Gelcoat cracks 1976 Catalina 22

[Frogman]

Hello Everyone,

So firstly I am very new to owning a sailboat and am already understanding "Bring on another thousand"
So when i bought the boat i noticed that it had a substantial amount of spider cracks in the fiber glass. So i have been sanding this down with a small Harbor Freight circular sander down to the fiberglass. I'm hoping to apply new gel coat when all done. What are all your opinions/ tips for applying new gel coat? Should i sand past the blue tape? I'm assuming this was the waterline.

Or perhaps I've screwed this whole thing up? lol

Some picture of the before and after.

Thanks all

 

[Ted]

If you plan on applying anti-fouling bottom paint, you don't need to apply gelcoat. You should use multiple coats of Interprotect 2000E before you apply the bottom paint.

 

[Frogman]

And the difference between anti-fouling vs gelcoat?

 

[Joe]

And the difference between anti-fouling vs gelcoat?

Two completely different things... start researching before you do anything else to your boat.

West Marine Advisor

Sailboat bottom care

Sailboat barrier coat

 

[Ted]

Gelcoat is a material used to provide a high-quality finish on the visible surface of a fibre-reinforced composite. The most common gelcoats are thermosetting polymers based on epoxy or unsaturated polyester resin.. Gelcoats are usually are applied to moulds in a liquid state as a boat is being built. They are cured to form cross-linked polymers and are backed with thermoset polymer matrix composites which are often mixtures of polyester resin and fiberglass.
Anti-fouling paint is an underwater hull paint. You apply it to slow the growth of subaquatic organisms like barnacles and slime that attach to the hull and affect a boat's performance.

 

[Davidasailor26]

I agree with Ted’s approach.

What you’re sanding down to is fiberglass reinforced polyester. It is a good sign that the cracks don’t seem to have gotten into that layer. Once you have all of the bad gel coat removed you’ll have a few options -

- Re-coat with gelcoat, which would provide a smooth surface that is UV stable, but would not prevent growth from forming in the water, and is not completely resistant to water intrusion.

- Re-coat with an epoxy like Interlux 2000e, which would provide excellent water resistance. It still doesn’t provide antifouling, and isn’t completely UV stable, so you’ll need to put antifouling paint over the top.

If you’re going to trailer-sail the boat, so it’s not vulnerable to fouling or water intrusion then gelcoat might not be a bad option. Otherwise an epoxy like Interlux followed by antifouling is likely the better choice.

 

[PaulK]

From the pictures, it looks like the cracks were in the paint - antifouling paint - that was on the bottom. If you have removed the paint AND gelcoat on the boat’s underwater surfaces - which is what it looks like you’ve done - you will need to replace the gelcoat layer with some sort of epoxy barrier coat as Ted has suggested. This is to help keep water from seeping through the fiberglass. (Fiberglass without gelcoat is more porous than you might think.That is one of the reasons a layer of gelcoat is used in the first place.) Then, after the barrier coat(s) is set, you can add antifouling paint. Applying gelcoat on the outside of things so that it is smooth and flat is REALLY difficult. It does not tend to flow and level out well, even on a deck. Imagine the fun you could have spraying it on the underside of the hull, where it would be trying to drip down. Sags and drips would harden, and then need to be sanded off. Not the way to go.

We had gelcoat sprayed on the overhead in our cabin by a professional after we repaired the cabin top. It is “nubbly” - sort of like the epoxy-coated cement block walls that you see in schools everywhere. That is NOT the type of surface you want under water. It would slow the boat down because of the additional wetted surface and provide nooks and crannies for things to grow in. When boats are made, the gelcoat layer is sprayed first, into a polished mold. This gives it the shiny, smooth surface you see on the outside of the boat. Surface variations on the inside (sags and bumps or whatever) are covered up by the layers of fiberglass that build up into the hull. Reading some books about all this before progressing any further might be advised. It could help you avoid expensive dead-ends.

 

[rgranger]

Barrier coat and then antifouling if you are leaving it in the water. If you are trailering, then Barrier coat and a high quality enamel to provide UV-protection to the barrier coat.

Let us know which direction you are heading and then you will get many great suggestions on which product to choose. We have all been down similar roads.

 

[Barnacle Bill]

Ya, I guess you first have to see if the cracks as displayed in the first photo are paint cracking off, or are the cracks in the gelcoat and maybe deeper. I fear that you have a dose of blisters and since you already have ground away a great deal of the bottom gelcoat in some places, you have committed yourself. So, you must treat it like a blister repair job, which means removal of the blistered gelcoat (it is usually done by sand blasting or stripping with a special tool). You can do as you are, though, - a hand grinder. It just takes longer. After that what I consider to be the best choice is Interlux' blister repair system which incorporates multiple levels of an epoxy water barrier called 2000/2000e. Depending on the temp during application, you can apply more than one coat a day and if the temps are in the 70's or higher, even several coats in one day. Interlux also introduced a few seasons back Interprotect HS which is a similar paint where you don't need to apply as many coats as the previous formula (2000e). If you need to fair the hull out to make it consistent and smooth, you also need an epoxy fairing compound. Interlux' compound is called Watertite. Its a two part mix and you spread it on with a flexible spreader. When cured, it can be sanded smooth. Then more application of the epoxy primer and then decide on what you want to finish the hull with. I wouldn't bother with gelcoat. If you want a paint that will inhibit growth (algae, mussels, barnacles, etc.) then you will finish off with an antifouling paint. That's another topic all together as they vary depending if you are in fresh or salt water, want a single season or multi-season, which also has a bearing on if you trailer the boat to different locations and color selection. There is a window between the last application of the Interprotect epoxy system and the first application of the antifouling paint which will mean you won't have to sand between the coats and you will get a chemical bond. If you wait too long, then you will have to sand the epoxy to get a tooth for the antifouling. Confused?

 

[Frogman]

Hello everyone again,

Thank you all for the information you've provided. It has been a bit of an overload but necessary and i appreciate those who have taken the time to explain some of the fundamentals. Some have mention if the cracks went deeper then the first layer. The answer to this is yes. When you look at the sanding ive done you can see the top layer in white and the under layer in a redish color. The cracks had gone through this red layer. The fiberglass itself does not have any such crack in it, aside from some pits that I will fill in. But the cracks were definitely deeper than surface paint level. That is why I went ahead and sanded her down to the fiberglass. My thinking was if i was going to do it then i should try my best to do a solid job of it. It has taken me a substantial amount of time to do the sanding and im happy to say that i am nearly done with it all. All that is left is the port side by the trailers wheel and a bit of the stern. Oh and also under the bunk which she rests on.

Questions:
1. In one of the images ive attached you can see toward the stern above the blue tape line a bit of brown dis colorization. My thinking was the last person to do the bottom didn't realize the boat actually sits a bit lower in the water. Should i sand above the blue tape or leave it as is?
2. This is a trailer boat in freshwater. Would it be less advantageous to apply interlux 2000e with an anti-fouling paint layer versus gelcoat? Id also like to weigh how difficult each are to apply. From what iver read and seen on youtube it seems like gelcoat can be quite difficult to get right.

Thanks all,

 

[madman960]

What did you end up doing? Progress pics? I know the post is kinda old but I just got an 82 Catalina 22 and am looking into exactly this? Thanks

 

[Frogman]

What did you end up doing? Progress pics? I know the post is kinda old but I just got an 82 Catalina 22 and am looking into exactly this? Thanks

Hey there madman. Sorry its been a while since I am on. Unfortunately not much progress on this. I finished taking off all of the gelcoat. When the temperature gets a bit warmer i will most likely apply the interlux 2000 to the bottom.