Paint or Gelcoat

[inair]

I did a fiberglass repair job to my swim deck this spring and then applied gel coat to the whole thing. It was a real learning experience. You can find out what every one else says about what you want to do but when you get started you'll find that most of what you saw and read will not work the way you/they thought. What I found is that I could easily sand through all the gel with 80 grit in the places that needed it and then finish with 120. 120 grit seems to be just right (and is recommended) for re-spraying. The things that make gel coat difficult are,

1. Gel coat is made to be sprayed onto a mold and then have the glass laid up on top of it. Which means it has to cure with out oxygen; that is, it can ONLY cure without oxygen. So after you spray on your last coat you must spray on a coat of PVA, polyvinyl alcohol, that will act as a barrier to oxygen and allow the gel to cure. If you spray PVA on too soon after you spray the gel, spraying the PVA on will deform the gel and you will have to sand it off and start over. You can also buy gel coat that has a wax added to it that is supposed to accomplish the same thing but there a lot of discussion as to whether it actually works. (check out all the boat repair forums)

2. Gel coat will not lay down or even out like paint, so you have to put it on thick enough to be able to sand out the orange peel or you will always have orange peel.

3. If you have a big job like a whole boat bottom, you will need a gun that will inject catalyst as it sprays because pot life of the pre catalyzed gel will be too short to get the job done unless you do very small sections. If you do small sections that will increase sanding time and make it more difficult to get an even layer over the whole job.

4. Instructions that are provided with what ever product you buy will be so minimal that you will have to find catalyst rates and cure times/methods from other sources. Even talking to a rep, you will find that they have never done this and may (will?) give you information that is inaccurate or contradictory to other information you already have so doing some experimentation with the product will be critical and will increase the amount of material you need and it's overall cost.

I like finished gel coat. It is beautiful, tough, and resilient. But it was designed to be used in a specific way. Working with it as a repaint or repair is a major PITA. Talking with those who have pained their boats it seems that paint would be much easier. But I don't know. I've never done it. I would also like to see what a painted boat looks like in twenty years? Some of the new paints available are supposed to be really good but without being able to really compare its hard to know.
Good luck!