Preparing GRP Deck for Painting

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Wandering Star

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Righty Ho, more very basic advice needed please! I’ve just completed the mammoth task of removing all the Treadmaster covering from my 27 footers GRP deck.

There are now a lot of patches of around an inch in circumference (probably 50 or more) where the surface gelcoat is damaged and has flaked off leaving the underlying fibreglass exposed.

So i presume I need to crawl round the deck and fill and fair all the damage. My questions are:

1. Do I need to prime the deck first BEFORE filling and fairing or do I fill & fair prior to priming?

2. Bearing in mind I’ll be painting the deck with a 2 pack epoxy paint system before applying a topcoat of Interdeck, is this product suitable for the filling & fairing

International Watertite Epoxy Filler​


Thanks in anticipation.
 
Thanks for the advice and links to the Inernational Paint guide. I know I’m stupid but. When it comes to priming & filling ……
I gather the primer goes on first followed by the filler? But I don’t need to prime the entire deck at that point do I? I can just prime the small random patches then after I’ve sanded the filler, I prime the whole deck including the filled patches?

We’ll, I warned you I’m stupid but I just need to be clear!
 
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You fill and fair first. If you were to prime first the filler would only be bonded to the primer.
Any flaws in your filler will show through the paint so filling/fairing is the major part of the job.
Car body filler is very similar to fibreglass resin so it's actually a very good match. Some say it can absorb water but ive not come across any problems and thats on 42yr old body filler. Your two pack paint will seal it anyway. Another advatage is you can be sanding it 10 minutes later as opposed to waiting until the next day with other fillers
You could also use fibreglass filler with chopped strands or go with your chosen filler.
 
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Rappey said:
You fill and fair first. If you were to prime first the filler would only be bonded to the primer.
Any flaws in your filler will show through the paint so filling/fairing is the major part of the job.
Car body filler is very similar to fibreglass resin so it's actually a very good match. Some say it can absorb water but ive not come across any problems and thats on 42yr old body filler. Your two pack paint will seal it anyway. Another advatage is you can be sanding it 10 minutes later as opposed to waiting until the next day with other fillers
You could also use fibreglass filler with chopped strands or go with your chosen filler.
Click to expand...
That’s my problem right there! You’re suggesting (and I’m not disagreeing with you) the filling and fairing should be done first before application of the primer paint ? The links to the International Paint “making small repairs” as posted by VicS suggest the areas need to be primed BEfORE filling and fairing. So I’m still confused and don’t want to get it wrong!
 
Wandering Star said:
That’s my problem right there! You’re suggesting (and I’m not disagreeing with you) the filling and fairing should be done first before application of the primer paint ? The links to the International Paint “making small repairs” as posted by VicS suggest the areas need to be primed BEfORE filling and fairing. So I’m still confused and don’t want to get it wrong!
Click to expand...
I thought the Tech data sheet and the Advice document were quite clear which is why I posted the links.

.
 
Well just do not do what a stupid newbie idiot did to a yacht in our club. It was a circa 20 ft boat, that had changed hands in the club several times. A bloke bought it & decided the decks needed painting blue. But he never got to sail it, so sold it to another club member. He immediately took his kids sailing on a nice windy day with lots of spray over the decks. His kids thought it great-- until their dad realised their nice new kit was all blue.
The last bloke had painted the decks in the left over erodable blue antifoul paint, which was now eroding over the kids new kit.
It took the new owner so long to get it off that he not only lost the season sailing, that I think he gave up sailing & he sold it - but no one in the club wanted it, so I have no idea where it went.
Lessons learned.
 
Wandering Star said:
the filling and fairing should be done first before application of the primer paint ?
Click to expand...
Priming before filling grp is something I've not come across before. The only time i would prime first is if the material to be filled is absorbent which in turn could affect the filler. An epoxy primer could be used first but for grp and a polyester filler then i would prefer the filler to be direct to the grp for better bonding.
I googled it and it seems one of those things where some say prime first and some say don't.
 
Sounds like a lot of work that fairing. I usually get in a rabbit hole of multiple goes trying to get it flawless.

When I did a similar job I just sanded off all the moulded non-skid gelcoat areas and two-packed onto the bare fibreglass.
Used a belt sander IIRC, cautiously. Probably used orbital for more intricate bits.
 
Priming something porous like bare timber is a good idea before filling/fairing but I can't see the benefit with grp.
Having said that if you've scraped and hacked off lots of tread etc you may have bits of loose ends and matting exposed in nooks and crannies not obvious to the eye.A flood coat of epoxy to stiffen things up to take the filler might be a good idea in areas hard to get too
 
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