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Antifouling Paint Has Mottled Finish

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sethp001
Mainsheet C-25 Tech Editor

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814 Posts

Initially Posted - 09/30/2016 : 18:28:21

My VC-17m bottom job never looks silky smooth. I don't think its an application issue because I follow the directions on the can carefully.

A few years ago, I sanded off all of the bottom paint so the hull was bare, and applied a number of coats of Interlux Interprotect 2000E barrier coat paint. The barrier coat was mottled in appearance.

I've applied a couple of coats of VC-17m every other year since then. The final result is always mottled in appearance, like the barrier coat was. If I went to a thicker bottom paint, like VC Offshore, might I get a smoother finish?

Seth
"Outlier" 1987 Catalina 25 SR/SK/Traditional Interior #5541
"Zoo" 1977 Morgan Out Island 30
"Nomad" 1980 Prindle 16
"Lost" 1988 Catalina Capri 14.2 (sold - yay!)
"Marine Tex 1" Unknown Origin POS 8' Fiberglass Dinghy
https://whichsailboat.com/2014/07/27/catalina-25-review/

Steve Milby
Past Commodore

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USA
5851 Posts

Response Posted - 09/30/2016 : 18:57:18

I doubt it. Interprotect leaves a surface like that when applied with a roller. When I did it, I sanded it between coats. I think that's the only way you'll get yours smooth. I never got mine silky smooth, but it was good enough for general purposes, including club racing.

Steve Milby J/24 "Captiva Wind"
previously C&C 35, Cal 25, C25 TR/FK, C22
Past Commodore

OJ
Master Marine Consultant

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USA
4382 Posts

Response Posted - 09/30/2016 : 19:44:47

Looks like stippling left by the roller. I had similar results the first time I applied Interprotect 2000. As Steve explains above, sanding between coats (and even sanding the final coat) will minimize or possibly eliminate stippling.
You might check the paint manufacturers recommendation on roller nap length and even what material the nap should be made from. You should also avoid rolling over the paint once it starts getting tacky, else you end up pulling on the paint, making the stippling even worse.
Good luck and let us know what you end up doing.

1989 C25 TR/WK, #5822
1973 McVay Minuet 19
1975 Jester 12
1981 C25 SR/SK, #2428
1981 C22 SR/SK,
Tanzer 16
Sunfish

"There is nothing, absolutely nothing half so much worth doing as simply messing about in boats." Kenneth Grahame

pastmember
Master Marine Consultant

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2402 Posts

Response Posted - 10/02/2016 : 22:02:41

Mine were always like glass. That looks like bad stirring or "wintered" paint (frozen in the can). I always used the short foam roller, I would never use any roller other than foam.

Frank Hopper

Stinkpotter
Master Marine Consultant

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Djibouti
9013 Posts

Response Posted - 10/03/2016 : 07:11:48

Frank loves to humble the rest of us with his pictures...

Dave Bristle
Association "Port Captain" for Mystic/Stonington CT
PO of 1985 C-25 SR/FK #5032 Passage, USCG "sixpack" (expired),
Now on Eastern 27 $+!nkp*+ Sarge

islander
Master Marine Consultant

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USA
3992 Posts

Response Posted - 10/03/2016 : 13:25:48

Putting the VC over a rough barrier coat isn't going to smooth it out. Sorry to say if you want a smooth finish you will have to sand again. Not all of it but just enough to get the surface smooth then use a foam roller like Frank said to apply the VC......Or you can save all the sanding and just live with it

Scott-"IMPULSE"87'C25/SR/WK/Din.#5688
Sailing out of Glen Cove,L.I Sound

bigelowp
Master Marine Consultant

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USA
1736 Posts

Response Posted - 10/06/2016 : 16:54:45

Looks like rolled with a "house paint" roller vs a thin foam roller. My guess is the quality of the adhesion is fine, just cosmetically not great AND if you race, it could drag more than others. Is it ablative or not?

Peter Bigelow
C-25 TR/FK #2092 Limerick
Rowayton, Ct
Port Captain: Rowayton/Norwalk/Darien CT

Stinkpotter
Master Marine Consultant

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Djibouti
9013 Posts

Response Posted - 10/06/2016 : 21:05:17

quote:
Originally posted by bigelowp
...Is it ablative or not?

VC-17 is a thin-film hard paint. That's the semi-gloss finish you see on Frank's boat.

Dave Bristle
Association "Port Captain" for Mystic/Stonington CT
PO of 1985 C-25 SR/FK #5032 Passage, USCG "sixpack" (expired),
Now on Eastern 27 $+!nkp*+ Sarge

Akenumber
Navigator

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USA
247 Posts

Response Posted - 11/05/2016 : 09:16:41

I have a similar situation from when I did my epoxy job. I blasted the bottom before the epoxy and it seemed to leave little pock marks 3/16 to 1/4 in diameter. It was basically where the outer layer of gell had lost its bond I think maybe where blisters were starting. There was a uniform pattern to it. The epoxy did smooth it out a bit, but it still bothers me as it does cover most of the bottom. My question is how much performance does or could be lost in my or Seth's situation?

Ken
San Diego
84 C25 SR/FK 4116
The KRAKEN

Steve Milby
Past Commodore

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USA
5851 Posts

Response Posted - 11/05/2016 : 10:50:03

quote:
Originally posted by Akenumber

My question is how much performance does or could be lost in my or Seth's situation?

You definitely lose some speed and consequently some pointing. A rough underwater surface causes a turbulent water flow over the bottom, instead of the smooth, laminar flow that is desired, and that constitutes drag. At slow boat speeds, less turbulence is created, but, as the boat speed increases, turbulence increases, and the effect is more pronounced.

Last spring I got rushed to launch my Cal 25, and did a horrible bottom job on it. It was as least as rough as in your photos - worse in some places. In light air, the boat was still very competitive, and won lots of races. In stronger winds, we got killed.

That condition won't hurt much in light air. It will hurt more in stronger winds, but, if you aren't a racer, it might not matter to you very much. It's a matter of your own expectations.