This is probably the worst gouge I have on the hull. I think I remember doing this last summer as well. In this photo, I'm using FSR cleaner on the hull, with some heavy elbow grease to get it clean.
Soft Scrub is a very, very mild abrasive cleaner, and in my opinion, it beats FSR hands down for getting rid of mean algae stains and the like. You can scrub forever with FSR, but Soft Scrub is like magic, and as near as I can tell, does no harm to the gelcoat.
This is just a close-up of one of the gouges in the boat. You can see that several of these go down to the weave of the glass. I've only been concerning myself with the repair of these, and not worrying about the scuffs and shallow scraping you can see around the main damage here.
This shows two gouges in the hull of the boat that go down to the glass. The gouge in the upper part of the photo has been sanded to help feather the repair into the original work. The gouge in the bottom of the photo has not been sanded.
I started this effort by sanding out the gouge to soften the edges and feather it into the existing coat, roughing up the surrounding area, masking this area off, and by using a plastic spreader, laying a thin coat of polyester gelcoat over the repair area.
On a level surface, a plastic spreader gives you an even coverage you cannot get from brushing. In hindsight, you don't need to concern yourself with this. It might save a little bit of sanding, but I'd prefer to have excess material to ensure a good solid cure.
Removing the masking tape after the material starts to harden leaves clean lines. It's not terribly important to do this since you'll be sanding to knock down these clean lines and feather them, but it does make life a little easier. If you have an uneaven line, you have to be sure not to sand down the original material when you're knocking down the new material. Make sense?
This is the application style I was aiming for, intending to sand this down to level after it fully cured. I've ended up changing my methods of application, which I'll explain later.
Here are two repair areas curing. Because I was doing this in temperatures hovering around 40 degrees F., I mixed the gelcoat with double the recommended catalyst per ounce. Even with this provision, it took a long time to fully cure. Note that in the upper repair area, you can see the gelcoat beginning to shrink into the hole that's being patched. A "hot" mixture of gelcoat & catalyst will cause more shrinkage, though a thin coat and cool temperatures will make even a hot mixture slow in its curing. Furthermore, I think that ideally gelcoat should cure sealed off from air. If you don't put some type of barrier over the wet gelcoat, the top layer will probably never fully cure. After two days, I could still put my fingernail into this upper layer. Using some acetone, I stripped off this soft layer to expose a perfectly hard layer underneath. This application condition is another reason why using excess material can help.
My friend Dale (who built a Pygmy stitch-n-glue in the garage last summer) came by to review the process.
Later that night we started up the firepit. Good times.
I mentioned a new approach to applying gelcoat. The plastic spreader which I had been using on relatively flat sections of the hull is nearly worthless on contoured sections. Further, thin coats will sink into the hole, forcing another coat or two at a later time. In the above photo, I've applied thick goopy coats using an artists brush with no masking. I think that it's important to create relatively clean and consistent lines with the brush, but I've abandoned masking completely. You can see a couple finished areas waiting for their second coat, and those lines are still clear as day. Breaking up the profile of these lines should help them blend.
A lot of sanding is necessary to take down these piles of gelcoat. My recommendation for sandpaper is to knock the pile down with 160G dry, move to 400G wet/dry, then 800 or 1k, followed by rubbing compound. More on that later, but I personally prefer this method of laying high-volume piles of gelcoat on the repair area - you can always sand off the excess. Note the lack of clean lines here. This is harder to clean up since it's hard to avoid sanding original material when running over these spokes of new gelcoat.
Something I've learned about gelcoat - be patient. Patient with the curing, patient with the sanding. Also, the top level of gelcoat will always be a bit soft, and I believe this is because it remains exposed to air. At low temps, it takes a LONG time to fully cure, but once it does, you'll notice that you can still dig a fingernail into the "cured" gelcoat. Take some acetone to wipe off this soft layer and expose the fully cured material beneath for sanding. I should finish this particular repair up today - it was the worst on the boat, and was deep enough to cause that pit in the center of what was an even application. Once this is level, I'll evaluate the need for a second coat.
Sorry, not the best photo here. This is pretty important though - This is my Vaper 11 amp, 7" right-angle Polisher / Sander. Forget using a random orbital sander for finishing work - you need one of these. My variable speed DeWalt ROS has a minimum speed of 7000 RPM. This variable speed Vaper has a maximum speed of 3000 RPM, and has necessary torque! Trust me - you'll spend all day using a ROS to accomplish what a right-angle buffer can do in ten minutes.
Using the 3M Perfect-It foam compounding pad (as seen attached to the buffer in previous photo), I applied 3M Marine Rubbing Compound to the areas I had finished sanding with 1000-grit wet/dry sandpaper. A little bit of time with this and medium pressure, and your new gelcoat will probably get into better shape than the rest of your boat. If you want to get crazy, go to the next step.
Seen here is a 3M Superbuff III 2 Plus 2 Buffing Pad. It's a two-sided pad that worked great for applying 3M Marine Finesse-It II Finishing Material. After you've finished using 3M Marine Rubbing Compound, I'm betting your work will look as good or better than the original work on the hull. Using the Finesse-It finishing compound will produce a beautiful "always wet" gloss. Later this summer I may treat the whole hull to this. Definitely something you'd want to do if prepping a kayak for sale.
In the reflected light on the hull, we're looking at a repair job smoothed out with 3M Rubbing Compound. Pretty decent blending job, and probably the best on the boat right now.
Here we're looking at the first patch I applied to the boat. In this area I used Finesse-It II Finishing Material after the rubbing compound, which produced a gloss that puts the rest of the hull to shame. That white stripe is reflected light.
I like this photo because in the four repair sites in the photo, you can see a progression of lessons. First, if you do a perfect, masked rectangle, be careful of creating a permanent outline of this rectangle when trying to knock down edges. Second, gelcoat shrinks as it cures, and while by the time I patched the job on the far left I had almost eliminated the bad edges of a masked job, the gelcoat has thinned over the glass, but it's still protecting it for the summer.
