PROP STRIKE IN TKOF PROC IN SMA.

Narrative

STARTED TKOF ROLL RWY 24 FULL PWR CONFIRMED. AT 70 MPH; AIRPLANE WAS STARTING TO FLY SO I PULLED THE YOKE TO ROTATE WITH MY L HAND (ANTICIPATING BECOMING AIRBORNE IMMEDIATELY) AND WITH MY R HAND PUSHED THE GEAR UNLOCK BUTTON AND SLID THE LNDG GEAR HANDLE OUT OF THE LOCKED POS. MY FIRST IMPRESSION THAT WE WERE NOT ACTUALLY FLYING WAS A SLIGHT DIP DOWNWARD OF THE NOSE OF THE ACFT. I REACTED BY 'SNATCHING' THE YOKE BACKWARD WITH MY L HAND. WE THEN BECAME AIRBORNE; AND I COMPLETED THE GEAR RETRACTION PROCESS. EVERYTHING SEEMED NORMAL ON CLBOUT EXCEPT THE RPM WAS INDICATING ABOUT 200 RPM LOW. DECIDED TO RETURN FOR PRECAUTIONARY LNDG. DID NOT DECLARE EMER OR REQUEST PRIORITY HANDLING OR EQUIP (STANDING BY). LNDG AND TAXI TO TIEDOWN WERE UNEVENTFUL. INSPECTION AFTER SHUTDOWN REVEALED PROP TIP DAMAGE TO OUTER 4 INCHES OF EACH BLADE AND PRESUMED ASSOCIATED INTERNAL ENG STRESS DAMAGE. PREVENTION: THE HAND-OPERATED LNDG GEAR IS DIFFICULT TO OPERATE (RETRACT) IF SIGNIFICANT AIRLOAD BUILDS UP AFTER TKOF; I.E. 90 MPH. SO; THERE IS A NATURAL TENDENCY TO RETRACT THE GEAR PRIOR TO 80 MPH WHILE THE HANDLE IS STILL EASY TO OPERATE. I NEED TO MAKE A LITTLE MORE CERTAIN OF BEING TRULY AIRBORNE AND 'POSITIVE RATE OF CLB' PRIOR TO UNLOCKING AND RETRACTING THE LNDG GEAR.