Re-painting phenolic with rough surface

I have an LOC NORAD that had a rough recovery (few weeks in the wild) I've been slowly repairing in my spare time.

There are parts of the airframe that have some pretty deep wounds.

I'm trying to figure out how to get any sort of smooth finish on this thing. Any suggestions? Would filler primer work on big areas like this? What about some wood filler?

I hope it is clear in these pics what I mean.

The bottom line: you’re going to embark on a love affair with a sanding block.

I’ve had success with wood filler, and primer; wood filler for particularly bad spots, primer after that.

Some people also like bondo, but you really need to wait for it to fully dry & that takes a lot more than the directions claim.

Start with the wood filler, and then:

1. Sand to something resembling uniform.
2. Paint it black (thin coat - just enough to look black. This is a guide coat.
3. Spray on a sandable grey primer. A few coats will give you some thickness.
4. Let it dry until you can’t smell the solvents. Could be a week or two in cold weather. If you don’t wait, your sandpaper will clog faster than you can swear.
5. Sand the primer. Use a sanding block (finger/hand hold will not flatten well). When you start to see black, you’re getting to the bottom of the primer, so move on.
6 It’ll probably look like a Holstein cow or zebra at this point, but will be a lot smoother.
7. Repeat steps 3-6 until smooth, or you’re sick of it. Anything that doesn’t look smooth Will show up. Paint doesn’t hide roughness.
8. Paint one last coat of primer. Sand it smooth, but DO NOT sand down to the guide coat. You just want to take off the roughness from the primer, and give it a uniform color.
9. Paint
10. Clearcoat
11. wax on
12. Wax off

Awesome, thank you!

I put a layer of wood filler on it last night, I'm going to wait and sang that down and see how it works. I'll probably try your method. This rocket has been sitting around for months so I don't care if it takes a while to repair.

Definitely use a sanding block.

The old “sandpaper in hand” thing will end up digging into the “crater” you filled. A sanding block will ensure it is actually flat.

Which will be tricky in that spot between fins, but there are sanding blocks as little as 20mm wide at most auto parts stores.

Your bondo may not be getting mixed properly. Most of the time I cannot use all of what I mixed as it is already hard. Much faster than wood filler. I also like to use a mouse sander on lots of stuff. Gets into tight spaces, makes quick work of most jobs. Then you can touch up by hand.

I use the Bondo spot glazing putty - single part filler in a tube. It's not good indoors but it drys very quickly. I would not use it for large areas but it is harder than most wood fillers so it works well in areas that need a more robust filler.

(edit - use several thin layers rather than a thick layer, otherwise it may shrink and crack)

Tony

David Schwantz said:

Your bondo may not be getting mixed properly. Most of the time I cannot use all of what I mixed as it is already hard.

Click to expand...

Any Body filler you mix would be the two-part curing kind.

I was referring to the original single part nitrocellulose bondo most auto parts stores carry. Its not terrible, but can shrink if sanded before it fully dries - most people think hard and dry to the touch is ok, but it’s not. (Well, not thick applications, at least. I doubt Rockets use layers that are 1/4” thick.)

That is why I use this stuff.