Gel coat repair

[talbot]

I have been trying to ignore the osmotic blisters in my gel coat for three years. After some half-hearted repairs, I have finally taken the plunge to flip the boat over, and am beginning the process of opening up the blems and sealing the hull.
At the point I started, the boat was just the original 40-year-old gel coat, with Interlux VC17 painted over the borrom and Interlux racing epoxy over the boot stripe.
Questions:
--What have people used for sealing their old hulls after sanding? West Marine says it should be a low-viscosity epoxy, but they only sell one (very expensive) product, from Interlux.
--What have people used for the main barrier layer? I gather this is a viscous epoxy, different from the sealer.
--I'm confused about paint. There is antifouling bottom paint, and there is "topside" paint. Is "topside" paint what you put on the hull above the bootstripe, or is it just for the superstructure? Suppose you wanted to paint the entire hull, above and below the waterline, with one paint that was -not- antifouling. What would you use? (Looking at the West Marine catalog, the only thing they sell is that Interlux racing epoxy. But it's not recommended for boats kept in the water. That's for sure. I have it on my bootstrip, centerboard, and rudder, and all have the same gel-coat issues as the bottom.)
--Back to using differing paints above/below waterline: How do you handle the transition from topside (or freeboard) to bottom paint? I get some gel coat blisters right at the margin. Do you overlap? If not, do you put the bootstripe across the transition? And if so, what do you use for the bootstripe?

Sorry for the long post. Any advice you can offer would be appreciated.

[GreenLake]

I've used the various products from SystemThree, they have various Epoxies with different degrees of viscosity. Their ClearCoat is probably the best combination of low viscosity for application but enough build. But their SilverTip laminating epoxy also works fine, but I've found that I prefer to apply the latter with a squeegee. That way I get a nice thin layer with just a few ridges between strokes that can be sanded off. (Brush marks wouldn't level).

Some (most?) topside paints are not intended to be immersed constantly. They are fine for the upper hull, even where it gets splashed.

[talbot]

So what do you use for the bottom paint, and what do you use on the upper hull between the water and the rub rail?

[GreenLake]

I sail my boat "dry" so I used SystemThree WR LPU (water reducible linear polyurethane) for the entire hull (I have plans to do the deck as well, but keep running out of time).

No fumes, roll and tip application, very hard and smooth. Does like an epoxy primer or pare epoxy - I have seen it lift off other primers. Cannot be immersed for more than 48 or 72h forgot which. About 15h is the longest I've been on a daysail, so that's fine for me.

If the bottom stripe was at the real water line when the boat is at the mooring, then you could use something like that between the stripe and the rail, no problem. For the stripe you'd use something that can be immersed and below that, you use whatever bottom paint works for your condition (lake etc.) where you moor the boat.

[talbot]

Thanks. My boat lives in the water (fresh) from April-September, so I need to know about immersible paints.

[GreenLake]

Thanks. My boat lives in the water (fresh) from April-September, so I need to know about immersible paints.

Right, from the waterline down.