Bottompaint blues

[TrueBlue]

Last weekend, I visited my boat, which has been hauled out for the winter. To my astonishment, I discovered the bottompaint is beginning to separate from the bare hull in sheets - strangely though, only on the starboard side.

During winter layup at the seller's boat yard, just after buying True Blue in 2004, I hired the yard to repair some minor hull blisters - minute in size, but since osmotic, my surveyor recommended a proper repair anyway. This yard is a long-time family business with a reputation for excellent work, so I was confident in thier work and quoted price (cost covered by seller's negotiated, post survey price reduction).

The yard stripped the antifouling paint, drilled out all blisters and tented the hull to a heated slab in the paint shop for a few weeks until favorable moisture meter readings were obtained. Next, the hull was faired smooth and an 8 ml coating of Interprotect 3000 was sprayed on, exceeding minimum Interlux thickness recommendations. I was pleased with the results and so was my surveyor. The boat was then shrinkwrapped and moved outdoors in February, to wait out the remaining drydock season.

The bottom was as smooth as silk - looked like the hull was just released from the mold. The yard manager/owner, informed me that nothing else needed to be done except apply bottom paint. "No further surface prep is necessary?", I asked . . . "Nope, she's all ready for paint, nothing else is needed.", was his reply. So, I applied three coats of dark blue Interlux Micron Extra, with Biolux - directly to the hull and the boat was splashed a couple days later. I then sailed her the few miles south to my marina slip, which we had for ten years with the prior boat.

There were a couple of small patches of paint peeled off after haul out last season, which I spot coated before applying a fresh coat of Micron Extra, in Spring of this year before launch. I just attributed this to an over-aggressive pressure washer. After this season's haul-out however, the peeling is very extreme. About 20% of the paint is flaking off and more can be easily chipped with very little effort.

What may have caused this to occur, and what is recommended as a solution to this problem before Spring launch? I can only assume, the newly sprayed epoxy barrier coat, should have been treated before my applications of bottom paint, 2 years ago. I am now fearful that a spot repair would only be a temporary fix, but am not looking forward to total paint removal.

[T37Chef]

I am surprised that they didn't tell you or apply it themselves, a bottom paint coat to the barrier coat before it cured so they bond together. Otherwise, you typically have to do light sanding before the bottom coat application.

Tip: If you ever do this again or remove this bottom paint. The first 1 or 2 coats should be of a different color so that you have wear indicator. Then you can see when another coat of paint is needed when you begin to see the 1st or 2nd coat of another color. Ex: my first two coats are red, the third is blue.

I do have a question for others...Would it be good practice to apply 1 or 2 layers of hard bottom coat first and an ablative on the second or third coats???

[firehoser75]

I don't profess to be an expert on this subject, but my understanding is that you should actually apply the first coat of anti-fouling before the last coat of barrier coat has totally set up. This allows for a good "bond" between the two products.
It sounds like you didn't apply the anti-fouling for quite some time after the final coat of barrier protection. That might be the cause of your problem. As to the best method to correct it, I suggest contacting the product manufacturer for advise.

Good Luck,
Tom

[sailingdog]

I think, since they allowed the barrier coat to set, that it probably required a light sanding to prep the surface for the bottom paint.

T37Chef's idea of using two different color paints is an excellent one. The idea of using a hard epoxy-based paint under an ablative is an interesting one, but most hard anti-fouling paints require the boat stay in the water... so if you haul annually, it may not be an option.

[T37Chef]

In the spring I did my own blister repair work. Using Petit Barrier coat and Petit Bottom paint. (Interlux is also a fine product) I called the manufacturer just to clarify and they said you SHOULD apply the first coat of bottom paint with in the 8 hour cure time, or the barrier coat is still slightly tacky. It has been 6 months now and I don't any signs of it peeling, flaking, etc.

I would speak to the people at the yard and demand an explanation.

Thanks Dog, just a thought, I think your right about that.

[k1vsk]

There are a number of different Interprotect 3000 mixtures so not sure if they used the correct one - first possible cause.
Interprotect doesn't require any special prep prior to painting nor does it require timely painting before setup although it's a good idea. What is necessary is proper hull prep before applying the Interprotect and that's more often than not the problem. You didn't say whether the Interprotect peeled or just the antifouling. Presuming it's the barrier coat that failed, it is the hull prep which causes the peeling. Typically, failure of the barrier coat is caused by residual glycol, which is normally present in any glass laminate, not being thoroughly removed when the hull is washed after blister repair.
If the barrier coat is peeling, the yard failed to properly prepare the repaired hull.

If it's just the antifouling which has peeled (more likely), it's a paint proplem, not the barrier coat which requires no special prep prior to painting. From your description, I infer this is the second season for the paint before you found the peeling in which case it's no big deal. You should consider yourself fortunate that you will have an easy job removing the now ineffective epoxy bottom paint.

[pigslo]

I used the same system on my boat except I applied the bottom paint within hours of the last coat of Interlux 2000. That has been 2-1/2 years ago and it is holding up great. Interlux has a great site and super customer support. I would go to their site first to see if you can answer the question and then contact the regional market rep. The only thing different about mine was Micron 66 for salt water. I suspect you are going to need to go back down to the barrier coat and redo from there unless as kvisk above suggests the barrier has failed. Actually I just visited the site and a primer is required before bottom paint can be applied to the Interlux 3000 that you used. Good luck.
pigslo

[TrueBlue]

Originally Posted by sailingdog

I think, since they allowed the barrier coat to set, that it probably required a light sanding to prep the surface for the bottom paint.

I suspected that much at the time - but put too much faith in what I was told by the yard owner. Too late now.

Scraping/sanding the loose stuff off will involve the least amount of work before recoating. What I need to research is whether ALL of it needs to be removed. Perhaps this will be best decided when I see how sound the remaining paint is after scraping next Spring. Fairing all the depressed surfaces smooth will be necessary if area-treated - otherwise there sure is a lot of surface area, if all the paint is removed first.

[TrueBlue]

Thanks for the confirmation guys, suspected the same. The barrier coat is very sound, from what I could tell from exposed areas - looks great. Won't look forward to removal, but perhaps much of it is firmly bonded. At 200.00/gal, the bottom paint is not cheap though.

[pigslo]

Note my edited post after i went to the interlux site on your behalf. It is clear you needed a primer coat before bottom paint was applied.
pigslo