Leaky Rudder

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mack3737

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With yacht on hard for winter I have noticed a damp patch/ trail of corrosion product from about a foot above the bottom of my rudder. Thinking of drilling at the bottom to fully drain. Would like to neutraise the internal corrosion and prevent further ingress. No external damage visible, thinking of appling low air pressure to look for leakage path.What would you think of foam injection?- though worried about foam causing distortion through internal pressure. Any advice to offer on products and techniques to use?
 
It depends on what structure your rudder is - by the sounds of things it's aGRP case bonded onto a steel frame? If this is the case, then could potentially be some corrosion damage to the frame. if so you're loking at slicing the thing open, assessing and repairing the damage, and patching it back together. just like that... I did exactly this last month, and can give some pointers if you want.

however, I might have got the wrong end of the stick entirely - can you be a bit more specific?
 
My yacht is a Swan 43, 20 years old and this is the first year it has started leaking. I am pretty sure that the make up is GRP around a SS frame. I could drill some holes to look inside with a borescope to look for corrosion on the structural reinforcement, but I would think that most of it would be wrapped in fibreglass. I am trying the builder to get a drawing of the construction.
 
The worrying thing is the corrosion you mentioned - presumeably rust. generally speaking SS doesn't rust, which raises some questions! I suspect drilling hole and inspecting with bore scope wouldn't get you very far for the reason you mentioned - the frame will be glassed into/onto the GRP blade. One simple check you can do it to pass a compass around the rudder which can indicate the presence of mild steel. obviously you need to check for other things that will cause magnetic anomolies in the area e.g. engine.

I took my rudder apart because other members of the association had dismantled for inspection and found mild steel 'wings' welded onto a SS stock, which is probably fine if the item is not submerged in salt water for its whole life - water in your rudder is not something you can really avoid.

Inside my rudder, I found a full SS frame but with very poor welding which was totally rotten. I also found the original mild steel 'wings' that had been cut off the stock but not removed from the blade! all in all a pretty bodged repair. I cleaned the lot out, had a new frame welded up with much beefier material, glassed it all back together with epoxy and filled it with 2 pack foam as you suggested.

My boat is closer to 30 years old (sabre 27) but I don't know how likely it is you have the same problem re mild steel wings, but I am quite suspicious of the rusty liquid leaking out.

You are at an advantage to me in that your builder is still around! I'd try to find out if there'sany possibility of there being any mild steel in there first.

another point to consider is where has this leak come from? GRP doesn't just develop holes... is there any chanceit's had a knock? In any case you'll need to repair that too!

sorry to be the bearer of bad tidings, but fingers crossed there's friendlier explanation.
 
I took the rudder of my UFO 34 home (must weigh 100 kgs) because of the same symptoms described by mack3737. Looked like rusty water running down, always wet, impossible to paint over it. At first I thought there was some iron corroding on the inside. That would have been surprising, knowing that the UFO 34 was apparently built to go to war. When I started to drill holes and dig away material to investigate; I discovered the real problem: a previous owner had apparently tried to fill up a nasty wound with polyester, but this was badly cured. Looked brown, rotten, and smelled like polyester ingredients. I nicely cut away the brown stuff with a knife, which was not difficult because soft, revealing the wound, and the rudder is now in my garage drying out until launching time. I will then fill the gap with epoxy.
 
G'day Mack and welcome to the TBW forums,

Rusty stains do not confirm corrosion in a rudder, this can be any number of things and may only very minor, I did one a few months back for a client who was in a panic, only had it a single season and was about 10 years old.

On investigation I discovered some Twat had done a small repair and left a length of wire in the glass; I assume (that's dangerous) a small patch of material was pushed through the hole and pulled back to the inside of the glass then repaired. as the wire had little or no seal it rusted. Took about 15 minutes to complete the repair.

A common cause of rust inside GRP rudders is welds not being being treated or pickled when completed, welding destroys stainless steels ability to self protect itself because the very high temperatures required to weld bring the iron to the surface, pickling is a strong acid paste application and MUST be done properly by grinding the surface or the welds before pickling.

You need to establish the extent of water penetration, to this tap the rudder with a coin and listen for a change in the sound, water has a dull thud, air had sharper sound as does a fully filled rudder case.

Make the drill hole at least 2 inches above the last sharp sound and check the material on the drill bit for signs of moisture, if see any go up another 2 inches. When you hit dry material, continue drilling holes at 2 inch intervals till you get to the bottom of the keel and drill another hole at the lowest point.

Assuming you find water and rust:
Don't panic, repairing rudders is not rocket science.

You need to remove the rudder and stock, split the case, repair as required, reassemble and refit.

Let us Know what you find when you have completed drilling the holes and please mark any holes that hit steel when drilling.

BTW most rudders are not made by the boat builders, they tend to contract specialist rudder manufacturers, your dealer should be able to put you onto them.

Avagoodweekend......
 
Some comprehensive answers here mack. This is a very common problem on older boats. If you can find out the position of the welds in is possible to open a series of "windows" in the front edge of the rudder and attend to things in that way. Jeremy Rogers uses this method on the Contessa 32.
 
You don't need me to add to the excellent advice already received. However, on your question about blowing foam inside - definitely not. Any foam that an amateur can buy will not be water resistant and will absorb over time, in the case of a rudder quite possibly making the situation worse.

Just one other thing. I recall a post from many years ago in which a forumite had found out that his rudder was designed to fill with water and was not intended to be hollow. Reasons to do with the trim of the boat. Make sure yours is not like this before going to great lengths to seal it.
 
Vyv is right, some rudders were designed to be full, however they must be rare as we have never seen one yet. the steel rudder stock is not light and almost all hollow rudders will sink if dropped. Seems to me the craft they were fitted must have a poor design, with too much floatation aft or a high GM.

As for foam filling this can be done but only if 'closed cell' foam and - or micro balloons are used.

Also note, the location and length of the rudder s-steel tangs can found by drilling small holes, they will be filled automatically later when refitting the case skin and allow trapped air to escape at the same time.

Once you have located them you cut out a window or windows around them, giving you access to remove the glass fixing the tangs to the case; this all done from one side only to reduce the time and cost of a complete rebuild.

Hope this helps.

Avagoodweekend......
 
OH and and another thing... if you have a skeg, make sure you grind back the leading edge PLENTY to allow space for any repair (an entire split or the 'windows' mendtioned) to take up. you feel very silly when you go to put the rudder back and it fouls on the skeg...
 
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