Leaking rudder

[Mervnjudy]

We have had our Bavaria 46-4C 2007 yacht out of the water for general maintenance. We have slightly rust coloured water weeping from the trailing edge of the rudder...about one third the way up from the bottom. This has been happening over a period of 3 to 4 weeks. Is this a problem, and if so any suggestions for rectification? eg. Should the rudder be drained by drilling small holes in the rudder and re-sealing? Thank you in anticipation

[IslandAlchemy]

The rudders are hollow, water gets in.

Nowt to worry about

[Salty]

I think you will find there is very much to worry about, particularly if the rudder shaft where it extends down into the rudder is of stainless steel. I have mentioned in other posts elsewhere, that while stainless steel is great in most other areas, if it is allowed to remain in contact with stagnant sea water, which is what will happen here, it will corrode very rapidly. Best thing is to  find where the water is leaking in, then drill holes in the rudder when the boat is next ashore, in order to allow any water to drain out. Give it time to thoroughly dry out, then fill the holes and glass over the leak and the area where you drilled holes. Best to speak to a qualified yacht surveyor, and chose one that has a reputation for being pernickety.
The following reference is in regard to stainless steel keel bolts, while we are talking about the rudder shaft and its attachment to the rudder. The relevance of course is in regard to what happens to stainless steel in a stagnant sea water environment.
http://www.sailmagazine.com/boatworks/how-secure-your-keel
About halfway through the article is the following reference, but do read the rest of the article.

"Stainless steel: The most common keel-bolt material in America is stainless steel. This is dismaying to many, because stainless steel suffers rampant corrosion when immersed in stagnant seawater. Using it for keel bolts anticipates that the bolts will remain dry?which is optimism bordering on delusion. The good news is that if they do remain dry, they have proven to last for half a century or longer."

Your rudder shaft will not remain dry, while the water within the rudder itself will not be exchanged sufficiently frequent to re-oxygenate in order for the surface coating on the stainless parts to be regenerated. So don't be tempted to ignore the situation.

[Mervnjudy]

Thanks First Mate Salty for your thorough reply and link to the very interesting magazine article. We have followed your advice and very much appreciate your input.

[IslandAlchemy]

Based on that, 90% of all keels should be at the bottom of the ocean by now

[Salty]

Based on that, 90% of all keels should be at the bottom of the ocean by now

In the case of fin keeled boats, only if the keel to hull seal is not maintained leak free, or if any seawater accumulating in the bilge is allowed to stagnate which would be quite difficult to achieve on account of it sloshing around as the boat pitched and rolled and with the water being aerated in the process.
My previous boat was a bilge keeler with large flanges each side of the top of each keel, through which the keel bolts were fitted, and where it was relatively easy to visually check each one during annual maintenance. Each bolt had a countersunk head which fitted into the countersunk holes drilled into those flanges. The forward most bolt on the outboard side of the port keel had to be renewed. Seawater had got under the paint coating and the ensuing chemistry resulted in a large blister. When the blister was pierced some evil smelling liquid dropped out along with most of the now liquidised head of the bolt. Why it happened is evident from the link in my earlier posting. Once the new bolt was fitted, and having already prepared the area, the head of the bolt was glassed over with an epoxy resin, smoothed and then given plenty of paint. The subsequent buyer was informed and provided with the spare bolts I'd purchased incase any others needed doing.