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03-02-2018, 11:27 AM
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Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 5,297
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Quote:
Originally Posted by sblack
Just to be a picky PITA, it is not the fiberglass that breaks down, it is the epoxy resin that holds it together. I would use any good 2 part acrylic urethane primer. It is high quality, compatible with any paint, sticks like crazy, cures quickly and it will seal and protect the cowling. Being catalized it will be impervious to most things - thinners etc. They make it high build so you can fill the weave and other imperfections.
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Most 2K high build primers (even urethane) are porous. Base metals and F/G should be coated with an epoxy primer for protection. The purpose of the 2k primer is for filling and flattening, not protection. Standard 2 k primer, once covered with a 2k clear coat will provide protection, but it is the clear coat protecting. The general rule is that if it sands easily it is porous.
Larry
__________________
N64LR - RV-6A / IO-320, Flying as of 8/2015
N11LR - RV-10, Flying as of 12/2019
Last edited by lr172 : 03-02-2018 at 11:36 AM.
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03-02-2018, 11:33 AM
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Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 5,297
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Quote:
Originally Posted by RV10Pilot
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+1
SPI is all that I use. I'm is very high quality and affordable. You won't find better support for amateurs.
__________________
N64LR - RV-6A / IO-320, Flying as of 8/2015
N11LR - RV-10, Flying as of 12/2019
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03-02-2018, 12:47 PM
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Join Date: Aug 2005
Location: Atlanta, GA
Posts: 4,219
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Quote:
Originally Posted by lr172
+1
SPI is all that I use. I'm is very high quality and affordable. You won't find better support for amateurs.
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I have suffered from "Swiss cheese effect" from time to time with SPI's epoxy. There are several references to it in their forum. Effectively, it looks like a mass of fish eyes. Regardless of my efforts to eliminate it through longer induction time and thinner coats, I have not been able to consistently eliminate the problem.
__________________
Kyle Boatright
Marietta, GA
2001 RV-6 N46KB
2019(?) RV-10
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03-02-2018, 01:08 PM
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Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 5,297
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Quote:
Originally Posted by Kyle Boatright
I have suffered from "Swiss cheese effect" from time to time with SPI's epoxy. There are several references to it in their forum. Effectively, it looks like a mass of fish eyes. Regardless of my efforts to eliminate it through longer induction time and thinner coats, I have not been able to consistently eliminate the problem.
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Give Barry a call. He is the owner and the tech support number they give is his cell. He is VERY experienced and will help you through any issues. Tell him Larry from Chicago told you to call. He has helped me immensely. I have experienced this a couple of times (always limited to small areas and never the whole panel sprayed), but fisheyes are almost universally due to contamination (silicone is highest on the list) and will impact most all paints, though some handle it better than others. silicone is viciously invasive stuff and can also get airborne. There is a reason that paint shops work so hard to keep anything with silicone at least 100 yards from their shop. Try walking into a body shop with a bottle of Armor All and see how long it takes for someone to tackle you.
As an experiment, when you get fisheyes, shoot another coat. If they re-appear on the second coat in the same spots it is silicone. The silicone molecules rise to the top of the liquid paint and will affect each subsequent coat. It is insidious this way, as it can't really be covered up. It needs to be removed.
In my experience, the epoxy is most prone to showing the effects of the contamination. I feel this is because it is the first layer to go on the contaminated panel and the silicone is easier to remove from a freshly painted surface, so it is not a common to see it on the next layer.
You need to really work to get silicone off a bare, sanded panel. A few light wipes with wax and grease remover won't get it done. Typically you don't know it is there until the fisheyes show up and therefore don't take the extra effort to remove it, which is why you see it.
Good luck,
Larry
__________________
N64LR - RV-6A / IO-320, Flying as of 8/2015
N11LR - RV-10, Flying as of 12/2019
Last edited by lr172 : 03-02-2018 at 01:30 PM.
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03-02-2018, 02:47 PM
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Join Date: Nov 2012
Location: Launceston, Tasmania, Australia
Posts: 774
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I'm just now painting the interior or my cowl, so this post captured my interest. Whilst I don't deny that silicone may be a beast when it comes to fisheye problems, I for years suffered from fish eye issues when priming (both with water borne and traditional paints), and was told by local paint shops here it was silicone, but that appears to not be the case. The root cause ended up being moisture. The way I resolved this was running the compressor air through 8ft of copper pipe in a 55gal drum of water, then through a generic water trap. So long as the water in this drum is below the ambient temperature, you will pull the moisture out of the air. It is amazingly effective and I have only had fisheyes once since setting it up, and that was because I spent hours spraying that day (primed and painted both wings in a day) and the water heated to a temperature above ambient temperature. I just turned the water on again and cycled some of the water out of the drum, and problem solved. Way cheaper than a fancy desiccant dryer. I hope this helps.
Tom.
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03-03-2018, 06:00 AM
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Join Date: Oct 2005
Location: 08A
Posts: 9,500
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Quote:
Originally Posted by Charles in SC
I have the fiberglass parts about ready to paint.
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For most of us, "ready to paint" is determined by spraying the first coat of primer. That's when surface imperfections suddenly stand out.
I would caution against anything which really needs to be sanded off later. There is always a risk of sanding errors, like thinning an edge, or sanding through, spoiling a careful sealing job. The sander will also tend to put some waves in the surface which will show up later, unless the shop block sands a few coats of primer surfacer after sanding.
Beautiful paint is about prep work. Really finish that cowl up through two coats of epoxy primer. Make it perfect. Later when it gets to the paint shop, they can scrub it with detergent, and lightly wet sand just enough to clean and tooth the epoxy primer. Then they will probably shoot one fresh cross coat of epoxy primer followed wet-on-wet by a urethane primer-surfacer, or maybe go straight to the urethane.
__________________
Dan Horton
RV-8 SS
Barrett IO-390
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03-03-2018, 09:48 AM
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Join Date: Aug 2006
Posts: 703
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Thanks everybody for their input! The local paint store near me also suggested the SPI brand. Has anyone here ever accidentally used this and had the temp go below the 65 degrees called for in their brochure? If so what did you have to do to correct it ?
__________________
RV 7
Last edited by Charles in SC : 03-03-2018 at 09:50 AM.
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03-03-2018, 10:04 AM
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Join Date: Jan 2005
Location: San Antonio, TX
Posts: 1,024
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I agree with DanH.
Make it as good as you can before it goes to the paint shop. They will scuff sand it and spray on their own thin coat of primer to make it ready for the final color coats.
There's no reason why you can't continue to work on it and fly it too. Just work on a piece then put it back on.
I use PPG epoxy primer, as well as their off brand Omni, and typically fly the plane for 18 mos to two years before paint with no problems.
It comes in several colors and you can even tint it.
Used to be, there was no UV protection built into the primers, especially white, but if you ask them now they have fixed that issue quite a few years back.
I haven't had an issue with the two part epoxy primer being porous and soaking in oils but if you are worried about that, you can spray on the final coat as a sealer by mixing reducer in with the epoxy primer mix. Ask your paint supplier and they should be able to give you the mix ratios to do that.
Good luck.
__________________
Steve Formhals
A&P, Tech Counselor & Flight Advisor
RV3B
RV8
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03-03-2018, 10:30 AM
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Join Date: Jan 2005
Location: 57AZ - NW Tucson area
Posts: 10,011
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Quote:
Originally Posted by sf3543
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I haven't had an issue with the two part epoxy primer being porous and soaking in oils but if you are worried about that, you can spray on the final coat as a sealer by mixing reducer in with the epoxy primer mix. Ask your paint supplier and they should be able to give you the mix ratios to do that.
Good luck.
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With the Kirker primer just adding some reducer makes it a "low build" or "sealer" application. You can add up to 20% reducer and I found a 5% to 10% addition made it a bit easier to spray,
No additional reduction is required, though reducing the 1:1 mix may improve sprayability and will decrease the total film build, which is desirable in situations where a sealer is called for.
If your finish after resin sealing is good as previously recommended then you don't need the thicker coat for block sanding.
__________________
Gil Alexander
EAA Technical Counselor, Airframe Mechanic
Half completed RV-10 QB purchased
RV-6A N61GX - finally flying
Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ
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03-03-2018, 10:59 AM
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Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 5,297
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Quote:
Originally Posted by Charles in SC
Thanks everybody for their input! The local paint store near me also suggested the SPI brand. Has anyone here ever accidentally used this and had the temp go below the 65 degrees called for in their brochure? If so what did you have to do to correct it ?
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The SPI epoxy MUST be kept at 60* for about 24 hours or you will likely have it go dormant and the cure can't be restarted (requires stripping the coat off). After 24 hours, it will be fine below 60, just slows down the cure.
If you can't maintain 60* for 24 hours, maybe you can find a different brand that offers accelerators to deal with the cold. Accelerators designed for 2k paints won't help, as it is the epoxy component that is the sensitive one.
Larry
__________________
N64LR - RV-6A / IO-320, Flying as of 8/2015
N11LR - RV-10, Flying as of 12/2019
Last edited by lr172 : 03-03-2018 at 11:03 AM.
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