Gary,
For a rocket of that weight, the D12 is near the end of its limit for 5/1 thrust. Plus, this motor could have been on the lower end of the performance bell curve. Another factor is the wind, which you could see the effects on the barrier tape, which is not your friend on marginal flights. It looked like the rocket wasn't up to the required velocity at the end of the rod. Plus, the fins are somewhat small (but great for a high-speed design) which do not help much at lower velocities. I have launched heavier rockets on D12s, but the fins have a much larger surface area. Another consideration, was there much lug drag when you placed it on the rod?
When you say "balanced well", do you mean the relationship of the CG to CP? I was wondering what your CP calcs were and how close it was to the CG at launch.
Just "eyeballing it", you should be able to launch it on a D12, but I think you need at least a 6' rod. Regardless of what my eyeball thinks, you would be better off running sims to confirm that.
Finally, you could leave the D12 behind and launch it on an AeroTech RMS E18 or an AeroTech SU E20. Then you won't have to worry about rod length and light winds.
In summary, it looks like it flies fine, it just needs a bigger motor for extra "punch" off the pad or extra rod for D12s.
BTW, I'm glad it didn't hit the sun!
Greg
