Epoxy barrier coats?

[Doryman]

I do leave the Tom Cat in the water for 3 seasons, once for 4, so I'll think of it as extra insurance. AFAIK, barrier coat is permanent, and only the bottom paint will need to be maintained.

Warren

[thataway]

I have been following the blistering problem since the late 60's, mostly because of my scientific background. When we were cruising Europe in the mid 80's we visited many boat yards to evaluate how much blistering was occuring there. The only two boats I have seen rendered unusuable by osmosis were in the Med. (other than Uniflites and Valiants during a certain peroid) They had been laminated in the colder climates and were brands which had excellent reputations. They were then brought to the Med, and in a few years, actually had severe enough osmosis that there were holes in the hull. I have seen a number of boats which had zero blistering for the first 20 or so years, but then later in life developed severe blistering in the same waters. I have seen boats which were sand blasted, with no blisters, be hauled the next year, and have multiple blisters. We purchased a Cal 46 which had a blister repair and epoxy coating of the bottom, 4 years before we purchased it. There was no blistering when we took delivary of the boat in S. Calif. The next year it was sailed to the PNW and in 3 years had recurrance of the blistering, while only in the PNW waters.

There is another phenomen which is not discussed as often, but is somewhat related to the osmotic issues. That is a "floppy hull". Basically there is moisture migration along glass fibers, and breakdown of the stiffness of the hull. Part is do to resin decay, some is due to the boat working, and there may be other factors, such as freeze/thaw cycles. Some boats have been destroyed because of this. (Not trailered boats to my knowledge)

To answer Jacks' question about removal of bottom paint. Yes, you can remove it. There are chemical strippers. You can strip it off with sanding and scraping. You can have the boat lightly soda blasted (should be by someone who is very experienced, so that the gel coat is not damaged).
After that, you can put on epoxy primer, and then an epoxy based paint or some other enamals. You do not want to use two part Linlear Polyurethane under water, it will lift and blister under the paint layer.
It is almost impossible to get back to a good gel coat, and use that gel coat as the protective coating for the bottom. As Matt noted, you will scuff up the gel coat before painting, and this will allow small amounts of bottom paint to get in the small "cuts" made by the sand paper. Trying to re-gelcoat the bottom is expensive.

You might consider stripping off the current bottom paint, and putting on a hard bottom paint. It is also possible that ther various layers of paint were not compatable when they were applied. For example, a hard paint was applied over an ablative paint.

[onefam]

Just FYI, we wanted to report what we learned and decided to do on a hull that had never been bottom-painted, as we prepare to keep it in a slip.

We appreciate that many knowledgeable people here in the PNW do not see the need to spend for epoxy barrier coats, but we agreed with comments that it’s relatively cheap insurance, given that the boat would be hauled and sanded for bottom paint anyway.

Moreover, there isn’t unanimity of expert opinion on whether blistering is a problem in the PNW. Steve at B&J Fiberglass in Bellingham, where we rented space to do our painting and repairing, made two points. He said that he’s been doing boat repair in the area for 40 years and seen plenty of hull problems due to water migration. Second, while acknowledging that vinylester resins in newer hulls effectively resist blistering, he said these resins are frequently imported from countries like China where the exact composition of the material is not known for certain. He recommended barrier coats. Two gallons of Interlux 2000E gave us three coats.

There was also difference of opinion on the necessity of wiping the hull to remove any release wax that might be left after five years’ use. Again using the “cheap insurance” logic, we did it, using Interlux 202. After sanding, we wiped with acetone.

For bottom paint, we went with epaint EP-ZO, which is copper-free. We wanted to do our bit to reduce toxins, but also we notice a trend around the country toward banning copper bottom paint, and we’d prefer not to be changing paints when we recoat in the future. The epaint EP-ZO had a very impressive review in a multi-year study of 54 paints written up in Practical Sailor a couple years ago. We put on three coats, five on the water line, and hope to go two years between recoatings. We’ll see. Thanks for the help.

[thataway]

I have never heard of a "difference of opinion" about removing wax before coating with epoxy. That is something which must be done. If there is mold release wax left, the epxoy may not properly bond. Also the gel coat must be scuffed up, with sandpaper.

[onefam]

The question was, is there likely to be any wax to remove if the boat had been run for five years. As I wrote initially, I talked to a number of boatyards and “All say no wax is likely to be on the hull after five years of use,” making the solvent wipe-down prior to sanding unnecessary in their opinion. Posters here, however, recommended the step, as did Steve at B&J.

[Alok]

The Tomcat cruises at 28-30 knots. At these speeds, the Micron CSC that I currently have ablates more rapidly at the water-air interface halfway back from the bow and also towards the back of the tunnel.

The epaint EP-ZO, designed for "powerboats with average operating speeds of greater than 30 knots" caught my eye. However, it requires "visible sunlight" to be effective. My boat is kept in the shade in a covered marina

Oh well!

[onefam]

Not sure where you saw that quote, Alok, but it’s not correct. The 2008 Technical Data Sheet for EP-ZO says it is recommended for “vessels with average operating speeds of 0-30 knots.”

[Alok]

Not a big deal, but this is directly from the company web site. The italics are mine.

Recommended Uses:
For marine and fresh water immersion service; for racing sailboats; powerboats with average operating speeds of greater than 30 knots; racers who want to obtain a hard, fast, sleek racing finish; for drag reduction and fuel savings; boats that are frequently hauled and launched by trailer

And from the data sheet:
Visible sunlight and oxygenated water are required for
ePaint antifouling and release coatings to work effectively.


Anyway, the operating speed was not my concern- I just did not know how effective the paint would be in my situation. My boat is kept in a covered dock out of direct sunlight. This, in combination with warm Texas water that promotes marine growth may reduce he effectiveness of epaint.

But I also don't know about "visible sunlight" in Washington State- I have heard that it rains there all the time

[thataway]

[quote="onefam"]The question was, is there likely to be any wax to remove if the boat had been run for five years. It is not unusual for boats which are kept out of the water to have the bottom waxed, as the hull is waxed. I wax the part of my Tom Cat which is not on the bunk of the trailer.

I have considerable experience using two part LP paints, and the assumption is that hulls have always been waxed.

[onefam]

Alok: OK, I think I have this sorted out. The phrase you quote does indeed appear on the company’s web site (http://www.epaint.com/), but in reference to EP-ZO-HP, which (confusingly) is a different paint from EP-ZO. It is the high performance version designed for faster boats. I didn’t notice it myself -- that I was looking at the wrong page -- so I called the company (1-800-258-5998). Mike, a technical rep. set me straight, but he also said that the “greater than 30 knots” language -- even in reference to HP -- was misleading, not what they intended to say, and that he would take the reference out today.

He also addressed the “visible light” issue you raised. Again, he said the language used on the website and in brochures (written by sales people) was imprecise. Mike said he would address that one too. Meanwhile, he said, the technical data sheets, available at the website, are the best source of information on the paints.