Thread: Gelcoat FYI
10-22-2010, 05:55 PM #1
Just got off the phone with my marine fiberglass repairman. he has a helper(a newbie).. The repair guy was spraying a 40 foot boat.. had 1st layer on, all good..
Then the boat needed a second coat. he asked the newbie to clean the BRAND NEW pressure pot their boss just bought.. He cleaned it allright...
When the CUSTOM HANDTINTED gelcoat was ready(remember, gelcoat has only 15 mins before it starts to go off),, they go to spray and the gun on the pressure pot was clogged..
That mean. oh-no... grab the little gun quick!. Ha!. You can't spray a gallon of gelcoat with a little gun in 15 mins
Yep, you guessed it, it clogged that gun too, He managed to get it clean,, Now he has to sand about 15 feet of a 40 ft boat and respray the 120.00/gallon gelcoat.. and TINT IT perfect again(which took over 2 hours).
This is just to show you how hard it can be to spray gelcoat and the stuff that can happen.. the substrate,compressor,lines,gelcoat,hardener,clear coat, boat temps all contribute to how fast it will flash off..
What a PITA! Glad I dont have to sand that..
Goes to show, that EVERYTHING has to be cleaned thoroughly or else trouble WILL ensue.. Just a thought to all you that consider spraying gelcoat on your ski.. paint has a pot-life in the gun, some up to 7 hours and you can still spray it..gelcoat has 15-20mins and your done...
Keep LOTS of acetone around for cleaning!.
I have a horror story too about gelcoat..
02-19-2011, 06:49 AM #2
Ok, heres my tale.. nice hot 85 degree day, sunny, 14 foot boat ready to spray.. fill gun, walk up to boat, start spraying... all is well.
get up to half the boat done spraying then,,,,, the can falls off the bottom of the sprayer. The can hits the ground with a quart of gelcoat, all of it goes straight up in the air like wiley e coyote getting splattered by the road runner...
I'm standing there soaked to the bone from head to toe in curing gelcoat.. omg,,,,,, I could feel it cooking on me in the sun... I ran over and grabbed a gallon of acetone and basically took a shower with it. what a mess..boat,gun,me,everything,,,,,,,,ruined...
bought new gel,new gun,new everything, sanded entire boat again and resprayed it..
02-19-2011, 06:54 AM #3
Dude..... that sucks!!!!
Sorry to hear that story!!!
02-19-2011, 07:02 AM #4
Heres another one....Had boat to spray.. went n bought gel, hardener,ete.....spray boat, looks good... Now if the gel will cure we'll be all set... It never kicked off. the gelcoat was bad from the factory..probably some crap they had in the back sitting there forever... it was a blue that wasnt used very often.. Always buy clear or white because its sold a lot more often than any color will be and tint your own.
I had to sand the entire boat down and spray it again. It didn't even sand out really. it kinda peeled off in places all gooey what a f&*&)*()*) pain in the azz that was.. and I didnt get paid to sand it off either... errrrrrrrrrrrrrrrrrrrr//// Yeah go ahead, spray your boat, tell me how easy it is to do....
Just thought I would share my experiences with it so it doesn't happen to you..
Ask Urogol about sanding his hull down, Fun huh?
If you have your own gelcoat nightmare. I would be interested in hearing about it..
02-19-2011, 07:25 AM #5
Art, this is the boat I was spraying when the can fell off. This is the final paint job on it after the accident.
this boat was a 68,, has a 155 commercial sheriffs engine on it,, engine weighed 440 lbs, ass end was 4 inches from sinking and NO jetski could could beat me out of the hole with it. NOONE. I'd be 3 or 4 boats lengths away from you in 2 or 3 seconds.
It would be the same as a chainsaw pushing a paper plate. I think the prop was about at least 12 inches maybe 14,, big ol blades on it for torque. wouldn't go over 51. but up to that speed, hold on.
The sherriffs boat was a 26 foot boat with 2 of these on the back..Big ol cruiser looking thing. so to push a 400 lb boat instead of a 4500lb boat makes a BIG difference. It was fun while it lasted. I put a hydrofin on the cav plate and that really made it jump out of the water instantly when you hit it.
That hull was only 3/16th think! pretty scary flying over waves! hearing the hull crack as ya land! lol but it was fun as hell. I reglassed the entire boat and foamed it the next year I was so scared . lol used 1/4 inch roven everywhere. Then, someone stole the engine the next fall!.. figures.
This "noone" could beat me thing was back in 2001 so I',m sure it can be beat nowadays, but still, it was fun racing everyone with it. no replacemnet for displacement!
02-19-2011, 09:36 PM #6
02-24-2011, 09:56 PM #7
The first time I tried to do gel coat on my 15f it didnt kick and I found out that MEK (methyl ethyl keytones) will dissolve the uncured stuff and leave the cured gel coat alone. I have to re re spray my 15f because I didnt get the coat thick enough in a few spots and I sanded through trying to get the finish smooth. Any tips for a good even coating without bad orange peel? I reduced it last time and I am thinking about trying it straight this time.
02-25-2011, 08:55 AM #8
well first off, you have to remove all the old gelcoat that u sprayed. if any uncured stuff is on there still, it will happen in those areas again..
I reduce mine with 10% acetone. then apply thin coats. like 5 of them.. even if it orange peels on ya, you can still wetsand it down later on.. I also used a clear flattener on mine on the last couple coats.. no more than 25% or else it wont cure.. you would have to go to a gelcoat place to get the flattener.. its just like gelcoat, but it clear and help smooth everything out..
a warm hull, warm gelcoat and hardener,flattener, the gun,hose,compressor all need to be the same temperature. 65-80degrees is good. low humidity and not in the sun if possible.or a good partly cloudy day will work too..
spray all your tight spots and corners first. get them smooth looking and dont run it.. then go over the rest. you wont be chasing corners then while your spraying. dont spray all the corners and creaves first, just the ones in front of you as your sprayig.. a lot easier that way.
orange peel comes from solids in the material being thick(like new car paint is) and the other way is putting it on too thick each layer. check this out.... light coat will look like dry, slightly gritty and sorta smooth...thats too light,, then the next is perfectly smooth, then a slight orange peel,the heavy orange, then runs.
The idea is to lay the gel smooth each time. even it its really thin, thats ok, just do another coat after it flashes off a for 5 mins... watch how much you put in the gun, remember, it kicks off fast..like in 10-15 mins depending on temperature. 1 pt is good to spray each time..
hopefully you have a water seperator on the tank. that helps keep all the water out of the gelcoat.. I spray gel at 20-35 psi.. any higher and youll be spraying cotton candy out of the gun..
if the gun starts to sputter, the gel is about to kick off completly. clean the gun immediately and discard the gel. better to save the gun that ruin it,, keep lots of acetone around for cleaning everything, take the gun apart and clean the screen inside it and the needle, cap and everything else,, all the holes in the cap should be clear,, use a small copper wire to clean the cap holes with. metal will open them up, copper wont hurt it..
you can even practice laying it smooth on some cardboard first.. Good luck!
02-25-2011, 09:52 AM #9
When you set the gun up to spray do you add the hardner then adjust or do you mix the hardner? I live in houston so the humidity is rarely below 80% is there anything that I need to adjust in the mix? Will I be okay using gel coat with wax or should I use the laminating gel coat and use pva?
02-25-2011, 08:06 PM #10
[QUOTE=smokeysevin;1639541]When you set the gun up to spray do you add the hardner then adjust or do you mix the hardner? I live in houston so the humidity is rarely below 80% is there anything that I need to adjust in the mix? Will I be okay using gel coat with wax or should I use the laminating gel coat and use pva?
no, you add gelcoat first,then color,acetone, then hardener last always.. delete color if its clear or white obviously.
Paint at 11-00am. most of the humidity will burn off by then. nice clear day would be great for less humidity in the air.
I spray regular gelcoat, not the laminating kind. then just spray pva over the job after to help keep the heat in to cure the gel. no more than 20% acetone when thinning it.. more like 10%. thats 10% volume of total mix. so....16 ozs colored or plain white would mean 1.6 ozs is acetone,, subtract that from the 16 = 14.4 ozs gelcoat,,,,,1.6 ozs acetone =16 ozs sprayable material. the hardener is nothing.. 2% by weight.. read the can! to be sure, im not there watching.lol
go lights coats or else you'll run it and it will be a nightmare.. resist the temptation to cover it in 1 coat. 5 mins or so flash time between batches.. mix, spray, clean gun, refill, mix, spray, clean gun,,,untill you have 5 coats on it.., takes about 2 hours. be paitient.. let it flash off or else trouble will ensue. buy a gallon of acteone to clean the gun 6 times. by the fourth coat, it will go on nicely, then your just building thickness at that point. 5 light coats will give abour 3-5 mm's thickness. enough to sand lightly and buff.. never sand the edges. or hit it with a wheel at 3000 rpms on the edges, they will burn instantly.
use a prevail or clean the gun good with acetone before spraying the pva. its basically a plastic that forms on the outside of the gelcoat job. it washes off with water.. dont wash it till the next day.. let it cure all night..the gel will flatten out a little overnight too.
if you thin your last coat with 15% acetone, it will give you a flatter coat. but it will also run easier too. so be careful and practice on your cardboard when you get that far. see how it acts,, just remember, the more flat coats you put on, the easier it will run. cant stress enough, go light coats. good luck! we love pics!
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