How to properly prep and coat rudder?

[JPS27]

The spring haul out is snowballing predictably. My first time experiences are realigning an out of aligned engine, going to redo at least two through hulls. Those are for different threads.

I dropped the rudder and filled and faired a gnarly rudder top. I found no evidence of water damage. My first attempt a few years ago proved to be a C- grade. This time I think I did a better job. But now what to do? Looking at these pictures you can see several coats of paint. It's layered on pretty think and in places is coming off in small chunks with a little gentle help from a scraper.

To me it looks like the light grey is some sort of barrier coat or gel coat. Is that right? Main question, what is the best way to 1) coat the fix at the top of the rudder and 2) since I need to do something with the fix, how should I prep the rest of the rudder and what to coat it with?

I've done a lot of reading, but like so many things there are a lot of differing opinions. Thanks. Jay

 

[Afrakes]

Hopefully the light gray you see is barrier coat. Depending on how anal you are (I am) you could strip off all of the exfoliating paint down to the barrier coat and start fresh. I'd go so far as to add a couple more coats of barrier before bottom paint.

 

[JPS27]

Afrakes is correct. I must be anal. LOL. I stripped the bottom paint down to the barrier paint. It seems like barrier paint with a white and grey layer. Having read the recent thread on failed barrier paint, I'm even more concerned about getting it right. It seems impossible to get all traces of the bottom paint off and I still have some hand sanding to do on the edges.

Will it matter for barrier adhesion if I have traces (looks more like stains) of bottom paint? And I typically use the West Marine ablative paint which is a pettit product. Will mixing brands matter? And finally, does the timing of the bottom paint on top of the barrier matter regardless of brand or type of bottom paint? I guessing it does but obviously that will drive with I start the painting job. Jay

 

[JSM]

Last year we sandblasted what looked like ten years worth of ablative paint off of our bottom and applied two coats of Sea Hawk epoxybarrier coat.After hours of sanding there were still traces of the old paint.The new barrier coat didn't mind at all.
Sea Hawk recommended applying the bottom paint within (I believe) 24 hrs so that there would be a chemical bond between the two products. We were working on a warm day and the barrier coat cured quickly. We ended up rolling the bottom paint the same day to no ill effect.
The grey that you are down to on your rudder is barrier coat. Most of the barrier coat products are applied in alternating coats of white and grey. You'll probably be fine painting over it.