06 May Renewing Chalky Gelcoat
A few weeks ago, I wrote about the easiest way I’d found to clean non-skid decks. And I said something about our gelcoat being really chalky in general (it’s a common problem in older Gemini catamarans . . . well, in older fiberglass boats in general).
Tami Shelton, a reader who has become a friend, asked if I’d like to know how she got great results in renewing the gelcoat on their Catana catamaran. Of course I did! And several other readers left comments to that effect, too.
A year and a half ago, when our boat was on the hard, I worked to polish up the sides of the hulls on Barefoot Gal. But the results really weren’t as nice as I would have liked them to be . . . and and I still have a lot of the cockpit and deck to do. I’d love to know how to get Barefoot Gal looking good without having to paint her!
The total cost of the project, including buying the tools, is about $400 (plus your labor) – and you’ll have the tools for the next time you need to polish the boat (hopefully you won’t have to de-oxidize!) as well as most of the supplies. That’s an awful lot less than the cost of painting your boat.
Here’s Tami’s description of the process (all links are to Amazon):
The Story, including the Shameless Plug for Donnie . . . Mr Donnie Brennan, who is the Olympic boatwright and proprietor of Diversified Marine, Mobile Alabama, gave me an invaluable lesson in gelcoat polishing.
Buy good tools. A high-quality buffer-polisher is essential. I blew the dosh on a Makita 9237CX3 7-Inch Variable Speed Polisher-Sander with Polishing Kit and a couple additional WOOL high quality polishing pads for the polisher.
The compound of choice is 3M High Gloss Gelcoat Compound. I bought a gallon container, which is probably enough to do 20 of my boat’s hulls (40′ Catana) but I don’t think there is a smaller container available. Split the cost with friends?
So, the technique is… first, wash the boat.
Second: to quote Donnie, “if you want to bring your oxidised gelcoat back 100%, you’ll have to start with wet sanding.” I didn’t do that, but that was Donnie’s advice. I was pleased with my result without sanding – if you want best results, wet sand.’
After washing, I wiped the boat with oxalic acid hull cleaner and then rinsed again. If you’re doing this on the hard, do be sure to protect your bottom paint from the oxalic acid. (Carolyn’s note: The oxalic acid will remove a lot of stains. I’m not sure which brand Tami used, but the one I’m familiar with is Sudbury Hull Cleaner.)
Next, pick an area to start, about 2×2 feet at a time. Take a chip brush/paintbrush, and dip a bit of the compound out of the can onto the brush and dab that on five or six spots across the area you’ve chosen to work. Hold the buffer with the pad up against the work, and start the pad at a low speed. Work the compound around a bit, and then increase the buffer speed up to the recommended speed that 3M lists on the can (1500 – 2500 RPM).
[SAFETY NOTE from Carolyn: Watch out for the cord on the buffer! Hold the buffer so the cord doesn’t go “around” the buffer. The boater next to us in the yard tore the cord apart (luckily didn’t cause a fire) as his cord tangled in the buffer pad while it was on. There’s a lot of torque in the buffer and it’s easy for it to walk if you’re not gripping it tightly.]
As the compound begins to dry out on the pad, you want to stop and clean your pad. FREQUENTLY. Take a paint stir-stick, hold a corner of the stick onto the pad center and run the buffer at high speed, moving the stick from center outward rather like a vinyl record needle type movement. This will knock the dried-out compound and the oxidized gelcoat off the pad, and fluff the pad up. Then go back to the area you were just working and polish it again with your newly cleaned pad. Now, you’ll really start to see the area shine as you work the buffer around.
It takes some fiddling. Start out with lighter pressure and then increase as you get a feel for how the compound is cutting the oxidization. Don’t be afraid of it, but do start out gently.
After you’ve done three or four 2-foot square areas, you’ll note that your pad doesn’t clean as well with your stick, so then you need to change to another pad. Alternatively, clean your pad with a good rinse in a bucket with lots of fresh water. Put the wet pad back on the buffer and turn it to high speed and that’ll sling the water out and dry the pad pretty quickly. [Another note from Carolyn: think where the water will be flung and go to a place where you won’t spray people or the area you’re working on. Yeah. You know what I did the first time I dried a polishing bonnet.]
One of the keys that I found to doing this is to keep a clean pad. If the pad is gumming up, clean it or switch.
Using the best tool makes this job go far more quickly. The high-quality polisher ain’t like your old car buffer, a good tool makes light work.
Once your compounding is completed, be sure to finish it off with a high quality wax to protect your new finish. I like the Star Brite PTFE Marine Polish, myself. Re-wax every 6 months to a year.
Tami didn’t get photos of the rejuvenating as they were doing it, but did have these before and after pictures. Note the dull yellow color in the “before” shot and the glossy reflections in the “after”!
Carolyn again: Armed with these tips, I’m actually looking forward to working on our cockpit! I know from past experience that buffing is hard on the neck and shoulders but I’m happy to put up with it for a shine like that!
Our cockpit has a bunch of small strips of smooth gelcoat between nonskid as well as a few just plain small areas where a full sized buffer won’t fit. I have small 3” buffing pads that go on our cordless drill (I used these when rejuvenating our windows). If you have small areas, you may want some of these (make sure they’ll fit your drill).