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Leveling Foam with a Router
Fri, Jul 11 08 @ 05:47 AM Eastern Daylight Time
The NACA inlet is constructed out of urethane foam. The stuff is difficult to sand. Not because is hard to sand, but because it sands so easily. If you look at it cross-eyed, then you can dent it. I was concerned that if I hand sanded it level that I would not be satisfied. I could anticipate having a ding here or there, or not having good transitions through the the microed area.
I picked this idea up from Craig Kossowski (ChasingMars). Look under chapter 7, NACA Scoop. Craig built a very nice jig, but I wanted something a little simpler. I like using routers and this little jig only cost about $8 to build. It probably not any faster than the plans methods, but I'm pretty sure it was easier. I would definitely do this again, but next time I'd use a different type of foam for the NACA construction. Urethane is good for hand sanding a shape, but in this case we are after a flat surface. It made sense to machine the surface flat.
I have nothing against the plans methods; it has probably be used by 99 percent of the planes built. I'm a huge fan of jigs and fixtures when they're appropriate. A good jig will just make a part easier to build.
So here's my most recent video addition on using a router to level foam. It's ruthlessly edited to make it as short as possible. I think I've done it. It is 4 minutes long and about 10 megs.
....and yes I do realize I said a 3/4" diameter bit when I was holding a 1/2" bits. Ooops
