Just another fin jig

thingiverse

Just another fin jig - two in fact, one small and one large, plus an adapter sleeve to boot. It has slots for both three and four fins, with a cutout that lets a motor clip poke right through. The small jig fits snugly into an 18mm (BT-20) motor mount, and is spaced just right for fins up to 3/32" thick - the most common size by far. For thinner balsa, you can simply add some card stock to hold it in place. The sleeve slips over the 18mm riser and lets you use the small jig on a 24mm motor tube with ease. The larger version is 4.4 inches in diameter, and designed for use with 1/8" fin stock. It's built to fit into a 24mm motor mount (D/E/F), and can be used on bigger body tubes with a greater fin span. These jigs work best when the fins extend below the bottom of the body tube. I've personally used the small one, but not yet had the chance to try out the large one.