as possible. I can only think of one possible reason why a builder would use iron instead of lead, and that is to save money. Am I right to avoid internal iron ballast, or can it be a suitable material when done well?

Kelly Arnold

Via e-mail

You are correct in pointing out that there are some special considerations for cast-iron keels, whether they are encapsulated or external. Iron, as we all know, rusts quickly and freely when exposed to oxygen and moisture, so it would seem like a less than ideal material for modern sailboat keels. In fact, iron rusts in a more insidious manner than even ordinary steel. Iron tends to retain its general shape and size as it rusts, however, it decays from within. A piece of iron that appears sound may crumble if tapped with a hammer. This type of decay is called graphitization because when it occurs, all that remains after the rusting is complete is graphite residue. Indeed, iron is less expensive than lead, and it weighs considerably less than lead for a given volume (iron weighs approximately 450 pounds per cubic foot, compared to lead, which weighs over 700 pounds per cubic foot). Thus, more iron ballast is needed, with the consequent increase in volume and potential wetted surface and drag, to achieve the same ballasting as lead. In addition to its cost effectiveness, another reason that iron may be used in place of lead is its environmental friendliness. In many regions, such as Europe, lead is classified as a hazardous material (it is here in the U.S. as well; however, the standards appear to be more strict on the other side of the pond), so many European boatbuilders avoid its use for various regulatory and liability reasons in addition to cost issues. In general, if iron ballast is exceptionally well encapsulated, both inside the vessel and out, and shows no signs of corrosion, then it is probably safe to assume it will remain this way (looking at sister ships in the same class, particularly ones that are older, may provide valuable clues as to the longevity of the installation). That is, until you run hard aground and damage the fiberglass encapsulation, exposing the iron to seawater. Even if repairs are made quickly, once water enters this cavity, it may be difficult or impossible to remove completely. From the standpoint of both efficiency (itís denser) and its corrosion resistance, lead is preferred over iron for ballast.

sailing on ice

Are the principles and techniques of sailing on water the same as for iceboating?

Don Vanhof

Fort Lauderdale, Fla.

Whether it is, as the iceboaters say "soft water" or "hard water," the principles are exactly the same. However, because when iceboating the apparent wind behaves so much more radically, the sailtrimming techniques are considerably different. By the way, an airplane wing is just a sail turned horizontal; thatís why so many airplane pilots own sailboats or iceboats. And a windmill obeys the same laws of physics; early windmills used cloth "sails." All of these devices depend on the air pressure difference on the two sides of any plane surface canted in the wind.

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