Aluminium Rudder Stocks How to Prevent Corrosion?

savageseadog

savageseadog

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How is corrosion prevented in GRP construction rudders with aluminium rudder stocks. I've come across stainless steel/GRP construction rudders which I understand and normally seem OK but how do aluminium/GRP ones go on? As a point of interest how are these things constructed? Are there welded aluminium webs and so on like stainless steel ones?
 
Can't comment on how the webs are attached - but probably welded.

For a comprehensive discussion on corrosion with aluminium stocks see the Irish report on the failure of the (aluminium) rudder stock of the Hanse 37 which sank in the Irish Sea.

Literally thousands of boats are in service with aluminium rudder stocks with no record of systemic failure. Corrosion can be a problem if the exposed part is antifouled, and there can be pitting caused by marine fouling, which in turn can wear lower bearings.
 
I remembered to look at the Jefa site after the OP. The advice there is to electrically isolate the rudder, it doesn't however get round the fact that unattached outboards will corrode unless they have a zinc, perhaps the metal is different?
 
SavageSeaDog,

I don't think aluminium varies that much ! If one must use it I'd think an anode a jolly good idea. Personally I care not whether thousands of boats get away with it, I wouldn't dream of using alloy for a rudder stock, this must be a job for stainless if ever there was.

I wouldn't entertain carbon fibre either having dealt with the stuff, so all this adds up to either

A, I'll never win races

B, I might if the other boats' rudders have failed !
 
Tranona said:
Can't comment on how the webs are attached - but probably welded.

For a comprehensive discussion on corrosion with aluminium stocks see the Irish report on the failure of the (aluminium) rudder stock of the Hanse 37 which sank in the Irish Sea.

Literally thousands of boats are in service with aluminium rudder stocks with no record of systemic failure. Corrosion can be a problem if the exposed part is antifouled, and there can be pitting caused by marine fouling, which in turn can wear lower bearings.
Click to expand...

Do you know where to find this report?Tried googling it but no luck.
 
Aluminium rudder stock, copper antifouling. Anodes please

Alloy is soft so unless the bearing surfaces are well engineered, pitting, surface abrasion, all sorts just waiting to happen..
I owned an US 1970s built boat where aluminium shafted spade rudders were used, failure not unusual at all, a clean break across the lower bearing usually.

As always the devil is in the detail and we, the users, get to rack up lots of testpilot miles for the manufacturer!
 
I was thinking of retro fitting and anode(s) possibly one near the top and another near the tip or would a hanging anode do attached to steering gear? To fit the anodes I'd have to excavate areas of stock. A lot of boats with this type of construction are dry sailed and millionaire owners treat bits breaking off as consumables. Racing round the Irish Sea is not the same as trotting round the Solent either. It's something I'm going to have to resolve.
 
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Jefa, I understand, make rudder stocks for just about every make of boat out there, most being aluminium. Megawatts stock did not fail because of corrosion. And if you are concerned about having a rudder stock made of aluminium, then your choice of boats becomes very limited. Ours incidentally is SS.
 
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