Brush-on Roll-on Gel Coat

[Bayou Bum]

I understand any type of topside paint (epoxy or poly) on the bottom will require a coat of bottom paint over it to protect it from marine growth. Additionally I understand any type of topside paint will also require a coat of bottom paint just to protect it from the water and blistering. Boston Whaler even says you need a coat bottom paint over the factory gel coat if you plan to leave the boat in the water for more than a few days.

I'm not worried about marine growth, but I hate the thought of a damaged finish just due to having the boat in the water for a week or so. In my search for a bright white, high-gloss bottom paint I have come to the conclusion what I'm looking for is actually roll-on or brush-on gel coat. I know it's not going to be any better than paint with regards to marine growth, but at least it's not subject to all the problems of paint under the water line.

Am I over complicating this?

[NLA01]

Visit https://www.fgci.com.

Do a search for brush-on gel coat that flows out like paint.

There is absolutely nothing wrong with your thoughts on the gelcoat. You have done your research.

If it were me I would do gel coat even if I was going to paint over it. Gel coat helps seal the raw fiberglass and helps the fiberglass become a smooth surface. Don't apply it too thickly and be prepared to do some sanding when done.

If just looking for a durable bottom coating that will not blister like a top coat paint would on the boat hull bottom, then gelcoat is the way to go.


Archie

[jimh]

Am I over complicating this?

Yes. Follow Boston Whaler’s advice.

I have never heard of applying gel coat on top of gel coat.

I never heard of applying gel coat over a topside gloss paint.

Polyester gel coat resin is not waterproof. Polyester gel coat on a hull bottom needs a barrier coat applied to it that is waterproof.

[NLA01]

What is the condition of your hull right now. I assume you are restoring the boat. Did you do repairs to the bottom or is it mainly original gelcoat?

[Bayou Bum]

The boat is a 1963 13' classic. It's been repainted once before and the old paint is coming off fairly easily, both top and bottom. I'm going with all Total Boat products. Epoxy barrier and new brush on gel coat on the bottom, one coat with no wax, the final with wax. Standard primer for the top side and wet edge topside paint for that. LOTS of sanding but I want the new stuff to stick. Probably won't wet sand or buff the gel coat, just want the protection of gel coat and no anti-fouling paint.

[jimh]

Polyester gel coat resin is not waterproof. For immersion in water as on a hull bottom, gel coat needs a waterproof barrier topcoat. Follow Boston Whaler’s advice. Read the owner’s manual that I have reproduced on-line at

http://continuouswave.com/whaler/refere ... tml#bottom

Or invent your own solution.

[biggiefl]

I don't what all the fuss is about. Gel is what comes on boats and boats sit in the water without any kind of barrier coat on them. I agree that topside paint is not the answer if time is a week or so. I also would recommend Petit as they make a bright white bottom paint and that may be an easier solution.

[NLA01]

That sounds like a plan, but the old paint must be removed where you plan to gelcoat. It needs to be removed passed the primer. All paint and primer must come off.

I figured you probably knew that but had to say since Jim said the Gelcoat cant go over paint.

I would fair, get the polyester fairing compound, and the fair the holes and crack and board sand it and you will be much happier with the results. I have rolled gelcoat before using a 4" thin roller made for polyurethane and put many thin coats. I do not put wax in the mix on these coats. I let them set until they are tacky. Then put my last coat with wax mixer in. I had good results but in the end it will look like you rolled on gelcoat, and it required sanding to look nice. I sanded the progression ladder up to buffering it and it turned out very nice. Lots of freaking work though
Archie

[Bayou Bum]

Thanks guys. Old paint is gone both top and bottom. LOTS of sanding. Nothing but the old original gelcoat left on the boat. Dealing with the spider cracks per guidance on the board. Using a Dremel tool to clean them out and get to the glass mat. Paint is on its way. May hit the bottom early next week.

All old paint is gone. All new fairing done with West System polyester putty and/or structural putty. Some old fairing will be primed with epoxy barrier to be safe. The new gel coat will be every-bit as waterproof as a brand new Whaler.

[rtk]

I have been going through the same process of choosing a primer and top coat method for my 1971 Outrage 21. I do not think that you are over thinking this decision. Get it wrong and you have spent a bunch of time prepping and painting to only have a top coat that does not meet your needs.

A waterproof finish is a tough standard to meet. Factory gelcoat of all models of boat can most certainly be damaged by immersion in water for extended periods of time even if the bottom has been properly painted without a barrier coat primer. I have also seen gelcoat damaged in deck sumps and transom wells of the original Boston Whaler models from water sitting there. These areas do not drain 100% of the water and over time could become damaged- looks like pock marks in the gel.

Gelcoat and other marine topcoats are extremely water resistant but not 100% waterproof. To me waterproof means 100% resistant to water. It may seem like semantics but it is a very necessary distinction when exploring marine topcoats and having reasonable expectations with regard to the longevity of the finish.

Rich

[jimh]

RICH—more good advice. Perhaps if enough people join this thread to repeat the warning that polyester gel coat resin is not suitable for continuous immersion in water the message will get through.

[NLA01]

I understand any type of topside paint (epoxy or poly) on the bottom will require a coat of bottom paint over it to protect it from marine growth. Additionally I understand any type of topside paint will also require a coat of bottom paint just to protect it from the water and blistering. Boston Whaler even says you need a coat bottom paint over the factory gel coat if you plan to leave the boat in the water for more than a few days.

I'm not worried about marine growth, but I hate the thought of a damaged finish just due to having the boat in the water for a week or so. In my search for a bright white, high-gloss bottom paint I have come to the conclusion what I'm looking for is actually roll-on or brush-on gel coat. I know it's not going to be any better than paint with regards to marine growth, but at least it's not subject to all the problems of paint under the water line.

Am I over complicating this?

With the all the replies posted warning of Gelcoat allowing water intrusion I am not seeing in the original post saying he is keeping the boat in the water. What I am understanding from his post is that is refinishing the boat and that normal topside paints are not used on boat bottoms. Then he concludes that gelcoat is the solution for recoating. I am not seeing in his post that he is storing the boat in the water. I believe this is an assumption from the readers.

So bayou bum, are you leaving the boat in the water or storing it on a trailer.
Archie

[rtk]

I do not believe anyone has made an inaccurate assumption.

I'm not worried about marine growth, but I hate the thought of a damaged finish just due to having the boat in the water for a week or so.

I believe Bayou Bum did state that he is contemplating leaving the boat in the water for a period equal to or greater than a week. I cannot speak for anyone else but that simple sentence was a very good indicator to me that the original author of this article intends to store the boat in the water for a period equal to or greater than a week.

Thus excellent advice and discussion by many people on the capabilities of various marine topcoat finishes has been offered to assist Bayou Bum with the decision making process of choosing a finish topcoat. The technical comments on gelcoat, Imron and Awlgrip topcoats are 100% accurate and very well spoken.

Rich

[Bayou Bum]

Yes, I want to be able to leave the boat in freshwater for up to a week, if I decide to take advantage of my sons house on the lake and some spring time crappie fishing. It would not be common,but I want the option. Otherwise it will be on a trailer. I'll be honest, it's hard to process all the different information because there are folks who see polyester gel-coat as NOT waterproof for a week, and those who do. I personally have a hard time understanding why the same product used from the factory, polyester gel-coat, is not considered adequate for a week of being moored at the dock. Would a brand new Whaler be at risk of gel-coat failure if it sat for a week in fresh water ? To think it wouldn't last a week is to me absurd. I have owned one or more boats for over 40 years, some offshore rigs and many many fiberglass lake/bay boats.

I seriously do appreciate the help and guidance, I do, but I'm comfortable the gelcoat will preform adequately for my needs.

[rtk]

Would a brand new Whaler be at risk of gel-coat failure if it sat for a week in fresh water ?

To me the operative word is risk. Unfortunately there is no absolute assurance that a gelcoat finish will not be harmed or be harmed by keeping the boat in the water for a week. There are too many variables involved that contribute to the degradation of a marine topcoat finish to develop a high level of confidence that there will be no damage.

Gelcoat is an exceptionally durable and water resistant marine finish. It is highly possible that leaving your boat in the water for a week at a time a couple times a year in clean water without an anti-fouling bottom paint will not cause damage to the finish. In my opinion a proper gelcoat finish will withstand it with little or no ill effect.

Back in the 1980's was when osmotic blistering of boat bottoms started to rear it's ugly head in a significant manner. That is because the widespread use of gelcoat only had a twenty five or so year history. There seemed to be no rhyme or reason why some finishes failed and some did not. 5 year old boats blistered and 25 year old boats did not; same manufacturer different manufacturer. Same marina, same bottom paint. There were some brand of boats that seemed to be more prone to blistering but no 100% absolutes.

But there are always outliers to a point of central tendency. And it would be a shame that you put a bunch of hard work into something and wind up with a damaged finish.

You are doing an excellent job on your boat and you are going about the decision process correctly. If it were my boat i would likely risk it. But it is not my boat so it is not my place to advise you to do so.

Rich

[NLA01]

The gelcoat will be fine for one week here and there and the boat on the trailer. Like you said, that is how they come from the factory.
Archie