Forget wax paper and additives
Instead, just buy “Finish Gel Coat” that already contains wax. Here’s one source:
http://www.westmarine.com/gelcoat-repair
It’s one less thing to worry about and it works fine.
Here’s some more fuel for the fire
http://www.roguepaddler.com/gelcoat.htm
All gelcoats are not created equal. Waxpaper is not needed for some types. It depends on whether there is wax in the gelcoat or not. Use a foam “brush” to apply the gelcoat if not spraying. This will reducing the “brush lines”. For me, its always about the temperature and hardener balance so probably expect a few quirks in the attempts but if you can setup a work area that can be environmentally controlled you will probably have better success.
Take a look at Evercoat polyester gel paste for one perspective.
Exactly - NM
Repairing from inside?
Thank you everyone for all the great information on gelcoat and repairs! My 20’ older Necky has a slight leak in tail end and I want to repair it from the inside so I can keep using it until later in the year when I won’t be on the water quite so much and have time then to do the outside repair. Since the yak is very narrow is it possible for me to use something like Flex Seal or Rust-o-leum Leak Seal to just spray down inside for a quick fix? Will these products stick to the fiberglass do you think? (And not add too much weight?)
answering tatoo lenny
You can add a fiber glass patch in the inside really easily. A piece of fiberglass cloth and some epoxy resin. It’s only going to add a couple ounces to the weight of your Kayak and it will only take you about 15 minutes.
I don’t know enough about the products you want to use to stop the leak, but I would expect you would have to remove them when you try to repair it properly in the summer with fiberglass. It’s so easy to patch on the inside with fiberglass and do it right now.
Sealing final gel coat
I went to a local place called plasticworks that specializes in fiberglass and fabrication too. I spent about half an hour talking with the owner and he was super patient and helpful.
I was asking about sealing that final coat of gel coat (the reason I asked about plastic was because I can’t imagine using 21" long strips of wax paper) and he said to just use Future Floor Wax on it. Basically wait till it is hard (cant make a mark with a credit card) and then wipe on the floor wax and it will harden the surface. He said it would be cheaper than buying wax to add to my gel coat.
I decided to buy one quart of white to start with so I could do a bit and then get an idea of how flat it is when I paint it on. How much sanding! The owner looked on the shelf and says, “I don’t have any left, but I have a gallon opened in the back and have used about a 1/4 of it. If you want that I will sell it to you for the price of a quart!” Then he gave me a break on that price and I walked out with about 3 quarts for $35.
So my thinking is we will do the bottom with gel coat and in the process get an idea of the quality of finish we can produce. If it doesn’t require much in the way of sanding I will get pigment and do the top with gel coat too. If gel coat is too much work we will shoot the top with urethane paint. They actually had a bright yellow two part urethane paint that was 75% off because they don’t carry that brand any more. So I may go that way too.
CapeFear inspired gel coat!
So, inspired(shamed?) by Capefear I have set out to at least gel coat the hull. Depending on amount of work we will either gel coat or paint the top. If this goes well I will have to track down capefear and buy him a beer…if not, his name may become a new swear word in my household 
The hull had many many scratches and scrapes in the existing gel coat. We considered filling them then sanding, but instead we put 80 grit on the orbital sander and sanded them out last night. Took a bit over and hour. Only sanded until the scratches were gone…not right through the gelcoat. Looks good so far. Will be filling tiny voids in repair areas and sanding through 400 today to prep for gel coat.
I sure hope it goes well.
I always enjoy a good beer, and I’d hate to become a household cussword.
You’re kind of to the heart of the matter of why I would figure gelcoat. It’s the preparation. You did glasswork, patching up some cracks. You’ve sanded down to a uniform finish, and now probably filling in the leftover deeper scratches. Getting everything set up (work area, tools) and the surface prep and gathering the products is the meat and potatoes of the operation, and it all has to be done no matter what you use. Applying the gelcoat should be the easy part in relation to everything else. One extra final polish and buff of a clean, newly applied coat? You feel like you’re done and just appreciating the new finish by the time you get to that. If it lasts longer before you have to set that all up again, it seems an easy choice.
Thanks for sharing your experience, good or bad.
Gel Coat day.
I have been waiting for the right weather and have been asking a lot of questions. I was talking to a grand parent of one of our Kindergarten students and he was talking about his days as a pit crewman for race cars in the 60s and 70s. Somewhere in there fiber glass repair came up.
He did it a lot of it in his 20+ years with racing. Mike said he would fill the sink with hot tap water and then put his container of gelcoat in a plastic bag and warm it up in the water. Being warm makes the gel coat flow better and you get a smoother finish. You just want to be careful not to add to much hardener and have it set up too fast on you.
The weather looks perfect so I will test his advice today.
How much does it weigh?
I wonder how much gel coat it takes to spray an entire kayak. I understand some manufactures offer boats without gel coat and they are about 10 pounds lighter. So a second coat would make a boat ten pounds heavier and add no strength? I’m very interested in how this turns out because I’ve not seen it donw before.
Weight.
Well a gallon of gel coat is 9 lbs. My first coat for the bottom took 1/2 quart. My plan is to put 3 coats on the entire kayak so it should take me a total of 3 quarts to do the whole thing. So won’t be adding more than 6 3/4lbs. I also have sanded a chunk of the old gel coat off and I will be wet sanding the final coat of gel so the additional weight to the kayak is likely going to be around 4 pounds. The Southwind is around 95 pounds to start with.
I only put one coat on today, but the thing I learned is that I can’t get it flat enough rolling it on to avoid wet sanding when I am done. It is going to need wet sanding to get the nice perfectly level finish I want.
Easy part was mixing a bit of tint in. Doesn’t take much to get to the “off white” color I wanted.
Also, really helps to roll length wise just because of the overlap lines going in the right direction.