Gelcoat Repair

How to Apply Gelcoat and Make a 47 Year Old Boat Look 'New'

I've been thinking about what to do with my worn out decks for years. High wear areas have also worn smooth the thin layer of gelcoat in the smooth areas. Chips and cracks have become home to a tenacious type of mold that only comes off with a wire brush. Wire brushing is effective but doesn't solve the problem, and allows the growth to return after a few short months.

BEFORE and AFTER
   
Left: High traffic areas in the cockpit showing a bit too much 'love'. Right: New gelcoat on port non-skid, old on starboard.

The debate has always been to paint like most folks (and then re-paint every couple years) or try to gelcoat the worn areas. Gelcoat, despite its polyester base and nasty smell seems like the best choice. Gelcoat with its quick dry time and ability to mix small quantities is perfect for me when I only have a couple hours to work. Only time will tell if it's the right choice.

After much research and internal debate the solutions I've chosen is to purchase and apply the gelcoat using two very different techniques; using waxed gelcoat for the non-skid and unwaxed gelcoat for the smooth parts.

AFTER
   
Using a chip brush a light coat gives a finish that doesn't compromise the non-skid and will (hopefully!) last for another 40 years. Bottom photo shows the purple PVA (polyvinyl alcohol) that is used on the unwaxed gelcoat to create the air barrier to speed up drying. It's applied with the Preval sprayer and removed with a wet rag after the gellcoat has dried, about 3-4 hours.

NON-SKID
The waxed gelcoat allows me to brush on two thin layers without having to tape off any areas. A wire brushing using a wire wheel on a drill removes the dirt and oxidation from the surface. An acetone wipe with a clean white cotton t-shirt removes the dust. A second wire brushing between coats ensures good adhesion and provides excellent opacity and thickness without adversely affecting the grip of the non-skid. Clean up with MEK 5 to 10%. Color: Greystone. Quantity: 5qts.

       

DECK
I first removed the propane locker hatch, cleaned it, and took it down to Fiberlay so they could match the gelcoat color. Because the deck is in pretty good shape, I had them only mix one quart or unwaxed. This should allow me to thin the gelcoat (5% best but no more than 10%) with MEK, and apply 2-3 coats. I can also easily feather between different areas I'm working and patch sections if I need to rebed deck fittings.

Prep by sanding with 80-100 grit sandpaper and wiping with acetone.
Option 1) Apply gelcoat in one Preval sprayer. Then coat with polyvinyl alcohol in a separate Preval sprayer.
Option 2) Brush 90° and then come back another 90° with a fully loaded brush.

MIX
4oz gelcoat to .04oz monomer catalyst (14 drops per ounce)
Thin with methylethylketone (MEK) up to 10%
Use Acetone to clean up

FINISH
Take down the orange peel with 240 grit wet sandpaper.
Wet sand with 800 grit
Buff with 3M 05954
Wax with Collinite Heavy Duty Paste Fleetwax

NOTES
Temp 50deg or warmer ... let dry overnight
Temp 80deg ... will dry much faster
Thinning seems to add to dry time, significantly

MORE ON SANDING PREP
The heavier fast-cut grits (40/80/100) are used to feather sand and ground out a routed area prior to filling. Also, they are used for the first sanding of gouges, dock dings, scratches, and blisters. When sanding areas that have been filled with putty I suggest using 40 or 80 grit sandpaper, depending on how large the repair is. Once the fill area is level or contoured to the desired shape, sand with 100 grit paper to remove the course scratches from 40 or 80 grit. You should also feather the surrounding area of the gelcoat repair with 220/330. At this point, the repair is ready to prep and spray/brush with gel coat. When sanding flat areas use a rubber block.

FIBERLAY
http://www.fiberlay.com
6608 S 211th St #105
Kent, WA 98032
(206) 782-0660

MORE INFO
How to apply gelcoat