Water rocket ring fin

This is a 3D printed fin can for a water rocket, based on the water rocket fin mount system developed by MagicSmokeSTAT (file name is “Fin 33d Mount Only 64mm bet a 2021-12A.step from the “Remix” link). Retain it on the end of a (US) soda bottle by either trimming a bottlecap or printing this part . Be sure to check out his launcher design, it is fantastic and works really well. This fin can with 3D printed retainer is aerodynamically unstable (as in, it may have a tendency to turn the rocket around and land fin-side down) with the 2L Coke bottle shown in the cover picture (according to the string test). Taping the top end of another soda bottle as a nosecone adds sufficient weight to make it quite stable, but beware, it will likely come down very fast and quite probably break the fin can on impact. As of right now this design has not been tested. Video of first test here , I couldn't figure out how to upload videos to PrusaPrinters.org.