Hull prep for paint issues?

[CowboyWay]

On a 2000 Catalina 310... I'm doing some prep for the summer season and wanted to get advice on how best to address some of the paint issues I see in various spots around my boat. There is a barrier coat that was applied somewhere around 7 or 8 years ago before we bought it. Since then we've kept up with bottom paint each season. The boat has always been in fresh water. In the picture there's yellow and blue areas I marked up to see what folks think is the cause of that and treatment for it? Is sanding with 80 grit to smooth the edges on the these the right move followed up with ablative bottom paint?

FWIW I use: Interlux YBB359 Fiberglass Bottomkote NT Green

thanks!

 

[Davidasailor26]

That’s a couple stages of paint flaking off the barrier coat. The blue circles are probably spots where the paint flaked off in the last season. The yellow circles look like the original paint flaked a season or two ago but the more recent coats are still adhered to the barrier.

You can try feathering the edges to smooth it out. In my experience as much as you think you may have gotten the loose spots off and smoothed out the roller with fresh paint will pull some new chips off. If the flaking keeps up the best way forward, if you want the bottom to be smooth, might be to get the old coats removed to start over.

 

[CowboyWay]

The blue circles are probably spots where the paint flaked off in the last season.

Are you thinking that it is layers of ablative paint that flaked off revealing the barrier coat (grey)? If so, I wouldn't have thought that type of paint would do that?

 

[jssailem]

If so, I wouldn't have thought that type of paint would do that?

It is possible. Boat is in a bathtub of water. The surface wrinkles a little ( just like we do sitting in the tub) and water slips slowly under the paint surface. Nothing you did wrong. Try to save it, but as @Davidasailor26 said you do the prep and may get away with it. On the other hand some new flakes appear. Eventually we all have to sand it down and begin again.

 

[Davidasailor26]

Are you thinking that it is layers of ablative paint that flaked off revealing the barrier coat (grey)? If so, I wouldn't have thought that type of paint would do that?

Yes, ablative is meant to wear away, but it doesn’t always wear away all that fast. Especially if you’ve been adding a layer each year eventually the earlier layers let go of the substrate and start to flake off.

 

[dlochner]

Yes, ablative is meant to wear away, but it doesn’t always wear away all that fast. Especially if you’ve been adding a layer each year eventually the earlier layers let go of the substrate and start to flake off.

And it doesn't wear away evenly. This problem is common on boats using ablative paint. If one reads the instructions they almost always recommend sanding before applying new paint, many boat owners don't leading to paint build up and poor and irregular adhesion. Contaminants also affect adhesion, some paint flakes off, some doesn't.

The remedy is removing all the ablative paint and start over. Sand each year before applying new paint. A pole sander, like one used by dry wallers makes it easier. The goal is to remove any loose or flaking paint and scuff up the surface to improve adhesion. Some yards may not allow you to do this without a vacuum attachment to collect the toxic dust.

 

[Hello Below]

Some yards may not allow you to do this without a vacuum attachment to collect the toxic dust.

Tenting of the boat may also be required in addition to the vacuum dust collection depending on the jurisdiction where the yard is located and how strict they adhere to environmental regulations .

 

[Project_Mayhem]

It took my friend about 120 hours to strip the bottom paint off of my C30 and apply IP2000 and VC17. There was no barrier coat before, just VC over gelcoat. He was using a pro grade Merka sander and netted sandpaper to save time. Just something to consider if you're thinking about stripping the bottom.

 

[dmax]

That's a good friend

 

[Hayden Watson]

My boat started doing that when I pulled it to paint in 2005 and I took it for a sign to start fresh. I used a hand scraper and removed all of the bottom paint down to the barrier coat. I found that as long as I kept the scraper blades completely sharp, I could clear all layers in a 3" strip with a single pull. I would only pull about 4-6 strips and then rotate to a fresh blade. After all four edges had been used, I would take a few minutes to resharpen them with my dremel.