BOTTOM PAINT and moisture sealant

K

kevin ware

New member
I have a 2007 Tom Cat with an original gel coat bottom which is in very good condition...almost like new. Am considering leaving the boat in salt water for several months at a time, and am therefore needing to put anti-fouling paint on the bottom.

There seems to be a dispute among service people as to whether the bottom of my boat needs a 'moisture seal' put on before the anti-fouling paint is applied. Some say this is only needed if the gel coat is in bad shape, others swear nothing but trouble will occur if the moisture seal is not placed first.

Has any one out there had any experience with this? If so, what did you do?

Kevin Ware
El Gato Thomas
 
Most say to use an epoxy barrier first. Then a primer and a different color for the bottom paint itself so you can see when it's wearing thin by the color change. I don't have bottom paint but if I were to take the dip I would go with the epoxy barrier coats first. IMHO it can't hurt. The epoxy barrier is not cheap but what is for a boat?
D.D.
 
Last summer we had our TomCat barrier coated and then bottom painted. The work was done at the C-Dory factory in Ferndale. Great service, great job, fast turn around, and a good price.
 
My boat had also never had bottom paint before and the gel coat was in tip top condition. This Spring I took the boat in to a professional marine body shop with a well respected name in my area. The bottom was sanded, then three coats of epoxy barrier applied, followed by three coats of Trilux T11 bottom paint. Was not cheap at nearly $2400, but at least it was done properly and from now on I can do touch ups as required.

Martin.
 
Hope I'm not interrupting the thread but how long would you let your boat sit in salt water, 1 month? And what are the disadvantages to bottom painting?
 
I think more than a couple weeks you are pushing it. The warmer the water I think it happens faster like down in Florida. If the boat just sits it's even worse. It is a PITA to have scrap and rub growth off if you sit in the water too long with out bottom paint. This growth will really slow the boat down. We spent a month in the water in Florida in March but we were moving almost everyday. We did see very small white dots which I think were the start of barnacles after the power wash when we pulled the boat. I had waxed the whole bottom of the boat pretty well before the trip which I believe always helps retard growth for a little while anyway. There is a teflon based coating you can smear on and it is supposed to prevent anything from growing on the bottom for a couple of weeks it's name escapes me..
As to the negatives of boat paint, cost, rougher bottom slows the boat down and you lose some mileage. It has to be maintained so you have to keep adding coats from time to time. Sanding rough spots so the new coat adhere etc. Sooner or later it might have to have the boat sand or soda blasted and you start over. If you are in a situation were you can do with out bottom paint some recommend avoiding bottom paint unless it's absolutely has to be done. Many opt for rack storage or keeping the boat on a trailer. Based on the area and your type of use there are many choices of what to use. Local knowledge will provide the answers to find which product that will best suit your needs.
D.D.
D.D.
 
The purpose of the "moisture sealant" is to act as a barrier coat against water intrusion into the hull; this intrusion is known as blistering. Bottom paint does not act as a water barrier coat. If you're going to keep the boat in the water for during the summer, water can intrude past the gel coat and cause blisters. This site has mentioned that a few C-Dory's have suffered blistering.

That said, the best (only?) time to do this is before you put on bottom paint. If you want to do this afterwards you have to take off all the paint, either by sandblasting, grinding or some type of paint remover. So why not do it just before you slap on the bottom paint?

As to the need for bottom paint, I once had a trailerable boat that we put into the Sacramento Delta for 2 weeks. That hull never looked the same afterwards, even though we spent an afternoon scrubbing the bottom. Even for the Northwest, I'm a firm believer of bottom paint for any boat that's going to be left in the water for a month or greater. Though everyone gets to vote on their boat.

Boris
 
This is an ongoing discussion and there are varying opinions about barrier coating.

We will barrier coat a hull at customer request, but it is expensive, and we have done it less than a handful of times. In cold salt water blistering is less of an issue, and depending on the year, The C-Dory's have a vinylester resin used that is supposed to prevent water migration into the hull.

Another issue can be on older boats, where thare can be moisture in the hull already, and the barrier coat locks that moisture in the hull- which can then cause blisters.

I look at it this way- as a boat yard we can make more money on a barrier coat / bottom paint job, but our experience is that we don't see the need for it in our waters.

Other areas of the country have different conditions and requirements. If there is any doubt in your mind, I guess have it done now, because doing it later is incredibly expensive.

If it were my boat, and keeping it in Puget sound, I probably wouldn't.

Now, how about we talk about single / twins or single / tandem? :lol:
 
I had epoxy and petite paint made by rpm Corp three years ago and it's holding up just fine. Rpm is a quality company and is a leading company in all types of coatings.
 
I have barrier coated (Epoxy) every boat I have owned for the last 30 years. Before then I did not barrier coat. I owned one boat which developed severe blisters after it was 17 years old. But most of these boats were kept in the water full time, in S. Calif.

There are other possible issues with gel coat and water under the gel coat, which are not osmosis. Some C Dories have been afflicted with this in the last few years (at 2003 until 2010). This basically was poor adherence between the gel coat and base coat under this. Here having vinyl ester resin in a layer or two would not be of value. Vinyl ester resin is not as water resistant as Epoxy. There are some boats with vinyl ester resin which have developed blisters.

If I was going to keep a boat in the water for more than a week or so, in any waters, I would put on bottom paint. If you were going to only have the boat in the water for a few weeks, that it would be prudent to put on bottom paint. Yes fouling occurs faster in warm waters, but there will be fouling in PNW water.

As for the disadvantages of bottom paint. Cosmetic (?)--I happen to like the "Vivid" series by Pettit. The paint holds up well, in and out of water (trailered), and retains its color well. (My caracal is on its 3rd year of the initial bottom job (3 coats), and it still has good antifouling property.

Speed. I doubt that most C Dory owners can tell the difference. In a prior life, I raced sailboats. We would wet sand the bottom paint on a regular basis with 600 to 1200 wet and dry sand paper. Between sanding, we would burnish with the scotch pads. I dare say that the bottoms were as smooth as any bare glass boat. (There are some coatings which will slightly improve boat speed).
 
It seems the consensus favors applying a moisture barrier before the anti-fouling paint...with greater certainty about it this way, the warmer the water.

Perhaps the strongest arguement is that as the boat ages at some point a moisture barrier is going to be required anyway, and any antifouling paint on at that time needs to be completely removed...an expensive and messy job.

I think I will have the 'full meal deal' bottom paint done in the fall.

All helpful comments. Thank you.

Kevin Ware
 
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