tips on spraying gelcoat?

[H2Only]

I'm doing a repair/resto job on an older ,small whaler and would appreciate any tips/tricks for spraying gelcoat. Also have considered painting it, but would like to stay original if possible. i have access to a spray booth and all equipment.
thanks, paul

[jimslade]

spraying gel properly is difficult at best. if its a small repair brush on and sand and polish. If your set on spraying, thin the gel with duratec or 10 percent styrene. Practice on a sample piece first and dont forget to clean the gun before the gel kicks.

[gonzo]

I use Duratec exclusively. It gives a very shiny and even finish.

[marshmat]

Duratec's nice, if you're good with it. I generally prefer a good polyurethane paint, but if you're good with the sprayer then a good gelcoat is also good. Practice on scrap panels first, to find the right thinning ratios. Remember that all gelcoats are extremely sensitive to catalyst ratio and good mixing.

[Guy G]

The moment you put paint on your boat, you will be always doing repairs. Gelcoat is always best if you don't mind wet sanding. The guys are right about using Duratec. But I found that thinning it with laquer thinner works better that styrene. Best thing you can do is try each thing and find the one easiest for you. It doesn't take much for practice. What you want to keep down is your orange peel when your practicing and getting the best build up of material. Best wishes!

[fiberglass jack]

first sand the area u want to spray with 80 grit gelcoat needs this to stick,then feather out with 120 then 180 and finish with 320 about 1 to 2 inches with each a trick the pros will not tell u. then wet sand a good 4 to 6 inchesaround the 320 with 800 this will remove the wax and shine and will help to blend in easier.before spraying wipe and clean the sanded areas with styrene this will give a chemical bond and help blend in,do this 20 minutes before u spray the styrne will soften the old gel coat,once u have ur gelcoat color matched and happy with it add 2% mepk catalist stir well for a minute then add 1 part acetone to thin it dont use styrine if u use styrine it will discolor after a season u dont need any fancy spray gun get a prevail its a disposable spray bomb with a glass jar u put the catalisted and thin gel in the jar srew the aerosol contaner and bobs ur uncle,have a peice of cardboard say 1 foot square hold this beside what u want to spray start the spray on the card and pass on to the repair area spay a little wait and let the acetone to gas off about 15 20 seconds then do it again say up to 10 time or so to u get a nice look dont be scared if u have a run or 2 this will sand out in worse case wipe clean and do again,after u have sprayed and see a pin hole or 2 talr a toothpick and drop a little gel gently into the hole this will clean up during sanding,after its all dried sand with 320 then 600 800 1000 and polish u may need to sand a litlle more and polish again let me tell u it takes alot of experamce to gel repair so have fun

[fiberglass jack]

make sure the gelcoat has wax in it if not add 2 to 3 % airdry wax to the gel before u add hardner

[makeitfly]

Originally Posted by marshmat

Duratec's nice, if you're good with it. I generally prefer a good polyurethane paint, but if you're good with the sprayer then a good gelcoat is also good. Practice on scrap panels first, to find the right thinning ratios. Remember that all gelcoats are extremely sensitive to catalyst ratio and good mixing.

Not only sensitve to catalyst ratio but also the types of thinners used as well , it can change the colour and the eventual hardness .
Me i use pure clean acetone and blow it gently with air to evaporate it away after each pass of the gun .
Styrene wax needs to be used as well to seal the air off the surface so it will dry right to the surface and you can sand and polish it
Humididty is another factor overlooked by a lot of people and they wonder why it didnt work as good as last time .

[fiberglass jack]

gelcoat takes a lot of practice and will be different every time.weather temp amount of hardner can change the end result . even the air presure on the gun can change the end color so csn wax and duratec. i sometimes spray gelcoat neat just with acetone to thin, then spray a coat of pva just after the gelcoat is on the verg of geling to block out the air this is a trick thats not well knowen and it works very good

[makeitfly]

Gel coating is a very fickle process . Using the same gel out of the same container , the same catalyst and all should be the same colour but 99.99% of times it is a shade or two differant in colour or texture or shine . If its a repair sometimes a whole panel has to be painted to the corners or edges to loose the differance after sanding and polishing . Dark colours are the worse ,the lighter the colour the easyer to match the repair colour closely .

[War Whoop]

Gonzo nailed it!!

[zerogara]

Originally Posted by fiberglass jack

make sure the gelcoat has wax in it if not add 2 to 3 % airdry wax to the gel before u add hardner

If wax is not used the gel coat might never fully cure and stay tacky. But if it is covered by a few layers of PVA and let cure in higher than ambient temperatures it cures and hardens.

I've always felt there is a risk involved with delamination when using wax in resin or gelcoats so I avoid it. But I never use gel coat externally.

KoZ