She’s back on the carpet again… With the containment blocking me at the dock, I took advantage of the first two weeks of containment to advance the work I had planned for later.
Until now, I had mentioned several times the work and the problems encountered with regard to the let which is located in the front part of the keel. In this article, I talk about the treatment of the back part which it is hollow.
During my first inspection of the boat, I was largely optimistic about the condition of the rear part of the keel. The reason for this is that it houses the three freshwater tanks, and therefore access is very limited.
Freshly owner of the boat, my approach was to modify the boat’s systems as little as possible. I assume that the person who set them up had good reason to do so. So I prefer to understand using it first, and then adjust what is really important. The goal is not to immediately throw me on changes that would prove to be useless in the future.
The idea is right on paper, but when it comes to the inspection of the bilges, you have to do the things right. Then and anyway if I hadn’t pretended to look, I would have scratched at the entrance of the compartment and noticed the damages.
In short, I am confined thanks to covid-19, I check the bilges and find that I have a small leak of fresh water. I then went into the dismantling of all this, to do at the same time the sloppy inspection that was still lying in a corner of my head, like an old silent guilt.
Just visually, the rust is obvious and it will be necessary to do a thorough treatment. Scratching with a flat screwdriver confirms this, a 10cm plate of paint removes itself and falls down! We’re off to a new construction site.
A disused tank
This particular area of the keel is located under the engine. It was originally the diesel tank. The previous owner had it in a dirty condition and had opened it and processed it in 2012 or 2013. So it became a new space, a compartment.
At the time of the operation, he had found a “muddy” deposit at the bottom. Everything has been cleaned and sanded as much as possible. Parts of the walls are still greasy today.
To make the compartment accessible for processing, non-structural steel plates have been removed. Only one last little one remained in place, at the bottom.
I say non-structuring because they are welded only on starboard by a few welding points. I therefore assume that their function was to give the keel its profile when the starboard plate was closed during construction. Or it was to prevent the diesel from dangling back and forth while navigating.
The bottom of the compartment (the sole of the keel) could be completely cleaned and therefore a layer of epoxy was laid. For the walls, having failed to obtain the right surface, a bituninous paint had been preferred.
Evolution after eight years
The water tank in this compartment is a 90L bladder that rests on the walls when it is full. The temperature difference between the water in the tank and the wall was a source of condensation. So we have the ideal conditions for rust.
Eight years later, the result is unquestionable: the part under the epoxy is smooth and clean while under the bituminous the sheet is all rusty, greasy. At the top, where the tank does not support the wall is slightly stung, but not much more.
The small cavity at the bottom
At the bottom of the compartment is a last partition. At the bottom of this partition is a hole from which one can see pieces of rust.
It’s worrying to know that there’s a cavity behind it that hasn’t been treated in 45 years and from which it is falling down rust.
No room to pass a grinder, actually yes but with only one arm I would not do it. So I made a hole, which allows me to take a picture and inject products.
The curative treatment
On bituminous paint, you can’t put anything but bituminous paint. Unless you remove the previous coat completely… The compartment is 30cm wide, so I wouldn’t make it.
So I fell back on the following solution: I’m going to do the same thing again, i.e. Epoxy at the bottom and bituminous at the top. I will try to remove as much as I can from the bituminous coat with a chisel so that I can increase the area I would treat with epoxy, thereby reducing the area I would cover again with bituminous. I couldn’t strip the surfaces properly, so before I painted them I’d handle them with phosphoric acid. The phosphatation that takes place between rust and acid stops the rusting process in a chemically manner.
As for the little cavity, I’d end up with this. I clean it with a small brush through the hole I made in the partition. Then I treat it with phosphoric acid and would leave it after rinsing/drying and spraying Rustol. Next time I’ll put the boat on land, I would cut the partition with the ideal tool that I have been advised by then.
The preventative solution
Errare humanum est, perseverare diabolicumSeneca
If I’m not really able to change the steel protection for a better one, I can quite try to limit the conditions conducive to the development of rust. So why deprive myself of it?
As described above, I suppose the humidity condenses on the walls of the water tank. This one is flexible, it relies on the steel shackles, it oozes, remains constantly wet and therefore rusty.
In addition to installing an insulator, my idea is to make a structure holding a space in between the tank and the wall. By doing so, It would ventilate and remove the contact area. In my boat in Norway, I had moisture that appeared under my mattress, I had built a box spring to solve this problem, and successfully. I think doing the same with my tank should at least double the life of my treatment.
The ideal would be to be able to renew the atmosphere below, automatically and constently. Better than ideal again, it would be to install a sensor measuring moisture, which would trigger the renewal of air above a threshold.
But hey, first the insulation, then maybe a box spring!
A task that is, so to speak, unpleasant. With room for only one arm, it proves to be long and tedious. The sole being covered with epoxy and fiberglass, every millimeter removed is a victory. I put down my wood chisel, take my hammer with my only operational hand and hit the chisel. I let the chisel resting vertically, I strike it, and so on…
Once the bulk of the rust is removed, I treat the rust with phosphoric acid and this 4 times. I apply it with a brush, wait 10 to 12 hours and clean with great water. Cleaning filled the keel, so I pump it with the bilge pump and then finish with the scoop and finally to the sponge. I need an hour between the start of the clean-up and its end, completely dry.
The phosphatation is obvious and the rust turns from orange red to silvery blue. I think it changes volume also because between two treatments I manage to scratch areas that take off more easily.
Epoxy and bituminous paints
Once the rust is converted, I switch to epoxy. These are six layers that I put down, with a drying time of 12 to 18 hours. Despite the spring and my heating stalled at the bottom of the keel all night, the water temperature requires a relatively long drying and polymerization time.
The practice is quite complicated. I have to go down there breath-holding because otherwise the humidity of my warm breathing condenses against the walls cooled by the sea. However, it is important that the wall is dry before the paints are laid, especially for epoxy. In addition to apnea, I do in two times between which I post the heating to be sure that it is well dry.
The worst is with the bituminous paint. This kind of paint is something like blaxon or coaltar. So there I really have to hold my breath and do in several times between which I go out to get air 5 minutes so that my head stops turning.
A good thing done.
Bubble wrap, double-sided scotch and finally a beer.
Last Updated on 9 June 2020 by Vincent