WINGTIP STRIKE BTWN 2 SMAS; DEP TAXIING TFC.

Narrative

MY BEGINNING STUDENT AND I WERE CLRED BY SNA GND TO TAXI TO RWY 19L AND HOLD SHORT AT TXWY K. LCL PROC ALLOWS SMALL ACFT TAKING OFF FROM THE L RWY TO HOLD SHORT ON TXWY K WITH AN OFFSET TO THE L SIDE OF THE TXWY CTRLINE TO ALLOW TFC TAXIING FOR THE R RWY TO TAXI ON THE R SIDE OF TXWY K AND CROSS RWY 19L TO RWY 19R. AS WE PULLED UP AND HELD SHORT OF RWY 19L I WAS LIGHTLY ON THE CTLS TO ASSURE THAT MY STUDENT WOULD NOT VIOLATE THE HOLD SHORT MARKINGS AND TO CHK THAT WE WOULD STOP IN A POS WITH OUR R WINGTIP CLRLY TO THE L SIDE OF THE TXWY CTRLINE; AND WE DID. I ESTIMATED THE WING CLRNC TO THE TXWY LINE TO BE ABOUT 3-4 FT. AS WE WERE HOLDING SHORT WE CONTACTED SNA TWR ON 119.9 AND WERE INSTRUCTED TO HOLD SHORT FOR LNDG TFC; SO WE ACKNOWLEDGED AND HELD. WHILE HOLDING ANOTHER ACFT; A C172 TAXIED UP TO HOLD SHORT OF RWY 19L AT TXWY K AND OFFSET TO THE R SIDE OF THE TXWY CTRLINE. WE DID NOT HEAR THAT ACFT ON FREQ AND ASSUMED THEY WERE TALKING TO TWR ON 126.8. TWR THEN CALLED US CLR FOR TKOF ON RWY 19L. MY STUDENT ACKNOWLEDGED THE RADIO CALL FIRST AND THEN ADDED PWR TO STRAIGHTEN OUT PARALLEL TO THE TXWY BECAUSE WE HAD PURPOSELY STOPPED AT AN ANGLE TO FACILITATE CHKING TFC ON FINAL APCH. AS WE WERE ROLLING FORWARD SLOWLY I WAS LOOKING OUT THE R SIDE CONTINUOUSLY TO CHK OUR R WINGTIP CLRNC WITH THE C172; OUR WINGTIP REMAINED ON OUR SIDE OF THE TXWY CTRLINE AT ALL TIMES. I THEN OBSERVED THE C172 BEGIN TO MOVE FORWARD AND THEN TURN TO THE L TO PARALLEL THE TXWY. THE C172 WINGTIP CAME FROM BEHIND OUR WINGTIP AND HIT OUR WING AND SCRAPED ALONG AND I OBSERVED THE PLT IN THE L SEAT OF THE C172 AND HIS PAX BOTH LOOKING TO THE R TO CHK FOR TFC ON FINAL. THE OTHER PLT NEVER SAW THE COLLISION AND NEVER ACTED AS IF HE KNEW. NO DAMAGE OCCURRED TO OUR AIRPLANE. MAYBE THE PROB COULD BE AVOIDED BY NOT HAVING 2 AIRPLANES SIDE-BY-SIDE TALKING TO 2 DIFFERENT CTLRS.