Skeg/rudder bottom fitting

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cindersailor

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My Varne 27 has a substantial skeg with the lower rudder fitting attached to the bottom of it via a 10mm thick stainless plate which the bottom of the rudder post bears on. This plate is held to the bottom of the skeg with 1/2" BSF (!) studs which are glassed in. The studs, nuts and the plate are all corroded and I do not trust them for another season. I suspect that they are not 316 stainless. The question is how do I replace the studs? I envisage having to drill several holes around each stud in the hope of loosening them enough to be able to pull them out. If they are actually hex headed bolts this will be a fun job! However, this should be possible with a little perseverance. However, I need suggestions on how to glass in the replacements - I intend to use M12 Bolts and epoxy. However, how do I keep the epoxy and bolts in place without it all flowing out before it sets? Thickening the epoxy with fibers will work to a certain extent I suppose, but has anyone had to do a similar job and found a cunning solution to this?
 
I did a similar job on my Macwester last year. I don't fully understand what you have. Is it a flat plate on the underneath of the skeg that is fixed by bolts/studs that go up vertically into the skeg. If so is the skeg hollow and are the nuts/boltheads in a bilge in the skeg?
OR does the plate have sides on it to form a shoe(which is what I have) and do the bolts/studs go horizontally through the shoe and sheg?
Either way I would try to extract the bolts/studs without damaging too much of the skeg. I would use a wrench like this
http://www.screwfix.com/app/sfd/cat/pro.jsp?cId=102591&ts=35037&id=27604
to unscrew the bolts. If necessary put a bit of pipe on the end to apply more turning force and I think the bolts will undo.
When it comes to refixing the new bolts you need a very thick mix of epoxy and filler powder so that it does stay in place. If necessary make some sort of shoe out of tin covered on the inside with clingfilm to hold it in place whilst it sets. The clingfilm stops the epoxy sticking to the tin, or whatever similar material you have to hand. Paul
 
My Catalac has a stainless fitting at the base of the skeg for the rudder. When I bought the boat, this was just about to fall of due to crevice corrosion on the bolts. I now have one of the bolts slightly longer, and use it to attach a circular anode. I no longer have the same corrosion problems, and I replace the bolts every other year (just in case) when also changing the anodes.
 
I had similar problems. I had crevice corrosion on all of the 3 bolts holding the rudder step on. My surveyor told me to make sure I coated the hole and bolts in Sikaflex so water could not get to the bolts. It is water with a lack of oxygen that causes crevice corrosion. I also had galvanic corrosion on the rudder step and like Talbot fitted an anode to prevent this happening again. An anode will not stop crevice corrosion.
 
My prout had rudder skegs fitted with stainless steel plates and bolts. When withdrawn the first time after 10 years in the water, the bolts which ran through the GRP had corrosion like worm holes in them, and a couple came out in 2 pieces.

You cant prevent this with commercial grades of stainless, even 316. It comes about because of the stagnant water surrounding the bolts or alternatively because of the rubbing of the rudders in motion removes the protective oxide coat.

I replaced the bolts with 316 - there were enough of them not to worry, and they were cheap enough to replace every 5 years or so. I bedded them in silicone rubber (they were through bolts) to prevent stagnant water getting to them and this seemed to work. I never actually had to replace them after all.

In your position I would be inclined to bed the bolts in West epoxy (you can thicken this so it doesnt run too much) holding it in with polythene and sticky tape and creating a small recess at the bottom which can be filled with silicone to prevent water creeping up the interface between the bolt and the epoxy if any gap materialises.

For digging the bolts out, Aldi have cheap Dremel copies for sale (about £25) that are quite good and eminently suited for this sort of work.

West epoxy is wonderful stuff - once repaired our toilet cistern at home with this and some woven roving - it had cracked from lip down to the central outlet pipe. The reapir was leakproof and still there when we sold the house a few years later. Mind you, thats nothing compared to the blob of it that is on one of my boatyard sweaters and is still there after 11 years of washing!
 
Totally correct. Secret is not to leave any voids and use a flexible sealant like sika not epoxy or any other hard resin.
 
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I also had galvanic corrosion on the rudder step and like Talbot fitted an anode to prevent this happening again. An anode will not stop crevice corrosion.

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Thats what I meant - senior moment sorry!
 
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