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  • Writer's picturePeter

Time to look at her bottom

It is almost a year since we took the boat out of the water to change the anodes and give her bottom a good scrub.

The objective then, was to remove any unwanted vegetal growth and the attachment of shellfish such as mussels and barnacles. Here in Sicily, the boatyard is only 100m away from our berth, so we thought it would be a good opportunity to have another look at her bottom, check the anodes and vegetal growth before our sailing plans for the year ahead get under way. In addition, we are not sure when the next opportunity for a lift out could be, so this timing is good for us.

Ultrasonic Antifouling

Just over a year ago we installed 2 ultrasonic transducers from Sonihul as we thought that this was an environmentally friendly way of keeping the boat’s bottom free from growth and reduce our long-term costs for haul outs and anti-fouling paint application.

We chose this product as it had a good review by Nigel Calder (Bad Vibes for Barnacles - PYI Inc.) and it was known to be the quietest transducer on the market. With transducers below the floor boards in the fore and aft cabins, we did not want to be kept awake by noise from the system.

The Ultra sonic anti fouling works on the principle of creating vibrations to the boats hull through strategically placed transducers. The vibrations in turn create micro bubbles that disturb to attempted attachment of marine life to the hull.

Before the lift out we were not sure what to expect as there was clearly some weed growth on the water line and the hull had a greenish film of algae.

With the lift out we could see that the hull was overall quite clean and the thin film of green algae was washed off easily with the high-pressure water hose.

There was, however, some significant growth on the prop, bow thruster and on the strainers for the water intakes. I contacted Sonihul for this and sent them a number of photos of the hull to see what they thought. Their comment is as follows:

“To be honest that doesn’t look too bad, the growth around the bow thruster propeller and intakes is Coralworm/Keelworm, it is an invasive species that nothing in the world can fully eradicate. It is not prevalent in all waters, however the yacht must have stayed in a marina that has been infected.”

To keep our boat protected as best as possible, we have also opted for another 2 coats of “Hempel 71880” Black Antifouling on the hull and “Prop Speed” coating on the prop and bow thrusters. The Prop Speed coating is quite expensive but it is clear that something is needed to minimise growth on these areas, especially the bow thruster that is quite inaccessible for a clean with a brush. The dismantling of the bow thruster propellers to have the Prop Speed applied has also enabled the complete tunnel area to be well coated and protected.

In conjunction with the ultrasonic antifouling, we hope that this setup will give us the best conditions for a clean bottom that results in optimum sailing performance with minimum antifouling costs.

Time will tell us if our choices were the best, but so far it seems like the Ultra sonic antifouling transducers are a positive contribution.

Anodes and Corrosion

Some of our anodes were changed in April last year and so we thought that this was also a good moment in time to check and change these items for our long-term corrosion protection.

Many boat parts are made of steel or have stainless steel items in the structure for additional strength and are highly susceptible to corrosion in the marine environment. Seawater acts as an electrolyte, which causes a transfer of electrons from the steel parts through oxidation. If not dealt with, this process of gradual material reduction can degrade the structural integrity to the point of failure.

Besides coating, the standard protection method is the use of sacrificial anodes. These are made of a more active or less noble metal (usually zinc or aluminium). The sacrificial anodes are attached to the steel parts and since they oxidize more easily, they turn the structure itself into a cathode. The electrons leave the structure through the anodes which slowly dissolve. Applying this physics principle, anodes protect the steel components against this galvanic corrosion – hence the need to check and replace them on a regular basis to ensure that the steel components do not become anodes and start to corrode.

On this occasion we were a little shocked to find corrosion on a steel bracket that stabilises the bottom of the rudder shaft to the partial skeg. The steel plate was corroded through at the top and seriously weakened in a line that would have eventually broken – probably at a critical moment.

It was not possible to replace the part without completely dismantling the rudder from the boat, so it was decided to clean it up and weld a new plate onto it and give back the lost strength. In addition, anodes were installed on this plate to prevent future corrosion in this area.

Maybe other CR owners have had the same problem ? I would be interested to know. However, on a next haul out I would recommend other CR owners to check this area for signs of corrosion.

For me, this is the first time I have looked at this part of the rudder, so I don’t know if it has been like this since purchase from the last owner or if it is a more recent development.

In case we had any doubts, finding and mitigating this problem makes our decision to haul out and check to boat totally worthwhile.

All anodes are now replaced – the prop shaft and prop end showing the main loss through corrosion which were also the ones we replaced last year. The bow thruster, anodes on the drains (starboard side) and rectangular anode on the port side were less corroded but replaced in any case as this is the most convenient time to do it.

We also replaced the anode on the prop shaft with a rope cutter for a safety precaution as there seems to be no end of unmarked lines from fishermen in the water. So far, we have never had a problem, but the two problems we witnessed are sufficient to make us extra prepared. One situation was with a friend who was forced to make a “Panpan” call and had to be towed back to harbour by the coastguard. The other boat lost control in a narrow channel and was washed onto the shallow sands in a very stormy sea. The mayday call saved his boat and life but the whole interior was completely water logged and pumping out was quite a sight.

With the boat out of the water we had an opportunity for a few other small works. When we installed the water maker in Gibraltar we linked into a salt water inlet for the toilets, but the ½” seacock was too small to allow sufficient water to be sucked in while sailing. We have increased this to ¾” and added a strainer in the direction of the water flow to help force water into the system.

We also had the outside hull waxed and polished, so our Ocean Deva could remain looking as beautiful as ever !

One final note, we found the work done by and the communication with the CMR Cantiere Navale of Marina di Ragusa to be of excellent quality - we were very pleased with their service.

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Feb 25, 2022

We are very pleased with the work done by the boatyard in Marina di Ragusa. With the many jobs we have done, I am so pleased we started immediately last year when we arrived as things seem to take a long time to organise. At least we have done it at a relaxed pace.


Ocean Deva looks so shiny! I imagine Ingrid is very happy. I'm also a little envious. I still have all this work ahead of me, however for now Monica and I are taking a breather in Perth. I agree with the thoughts on the ultrasonic fouling reducer which appears to have done a great job on the main hull, especially as you have probably been largely stationary for the last few months. The thruster tunnel does look a mess though and I'm sure your work on cleaning this up will pay off.

Good catch on the rudder - hopefully you are now ahead on the maintenance and spotting these things before they get too serious/expensive.


Feb 23, 2022

A weld, if correctly done should not fracture like that. Maybe there was some corrosion to create the weakness? Very interesting that you have a weakness in the same area !

I am interested if there are other CR owners with similar problems.

Simon Currin
Simon Currin
Feb 23, 2022
Replying to


well, it’s broken twice. The original was 4mm stainless plate and the second time was with replacement 6mm plate and after only 4 months in the water. On neither occasion was there any visible sign of corrosion on either the weld or the plate. The new solution I have commissioned creates. new heel piece to wrap around the whole recessed area of the skeg to reduce movement as we have noticed that the skeg bolts have spontaneously loosened. I suspect that movement contributes to the fracture. It’s in build at the moment and I’ll share photos of the finished piece before we launch in May. We also get quite a lot of noise from the divinyl shims within the…


Simon Currin
Simon Currin
Feb 23, 2022

very interested to read about your skeg rudder bearing mount. We (Shimshal II ) have broken this bracket twice though not due to corrosion. We are having the whole thing re-engineered this winter in Nova Scotia. I’ll send you pictures of before and after.

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