Can I antifoul a varnished rudder?

[MissFitz]

The rudder on my Sonata has never been antifouled as the previous owner took if off between races. I’m finding this a bit of a pain so would like to antifoul it. At the moment it is varnished. Can I just put antifoul (hard) on top or will it need to be prepped/stripped? Also, some of the varnish has worn off the leading edge of the rudder above & below the waterline. If I dry it out can I just revarnish the bits where the wood is showing through or will that not work? If so, what else do I need to do before antifouling?

 

[Quandary]

The varnish is not suitable for continuous immersion, strip it off, use a good underwater primer, my favourite is Jotun Vinylester 88 but others are available in smaller quantities, at least three coats followed by the first of two coats of antifouling.
Or perhaps just keep taking it off?

 

[Tranona]

Not sure you actually need to strip it off, although not that difficult depending on what type of varnish it is. Just abrade with 60 grit and either the Jotun primer or International Primocon and antifoul.

 

[lw395]

Depends on the varnish. Some will be attacked by the solvent in AF and may craze, peel or otherwise get messy.
Ideally you want the wood sealed as AF is porous. If the varnish comes off easily with a hot air gun, I'd probably do that, then epoxy it. If it doesn't come off easily, then it's probably epoxy or 2-pack paint already. So touch up any dings with epoxy and AF it.
I would use a hard AF, so the rudder can be scrubbed or wet'n'dried.

 

[JumbleDuck]

The varnish is not suitable for continuous immersion, strip it off, use a good underwater primer, my favourite is Jotun Vinylester 88 but others are available in smaller quantities, at least three coats followed by the first of two coats of antifouling.
Or perhaps just keep taking it off?

The rudder on my Hunter 490 is varnished and has survived four seasons in fresh water without undue problems. I might just have been lucky or unobservant, though. It's remarkably hard to find any underwater paint except antifoul - the Hunter is painted in quite unnecessary Trilux because the only alternative I could find was some Jotun stuff I would have had to buy by the barrel.

 

[William_H]

Yes a/f over varnish should be OK. I imagine it is a transom mounted rudder a bit like mine. The rudder hangs a long way down from the bottom pintle so bottom pintle and gudgeon take a lot of hammering especially if you leave tiller tied off as i do and you get a bit of wave side on from passing boats. I have over the years had bottom pin wear down to give too much free play. Also on 2 occasions had mount bolts into transom come loose and even break off. (6mm). What i am saying is keep a close eye on this very fragile and susceptible part of the boat. olewill