Brodak sanding sealer is great. I’ve also experimented lately with Elmer’s Wood Filler. It will warp fins if you don’t do both sides at the same time. Some have posted that once you fill the opposite side, the warping goes away. That was not my experience with thin balsa. I prefer it on thicker balsa to minimize or eliminate warping. Works really well on nose cones. If the balsa has any dings, the wood filler will work well to fill them. If you are using a sanding sealer, you could still fill dings prior to use. I prefer to us an RC Covering Iron to raise dents in balsa. Wet the dent and run the iron over the area to lift the dent. A regular clothing iron would probably work if set to a low setting.

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Lee Reep
NAR 55948

Projects: Semroc Saturn 1B, Ken Foss Designs Mini Satellite Interceptor
In the Paint Shop: Nothing! Too cold!
Launch-Ready: Farside-X, Maxi Honest John, Super Scamp