Tip: Cutting and Buffing Paint

[snopercod]

Originally Posted by uk_figs

you can get a metal block that can shave cured paint.

A Run Razor, perhaps? I have one of those but it's made out of plastic. It contains a single-edge razor blade and has a screw that bends it down slightly.

I like your blog.

[uk_figs]

No not a run razor, looks like this https://www.eastwood.com/painters-ni...yABEgL5UfD_BwE, called a painters nib file and is used to cut down painr runs. Tedious but works.
Figs

[snopercod]

Oh! That looks very handy. Thanks for the tip!

[Aluminum]

Originally Posted by uk_figs

No not a run razor, looks like this https://www.eastwood.com/painters-ni...yABEgL5UfD_BwE, called a painters nib file and is used to cut down painr runs. Tedious but works.
Figs

These metal blade solutions can make a sneeze into a two-day repair...
I find that the 3M thin rubber pad found at auto stores works best for runs and sags, and for blending too. It is just slightly convex and thin enough to focus pressure on the run/blend but still keep the flatness around it.

[snopercod]

Originally Posted by Aluminum

I find that the 3M thin rubber pads found at auto stores works best for runs and sags

What grit do you start out with for a run?

[Aluminum]

Originally Posted by snopercod

Anyone know the best way to blend something like this? It's single stage Full-Thane.

A quick googling doesn't reveal whether "Full-Thane" is a polyurethane or "acrylic urethane" blend, but in general polyurethane cannot be repaired. It won't bond to itself once fully polymerized. You'd have to strip the entire cowl and re-do. There may be chemical ways of altering it so it takes on more paint, but probably not worth the effort given the potential for damaging the surrounding paint.

Edit: one of the advantages of siloxane-epoxy resin is that it will chemically bond to fully polymerized epoxy (or to itself) without sanding. I wonder if it would stick to polyurethane too? Any chemists on here who can chime in?

[Aluminum]

Originally Posted by snopercod

What grit do you start out with for a run?

If before recoating I use 220 wet. On final coat 500-1000 wet for rough cut, then 1500 wet to eliminate all orange peel before buffing and polishing.

[uk_figs]

That is one of the nice things about the PPG DCC concept in that you can scuff up the surface and shoot another coat to fix dings etc. In addition the local automotive paint supplier can prep a matched paint rattle can for about $30. Did this last annual to touch up the wheel pants and it worked well enough for me.
Figs

[snopercod]

Originally Posted by Aluminum

A quick googling doesn't reveal whether "Full-Thane" is a polyurethane or "acrylic urethane" blend...

Sorry, I was misspelling it. It's Ful-Thane and is a "urethane single-stage topcoat". I used Nason® SelectSeal™ 422-51™ 2K Urethane Sealer (white), underneath. I sprayed the top coat on the sealer after a 30 minute wait. I originally painted my plane with PPG Durathane which I dearly loved but you can't buy it any more.

[snopercod]

So today I used the razor blade trick to taper down the new paint. It worked pretty well but I have two recommendations. First, putting the razor blade in a vice and using a steel rod to curl over the edge seemed to work better than the 600 grit. I tried it both ways. Second, be sure to put a small piece of tape on the side facing you because it's almost impossible to tell which edge has the curl.



After using the razor blade, I went to my tiny little Ace Hardware sanding block with 120 grit on the raised edge.



After that I went to 320 grit on a 3M hard rubber pad, then 600 grit. It came out nice and smooth, but I can see different color bands. Whether I sanded through the top coat and exposed the white sealer, or whether the paint match wasn't quite perfect, I don't know, but it's good enough for now. Eventually, I'll have to reprint the entire canopy top (if I care).