Gelcoating Vertical Surfaces

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STATUE

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I originally thought gelcoating was like painting - wrong I think ?

I have come to the conclusion that you should build up sufficient thickness, not worrying too much about sag etc., and then sand and polish.

Is this correct and has the sanding got to be done by hand or is there a drill/sander device sufficiently tender enough not to take your gelcoat back to the orignal surface.

NB: this is for the 'walls' of a cockpit.

Help please
 
Will be really difficult to get a good finish gelcoating a vertical surface. That is a low wear area and straightforward painting would seem more sensible. Unlike a hull any recoating of areas like decks and cockpits are fraught with problems because of the changes in planes, angles and radii. The only really effective way is to strip all the hardware off and spray it.
 
We watched a Swedish couple re-coating a complete 38 ft boat a few years ago. The hull topsides were gelcoated using rollers, which we were told was a very simple process. They started using the same process with the cockpit but found it too problematic, gave up and used two-pack paint applied by brush instead. Also a skippered charter friend did his large cockpit by spraying in two-pack a couple of years ago. Intensive work but results were good.
 
There's a few differences between painting and gelcoating that cause issue, it's possible as I do it often, but unless it is important to match existing gelcoat I would opt to use paint if I were you.

Gelcoat doesn't self uniform on the surface on its own like paints, so if you were to roller it on, the roller material / type itself would define the finish of that coat. Forget tipping it won't work. A second coat would only build apon the texture of the previous coat.

The issue that is intertwined into the differences between paint and gelcoat is curing, gel needs blocking off to oxygen to fully cure and be sandable, this can be done by covering the coat with a membrane that wont adhere to the gelcoat, or as a wax additive mixed into the gelcoat that then rises to the surface sealing off from oxygen.
Gelcoat (raw) cures tacky and bonds well to the next layer / coat, but this tackyness stops you from sanding down the highs of the previous coat.

As an example of how this is possible would be to roller on a gelcoat layer, allow to tack then spray over with PVA to provide temp seal, once fully cured you can then light sand the highs and add another coat. As you can see this would be the long way round and has a stack of other issues.

There are sanders that work very well, (Mirca are good) but sanding highs down tender enough to a uniform level and recovering the surface is a massive task list I won't get into unless you are set on doing this with gelcoat.

International perfection paint is very good to work with.

Tony
 
STATUE said:
I originally thought gelcoating was like painting - wrong I think ?

I have come to the conclusion that you should build up sufficient thickness, not worrying too much about sag etc., and then sand and polish.

Is this correct and has the sanding got to be done by hand or is there a drill/sander device sufficiently tender enough not to take your gelcoat back to the orignal surface.

NB: this is for the 'walls' of a cockpit.

Help please
Click to expand...

There are a few guys who know how to do this and generally when doing a hull they do lots of very thin coats applied almost continuously (in decent temperatures) to build up the thickness and avoid sagging. The finish is achieved by long boarding by hand, working down through the grades to 1000 or 2000 grit before cutting and polishing. Small areas will require a lot of work by hand with great care to avoid over sanding. You have to be prepared to go back and fill any voids with more gelcoat so you can sand off a high point rather trying to sand down to remove the indentation.

Yoda
 
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