Gelcoat or paint?

[dhillis]

Re: Gelcoat or paint?

Bond-o, if you have followed this thread whatsoever, you would find that I decided on gelcoat and wanted more information on it. This is not another typical thread gone wrong, it's indirect answers to direct questions. I never said the experts are wrong either, if you would take the time to read my posts. Even though you have an insane number of posts, it doesn't make you God on this forum and I don't appreciate you cluttering my questions with unnecessary posts/statements.

Dan

 

[Yacht Dr.]

Re: Gelcoat or paint?

Drewpster..that gun is called a "dump gun" and is used for very high volume dump painting..

Basically you would kick your gel .. put it into the cup..tip the gun upwards..pull the air trigger and finally tip the gun over for your spraying.

Kinda like a hopper accept there is no way to control the rate of flow.

As for the spraying of gel..there IS a very short pot life ! So basically get everything ready..and GO.

Have some Acetone on hand to flush your gun every once and a while.

The prep for gel is simple..the sanding/buffing is simple..the SPRAY ( for full spray jobs ) is a little complex and stressful. Use your 2 qt pressure pot that you bought from harbor F. for 30 bucks ( buy the $10 insurance on it incase you kick your gel off in it ) .

Mix about 1.5 qts and go go go..dont put on too heavy ( just enough to make it wet ) around and around..dont stop untill your done. flush a couple of cups of acetone every 2 fillups.

Aye..I do make it sound EZ but Ive done lots and lots of full sprays. Im glad you like a challenge cause until you have the hang of it, it will be but just like anything you have to get used to It. Just like Paint..if you never done it b4..im sure when you get done you will grab a surfboard as you probably ran the crap outa it lol.

YD.

 

[dhillis]

Re: Gelcoat or paint?

YD, can you provide a link to the harbor freight 2qt pressure pot gun. I have checked their website and they have a boat load of guns. I can't find any that specifically state that they are "pressure pot" and I wouldn't know one if I saw it.

Thanks,
Dan

 

[Yacht Dr.]

Re: Gelcoat or paint?

I bought 2 of these on sale for 30-40 bucks..

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=93312

As I dont take chances with my jobs I always have a backup on hand.

BTW..Always flush your new guns with a full pot of Acetone b4 use !

oh yea..one other thing..with a pressure pot you have 2 pressures..one is for the air at the tip..the other is for the pressure in the pot ( your not siphoning..your forcing the paint to the tip ..)

now you have 3 adjustments for how much paint/gel comes out..one at the gun ( the lower backside thumb screw on your gun ) and your main how much pressure you dial the pot up with. norm max is 50psi but you wont go there..your like 10-20 psi on the gage depending on reduction of your gel product . ( paint is like 8-12 ). the 3rd and comes in handy is just how far back you pull that trigger on the gun..

Lets say you come into a tight corner..or relief. Instead of re-adjusting your settings ..just dont pull that trigger all the way. you can do some fine spraying in spots with this technique.

your gonna wanna buy a small air valve that you connect at the base of your "red" or "air" line at the gun ( to quickly adjust air flow for the tip

when you clean your gun turn your air OFF at this valve ( making a solid pee stream of cleaner ( Acetone ) from the tip of your gun. Dont spray your acetone out..let it flush your hose independantly.

Buy it..play with it..know this gun..and you ( i guarantee ) like it.

Ive sprayed a condo with latex paint with this little jewel

YD.

 

[dhillis]

Re: Gelcoat or paint?

Thanks YD, does this gun come with different tip sizes, or is the one provided ideal for most jobs? It sounds like you've done a lot with this gun. I believe I will order it, as I also have to paint the boat trailer. Although I already have two HVLP guns that I have successfully painted with, however, this gelcoat deal is tickin me off!

Dan

 

[Yacht Dr.]

Re: Gelcoat or paint?

Nope..just the one size that comes with the gun..

However you can look at different guns on sale with larger tips and hook that gun up to your pot system. Ive never had to.

The best gun I used was a Binks 2001 gun with a 66 tip. but thats expensive.

HVLP is a pain..it does work..but not as nice as a nice 50psi air breaking the paint up.. ( some peeps swear by them..I have not had mirror finishing from them..but Im old school anyways.. )

YD.

 

[dhillis]

Re: Gelcoat or paint?

Is the gun you recommended from HB a HVLP then? I noticed they have a similar gun for less money than the one you linked me to. It states that it is an HVLP, however, both systems look the same.

Dan

 

[Yacht Dr.]

Re: Gelcoat or paint?

Nope..no HVLP..the link is correct. conventional spray gun m8.

YD.

 

[dhillis]

Re: Gelcoat or paint?

Thanks YD, I hate to keep asking you questions, but will the conventional gun use more gelcoat? I mean, will there be a noticeable difference between material costs with an HVLP or conventional gun?

Thanks,
Dan

 

[Yacht Dr.]

Re: Gelcoat or paint?

ask questions all you want m8

naw..this set up will allow you to spray with not too much overspray.

yea..you will use a little more..but I dont think its gonna be that large of a factor. and you have to remember that laying on gel is a skill..you want as little orange peel as possible..HVLP or conventional..you will lay on the same amount ( yes HVLP may..mebbe help with air pressure blowing some peel on but ive learned how to lay it with my mix )

more orange peel..more abrasives..and thats big bucks in the long run if your not careful.

try both guns if you like..in a test to see your spray pattern. just swap guns ( if your HVLP isnt gravity feed ).

Ill bump my post on my project soon and Ill include pics of my gun and results.

YD.

 

[dhillis]

Re: Gelcoat or paint?

YD, thanks again. I practiced another 1/2qt today and have no orange peel or anything, but... Plain and simple, this gun is not equipped for gelcoat. In order to get a good spray, the pattern is so small that it would take hours and hours of shooting to do the entire hull. No matter what I do to the gun, if I attempt to fan out it splatters like crazy. I guess I did have one victory, and that is the fact that I was able to spray it without surface defects. If only I could do that with a larger pattern. While spraying gelcoat, what would be an example of a good spray pattern? With this gun, my pattern is oval and approximately 3" vertical. Would this improve with a setup like the gun from HB that you suggested?

Thanks,
Dan

 

[Yacht Dr.]

Re: Gelcoat or paint?

yes..your trying to siphon the material...

how are you reducing and catalizing your gel ?

my setup will give you more material yes..

I must Sleep now..will be back tomm.

Yd.

 

[dhillis]

Re: Gelcoat or paint?

I was reducing 25% with acetone, then switched to 5% when I read that I shouldn't reduce too much. I am using 2%MEKP, which was supplied with the gelcoat.

Dan

 

[Yacht Dr.]

Re: Gelcoat or paint?

you cant reduce 5% and spray..wont happen..

Give me your link for risks of reduction pls..

reduction is about 25%. Acetone alone isnt good..ive tried acetone and styrene..or even MEK ( NOT mekp )

Now I use Patch Aid and Acetone. ( sometimes spray PVA over it just in case )

YD.

 

[dhillis]

Re: Gelcoat or paint?

YD, I can't remember the thread that stated too much reducer is bad... I was up late one night reading just about every gelcoat thread there is on the internet. The chemicals I currently have in the stable are acetone, laquer thinner, MEK, and MEKP (which came with the gelcoat). I did some more experimenting today with about 40% acetone and that really thinned it out and made it spray considerably better. I also added more hardener than usual in case the acetone prevented it from curing. I doubt 40% reducer is a good thing, but I wanted to try just to see if my gravity feed could spray anything. I should also note that the gelcoat already came with wax and styrene premixed.

Dan

 

[ondarvr]

Re: Gelcoat or paint?

You won't see a big difference between the HVLP and the old style gun, HVLP will only make a difference if the gun is adjusted correctly and most people don't use it that way, they just adjust it like they always did before.
So you won't use any more or less gel coat with either one.

I've used a bunch of these guns, most work very well for gel coat, I never worried about which type I got. I have a bunch of Binks Model 18s, 7s and 2001s, they can be adjusted to spray paint better and you can get other tips, nozzels and needles to fine tune them, but for one time gel coat use the HB ones work very well.

Gel coat is very temperature sensitive, the viscosty will change dramatically as the temp goes up or down and it's formulated for use at 77F. The colder it gets the thicker it will be and it won't spray or level as well as when it's warmer, so it will be more difficult to get a good job. For spraying, the warmer it is the better, but it will also shorten the gel time, meaning you will have less time to work with. At 77F you will have about a 15 minute gel time in 100 gram (CC) mass, about every fifteen degrees higher or lower you will cut in half or double the gel time accordingly.

In the a larger mass, as in the pot, it will gel faster, so you need to work quick, If you don't think you can spray the entire pot in 7 to 10 minutes, then mix less at a time. Catalyze a 2%, lower and you may not get a good cure, higher and you may run into other problems.

Only thin it as much as needed, too much of anything isn't good, although it will make it spray better.

 

[dhillis]

Re: Gelcoat or paint?

ondarvr, thanks for the info. What would be a maximum % for reducing gelcoat? I had very good luck today with 40%. This is all being done on cardboard, mind you, so who knows what will happen on a prepped gelcoat surface. Which solvent is the "best" for reducing gelcoat?

So far I have been mixing up the gelcoat in 200cc portions. I'm getting a good curing surface (as in no orange peel), however, it seems to be a little tacky after a full 24 hours of curing. I think I need to add more hardener, which I have used sparingly because I don't want it to cure in the gun while I practice. But before I spray the boat I want to make sure I have a good formula that will cure hard and fast.

Thanks again everyone, this is actually becoming quite fun to learn!
Dan

 

[ondarvr]

Re: Gelcoat or paint?

You said that your gel coat had wax in it already, if it does then the surface should be tack free in a few hours if it is catalyzed correctly.

Acetone can and will retard the cure when too much is added, it can also change the color, if you stay at less than 10% it should be OK.
Not all gel coat will cure tack free even with wax added, this goes back to it not being formulated to be used like this. There is no QC testing for backside tack when it's being made, and some batches don't cure as well on the backside others. Plus higher grade gel coats, like what's used in the marine industry, don't cure as tack free as general purpose ones do, so if conditions aren't right the surface can be sticky. If it is tacky, you will need to wash the surface down with acetone so you can sand it without gumming up the paper.

With the gun you have now and with the amount of acetone your adding, you won't be able spray on enough for it to cure well without it sagging or running. You need about 20 mils for it to cure properly and then more so you will be able to sand off the orange peel without going all the way through what you just put on.

The wax will also come out of solution if the gel coat gets cold while it's sitting in the container, so you need to warm it up and stir it very well before use. Another thing that can happen when acetone is used, acetone evaporates very fast and will cool off rapidly, this cooling causes the wax to solidify as it is being sprayed. When this happens you end up with small chunks of wax leaving pits in the surface as you spray.

If you feel there is not enough wax in the gel coat you have, you can always add more (2%).

It's a little misleading when spraying onto cardboard, the cardboard will absorb the solvents rapidly and this may include some of the catalyst.
So you will get less sagging and it may cure differently than when sprayed on a less porous surface.

For thinning, patchaid is what's recommended, but you may not be able to find it easily if there are no fiberglass supply store in your area. So acetone is about your best bet, at less than 10%.

 

[dhillis]

Re: Gelcoat or paint?

Well, I guess I just assumed the gelcoat came with the wax alread in it. The gelcoat is labeled for exterior use and does not indicate in the instructions to add wax. I will call my supplier on Monday and clarify if wax is already in it. I was under the impression that gelcoat labeled "exterior" meant "wax included". If it doesn't, I have been considering a gloss inhibitor (Duratec?) to help thin it out and gloss it up better for less post spray prep.

Dan

 

[ondarvr]

Re: Gelcoat or paint?

Duratec Clear works well to help the gel coat level and cure tack free, but you will lose some water and weather resistance. Like other types of products used to thin gel coat, use as little as possible.