Bottom paint. What have I gotten myself into?

[Justin_NSA]

I'll get to my question, but first; My bottom paint is thick and flaking in spots so I decided this time to take it all off and start fresh. I hand scraped most of 3 layers off, a couple black and then red. There's another layer of black under the red. So I started orbital sanding from there. It is real slow going. I was hoping to stop at the barrier coat. What I'm discovering is that under the lowest black layer, appears to be gelcoat. Hard and smooth. Is it possible that there is no barrier coat?. Is the black layer a barrier coat? I'm finding a couple patches and needle width cracks at the bow under the black coat. I'm losing sleep wondering what I've gotten myself into. I'm thinking can I get what needs to be done finished before sailing season? Should I just leave the last layer on and paint over it?. Never has the old expression "ignorance is bliss " been more relevant to me.

 

[dlochner]

You didn't mention the color of the alleged gelcoat. If it is white, then it is likely gelcoat. It is unlikely that you have hit black gelcoat, because most (all) boat builders spray the same color gelcoat in the mold. It would be too expensive to spray multiple colors on the hull. It may or may not be a barrier coat, I can't recall seeing black barrier unless it is a coal tar paint. Coal tar paints never really harden, they do become dry and will dissolve a bit with acetone or mineral spirits. It could be a hard bottom paint.

 

[RoyS]

That build up is usually caused by boat owners applying a new coat of bottom paint every Spring. In the future you may want to just touch up the chips and only do a full re-coat about every four years. Further, if you are not experiencing blisters you do not need to apply a barrier coat IMHO. There are older posts here that describe chemical strippers that may appeal to you. Wear a mask.

 

[Davidasailor26]

My guess is the black layer is some hard paint that was used the boat’s first season, and under that is either barrier coat or gelcoat. If the color matches the topsides it’s probably gelcoat. If it’s flat white or gray I’d guess barrier coat.

Assuming the black layer is a hard bottom paint and it’s well adhered it’s *probably* safe to apply new paint right over the top of that. If you don’t have any blistering issues it may not be necessary to go further and apply barrier coat. Just depends on what it really is and what shape everything’s in.

 

[Justin_NSA]

Dave, the gelcoat is white. It comes thru once I get past the lowest black layer. If that black layer isn't coal tar paint like you mention, then I seem to be lacking a barrier coat. Is that possible!?
Thx Roy. No blisters, just those 2 patches and several thin cracks. Doesn't appear to be any water intrusion. I agree about too many layers. We have owned her about 5 years. It has been flaking off down to the red layer. About 3 deep. It was time to do something! The chemical stripping and soda blasting were too expensive. I have more time than money so I went the scrape/sanding route. I wear full protection and a shop vac attached to my sander. Caught the scraping on a tarp and disposed

 

[Justin_NSA]

Thx David. I like where this is going. No blisters thank God. What I'm calling gelcoat isn't shiny like above the waterline so maybe it is a white barrier coat.
I'm wondering if I should stop at the last black layer or remove it too. It's pretty easy removal effort until I start removing that final, black layer. Most everything else scrapped right off. I think there is a compatibility issue between the deep red layer and the black Hydrocoat over it. It has been flaking down to the red stuff. I think the red paint under the Hydrocoat may be a "soft" ablative. I know the upper paint is Hydrocoat from the PO's records.
Is this making sense? I really appreciate the advice from you all.

 

[dlochner]

Yes, it is quite possible no barrier coat was applied. It wasn't until the 1990s that applying barrier coats was considered mandatory. Prior to 1990 it was still debatable whether barrier coats were necessary. In the mid 80s there was only Interlux Interprotect and VC Tar.

 

[shemandr]

I'd focus on smoothness more than blister protection. Prepare a smooth surface on whatever layer you can achieve smoothness and paint with an ablative bottom paint. Re-visit next year if necessary.

 

[Davidasailor26]

I'm wondering if I should stop at the last black layer or remove it too. It's pretty easy removal effort until I start removing that final, black layer. Most everything else scrapped right off. I think there is a compatibility issue between the deep red layer and the black Hydrocoat over it. It has been flaking down to the red stuff. I think the red paint under the Hydrocoat may be a "soft" ablative. I know the upper paint is Hydrocoat from the PO's records.
Is this making sense? I really appreciate the advice from you all.

The absolute safest thing to do is to remove it all down to the white layer, barrier coat, and re-paint. If I were in your position with the well adhered black layer and lack of blisters I probably wouldn’t go that far. I’d smooth down to the black layer, apply 2 coats of ablative (ideally one in a different color as a tracer), and go sailing.

 

[Justin_NSA]

Unless there's a strong argument otherwise, I think that's my direction. Fill the tiny cracks at the bow and sand down to a smooth black layer. Last year, in anticipation, I bought 2 gallons of Pettit Odyssey in dark blue.

 

[jssailem]

If I were in your position with the well adhered black layer and lack of blisters I…

Would stop.

I’d smooth down to the black layer, apply 2 coats of ablative (ideally one in a different color as a tracer), and go sailing.

What David says.

I would add that the cracks you mentioned should be treated. Where they occurred would make me suspect the boat hit the dock a little fast at some point and that the damage was not addressed as it “didn’t look that bad”. Make sure the cracks are superficial. Clean up the area. Acetone. Some thickened epoxy. Sand and fair smooth. Use your barrier coat to cover your repair. Then paint with bottom paint.

Barrier coat is a 2 part epoxy paint with UV inhibitors mixed in. Epoxy is not UV protected. It serves as a water inhibitor. Gelcoat provides UV protection and why used over resins like vinyl ester and epoxy.

 

[Justin_NSA]

Perfect! Thanks guys! It's not as bad as I was thinking. I'll take a picture of the patch and the cracking.

 

[rgranger]

There is a very easy way to get all of the old bottom paint off... I post on this a few times each season and here is a link to an older post

Removing old antifouling applying new gelcoat?

The unfortunate fact is that my trailer sailer will never be on the water for more than 5 days at a time. If I get extremely lucky, maybe I can take a 2 week trip in the next half decade some time. A simple rag and hose should keep the Great-Lakes the critters off. So, this winter it’s time for...

forums.sailboatowners.com

scroll down to post #13.

 

[sailme88]

my experience with barrier coating is that there are 2 colors.. White and gray. If you are at white and it's gelcoat, then you'd use the gray barrier first, followed by white, back to gray and finally white again.. Interlux system 2000 recommends that when the 4th barrier is still tacky that you apply your first bottom coat in a color different from your intended color. This enables you to see the coverage and have a reference coat to see when it needs touching up.

 

[Dalliance]

I did the same project back in 2012. Orbital sander, many layers of old paint, new barrier coat and bottom paint. A big, miserable job and worth doing right because you don’t want to do it again as long as you own the boat.

Just because you found no blisters, doesn’t mean you can skip the barrier coat. You’ve taken many layers of mystery paint off, the earliest of which may or may not have been some kind of barrier coat. I would recommend sanding to the gel coat and applying a new barrier coat before the bottom paint. You’ve come this far and barrier coat is the recommended best practice for boats of this age. Further, applying new bottom paint over an old coat of seemingly sound paint, if that’s what you are considering, is just risky. The new bottom paint might not be compatible with the old and you have no way to confirm compatibility if you don’t know what the old paint is. You also don’t know that the old paint won’t decide to let go in a few years. Best to start with a solid, known substrate.

One more note. My ‘82 H30 actually had blue gel coat below the waterline. It caused a little confusion at first. May have been the only year and/or model with blue gel coat. So black gel coat sounds possible to me.

 

[Project_Mayhem]

If you need to get down to bare gelcoat or barrier, I'd recommend some chemical stripper and an orbital sander. As Dalliance stated, it's a miserable job

 

[Justin_NSA]

I did more sanding yesterday. So far just to the last layer. It was windy, so it kept whatever wasn't getting sucked by the shop vac, out of my face. I wear a respirator and suitas I'm working. I'll post pictures of some of the cracks I think I need to address.
The only area where I see what might be barrier paint is on the rudder and it flakes off as I sand. I may drop the rudder, again, and redo it in my garage. This is way more work than I was anticipating. My plan was to get to the barrier coat and apply bottom paint. As far as painting on an unknown paint type, I could use a Pettit primer.

 

[rgranger]

This is way more work than I was anticipating.

I hate to but see my post (above) on how to remove bottom paint easily and without sanding through your gel coat.

 

[Justin_NSA]

I hate to but see my post (above) on how to remove bottom paint easily and without sanding through your gel coat.

I may try this. Sanding overhead is killing me! I don't suppose the mix will keep very long. Has to be done all at once?
Here are some pics of my hull. The "biggest" cracks are at the bow. I pointed to give some scale. Where the white spots in the black paint are seen in the pic are more tiny cracks, almost exclusively on the port side. All are up closer to the waterline. Below is fine. No blisters anywhere.



If I can remove everything. I think Pettit Protect would be a good start to the finished project. Fewer coats and reasonable wait times.

https://www.pettitpaint.com/media/4000/pet-722-bru-petprotmanual2018-catalog-size-web.pdf

 

[rgranger]

You don't have a lot of paint left on the hull. I would brush on a little citrus strip on the remaining areas and then use a scrapper once it bubbles up. You could try a can of Easy-off oven cleaner.

Regarding how long a batch of the homemade peel away lasts... I made it up in a PVC bucket. So long as you put the lid on, there is nothing (chemically) to go bad. You will just need to stirr it and maybe add a little water if it starts to dry out.