Aluminium sailboat. Water in rudder

[double u]

...oxygene starvation resulting in corrosion...
when I discovered water in our aluminium rudder I drained (hole on bottom) & rinsed it (second hole high up), tapped threads in both holes & screwed aluminium threaded plugs in & made sure (filler) that it was watertight afterwards.
wouldn't want internal structure in the rudder come adrift...

[xslim]

What did you use as a sealant for bolts? Sikaflex?

[double u]

I really can't say with certainty as it was in 96, but it could have been Sika. epoxi filler & primer over it, antifouling
water didn't come back (last haulout 99)
(a very sensitive spot btw on "old" aluminium boats is corrosion inside the keel! next owner had holes corrode through from inside out & I found the same twice in the net. that is of course if you've got a hollow keel with lead inside & "insulated" with resin)

[xslim]

Well I'm not sure what is inside my keel. It is welded to the body, and so far I don't see any corrosion spots.
We did ultrasound on some spots and it showed 6mm on body.

[estarzinger]

Originally Posted by xslim

Well I'm not sure what is inside my keel. It is welded to the body, and so far I don't see any corrosion spots.
We did ultrasound on some spots and it showed 6mm on body.

^^ yea, you will not see corrosion spots on the outside from this. What happens if there is water inside the envelope is it eats small pinholes thru the weld lines from the inside - you dont find them with ultrasound and they are not visible until the pop thru and you get a small wet spot on your bottom paint that does not dry as quick as the rest.

Typically this poses no significant structural concern, as the keels are usually way way overbuilt.

If the keep has ever hit ground very hard it is not unlikely to have created a very small crack or pinhole in a weld somewhere just from the shock load (even with a very well built keel). How much water would be inside depends on how the ballast was placed - some methods leave decent size voids (putting lead bricks in and then pouring hot lead over), and some other methods leave pretty much none at all (pouring 'lead shot in epoxy' mixture in).

These holes can be a bitch to close up, because there is both lead and moisture behind, which can make the welding difficult. It can be done with correct procedure.

That's all just for your interest . . . I would not suggest you worry about it at this point.

[double u]

I saw pics of an alloy Tatoosh keel - they'd worry me alright!!!

[xslim]

Rudder down, found the leak place