Gelcoat or 2 PAC Paint

[EdBerg]

Just for clarification seeing as this has been going round and round, Flowcoat is basically Gelcoat with a styrene solution with 2% wax added to it and you add it to gelcoat at 20ml per kilo of Gelcoat or resin) you then have flowcoat or waxed resin but there are some small differences between the two though. Flowcoat doesn't self level as much as Gelcoat, it probably has more thixotropic (gelling agent) in it. The added 2% wax in the styrene floats to the surface and forms a film which prevents moisture from reaching the contact surface so it stops it from being sticky exactly the same as if it was touching the inside surface of a mold.

Now if you want to go over the Flowcoat then you need to remove the wax by abrasion before you can add any more flowcoat or resin/laminate to it. Using acetone helps but it will primarily just smear the wax around so I don't recommend it, use abrasive material as it will gives a better bond (mechanical as well as chemical), the wax forms a thin film which has to be removed.

Yes you can add Gelcoat over Gelcoat, when ever we applied Gelcoat by hand in molds we did a second coat to make sure we got rid of any thin sections and to get rid of any thin brush marks but we did it as soon as possible after the first coat had cured so that it would give a better chemical bond to the first coat. Now if you are going to go over any waxed surface such as a waxed laminate you need to sand it flat as possible to get rid of any wax film, so as the laminate or flowcoat has little dips and valleys you need to sand down to the bottoms, other wise the new coating/laminate will just stick to the peaks and hills but cannot stick to the bottom of them because of the wax coating there which wasn't removed, so if the laminate flexes a bit it may eventually let go because of the areas that weren't bonded properly.

I have repaired many boats where someone didn't know what they were doing and just applied a laminate or gelcoat/flowcoat over an unprepared surface and you can just put a chisel/spatula between the two layers and just pry off sheets without too much effort. Preparation is key! If you are doing a repair using Gelcoat you can go over it with a second coat of Gelcoat to fill in the low spots but afterwards add a coating of flowcoat, Otherwise sanding down the high spots on unwaxed Gelcoat will take 5 times as long, because the sticky unwaxed Gelcoat will clog up the sandpaper very quickly and and having three coats will mean a lot more sanding as you now have more coats on the highs spots as well. Just my 2 cents worth!

[Getout]

Very good explanation Ed!

[Cox76y]

Hi Ed,
My thoughts were that Gazza was referring to adding the gel coat to a damaged hull.. Also, we apply numerous coats of flow coat as long as the first coat has not completely gone off. Just like you apply the gel coat. As long as the flow coat is still tacky then your good to go.. No sanding between coats unless it's completely cured.. I understand others may do it differently tho..

Just to throw another spanner in the works. I spoke to 2 laminators at work today. 1 prefers to use gelcoat when re spraying the outside of the hull and the other prefers to use flowcoat. It appears there are work arounds for using either and it is a little up to personal preference. The laminator that prefers to use the gelcoat, adds wax n styrene to the mix. The laminator that prefers to spray with flowcoat adds more styrene only as it thins it out. Both have been in the game for years. The flowcoat we use is quite thick and is meant to be either rolled or brushed on so by adding styrene it thins it out so it can be sprayed. It is apparently more succeptable to runs than the gelcoat though.

[Dirtyfuzz]

Gelcoat everytime! Paint is easier to apply but will chip and probably need repainting again in 10 years time! The gel coat probably just needs a bit of tlc, If it was my boat I would give it a a clean with acid wash then maybe wet sand a test spot with 800 sand paper on an orbital sander get some black faring powder to show the scratches then a heavy cut and polish if still not happy with the finish then re gelcoat the lot!