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Go Back   SailNet Community > On Board > Gear & Maintenance > Spraying gelcoat
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Thread: Spraying gelcoat Reply to Thread
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Topic Review (Newest First)
08-04-2012 11:29 PM
j34035
Re: Spraying gelcoat

Do not forget a good respirator. Never spray without one!
DD
08-04-2012 04:47 PM
tommays
Re: Spraying gelcoat


http://multimedia.3m.com/mws/mediawe...y%20System.pdf

3M™ Accuspray™ System. HVLP Primer Gun which runs on about the lowest air possible (a good 3 HP will keep up )

It is a kick-ass product the disposable parts are CHEEP and the PPS cups let you spray solvent in seconds with ZERO mess

The PPS cups come in a bunch of sizes and save you a LARGE fortune in clean up solvent use and disposal


Its still really dangerous once you go beyond the preval sprayer or a small gun like the SATA mini-jet
08-04-2012 02:31 PM
bljones
Re: Spraying gelcoat

Any decent quality air tool will have the cfm req at either 40 psi or 90 psi listed on the box.
08-04-2012 12:26 PM
SloopJonB
Re: Spraying gelcoat

Quote:
Originally Posted by bljones View Post
a compressor or turbine capable of the cfms required at the end of 50-75' of non-kinking hose and a swivel chuck, and a decent air filtering system.
BL, how many CFM do those HVLP guns require? I don't know why, but the CFM requirements of air tools is damned near impossible to obtain. Since it's the air equivalent of wattage or amperage draw on an electrical tool I fail to understand why it is never listed in the specs of air tools.
08-04-2012 12:09 PM
bristol299bob
Re: Spraying gelcoat

Doug, bljones, hello sailor: wow, great advice.

I was hoping that I could do small sections at a time but this does not seem viable. Thanks for averting that disaster :-)

I have some spare car body parts, thats a good call. I will be practicing on those. I'll start with a few preval sprayers and then move up to a proper gun (or two ...)

I'm also going to see what can be done about bringing back the original gel coat a la mainsail 's how-to. I that will work for the vast majority of the deck. If so it leaves just the cockpit to spray, a more manageable piece to bite off.
08-04-2012 11:23 AM
hellosailor
Re: Spraying gelcoat

bob, with "body work" the usual suggestion is to buy a hood from a junkyard, or a door panel, and use that as your practice material. You're looking for a smooth finish, and the wood is rough and porous. Maybe the smooth side of a sheet of masonite would do, or a sheet of formica, but I'd aim for smooth and not porous.

When professionals spray, they use different spray guns for horizontal and vertical surfaces. I think we've got some pros on the forum, maybe they'll chime in about this.

But for a whole deck? Considering the fast kick-off time for gelcoat, the small amount a Preval sprayer holds, the fact that fresh gelcoat isn't going to adhere over fresh gelcoat until that has been de-waxed and cleaned...I'd expect to need professional tools, so you can do the entire job in one operation, one pass from stem to stern. With plans to mix fresh batches as needed, and to anticipate any clogs or other issues.

I couldn't extract a clean URL out of this, but there's a Google link to Valspar's guide to using gelcoat. As bl said...planning. And spares.

[PDF]
Gel Coat Application Guide - Plasticarewww.plasticareinc.com/Merchant2/MSDS.../Gel_Coat_Guide.pdfSimilar
You +1'd this publicly. Undo
File Format: PDF/Adobe Acrobat - Quick View
Gel Coat Application Guide. Page 1. Introduction. Gel coat makes fiberglass reinforced products attractive and practical. Technically, it is a surface coating of ...
08-04-2012 10:06 AM
j34035
Re: Spraying gelcoat

Spare gun is a great bit of advice.
DD
08-03-2012 11:28 PM
bljones
Re: Spraying gelcoat

The toughest part of spraying gelcoat over a complicated surface like the deck and cockpit is planning your spray plan so that you keep a wet edge and don't trap yourself in a corner. Plan your stop points, and when you think you have prepped enough... keep sanding and filling and sanding again.
IMO prevals are great for touchups, frustrating as hell to do large surfaces. If you're going to invest the time and energy in gelcoat, invest the money for a pair of decent HVLP guns (one will get gummed up when you least expect/want it, so a spare is good), a compressor or turbine capable of the cfms required at the end of 50-75' of non-kinking hose and a swivel chuck, and a decent air filtering system.
08-03-2012 11:27 PM
j34035
Re: Spraying gelcoat

Follow Mainsails advice step for step and you will be surprised with what you can do with old gel coat. If you do decide to spray gelcoat, buy a gun unless you are only doing small touch up areas. I have used cheap hvlp guns with good results. Wood is a lousy substrate for practice. Do you have an old piece of glass? That gives a good smooth surface to shoot, and you can wash it off after you are done. Thin your gelcoat and set your gun up shooting gelcoat without the hardener and that allows you time to play. The gelcoat will dry but not harden and will wash off with acetone. I have even shot without the hardener on my boat to see color match and then washed it later. Once you add hardner the clock starts ticking. Work on small pieces before you tackle anything like a deck. Good luck with your project!
DD
08-03-2012 10:25 PM
bristol299bob
Re: Spraying gelcoat

Mast: that's a great write of the process, thanks for the link. It will definitely help

PorFin: Thanks for mentioning MaineSail's excellent how-to. I have seen it but it actually didn't occur to me to try to bring back the original gelcoat on deck. I'll be down at the boat next weekend and take a closer look with an eye towards refinish.

I suspect that most of it will respond well as you suggest. Most of the gelcoat is still quite good. However there are a few areas, particularly in the cockpit, that seem particularly worn. Specifically there are areas that appear to have small pinholes, and these invariably collect dirt and whatnot. I might just do a little hand sanding/compounding in those areas to see if it can come back.
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