I just got back into rocketry after about 15 years of absence. Of course, right off the bat, I'm building my own. Sticking with Estes parts for now, I've built a rocket that is about 36 inches tall, with a BT-55 body, three fins, D sized motor -- pretty much a standard shaped rocket, nothing fancy, but a little tall maybe.
Checking it for stability using the CG/CP method, I calculated the CP using a cardboard cutout finding the balance point. I calculated the CG by balancing the rocket loaded for launch. Sure enough I had to add some weight to the nose to get put the CG higher than the CP. Now they are about 3 inches apart.
Even though it looks right, but I can't seem to get the rocket to pass the "tie a sting at the CG and twirl it" method. Maybe it it too tall and I can't quite get started straight into the wind. However, I keep adding weight, hoping it will straighten out, but that does not seem to help. Already, loaded for launch, the thing it up to 7 ounces. All it ever does is point straight up, flying sideways, rather than into the wind.
What do I do now? Should I just rely on my determined points for CP and CG and hope its right, or should I give up and not fly the thing? Usually, we launch rockets during club sponsored launches, and I'd hate to fly the thing if it is unstable and there are lots of kids around.
- Dave