THE PILOT & HIS WIFE HAD PICKED UP THE AIRPLANE AFTER MAINTENANCE HAD BEEN PERFORMED. DURING THE TAKEOFF ROLL THE PILOT ROTATED, HE SAID, AT WHAT HE BELIEVED WAS ROTATION SPEED. THE AIRPLANE BECAME AIRBORNE IN GROUND EFFECT. SHORTLY AFTERWARDS, THE LEFT WING DROPPED, AS IT STALLED, & THE NOSE FELL THROUGH. THE AIRPLANE ACCELERATED AS IT DESCENDED TO IMPACT ON THE LEFT WINGTIP. IN HIS REPORT THE PILOT SAID THAT HE ROTATED AT TOO SLOW AN AIRSPEED & FAILED TO APPLY SUFFICIENT RIGHT RUDDER.