Centuri Astro 1, Build, Part 5, Basics - Rounding Fin Sides

Once in a while I'll do a basic rocketry technique, there are some new builders following the blog.

On the left is an Alpha style fin with sharp corners.
On the right is the same fin silhouette after a beginner has rounded  the edges. The corners aren't as sharp after using too rough a sandpaper and not using a block.
There is nothing wrong with the finished shape, the rocket will fly just fine. This post could help you keep those corners sharp and rakish.

As I've said before, this is how I do it. Everyone has their own techniques that work great for them.




Initially I knock the edges with a sanding block. This is a well worn piece of 220 grit on my Great Planes Easy Sander Block.
The block helps keep the sides straight and square.
Simply rolling sandpaper over your fingertips works but doesn't keep the sanded edges square and flat.

You don't have to get a complete "half round" fin edge using just the first passes of the sanding block. Just knock off the corners. Use light pressure.

Come back with the finer grade 400 grit, now with the sandpaper rolled over your (cushioned) fingertips. Hold the fin edge under a bright light to see if there are any sharp edges remaining. Sand lightly with the 400 grit.
Go easy on the corners, keep them sharp.
It's better to take off a little at a time instead of taking off too much balsa that you can't replace.





The Astro I has a round trailing fin tip. On a rounded surface use sandpaper over your fingertips.