So I finally got in there and took a good look at the rudder post today. Now wishing I hadn’t and that I’d just continued to bury my head in the sand.
Here’s what I found: Galvanic corrosion.
Last time we had the hull scraped at Paradise Village the diver told me I needed to replace my zincs and told me which ones to go buy. To be honest I didn’t know the rudder had zincs. The rudders on the catamaran didn’t. Anyway, I bought new ones, the diver put them on, and then came up with the old ones, which were just paper thin sheets of metal. This was a couple of months ago.
Anyway, you can see in the first picture of the post how it looked when I first climbed back there to have a look. The other pics show what it looked like after cleaning it up. It’s pretty clear that the water is getting in because of the corrosion of the shaft.
Now, what exactly does this mean? I don’t know. I do know that it means a little stuffing flax isn’t going to stop the leaking. I don’t think it means the rudder is going to fall off and we are going to sink. And I don’t think it means this is something that can’t wait another few months until we are ready to haul out for the season. I also think I know that this is going to end up being a very expensive lesson in the importance of avoiding galvanic corrosion.
6 Comments on “Rudder Post Blues”
The pinkish color is indeed an indication of galvanic corrosion. In this case the less noble metal (tin?)in the bronze giving it up to the stainless and leaving copper behind. However, you may not have as big a problem as you think. Could just be the surface that’s been wet with salt water. Don’t give up just yet. I agree that you probably don’t have an immediate problem. If you can get it all apart without breaking anything you are probably golden. Go back with synthetic packing with teflon (PTFE?, not flax.
As Ford Prefect would say… “Don’t Panic”.
George
Doesn’t look like it will be a cheap fix thats for sure. Something I just never understood is why so many boat manufacturers use stainless rudder shafts when they should have been using silicon bronze the entire time.
Stainless corrodes when it is permanently under salt water. I have read so many articles online of owners having to replace the rudder shafts. I guess they were just to cheap to use the good stuff.
Chris
This is what happens when you dis Christmas. ;*)
Rudder problems are a drag. We had to haul our boat and redo the rudder 2 years ago. Completely different problem but it was around $2k. Here’s hoping yours is minor.
When you do get the shaft out (whenever that is), be aware that stainless steel is subject to “crevice corrosion.” In a nutshell, this means that what might look like just a tiny pit on the surface, can be like an ant gallery underneath where you can’t see it. That means things can suddenly break. If you replace the rudder shaft, consider going back in with something like Aquamet 50, which is a type of stainless that’s good for shafts. If your boat was built in Asia (I don’t remember), then it’s likely a “lesser” grade of stainless is used. I mean, not to dis it (and not that all boats built in other countries don’t use lesser metals), because hey, it’s lasted this long — but just explaining. Bronze might also be an option.
I would definitely go back with bronze instead of stainless. Since the boat has to come out, go back with something that should give a long service life.
I had a similar issue with the packing on my Islander 32 – but after having the yard replace the packing, no worries.