epoxy over gel coat

[seatotaler]

Yes I know there have been a few threads on this sort of topic but I didn't see anything directly related to what I want to do. My aft deck has a few low spots where rain water pools. Two spots about 6 “ x 2 feet along the outer edges, and one about a 2 foot circle, right where my chair sits. The worst one needs to be built up about 3/8” at the deepest spot feathered out to nothing. The others need to be built up about 1/4” . My plan is to ruff up the gel coat with 80 grit and then apply a bonding unthickened coat of epoxy. Followed by layering up fibreglass cloth and more thin coats of epoxy until the areas will shed the rain water. I'll be using West Systems which I've used for over 35 years regularly, so I'm very familiar with it. I've had good success applying it over fibreglass. But I don't know much about the properties of gel coat. My concern is around the outer edges as I'm feathering the epoxy out to nothing. I'm wondering if it will retain a good bond over time. In between coats I'll be ensuring the amine blush is scrubbed off. After the epoxy is cured I plan on putting on a coat of Interlux Interdeck. As everyone knows the secret to getting a good bond with anything is meticulous prep work and no contamination. I don't want to grind down the gel coat until I get to fibreglass. That just seems excessive and I'd still have to deal with the fine feathered area where the epoxy stops and the gelcoat starts. The finish on the aft deck is sort of a dimpled texture. Almost the opposite of anti skid. Lots of tiny potholes so to say. I guess it was the thing in the mid 80's. I'm allergic to fibreglass fumes otherwise I'd use fibreglass resin.

[Wotname]

AFAIK, there isn't an issue with using epoxy over gelcoat providing the gelcoat is well abraded and clean. After all, it is principally just polyester resin.

[GrahamMatthews]

If the core is rotten this would be a waste of time, money and materials.

[paulajayne]

Originally Posted by GrahamMatthews

If the core is rotten this would be a waste of time, money and materials.

How does this equate to the OPs question?

[GrahamMatthews]

Originally Posted by paulajayne

How does this equate to the OPs question?

I have only seen depressions in fiberglass decks that have been caused by a.n alternative problem.
Was that thirty five years experience using West System?
Sounds as though it will be needed.
Epoxy sticks to gel coat if properly prepared.

[valhalla360]

No problem getting it to stick (assuming clean and abraded).

But as mentioned, is it a sign of another issue.

[seatotaler]

There is no other issues. I'm a liveaboard and I don't go out too much so it doesn't make sense to fill the 350 gallon tank with gas, it would just go bad. I'm thinking if the tank was full, the extra weight would be enough to set the stern slightly lower and the water sitting in those 6" x 2 foot low spots would then flow back to the drains. As for the round low spot, it's right over the gas tank. It's a large unsupported area of maybe 1" thick fibreglass. spanning about 4' x4' feet. There is no flex or bounce in it at all when standing on it so trying to wedge something between the top of the tank and bottom of the floor doesn't sound like it would give good results. That distance is about 6 inches between the bottom side of the deck floor and the top of the middle of the gas tank and almost impossible to get at. If I could get a wedge in there, I'm guessing the top of the gas tank would just depress before the floor would raise.
Most boaters using the boat regularly would keep the tank toped up and these low spot were probably never really a concern in the past or even detected possibly.

[Scout 30]

The best practice would be to get a stringer under the unsupported area. I think you are on the right track using epoxy because this area is probably flexing & epoxy will flex with it. I'm a strong believer in the use of a primer before you paint.

[oldjags]

Maybe add some ballast near the stern. But to answer your question, epoxy will bond to gelcoat. Gelcoat will not bond to epoxy, however, so painting the surface once you are done is the best solution.

[coastalexplorer]

Putting Epoxy on a polyester resin boat is pollution. As already stated once epoxy resin is applied the only material that will stick to it is more epoxy, So once the mistake of using it is made. any subsequent adjacent repairs have to be made with it...why not eventually cover to whole boat in the stuff!? How did epoxy get marketed in top head space as the miracle cure for all ills?


Grind back on a reinforced polyester resin boat with a mini grinder using a 36 or 40 grit soft disc.

Shop vacuum clean, keep dry no solvents

lay up more resin and glass fiber,

board sand flat, and apply new gel coat.

job done correctly much less cost for materials. and no future repair problems If an adjacent area subsequently gets Damaged.

[Cadence]

Originally Posted by GrahamMatthews

If the core is rotten this would be a waste of time, money and materials.

You saved me the post. I hope the OP gives it consideration.

[Jim Cate]

As for the round low spot, it's right over the gas tank. It's a large unsupported area of maybe 1" thick fibreglass. spanning about 4' x4' feet.

Are you sure about this? A one inch thick solid glass deck is beyond comprehension on a motor yacht below Russian mafia size. I suspect that if it is really a whole inch thick that it is indeed cored... with something, likely balsa.

It would be helpful if you told us what kind of boat she is... aids us in our efforts to help you.

Jim

[jharding]

sounds to me like it would be a lot easier to just fill up the tank

[MartinAdelaide]

[QUOTE=coastalexplorer;2682724]Putting Epoxy on a polyester resin boat is pollution. As already stated once epoxy resin is applied the only material that will stick to it is more epoxy, So once the mistake of using it is made. any subsequent adjacent repairs have to be made with it...why not eventually cover to whole boat in the stuff!? How did epoxy get marketed in top head space as the miracle cure for all ills?

I'd just use polyester on gelcoat but I'm stunned people still use an epoxy that forms an amine blush.
I've been using blush-free epoxies for over 20 years.

[mawtty]

"Coastalexplorer" got it right