Gelcoat or Flowcoat?

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Plevier

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I need to refinish a scratched area of topsides. The scratches are too deep to polish out but not deep enough to need filler. In some parts I'll be able to brush it just into the scratch, in some I'll probably have to brush overall and then rub the whole area down. Can I use gelcoat or does it need Flowcoat? Does the tacky finish of gelcoat disappear when you wet or dry it?
Thanks for advice.
 
Polyester gelcoat will not cure until air is excluded, which can be done by spraying on a wax (see Boatworks on YouTube for an excellent tutorial). Although mostly it is used as the first coat when building up layers in a mould - in which case the tackiness is desirable for a better bond to the following fibreglass layers.

Polyester flowcoat has wax blended in, which will migrate to the surface and do the air exclusion job for you.

Both are fairly thick, as both as typically used to make a new gelcoat layer in one application, where you want at least 1mm thickness and no sagging during application on vertical surfaces. You'd end up having to sand down a lot after brush application, and it's tricky not to leave brushmarks as well.

Gelcoat filler has a hardener that does not require exclusion of air and you can apply it thinly with a putty knife and then sand/polish back down. It also cures very quickly, so if you don't catch all the scratches the first time you can just put another layer on in 30 minutes. That's what I would do.
 
Just a caution. When I have done these small scratch repairs I have found that the post repair sanding down does a great job on 'deep cleaning' the whole gel coat area which the clean patch can be more offensive looking than the scratch so I then have to partially 'rub down' a larger area to 'blend' the patch in ( or do the whole boat!)
 
Plevier said:
I need to refinish a scratched area of topsides. The scratches are too deep to polish out but not deep enough to need filler. In some parts I'll be able to brush it just into the scratch, in some I'll probably have to brush overall and then rub the whole area down. Can I use gelcoat or does it need Flowcoat? Does the tacky finish of gelcoat disappear when you wet or dry it?
Thanks for advice.
Click to expand...


Any pics?
 
Hi all,

I'm also looking for some advice please. I have a ribcraft and the hull and chimes have a lot of scratches/chips, I want to just completely re gel the hull rather than repair individually, I'm not entirely sure on the stages but I was going to sand the entire hull down, open the cracks on the chimes clean them and fill them with a marine filler then brush white gel coat onto the entire hull leave it to go tacky and the repeat but this time add surface wax to the gel coat.

Would this be strong enough to stay on the hull?

much appreciated if I could get some help thanks.

James.
 
Previous post accidentally deleted. PP gelcoat filler is too white, hull is RAL9003. I have found adhesion of PP a bit suspect too.
 
Plevier said:
Previous post accidentally deleted. PP gelcoat filler is too white, hull is RAL9003. I have found adhesion of PP a bit suspect too.
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Reviewers on Amazon add a little pigment to the filler to get the right colour. One poster mentioned grinding up a little pencil lead to get powdered graphite which toned down the whiteness until they got a perfect match.

Richard
 
I don't understand why you'd mess around with gelcoat and cover it to make it dry, when flowcoat is available. It just does the job, no messing around.
 
Plevier said:
That was my starting question! However now being aware of release film I think that may be the best.
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Why ?

Option 1) Gelcoat : paint on, cover with something to exclude air, hope you didn't miss a bit. Hope it isn't in an awkward place. Hope it peels off cleanly. Whatever, extra stuff to buy and extra steps to take.

Option 2) Flowcoat : this is gelcoat with added wax (or you could buy gelcoat and wax in styrene and mix your own, not sure of any benefit there for small repairs). Paint on, wait for it to dry, job done. It's not like you're using a different material, it's the same stuff with wax added to exclude the air.
 
I have used PP filler on my hull and been very pleased with the results. Next I have a few dings on the coach roof to sort out though the gelcoat here is very much an off white. Has anyone tried (other than using the graphite already mentioned) to tone down the brilliant whiteness of the PP?
 
PaulRainbow said:
Why ?

Option 1) Gelcoat : paint on, cover with something to exclude air, hope you didn't miss a bit. Hope it isn't in an awkward place. Hope it peels off cleanly. Whatever, extra stuff to buy and extra steps to take.

Option 2) Flowcoat : this is gelcoat with added wax (or you could buy gelcoat and wax in styrene and mix your own, not sure of any benefit there for small repairs). Paint on, wait for it to dry, job done. It's not like you're using a different material, it's the same stuff with wax added to exclude the air.
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I would hope with release film greatly to reduce the subsequent rubbing down. Before knowing about that, I was thinking of Flowcoat but wondered if it might be more difficult to apply more on top if needed. I know gelcoat doesn't cure properly on the outside but thought the sticky surface might come off as soon as one started rubbing down.
 
Plevier said:
I would hope with release film greatly to reduce the subsequent rubbing down. Before knowing about that, I was thinking of Flowcoat but wondered if it might be more difficult to apply more on top if needed. I know gelcoat doesn't cure properly on the outside but thought the sticky surface might come off as soon as one started rubbing down.
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If you think you'll need more coats you can rub flowcoat down and recoat. Or, you could buy gelcoat and a tin of wax in styrene. Use gelcoat on all but the last coat, which you add the wax to. If you were to need to repair any minor chips you could use gelcoat mixed with wax and do the job in one hit. Either is pretty thick, so chips can often be touched in with one coat.

Edit : You cannot rub gelcoat down unless it has cured, it would be like trying to rub wet paint down.
 
Noahsdad said:
I have used PP filler on my hull and been very pleased with the results. Next I have a few dings on the coach roof to sort out though the gelcoat here is very much an off white. Has anyone tried (other than using the graphite already mentioned) to tone down the brilliant whiteness of the PP?
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Not all gelcoat/flocoat is bright white. Google a GRP supplier, rather than looking in the chandlery. You can also buy pigments in a multitude of shades, which is what the pro's use.

A reasonably bright white gelcoat/flowcoat and a tin of pigment would be a good choice, as you will find the colour of your GRP will vary in different places around the boat.

You could buy a tin of bright white and a tin of off white and blend the two as needed, which might be easier than using pigments as the pigments are very strong and it's easy to overdo it, and almost impossible to go back.

http://www.ecfibreglasssupplies.co.uk/c-726-polyester-gel-coat-coloured-70-colours-available.aspx
 
PaulRainbow said:
Not all gelcoat/flocoat is bright white. Google a GRP supplier, rather than looking in the chandlery. You can also buy pigments in a multitude of shades, which is what the pro's use.

A reasonably bright white gelcoat/flowcoat and a tin of pigment would be a good choice, as you will find the colour of your GRP will vary in different places around the boat.

You could buy a tin of bright white and a tin of off white and blend the two as needed, which might be easier than using pigments as the pigments are very strong and it's easy to overdo it, and almost impossible to go back.

http://www.ecfibreglasssupplies.co.uk/c-726-polyester-gel-coat-coloured-70-colours-available.aspx
Click to expand...

I only said the Plastic Padding filler is too bright white, ECFS do both gelcoat and Flowcoat in RAL9003. Likely to be closer than anything I can mix.
I see they also sell release film.
 
PaulRainbow said:
Why ?

Option 1) Gelcoat : paint on, cover with something to exclude air, hope you didn't miss a bit. Hope it isn't in an awkward place. Hope it peels off cleanly. Whatever, extra stuff to buy and extra steps to take.

Option 2) Flowcoat : this is gelcoat with added wax (or you could buy gelcoat and wax in styrene and mix your own, not sure of any benefit there for small repairs). Paint on, wait for it to dry, job done. It's not like you're using a different material, it's the same stuff with wax added to exclude the air.
Click to expand...

No sags or runs, to sand off using peel ply, leaves a smooth gel-coat surface ready to polish, without having to get rid of the waxy surface.
 
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