Gel coat repair ..should i tackle?

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Ian MacAulay

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Morning all


I have a 1/2m2 area around a sea cock that's suffered some attack via a chemical or such like that has eaten away at the gel coat causing it to go soft.

I'm planning to have the boat lifted over the next month or two to do this job and antifoul too.

I've very hands on person and HV electrical engineer by trade but never touched fibreglass work. am I mad to tackle this job my self or should I get someone in? my understanding from the surveyor is that it needs grinding back to the matting and then a new coat applied in the affected area.

what's peoples thoughts a..am unjust worring over nothing and is there any tips and help on gel coating .. ie is one thick layer needed or multiple thin layers...


all the best


Ian
 
assuming its a fairline targa 43:
I would take the seacock/skin fitting out and check the state of the hull with it out. You can see the state of the fibreglass internals then and check its nothing more sinister. Also you can get at the gel coat under the skin fitting too. Not difficult but they can take a bit of work to free them off.
If it's just damaged gel coat then I would grind the affected area away (carefully) and repair with epoxy filler.

as for repairing it fibreglass is pretty easy - multiple thin coats give the best strength.
 
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I think a half sq metre around a seacock and below the waterline needs a pro to check what is really going on underneath the gel. Grp repairs are not expensive..more likely hundreds ...I'd rather have absolute confidence in that area when out in the rough stuff than start worrying if I really knew the score on my DIY job.
 
gjgm said:
I think a half sq metre around a seacock and below the waterline needs a pro to check what is really going on underneath the gel. Grp repairs are not expensive..more likely hundreds ...I'd rather have absolute confidence in that area when out in the rough stuff than start worrying if I really knew the score on my DIY job.
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Thanks all


so with epoxy primer and filler will I need a topcoat after?

This is what I'm toying with but it had a survey 2 months ago and the thought was by the surveyor was that a industrial cleaner had been put down the toilet and sat round the sea cock causing the gel damage...We believe currently only the gel is damaged and if done shortly will stay as just the gel too.

plus I do like to try and tackle as much as Incan myself to learn too not just save.
gjgm said:
I think a half sq metre around a seacock and below the waterline needs a pro to check what is really going on underneath the gel. Grp repairs are not expensive..more likely hundreds ...I'd rather have absolute confidence in that area when out in the rough stuff than start worrying if I really knew the score on my DIY job.
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Its not quite half a meter either tbh.. but it was suggested that we cut back abit extra to ensure all the faulty gel was taken back... its about 300-400mm patch in diameter


Ian MacAulay said:
Thanks all


so with epoxy primer and filler will I need a topcoat after?

This is what I'm toying with but it had a survey 2 months ago and the thought was by the surveyor was that a industrial cleaner had been put down the toilet and sat round the sea cock causing the gel damage...We believe currently only the gel is damaged and if done shortly will stay as just the gel too.

plus I do like to try and tackle as much as Incan myself to learn too not just save.
Click to expand...
 
it shouldn't be too difficult. take out the skin fitting, grind off the gelcoat well back into the sound areas. Its usually only a few mm thick so go easy with the power tools. Don't dig into the fibreglass itself. The strength of the hull is in the fibreglass, the gel coat is more cosmetic/protective.
I used to have a targa 43 and I cut a new hole in the hull for a forward looking sonar. The fibreglass was 3/4" thick.

Feather the edges and have a look at the fibreglass. It should be rock hard and dry. You can always get a second opinion at this stage if you aren't 100% sure.
Once you are satisfied with the state of the fibreglass (it's a Fairline it will almost certainly be OK), fill back in with epoxy filler. You could use gel coat but epoxy filler is better. Don't try and fill it all in one go, do a few layers. Use a stiff long straight edge to make sure its properly flat. Sand it back nice and flat (depending on the areas shape and size getting that spot on might take a few goes but worth the trouble to produce an invisible repair)
Refit the skin fitting with lots of proper underwater marine sealant. When its all nicely dried out, coat of primer-con then your favourite antifoul. Sorted.
 
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Thank you ...thats a very informative post and also puts my mind at ease.. I've just looked at the two photos from the surveyor and there is two patches given the total amount of area given to me.

I understand the materials needed for gel work but what's needed for fillers and where is best to obtain these. Also so I need a top coat of gelwith added wax to finish?

thanks again

Ian




kashurst said:
it shouldn't be too difficult. take out the skin fitting, grind off the gelcoat well back into the sound areas. Its usually only a few mm thick so go easy with the power tools. Don't dig into the fibreglass itself. The strength of the hull is in the fibreglass, the gel coat is more cosmetic/protective.
I used to have a targa 43 and I cut a new hole in the hull for a forward looking sonar. The fibreglass was 3/4" thick.

Feather the edges and have a look at the fibreglass. It should be rock hard and dry. You can always get a second opinion at this stage if you aren't 100% sure.
Once you are satisfied with the state of the fibreglass (it's a Fairline it will almost certainly be OK), fill back in with epoxy filler. You could use gel coat but epoxy filler is better. Don't try and fill it all in one go, do a few layers. Use a stiff long straight edge to make sure its properly flat. Sand it back nice and flat (depending on the areas shape and size getting that spot on might take a few goes but worth the trouble to produce an invisible repair)
Refit the skin fitting with lots of proper underwater marine sealant. When its all nicely dried out, coat of primer-con then your favourite antifoul. Sorted.
Click to expand...
 
you can get epoxy fillers from most chandlers or online. International do one called vc watertite. Don't use any kind of car filler - it must be for marine underwater applications. It doesn't matter what colour it is either as once its primed and antifouled no one will ever see it again. Make sure you read the instruction properly for mixing ratios and the best temperature range to do the work in. Epoxies don't like being too cold or too hot when you use them so you may have to wait for a weather window.

Apply the filler in layers - don't rush it. If you put it on too thick it will sag. Once it's on and smoothed out don't mess with it. Patience is key.
Don't put anything on top of the filler except primer-con (another international product) to give a good primer surface for the antifoul. Also don't sand the finished surface too fine as you want a good "keyed" surface for the primer etc. @ 300 grade sandpaper should be ok as a finish surface.

Just another thought, it will be worth scraping back the existing anti foul well away from the affected area so you can use the long straight edge against the good gelcoat to get the level finish. (scrape it off don't sand it as its not good to breathe it in)

When a boat is brand new, the first thing that has to be done is sand the underwater surface to remove any traces of wax, grease, mould release agent etc to create a rough surface so the primer will adhere really well to the surface. Other wise the anti foul won't stick properly- so definitely no waxes or polishes on the repaired surface.
 
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Thanks again


looking at hempel high protect epoxy primer and Hempel epoxy filler. Do i need to prime the fibreglass before applying filler?


All the best


Ian

kashurst said:
you can get epoxy fillers from most chandlers or online. International do one called vc watertite. Don't use any kind of car filler - it must be for marine underwater applications. It doesn't matter what colour it is either as once its primed and antifouled no one will ever see it again. Make sure you read the instruction properly for mixing ratios and the best temperature range to do the work in. Epoxies don't like being too cold or too hot when you use them so you may have to wait for a weather window.

Apply the filler in layers - don't rush it. If you put it on too thick it will sag. Once it's on and smoothed out don't mess with it. Patience is key.
Don't put anything on top of the filler except primer-con (another international product) to give a good primer surface for the antifoul. Also don't sand the finished surface too fine as you want a good "keyed" surface for the primer etc. @ 300 grade sandpaper should be ok as a finish surface.

Just another thought, it will be worth scraping back the existing anti foul well away from the affected area so you can use the long straight edge against the good gelcoat to get the level finish. (scrape it off don't sand it as its not good to breathe it in)

When a boat is brand new, the first thing that has to be done is sand the underwater surface to remove any traces of wax, grease, mould release agent etc to create a rough surface so the primer will adhere really well to the surface. Other wise the anti foul won't stick properly- so definitely no waxes or polishes on the repaired surface.
Click to expand...
 
Lots of good advice. One thing to check before epoxying is that the fibreglass is completely dry. Try getting hold of a moisture meter.
 
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