Bottom Paint - Buildup and Lifespan

[down_shift]

Sorry, I did search for the answer .... If your boat has a barrier coat, no history of blisters, and CSC was installed every other year for a decade or more (the exception was ACT last June), and there appears to be a LOT of bottom paint still on the hull, is it necessary to continue to apply bottom paint each or ever other year? Meaning, if you see the ablative bottom paint, does it still retain 100% of its anti-fowling properties? Or do these properties diminish over time regardless if the paint remains (well, looks) intact. I am a believer in preventive maintenance. However, I don't want to overdue it. Similar to modern car running synthetic oil and the mfr recommends changing it every 7,500 miles. Your local Jiffy Lube says every 3,000 where oil samples and other supporting data says you are throwing $$ away inside of 15,000. So Interlux, boat yard, real world, respectively. What is the true story of ablative paints?

 

[Captn TJ]

I believe it depends on what the bottom looks like when you pull the boat. If there's a lot of growth then you'll need to apply a new coat

We apply an ablative (1) coat every two years (boat is in the Great Lakes). And every year we apply a touch up on the leading edges and waterline.

However prior to applying a new bottom coat I 'buff' down the old AF paint with a drywall sanding pad (loose screen type). That way we don't get a build up. I've seen boats in the yard with the paint so thick after multiple applications that it was starting to come off in small chips.

Your boat your choice.

 

[down_shift]

There was some growth that was power washed off in Aug (survey) and again in Nov (on the hard). The bottom looks great. The blue is uniform in color and appearance. No flakes. The yard who applied the ACT in June said it was a "1-year" paint and recommend that I paint it again this spring. I am okay DA'ing the surface with 80-grit and painting the bottom this weekend (provided the weather holds out) with CSC with the goal that remains in the water next winter. The occasional diver cleanings as necessary. I just want to avoid unnecessary buildup. Seeing too many boats around me that have been scraped/sanded clean to the glass. Looks $$ and preventable.

 

[wufibugs]

I used to have a growth problem, but not since I leased the agricultural rights to my hull to a local pot dispensary.

 

[gettinthere]

All of these paints loose effectiveness somehow.
The ablatives leech their copper slowly into the water. Warmer water and more frequent cleanings speed up the process.

 

[Gunni]

Believe those are all ablative paints, so they wear off with time...a good thing. Prevents build up. What you have to watch out for is that they may lose their antifouling qualities from sitting out all winter. If it is working for ya, don't fix what is not broken. At some point too much bottom paint buildup will lead to lack of adhesion and flaking. Then you have to take it all down and start over. A BIG job.

 

[Davidasailor26]

ACT is not marketed as a multi season paint, and its datasheet says maximum time from painting to immersion is 60 days, so I'd be concerned that having it as the top coat may mean you can't just relaunch with what it's got. Since you have good adhesion of what's there you could put on one or two thin coats of ablative and try to avoid having to layer on too much going forward.

 

[down_shift]

Thanks for all of the feedback. This has been helpful. The technical data sheet for the CSC recommends Interlux Brush-Ease 433 when rolled. The tech data sheet says introduce it to the paint in "small increments." Does anyone have a ball park where to start? 1:10, 1:5, etc.

 

[Joe]

I'm a bit confused by the answers I've seen so far. It is my understanding that an ablative type paint is most effective on boats that are hauled out for long periods of time because their anti fouling properties do NOT leech out when exposed to sun and air....
the downside is they work mainly by sloughing off microscopic layers of paint when they move through the water to expose new antifouling elements.... You really don't need to worry about build up, as the paint erodes from the surface over time.... that is the reason many boat owners apply layers of different colors... so they can tell when it's time to replace the lost coatings... and it's also the reason they need to top off the coats on a seasonal basis.

Modified epoxy... or hard shell.. type paints work by emitting their anti fouling elements over time... there is no erosion of paint surface... just a loss of effectiveness as the anti fouling emission runs its course. These types of paints have traditionally been used on boats that are kept in the water year round... prolonged exposure to light and air accelerates the leeching action... unlike the ablative types.

Most of the boats in So Cal are slipped year round and not hauled out except for repairs or painting... therefore, most use the hard shell type... and most use a dive service to wipe the hull down on a regular basis. With the hard shell paint and regular dive service you can maintain the hull for many seasons.. Mine is due for painting this year... last bottom job was in 2010.

The down side to hard shell paint is that it will build up over time and at some point the boat owner will want to remove it and start fresh... but if you only paint every 3-6 years... stripping off the old paint is not often needed.

That said, there are many hybrid paint products that will differ from the two I've described... perhaps your boat has one of those..... but the essential comment is that if you're using ablative paint it does not leech away its anti fouling properties the way a hard shell paint would when you store it outside in the winter. That's the main reason for using ablative paints.

 

[Rich Stidger]

down_shift (where did that name come from?),

You asked specifically about CSC which is an ablative paint. FWIW, here is my procedure-

I thought that the common wisdom was to put a signal coat of one color and then two coats of a different color and this would last for two seasons in the northeast. Most recommendations say to use a 3/8" nap roller. Well I did exactly that for 10 years and ended up with a ton of paint on the bottom and serious flaking and chipping in many areas. Additionally I found that the second year anti-fouling performance was poor.

So my sailing buddy and I sanded the bottom aggressively with 80 grit every year for 5-6 years with a vacuum rotating sander. After each sanding we then rolled on ONE very thin coat of ablative paint with a 3/16" nap roller. We used Pettit SR-40 or SR-60 and currently the Pettit water based with slime additive. Our paint consumption for my 40' boat went from almost 4 gallons for 2 coats to 1 gallon plus a pint for one thin coat. At the end of the season a great deal of the paint we applied in the spring was gone.

After 5 years we changed to scrubbing the surface with a dobie pad instead of sanding, but we did sand any small spots that showed signs of flaking. The result is a reasonably smooth hull (not perfect), no long term buildup, and very good anti-foul performance each year.

I spoke to the Pettit factory reps and asked if there was a different recommendation for sail vs power regarding the thickness of the applied paint and I was told they were the same. That didn't make sense to me since I figure that a high speed powerboat would ablate the paint faster than a slow sailboat. Based upon that thought I went with a very thin coat each year.

 

[Capt jgw]

Not all ablative paints are multi season paints. Some ablatives will lose anti foul properties over the winter. Ablative just means it wears off, has nothing to do with anti fouling. Paints labeled as multi season can be dried out all winter and still work when relaunched, although I suspect some may perform better than others in that respect. Putting a single season paint over the multi season would screw up this process. I would remove the ACT then put on a coat of some multi season paint. The signal coat system works well, two layers of paint in two different colors. When the base coat starts to show through, it's time to recoat, and you really only have to touch up what's worn off. You'll find that the leading edge of keel and rudder, and along the water line wear off first, so any left over paint should be applied to these areas for a thicker coat.