Most steel-hulled yachts have a hollow keel, inside which the ballast is installed.

This keel is sometimes a source of anxiety for owners because there is no visual on the steel inside because of the ballast. Consequently, it is not possible to check for possible rust starts there.

Working in the keel means removing all floors, and spending hours operating in such discomfort.


Why would there be in there?
Because it is a chemical reaction that takes place between steel iron, water and oxygen, cf. my previous article “how to choose your yacht“. So on a metal structure any part exposed to water and oxygen will deteriorate through rust. Air contains both, so wherever it squeezes in, it will bring in water that can precipitate out by condensation.

Hermetic ballast

The question of ballast is central if we consider the problem of rust. It is that guy who takes all the space preventing to see and treat rust.
Often, the strategy is to try to have a ballast that leaves no access to the air. There are several methods for doing this, and I am not able to list them all. One method I have heard of many times was to drown lead in a coating. Many shipyards have used cement, privates have used epoxy-type resin, while others have done differently. I visited a Vulcain V whose owner had directly melted the lead and poured it into the keel.

Fallible sealing

As far as I am concerned, Øya’s yard had used cement. According to what I read on the net this method is obsolete. Many owners have rebuilt the ballast of their boat and Øya has of course does not escaped it.

The former owner therefore has:

  • Emptied the keel of the previous ballast, as much as possible
  • Applied an anti-rust treatment inside the keel
  • Fiberglass placed at the top of the keel, at the joint of the ballast with the air
  • Reused lead ingots from the old ballast
  • Spilled epoxy with only additional lead balls
  • Make a joint on top of it made of epoxy and quartz sand

Unfortunately, this method has also become unpopular… The resin would also tend to shrink over time and therefore allow air infiltration to take place. As a consequence we’ll hase a start of rust between the ballast and the keel, a very inaccessible place!

The worm in the apple

This is clearly what is starting to happen on Øya. More precisely, it is between steel and the anti-rust treatment that rust forms.

The screwdriver points the junction between the ballast and the steel of the keel. You can see the rust being lodged there without any problem.

In fact, the mistake that was made here was to trust the anti-rust treatment too much. This is effective indeed, but for a limited period of time. It seems that inevitably one day, rust will appear even after the best treatment. The major concern in this situation is that even with the best sealing implemented, it is the steel itself which “turns” into rust. So from the moment a very small place starts to rust, it will spread throughout the steel.


The theory

To correct the fire, I remove all the anti-rust as on another part of the boat. Namely, I tap my finger on it, and as soon as I come across a blister I remove it with a flat screwdriver. From there the treatment flakes off, and I remove anything that crumbles easily.

When you reach the ballast level, you can no longer scratch, that’s the actual problem. So, rather than removing the ballast – which would be extremely complicated to say the least – I will try to make a bevel of 3 or 4mm wide in the shape of a bevel at the junction of the ballast and the steel. This gap will allow me at first to confirm whether the rust is spreading well in there or not. Anyway and most importantly, it will allow to pour anti-rust along the steel. Strongly diluted, it should spread as well as possible within the rust, by capillarity.

Before making up my mind, I of course asked for the advice of a professional who validated this approach.


The ballast being an extremely solid block, making this channel is not an easy task. I was able to slip it in a grinder and make a first channel. First observation, the grinder with a metal cutting disc is extremely effective against epoxy. Then it is easy to break the remaining epoxy to finish the bevel between the ballast and the steel of the keel, a flat screwdriver does the trick. Second observation and we expect it, the rust continues its way well between the ballast and the steel of the keel.

Given the difficulty of access to the ballast, I was only able to make this famous channel at the front of the keel. So I directly applied the over-diluted treatment everywhere else doing my best to make it fit. Besides concerning the treatment, although over-diluted, I very much doubt that it penetrates in depth. If this is the case, I would not bet on more than 5 mm by being optimistic.

I return to this intervention in the conclusion of this article.

My solution

I asked myself the question “what would I have done” instead of the construction site or the former owner. Neither cement nor epoxy are effective solutions over time.

Why fighting against nature?

What bothers me about the tight waterproof ballast is that nature dislike empty rooms. Whatever we do, sooner or later a vacuum will be created, and nature will prevail. And even if we manage to make a perfect seal, there will come a day when we will doubt. “I believe what I see”, and I’m not the only one…

So in my opinion it seems to me wrong to implement a solution that condemns access to sheet metal. I would completely dismiss the idea of ​​making a permanent ballast.

Therefore, I would move towards a removable ballast. It may seem wacky at first glance, but why not?

Implementation of a removable ballast

Note: I am talking about a hypothetical method here, which I have not tested. In other words, I’m thinking here out loud, feel free to comment!

To do this, it would be necessary to put a temporary coating in the keel, a coating of a few millimeters thick and rather flexible. Then place hooks vertically in the middle of each compartment before pouring lead for the first time. Once the first stage is poured, you end up with an ingot in each compartment with its hook. So we can take them out one by one with for example a gaff.
For the second and subsequent floors, we want to prevent the second floor from merging with the first. Especially at the hook, a temporary covering will be laid which will mark the limit between the two floors.
Continue to do so until the desired ballast mass is reached.

Finally, a locking system should be implemented. In case of a hard blow, it would be unfortunate to receive 2 tonnes of ballast in the face so that in addition the boat remains upside down…

This idea is certainly long and tedious to set up, but once finished, the ballast could be removed. Every five years, for example, it would be possible to check the interior of the keel and treat it if necessary. Just like we do everywhere else in a steel hull.

And after all…

After a day and a half of work, I applied a first layer of treatment which will restore the seal between the ballast and the steel. It will only remain to add the following 4 layers… And above all pray a lot so that it is not the festival of redox in there!

I am rather optimistic because in view of a sheet which has not been treated for years or since the construction of the boat, the state of it is rather reassuring. It is ugly yes, but it obviously has not lost as much thickness as that and its solidity is beyond doubt.

So in the end, why bother that much? Treating regularly just above the ballast will slow down the progression of rust extremely (therefore enough). On the other hand, at the resale a good part of the interested parties will want to see this sheet, and it will be impossible to show them. Finally, a permanent ballast somehow condemns the boat to a major operation that will certainly have to be done very late in the life of the boat.

Do as you see fit, there is something for everyone!