Gelcoat over Epoxy Can it be done Yes or No

[73Chrysler105]

I just read an article by West Systems regarding Epoxy repairs from another thread on here and it made me think. I thought that you can not use Poly on Epoxy and based on that since Gel coat is poly based I would assume the same. Th West Systems Article stated you could gel coat over Epoxy though.

What's everyone's thoughts on this? I especially would like to hear from the experts on here.

This is important to me because I am using epoxy on my boat and am trying to decide whether to do all the outside repairs in poly so I can gel coat the hull back or whether to go another route.

 

[73Chrysler105]

Re: Gelcoat over Epoxy Can it be done Yes or No

here is the link to the West Systems Epoxy repairs
http://westsystem.com/ss/assets/HowTo-Publications/Fiberglass-Boat-Repair-and-Maintenance.pdf

 

[ondarvr]

Re: Gelcoat over Epoxy Can it be done Yes or No

No, it is not a good idea even if WS says it may work

 

[73Chrysler105]

Re: Gelcoat over Epoxy Can it be done Yes or No

That's exactly what I was thinking. Sometimes you have to question propaganda especially when its pushing a certain product.

Glad to have confirmation on it.

 

[andgott]

Re: Gelcoat over Epoxy Can it be done Yes or No

Lots of people do it. I've seen it done, and it CAN work just fine. Google it- You'll find more reading on the subject than you'll ever want to read... It's generally preferable NOT to do it, though- There is a higher chance of failure than using other finishing systems.

 

[oops!]

Re: Gelcoat over Epoxy Can it be done Yes or No

No, it is not a good idea even if WS says it may work

ondarvr is one of the top gellcoat experts in the country.

when he talks I listen

just because other people are doing it....doesnt mean its correct, or it will bond properly.

poly does not bond correctly to epoxy

I strongly advise against it.

use poly on the outside,,,,and you can gellcoat with no worries

 

[73Chrysler105]

Oops I agree would listen to ondavr over evrythng else. That's why I posted this question here in hopes to get confirmation from him, YD and you. I will most likely do the external hull repairs in poly so I can redo the gel coat there.

-- Sent from my Palm Pre using Forums

 

[Yacht Dr.]

Re: Gelcoat over Epoxy Can it be done Yes or No

I just read an article by West Systems regarding Epoxy repairs from another thread on here and it made me think. I thought that you can not use Poly on Epoxy and based on that since Gel coat is poly based I would assume the same. Th West Systems Article stated you could gel coat over Epoxy though.

What's everyone's thoughts on this? I especially would like to hear from the experts on here.

This is important to me because I am using epoxy on my boat and am trying to decide whether to do all the outside repairs in poly so I can gel coat the hull back or whether to go another route.

What is the application ? Why epoxy and not poly or VE ? Pics ?

YD.

 

[73Chrysler105]

YD if you happen to follow my main thread I already bought all the epoxy to do my boat. I know it's overkill but I wanted to make sure iit was solid. Basically I was tryiing to find out now based on what I read whether it was recommended to use the gel coat over the epoxy. My thoughts were still no and ondavr's comments confirmed that for me. I have quite a few repairs to do on or around the keel and will need to regelcoat that whole section.

Basically at this point I am probably going to do the underside/outside repairs with poly and keep the epoxy inside.

The boat is a 74 Chrysler Conqueror SIII 18.5' fiberglass inboard Jet

Chris

-- Sent from my Palm Pre using Forums

 

[Yacht Dr.]

Re: Gelcoat over Epoxy Can it be done Yes or No

Sorry..I missed your thread link.

Your in good hands .

YD.

PS. I would only apply gel over epoxy using a tie coat of Vinylester.

 

[73Chrysler105]

Re: Gelcoat over Epoxy Can it be done Yes or No

YD so what your saying is that if I had enough epoxy to do all my repairs which at this point I don't think I do, then I could possibly use Vinylester as a go between coat from the Epoxy to Gel? What do you think about using the Epoxy straight instead of the Gel coat with a white colorant? Would the Gel Coat hold up better than the Epoxy as a protectant on the bottom of the hull or vice versa or would it be a negligible difference?

Thanks again I appreciate your knowledge and your willingness to share that knowledge

 

[Yacht Dr.]

Re: Gelcoat over Epoxy Can it be done Yes or No

YD so what your saying is that if I had enough epoxy to do all my repairs which at this point I don't think I do, then I could possibly use Vinylester as a go between coat from the Epoxy to Gel?

Yes..I think given the proper procedures and prep this is a viable option. Understand that 'We' ( or at least 'I' ) do not recommend esters over epoxies simply because of the risk involved due to not doing the prep correctly. Nobody wants to recommend a procedure that could potentially fail. However..I will admit the potential of being able to do gel over epoxy is viable and sound correctly applied ( again..following proper procedures and materials .. ).

What do you think about using the Epoxy straight instead of the Gel coat with a white colorant?

If your asking if Epoxy ( I am going to assume you mean the West System products ) can be pigmented and just left alone apposed to using Gel on your last coat ??.. I Honestly do not have a definitive answer for you.

I can say that I have applied 'Epoxy based' bottom coatings that claim to be better then regular poly based bottoms ( basically Epoxy mixed with either colorant and/or copper powder ).

If your specifically asking about West System .. I would suggest you call up there Tech support ( they do have Very good Tech support over the phone ).

Would the Gel Coat hold up better than the Epoxy as a protectant on the bottom of the hull or vice versa or would it be a negligible difference?

As a rule Epoxy will 'hold up better'. I do not know of one Ester based product that claims to be a 'Barrier Coating' per say.

However..again..it depends on the application and situation. Do you NEED Epoxy on the bottom of a row-boat ? Do you Need an epoxy barrier coating on a trailer boat ? Do you Need an Epoxy coating on a 50' Hatteras that sits in salt water ALL of the time .. um yea probably would be a good idea..

Its all about Needs. .. But yes epoxy on the bottom is better then Poly or straight Gel ( apples to apples ).

Thanks again I appreciate your knowledge and your willingness to share that knowledge

Thank you.

YD.

 

[73Chrysler105]

Re: Gelcoat over Epoxy Can it be done Yes or No

YD

I understand the necessity for prep and all things being equal was really the questions asked and answered so thank you for that. On the West Systems no I am not using their stuff. I have done quite a bit of research and some may say too much so that's why I started this thread for that one clarification on using the gel over the top of the epoxy because of the west article when everything else I read said differently. I think if I really needed to use the gel since epoxy will properly bind with poly but not the other way around it would be better to layup gel in a mold and cover with epoxy. But we are in a repair world and that is almost never a possibility.

As I have said before I am probably going to be doing the external repairs with poly and covering with Gel as I am pretty sure my epoxy order won't cover all the repairs I need it for.

Thanks again for sharing your knowledge

 

[ondarvr]

Re: Gelcoat over Epoxy Can it be done Yes or No

True epoxies have poor UV resistance, pigmenting them helps a little, but doesn't come close to most other coatings in UV resistance. Many one part coatings use the name epoxy in them, but it's a very distant relationship and few of the epoxy benefits come with the name.

WS is the only company that recommends, or at least says using gel coat over epoxy, will work OK. I've done testing myself and never found the bond to be good enough for me to be comfortable with. The epoxy was well cured (many months), it was sanded with both 80 and 36 grit paper on grinders then cleaned. The gel coat was applied to the epoxy surface and left to cure for several days. On first inspection it looked good and the bond seemed OK, it was when I started to do the clean up and detail work that the shortcomings were noticed.

What I found was that if the bond was stressed, a chunk of gel coat would pop off easily and the bonded surface of the gel coat was a perfect mirror of the thoroughly sanded epoxy, it worked almost like a mold finish.

I have called WS about this (our companies work together on various projects like this) and they said while it does stick (in their testing), it may not be the best method of doing it.

There is also the variable of formulation, every gel coat and every epoxy is formulated slightly different. So it?s possible that if you were to choose the correct gel coat and epoxy the bond may be much better, but how do you know which products to use.

 

[Yacht Dr.]

Re: Gelcoat over Epoxy Can it be done Yes or No

YD

I understand the necessity for prep and all things being equal was really the questions asked and answered so thank you for that. On the West Systems no I am not using their stuff. I have done quite a bit of research and some may say too much so that's why I started this thread for that one clarification on using the gel over the top of the epoxy because of the west article when everything else I read said differently. I think if I really needed to use the gel since epoxy will properly bind with poly but not the other way around it would be better to layup gel in a mold and cover with epoxy. But we are in a repair world and that is almost never a possibility.

As I have said before I am probably going to be doing the external repairs with poly and covering with Gel as I am pretty sure my epoxy order won't cover all the repairs I need it for.

Thanks again for sharing your knowledge

Then why did you ask ME in the following post ????

YD so what your saying is that if I had enough epoxy to do all my repairs which at this point I don't think I do, then I could possibly use Vinylester as a go between coat from the Epoxy to Gel? What do you think about using the Epoxy straight instead of the Gel coat with a white colorant? Would the Gel Coat hold up better than the Epoxy as a protectant on the bottom of the hull or vice versa or would it be a negligible difference?

Thanks again I appreciate your knowledge and your willingness to share that knowledge

Then what is the point of this post you made Directly asking ME a question about VE,Epoxy and GEL ???

YD.

 

[73Chrysler105]

Re: Gelcoat over Epoxy Can it be done Yes or No

Then why did you ask ME in the following post ????

Then what is the point of this post you made Directly asking ME a question about VE,Epoxy and GEL ???

YD.

Because you brought up the VE which made me rethink it again. Sorry to be confusing. I need to stop reading and thinking cause i'm getting paralysis analysis again. I am sorry if it upset you I thought I had made up my mind until I saw your post but still think I am going to go the route I had made my mind up to go as I was thinking/typing through it. I think this thread has had its day and we can close it out question answered.

 

[73Chrysler105]

Re: Gelcoat over Epoxy Can it be done Yes or No

YD BTW I respect your opinion as much as ondavr and wanted to hear your view on it so I really appreciate your response. Sometimes I know I come out sounding unappreciative or rude so if I offended you again I apologize.

Thank you
Chris

 

[73Chrysler105]

Re: Gelcoat over Epoxy Can it be done Yes or No

True epoxies have poor UV resistance, pigmenting them helps a little, but doesn't come close to most other coatings in UV resistance. Many one part coatings use the name epoxy in them, but it's a very distant relationship and few of the epoxy benefits come with the name.

WS is the only company that recommends, or at least says using gel coat over epoxy, will work OK. I've done testing myself and never found the bond to be good enough for me to be comfortable with. The epoxy was well cured (many months), it was sanded with both 80 and 36 grit paper on grinders then cleaned. The gel coat was applied to the epoxy surface and left to cure for several days. On first inspection it looked good and the bond seemed OK, it was when I started to do the clean up and detail work that the shortcomings were noticed.

What I found was that if the bond was stressed, a chunk of gel coat would pop off easily and the bonded surface of the gel coat was a perfect mirror of the thoroughly sanded epoxy, it worked almost like a mold finish.

I have called WS about this (our companies work together on various projects like this) and they said while it does stick (in their testing), it may not be the best method of doing it.

There is also the variable of formulation, every gel coat and every epoxy is formulated slightly different. So it’s possible that if you were to choose the correct gel coat and epoxy the bond may be much better, but how do you know which products to use.

Ondavr Thanks for the clarification and the personal experience I think that goes a long way to helping people understand the reasoning. It's good to hear that even West says that it's not the best scenario puts me again to where I will be using poly on the exterior repairs and epoxy on the interior. The epoxy I have from aeromarine is supposed to be UV resistant since it can also be used on bar tops and other items like pebbled walkways but it does say should not be out in direct sunlight.

Again thank you everyone I believe the responses of clearly answered the question and we can put this to rest.

 

[73Chrysler105]

Re: Gelcoat over Epoxy Can it be done Yes or No

There is also the variable of formulation, every gel coat and every epoxy is formulated slightly different. So it’s possible that if you were to choose the correct gel coat and epoxy the bond may be much better, but how do you know which products to use.

I think the answer to that question is just to make samples of every type of combination and try them. I for one don't have the time or funds to do that so I will stick with just not trying it.

Chris