What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Pin holes?

bret

Well Known Member
When I did the pants and gear fairings I had some pinholes and now working on the cowl, ( Sam James ) I would like to not have any, so I did the epoxy spread and then a thin guide coat of black to spot the lows, doing the sanding of the spray paint consumed large quantities of sand paper, clogging, wet sanding helped, but after I got the guide coat off I was back to dry sanding. two weeks of sanding and it looks pretty good, but, how do you know if there are any pinholes without painting it? with the pants it looked all good until they got paint and then the pin holes magically appeared. The color will be black so it has got to be perfect......tips, tricks, black magic advice greatly appreciated, Thanks ;-)
 
Bret,
My process, clean the parts throughly blow them off, then apply a couple of thinned coat of "High Build epoxy primer" available in different colors, I like gray. the pin holes will then be quite apparent.
Dick
 
When I did the pants and gear fairings I had some pinholes and now working on the cowl, ( Sam James ) I would like to not have any, so I did the epoxy spread and then a thin guide coat of black to spot the lows, doing the sanding of the spray paint consumed large quantities of sand paper, clogging, wet sanding helped, but after I got the guide coat off I was back to dry sanding. two weeks of sanding and it looks pretty good, but, how do you know if there are any pinholes without painting it? with the pants it looked all good until they got paint and then the pin holes magically appeared. The color will be black so it has got to be perfect......tips, tricks, black magic advice greatly appreciated, Thanks ;-)

A cured epoxy skim coat doesn't clog paper, or certainly not enough to require wet sanding. I detect epoxy thinning?

If you sanded through the epoxy shell, you did it wrong. Doesn't matter what kind of sealer coat you use; if you break back through into the underlying glass, you'll probably open some new pinholes. Your goal here is to merely remove the squeegee, brush, or roller marks, leaving a skim coat of epoxy a few thousandths thick.

http://www.vansairforce.com/community/showpost.php?p=474996&postcount=11

In the end, the only way to know if you did a good job is to shoot the primer.

http://www.vansairforce.com/community/showpost.php?p=508983&postcount=22

A "guide coat", if used at all, is a last step before finish painting, after the sealing, epoxy primer, and high-build primer. It's rarely necessary in a shop with good lighting, as any real waviness or low spot is easily seen in low angle viewing. If used, a guide coat is a very light fog, just enough to dust the surface, using a contrasting primer, not a paint. Again, nothing about this should clog paper.

A better variation is to shoot an epoxy primer that contrasts with the high-build primer color. I use dark gray DPLF to contrast with K36's light gray, and when I block sand for flatness, the underlying dark primer shows clearly when the K36 gets thin on a high spot.
 
IMO, I think it best to finish smoothing before the skim coat of epoxy. Shoot a hi build primer that's easy to sand and sand as many times as needed to remove low spots. If the primer is grey and the cowl is white, you can easily see the low spots every time you sand. This also gives you the opportunity to fix those little imperfections you find along they way with a more aggressive filler if needed. When you are satisfied with smoothness and all the imperfections, then do the epoxy skim coats. Wet sand the skim coats to remove the brush marks. Then shoot primer and look for leftover pinholes. I used grey SS Eko prime for all of this and those pinholes popped right out and are easy to see. Fill the pinholes and I know its been debated on this forum but I used Bondo Professional Two part glazing putty (Auto Zone) on those last scattered pinholes as advised by Dan at Stewart Systems. Mix a dab and smear it in the pinhole and after 30 min sand it smooth and re prime the spot. It's a lot of work and very time consuming!

You may need to start over and get the low spots filled, then do another skim coat of epoxy.

I'm just sharing what I've learned, I've only painted 1 plane and its got plenty of imperfections!
 
Thanks guys, no, it was the spray can black paint that was clogging the paper, the west epoxy is good to go, man I was afraid you were going to say don't sand through the epoxy GRRRRRRRRRRRRRRRR! this is so much work, and so frustrating.........OK, back to square one......ill shoot some good primer on it and see where I am at. has anyone just painted the James cowl with not doing any of this, It looked pretty good out of the box, I hope I didn't go backwards with all this work.
 
Don't use "spray can black paint". It will clog your sandpaper. The easiest and fastest and best sanding is Duplicolor PROFESSIONAL lacquer primer. It comes in gray and black. The black is the world's easiest sanding primer. Duplicolor makes another version that doesn't say professional on the label. It's not near as good. The lacquer will not fight with subsequent coats of epoxy, poly, or even enamel.
 
Take epoxy primer, applying multiple layers of spray gun to clog the pores of the fiberglass, and then sand papers of not more than No. 240 with some water bars on the display surface. Maxim.
 
i used sheet rock mud! sands in seconds! primed/painted. that was 3 yrs ago and the still look great!
 
i used sheet rock mud! sands in seconds! primed/painted. that was 3 yrs ago and the still look great!

What? for real? never heard of that before....so this is water base right? so how well is the adhesion? do you have pics? what paint system did you use over it?
 
yes, for real. wheel pants and leg and intersection fairings. but I did the cowl the epoxy way and spent many many hours of sanding and sanding to the point I almost stopped building. it literally took minutes to sand. ratle primer and gloss white. when I fly over head on you can see flawless painted wheel pants!. lol also up close to. I point them out to other rv pilots and they take a second look and just smile. then some get right down on their knees to really look. some say we'll see what they look like in a couple yrs. I then say they were done in 2012. 200 hrs ago. oh by the way then they look at my cowl and say didn't use mud on this did ya? I can see pin holes. and you can see some.
fred
 
Back
Top