Iron Versus Lead in Keels

Posted by Darrell Nicholson with Steve D'Antonio at 07:44AM - Comments: (10)



On the outskirts of San Jose, Costa Rica, in a small foundry run by an American expatriots, steel railroad ties are melted down into ballast for the Cabo Rico 38. The photo was taken during the 1970s by Key West songwriter, artist and author Ben Harrison, whose book "Sailing Down the Mountain" recounts the early days of the Costa Rican boatbuilding industry and other sundry adventures on land and sea.

A reader recently wrote us that he was shopping for a used boat, and a late model Cabo Rico 38 was among the boats he was considering. He noted that the boat has an internal iron ballast — instead of lead. He was concerned that the boat's iron ballast (steel actually) was merely a cost-saving measure that brought with it a number of potentially serious problems, especially hidden corrosion.

His query raised another question, and that is, how do you know what ballast material do you have if it is encapsulated? Cabo Rico is one example of a company that produced boats with two types of ballast materials, both encapsulated.

Ben Harrison's fascinating book "Sailing Down the Mountain," recounts the early days of Cabo Rico and includes photos of ballast being poured for the early models. According to Harrison, difficulties getting a source of lead ballast led them to a local foundry outside of San Jose, Costa Rica who had a supply of old railroad ties. The steel was then melted down and poured into 11 different molds, which were later encapsulated into the keel.

According the Fraser Smith, the owner/ builder of Cabo Rico since 1987, the company switched from steel to lead ballast castings with the first 38 Pilot model. The change allowed more space for the engine which was moved forward on that model. This change to lead was also included the first Cabo Rico 34 and all Cabo Rica 38 models, years 1989 and later. (Practical Sailor's review of the Cabo Rico 38 covers some of this history).

However, the key factor with the older (pre-1989) Cabo Rico 38s and the even earlier Tiburon 36 models is that all the ballast, steel (and later the lead), is fully encapsulated in a resin and sand mixture that takes three full days to cure. No air, no rust on the steel ballast. The ballast pieces are wedge shaped so they can’t move.

Then the entire ballast area is covered over with structural fiberglass laminates added to the structural one piece hull. Cabo Rico's Jim Fraser reports that the company has never had a report of rusting ballast on the earlier yachts. The hull is very thick in that area, hence no real chance of a hole, he says. Fraser says, that in fact, he has have never had a report of a hole in a hull nor lost a rudder a sea—ever. (A challenge, perhaps?)

Darrell Nicholson
Darrell Nicholson

Iron swing keels present there own special problems. Here the rusty iron centerboard on a Catalina 22 is dropped for refinishing. Catalina now offers a fiberglass encapsulated substitute.

Iron keels are either externally bolted on to a keel stub, or fully encapsulated (typically sealed with FRP laminate) within the keel during construction. The same goes for lead keels. Lead is regarded as the better choice, but you shouldn’t disqualify a boat from your search merely because it has an iron keel. If there is iron in the mix, will want to closely inspect the boat for warning signs of larger trouble ahead. 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 graphtic corrosion, or 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 (it’s denser) and its corrosion resistance, lead is preferred over iron for ballast.

Comments (10)

We are told by experts in this field who consult with us that the process of graphitic corrosion or graphitization in iron ballast is well documented. There are several peer-reviewed articles on the phenomena occurring in other iron products -- like cast-iron pipes.
DHN

Posted by: sailordn | May 21, 2018 7:06 AM    Report this comment

I'm a chemist, but not a metallurgist. Parts of this article are not accurate at all; especially the paragraph about graphitization. Iron, as opposed to steel, is an element. Fe = #26 There is no way iron will decay to graphite, a form of carbon, short of nuclear fission. Graphetization occurs in steel, not iron, when it becomes exposed to elevated temperatures for long periods of time and the small amounts of carbon migrate out of the complex with iron that forms steel, leaving a brittle, inhomogeneous mixture. You can't reach those temperatures in a boat. Iron is more resistant to rusting than steel, due to the carbon in the latter. (I used to have a BB 11 that had iron fittings on deck.) But, as the article points out, to rust oxygen and water (a catalyst, I believe) are needed. In the center of a keel there is neither so it can't rust from the inside. Rust is actually heavier than iron/steel due to the additional weight of the oxygen. But it's also less dense. That means it expands, approx 7 times. So, as it rusts it expands and could put serious pressure on the (fiberglass) container it is in, perhaps breaking it.
I like the idea of Practical Sailor being an independent "examiner" of marine products. But too many of the articles I read are just not accurate enough to trust it in general.

Posted by: commocean | May 20, 2018 4:41 AM    Report this comment

I would surmise that an encapsulated keel made of solid iron could be a problem when it gets wet and expands. However an encapsulated keel made of iron punches would have many voids throughout the encapsulated area to accept some expansion should that occur. While I have heard this topic discussed before I have never seen a single photo of a boat damaged from the expansion of an iron encapsulated keel.

~ ~ _/) ~ ~ MJH

Posted by: MJH | May 19, 2018 12:56 PM    Report this comment

Fraser Smith owner/operator of Cabo Rico since the mid-1980s emailed Practical Sailor a statement to clarify the boat's keel a history, and his comments have been incorporated in the updated version of this post. He applauded the passion of the owners who comment here, saying: "Cabo Ricos are superbly built and finished and sail beautifully, so you will find all our owners are equally passionate about their yachts." Smith might be speaking from a biased perspective, but it's always good to have a boat builder involved in any discussion of construction. For a more complete review of the Cabo Rico 38 see Used Boat Review: Cabo Rico 38, PS March 2002.

Posted by: sailordn | May 18, 2018 10:50 AM    Report this comment

From a surveyors perspective all iron keels whether internal encapsulated or external are suspect. Irrespective of the "name" of the builder. Iron's only advantage is lower cost.
Removing iron or steel bolts from an iron keel is a mission impossible. Not difficult with lead.

Simply put there is no reason to buy a used sailboat with an iron keel. Especially in today's market with an unprecedented number of older sailboats available at attractive prices. Sooner or later every blue water cruising Boat has serious keel problems. Nothing beats an externally mounted lead keel. It can take coral reefs in stride, easily repaired and if need be can be easily dropped or have its keel boats exchanged.

Posted by: Piberman | May 17, 2018 9:45 PM    Report this comment

From a surveyors perspective all iron keels whether internal encapsulated or external are suspect. Irrespective of the "name" of the builder. Iron's only advantage is lower cost.
Removing iron or steel bolts from an iron keel is a mission impossible. Not difficult with lead.

Simply put there is no reason to buy a used sailboat with an iron keel. Especially in today's market with an unprecedented number of older sailboats available at attractive prices. Sooner or later every blue water cruising Boat has serious keel problems. Nothing beats an externally mounted lead keel. It can take coral reefs in stride, easily repaired and if need be can be easily dropped or have its keel boats exchanged.

Posted by: Piberman | May 17, 2018 9:45 PM    Report this comment

I owned a 1987 Catalina 30-II with a fin keel. I currently own a 1998 Beneteau 321 with a bulb keel. Both boats have lead keels. An advantage of lead keels that was not mentioned in the article is that if you "tap" a rock bottom at dead slow speed, the lead deforms slightly and helps to absorb the shock. I mostly sail on Lake Erie and I touched rock bottoms several times with these two boats in years gone by. The Lake Erie islands are mostly made of limestone and there are many limestone ledges that one can hit if you are trying to nose in close to shore, particularly when the lake levels are low. I go dead slow when I am in those rare circumstances. I have never had any damage to my keels other than a slight indentation and a minor scratch on my bottom paint.

In the last ten years I have sailed and done maintenance on two newer model Beneteau Oceanis sailboats with iron keels. I have not touched bottom with these two boats other than soft sand or soft mud. I have had problems zero problems with these keels.

Posted by: mark2 | May 17, 2018 12:36 PM    Report this comment

Yes, it would retain weight. The only bummer is when it expands and blows the keel apart.

Posted by: Possible Dream | May 17, 2018 11:48 AM    Report this comment

I have owned a 1991 Cabo Rico 38 Custom Offshore Cutter for some time. The above article is totally incorrect. The internal full keel contains lead ballast in the form of cast lead wedges set with the taper in opposite directions up and down when viewed from the top with a pair placed from side to side, from the front of the keel to the start of the aquaift area below the engine bearers. The remaining space is then poured full of a slurry made of resin and chopped mat / FRP material and covered with a topping of many alternating layers of hand laid fiberglass and isophthalic resin . I have a copy of William Crealock, the designers plans for the boat and I have also drilled into that keel on both ends and brought out pure, clean, shinny, non-magnetic lead. I know of no other CR 38's that have Cast Iron keel ballast ? I am not sure what the vessel in the photo accompanying this story is, however it is not a C/R 38.
I have seen a number of highly regarded brand name boats with a mixture of concrete and steel stampings or punch press remnants ( Scrap Steel or Iron ) used for ballast. This makes a nasty mess and the FRP delaminates and degrades as a result in a grounding that allows sea water to contact the ballast. Think about it !

Posted by: Garboard | May 17, 2018 11:28 AM    Report this comment

Purely hypothetical: If encapsulated iron in a molded-in cavity rusts, wouldn't it retain its weight? If it doesn't shift or leach-out somehow, what would be the harm? (Notwithstanding holing the hull and flooding the cavity with seawater.)

Posted by: DavidS | May 17, 2018 11:17 AM    Report this comment

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