Question for Paint Gurus.

[Freerider]

I pulled my rudder today after 6+hours of drilling and hammering out 3 bolts, while also damaging my bronze rudder shoe. The geniuses that built my boat thought it would be hilarious to use slotted bolts everywhere

I figure i will cut open the rudder and inspect the welds after seeing some rust stains since haul out. So far I've just begun sanding the bottom paint off and I've noticed maybe my bottom barrier coat is failing but I'm not sure yet.

You can see in the pictures where i've sanded down to bare glass but you can also see a layer of paint which is crazed and has completely failed in some areas. It actually looks like this may have happen a while ago and the PO's just kept applying bottom paint.

This is my 1st experiment with the bottom paint so far, can any you with experience tell whats going on from the pics?

Would you sand down the entire bottom and re-apply a new barrier coat? I think I know the answer, but I'm hoping for the best here.

[minaret]

Looks like a potential case of incompatible paints to me. I don't know that it needs a full peel, the barrier coat (if there is any) could be just fine under all that bottom paint. It definitely needs a bottom paint removal though.

[carstenb]

Go to Home Depot and buy a hobby sandblaster. Much easier and not too expensive. It will take it all off. Then repaint with two-component epoxy and then antifouling. If you find rust when you sandblast, make sure you get it all, then paint with rust inhibitor before the epoxy.

The goods news is that when you have done it, you boat will probably also gain a knot or so of speed................

[minaret]

Originally Posted by carstenb

Go to Home Depot and buy a hobby sandblaster. Much easier and not too expensive. It will take it all off. Then repaint with two-component epoxy and then antifouling. If you find rust when you sandblast, make sure you get it all, then paint with rust inhibitor before the epoxy.

The goods news is that when you have done it, you boat will probably also gain a knot or so of speed................

This is awful advice. This is a glass boat, not steel. And even if it was a steel boat, a hobby blaster would take a week at least to do this job. You need an industrial sized blaster with a huge compressor to blast a bottom, and then you have to deal with cleaning up the contaminated medium. In many places it's not even legal to do this in the open. This boat needs a 36 grit soft pad. Often when I see really heavy build up and flaking, as here, I start with a light pass with a 7" 16 grit grinder, the 16 grit never touches barrier coat or gel if you use a light touch, but it blows all that paint right off. Then you finish with 36 soft pad. Of course that method requires you to be a maestro on the grinder...

[Freerider]

There doesn't seem to be any gelcoat on this rudder (i don't think) is this normal? I'm assuming there will be a gelcoat layer on the bottom of the boat under the paint because the topsides are gelcoat.

I've seen some results of people using scrappers to remove bottom paint, is there any danger in destroying the gelcoat is way (if there is gelcoat)?

[minaret]

Originally Posted by Freerider

There doesn't seem to be any gelcoat on this rudder (i don't think) is this normal? I'm assuming there will be a gelcoat layer on the bottom of the boat under the paint because the topsides are gelcoat.

I've seen some results of people using scrappers to remove bottom paint, is there any danger in destroying the gelcoat is way (if there is gelcoat)?

It should have gel. It has probably been opened up before, and they removed the gel to glass it up at that time. This is a very common repair. Properly using a scraper to remove bottom paint is tricky to do without gouging the gel if the area in question has a lot of shape, but for a rudder it should be fine. Particularly if there IS no gel!