water in the rudder

[junkman]

I just pulled Blue Moon out of the water for the first time since I bought it, and was dismayed to find water dripping out of the bottom of the rudder. It took all day to drain out. Looks like it might be getting in at the top where the shaft enters, but obviously the water is happy to drain out the bottom too, so re-sealing the top seems pointless. I wonder what the condition of the stainless rudder shaft is like, since stainless does not like being in damp, oxygen-depleted situations. I am assuming the rudder is hollow fibreglass, but in this boat, which appears to have been modified and finished by the first owner, anything is possible (there is some rough workmanship in evidence). Has anybody had a similar problem, and does anyone have any suggestions. I am not planning to drop the rudder off during this slipping but will think about what to do. Despite the miles Shaun has covered in Blue Moon, I am reluctant to do any serious coastal passages with the rudder in this condition.

[percyverhance]

My rudder has done the same the last 2 times I have slipped Junkman.
When I slip next time I will open the side of the rudder up and have a look.

[Phillip]

There are previous posts on this subject. Just do a search.

Remember you will need a minimum of 800 below the keel to remove the rudder.
The rudder base slopes forward so you will need room to remove it.

On the Hard at Lawrie's Boat Yard..JPG (3.95 MiB) Viewed 3216 times

[junkman]

Looking at Troppo's rudder repairs, it appears his rudder is made out of plywood. The drawings however show 8mm fibreglass shells with foam infused into the hollow. Blue Moon's rudder sounds like it might be fibreglass. Perhaps the foam is water saturated. The boat is a Mk 3 built in 1984. Does anyone know what the rudders of this era were made of? Having slipped the boat in October, I won't be taking the rudder off for a while but am considering options. One option is to just ignore it for now and go cruising in 2020. After all, Shaun took the boat to the Whitsundays in 2018 and the rudder was apparently leaking water even then. I have found no references on the website to repairing a fibreglass rudder. Has anyone done it?

[steve]

The rudder of my Mark 3 has dripped water each time I have slipped for at least 20 years. This year I decided to investigate.

I removed the rudder and cut an inspection hole. Using a wire through this hole, and through the hole which accepts the pintle, I found that the shaft and its tangs are attached to one side of the rudder, and that the other side is attached to the first side only around its perimeter.

I am uploading two photos. In one I have attached blue tape to the rudder to show the locations of the shaft and its tangs. This shows that the drawing in the Mark 3 gallery is inaccurate, although correct in principle.

Once I knew that one side of the rudder is attached only around its perimeter, I was able to cut a large panel out of this side. The second photo is looking through this panel at the tangs and shaft which are enclosed in thick fibreglass.

It appears that the construction sequence was as follows. The tangs were welded to the shaft and the assembly was laid on one side of the rudder, with a bed of filler under the shaft and tangs. Thick fibreglass was then laid on top of the shaft and tangs to attach them to the side. Finally the second side was placed on top and attached around its perimeter by fibreglass.

With this arrangement, even if the void between the two sides is full of water, the water cannot reach the stainless. Although water in the void cannot reach the shaft and tangs, in my rudder water had penetrated from the top, washing out the filler alongside the shaft. I was able to insert a narrow rod about 200mm into this cavity. It did not appear to have affected the strength of the assembly.

I cut away the fibreglass to expose the stainless in a few places, including where the upper tang is welded to the shaft. The stainless was in perfect condition at each location.

The only corrosion I found on the shaft/tang assembly was on the shaft above where it enters the rudder. There is pitting corrosion. I have no explanation for this. I cover this area with antifouling paint but I am not aware of this paint causing corrosion.

The six pieces of stainless threaded rod which hold the shoe to the hull, and which hold the gudgeon to the rudder, were severely corroded. Their nuts were not corroded. I suspect that the threaded rod was grade 304 rather than 316.

Junkman, I hope you have found this reassuring. If I was you I would go sailing and put off work on your rudder for a year or ten. Maybe you should check the bolts or threaded rod as this is easy to do without removing the rudder.

You should also read Percyverance's post about his rudder a year or two ago. He found that his pintle was loose in the shoe, but mine is rock solid.

Steve

rsz_dsc_1347.jpg (108.55 KiB) Viewed 3133 times

[junkman]

Hi Steve, thanks for your informative and re-assuring reply. Very interesting to see inside your rudder. Blue Moon is a shallow draft version (the keel is 10" shallower) so the rudder is smaller, but the structure should be the same. The first owner of BM fitted a side shaft for his diesel and therefore cut a bit off the top as well! He filled the gap at the top with timber and glassed it but Shaun mentioned he had to reglass it as it was not done too well. Looks ok now and there is no sign if cracking anywhere. I also found a small amount of crevice corrosion just where the shaft entered the rudder at the top. A collar of hard putty had been placed around the shaft but water had permeated it. I cleaned it up and resealed it with glass tape and epoxy. I'll replace the bolts next time and see what it looks like. I feel much happier about going sailing now. Thanks again.

[percyverhance]

Thanks Steve for going to the effort to post up the pics.
I will need to also do some work on my rudder in the future and its a big help to know what is inside.
Cheers

[steve]

For anyone who is still interested in this topic, there is a thread on the PBO forum called "water in rudder". The thread was started several years ago but there have been a few new posts in the last few days so it is currently easy to find. There are a few interesting posts. The consensus seems to be that most boats have water in the rudder and it is not a problem, particularly if the stainless is encased in fibreglass.

[junkman]

Thanks, Steve, I will look at it. The rudder is not at the top of my priority list at the moment, so it is good to know it may be ok for now. Too many other things happening, like a brand new cambered junk sail recently fitted, Windpilot windvane and hard bimini. Hoping to escape the marina in Mooloolaba in a month or so and head for Moreton Bay for a few months of cruising, despite current social dramas.

[saintpeter]

John Harries has a good look at the situation here: https://www.morganscloud.com/2020/03/08 ... m-defined/ .
Part 2 he discusses the solution, which is basically an expensive new rudder.
... ... ... Peter