Fin Designs

NEW! My small contributions to the water rocketry hobby includes the following original fin patterns and fin design tools. They are licensed under a "By" creative commons license, so feel free to copy and send to all your friends, or even use in your book, magazine article or web site about water rocketry!

2 L Bottle Contour with grid – design your own fins with this handy guide. Just print it out and take a ruler to draw on your very own creation, cut out the design and trace the pattern on to your fin material.

Fin Design 1 – Use this fin design for a stable 3 or 4 finned rocket. Design is tested and flys well. The fins hug the contour of the 2 L bottle. These are the fins I use in my "WV2" rocket design.

Fin Design 1b – The same dimensions of Fin Design 1, but made for a rocket that uses a straight, 4.25" ferring. Good for 3 or 4 finned rockets.

My First Rocket: The Virginia (a.k.a. Virgin Galactic Mark I)

The VirginiaThis is a picture taken shortly before the maiden flight of my first homemade water rocket. I will have some more, better, pictures — once I've put her back together and repainted her. She won't be flying again, I'm afraid.

Launch Report

Launched at around 8:00 PM or so, too dark to video. The location was the yard across from Grandma's House in Albion, MI. The wind conditions were very light to still. Filled with water to about 27.5% of 2L volume. Pressurized to ~90psi. Launcher stuck on first countdown, reattached cord to pin/spring. Launched with a bit of an angle due to pull tension. Flew to between 200' and 300'. Noticed a little dynamic flight during ascent, but very stable during coast and at apogee. Payload/nose module failed to separate from the motor and the rocket went ballistic (lawn dart). Impact at terminal velocity (about 30mph) and damaged both engine and nosecone. Range ~100' (very near neighbor's house — close call!)

Success Analysis

Thrust phase very smooth. I think we got maximimum height. Very stable in flight. Fin design perfect for flight, but too tight for launcher design.

Failure Analysis

Primary recovery failure due to design and construction flaws. The nosecone did not disengage because the stop was located too far down on the motor. Raising the stop should help, as will more ballast in the tip. Even if the nosecone had come apart from the motor, however, the chute would not have deployed properly. The shock cord was too short and the chute too long. Need a drogue or some other mechanism to push out chute, or longer shock cord.

Launcher needs to be modified to not hold the spring pin in as far. Slots should be more shallow, to allow the pin to slip out to the side when under pressure.