It was a beautiful day to fly a beautiful rocket. Well, until launch. I measured out the CG which seemed fine but later discovered that my CP was further up than I initially calculated. This made the rocket just on the cusp of unstable. After the rocket cleared the rail it started to wobble, not loop, but was clearly not right. It lawn-darted, breaking the nose cone, crumpling the body tube, and spilling the electronics out on the ground like it had been gutted by a lion. Only after we got the bottom portion of the nosecone off did I realize that the Eggtimer Quantum altimeter was missing. Another expensive mistake, but I am learning (the hard way) and keep making improvements with each launch.