Reducing Rocket Spin for Better On-Board Videos
I've been building rockets to carry cameras for a while and getting rid of spin is a major goal. Here are some thing's I've learned.
Straight fins are a must and using four fins makes it easier to align the fins with each other and the rest of the rocket. If you extend the fins at least a little past the bottom of the body tube, you can use a simple jig made from peices of wood (such as rulers for a small rocket) to make sure opposite fins are aligned with each other and a right-angle to make sure the others are in line.
Larger fins are better as long as they aren't too large or misaligned.
The motor mount also needs to be aligned well, but that's easier than making sure the fins are on right.
A larger rocket spins less. My rockets have gotten bigger while the cameras have gotten smaller. I've found that larger rockets spin less. Maybe it's because small imperfections in alignment of the fins or motor mount make less of a difference.
Rockets spin more when the motor is burning. I think this may be due to the motor mount being a little askew or the motor's thrust being a bit off-center. So, a higher-thrust, but shorter-duration motor might help. The rocket spins less when it is coasting.
Less expensive cameras blur more when the rocket spins. The tiny, inexpensive cameras are nice because of their small size and low weight, but they don't take very good video. And the video gets worse when there is a lot of motion in the scene. A better camera will handle the motion better with less blur.
What You Can Do