C172 PLT LANDS ON RWY 36 GTU WHILE ANOTHER ACFT'S TAIL IS STILL ON THE RWY.

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I WAS DEMONSTRATING TO MY STUDENT HOW TO FLY THE TFC PATTERN IN A COMPLEX ACFT. THE MERLIN ANNOUNCED HIS POSITION ON THE CTAF TO THE S OF THE AIRPORT AND THAT HE WAS INBOUND ON THE GPS RWY 36 APCH. THE MERLIN LANDED WHILE WE WERE ON OUR DOWNWIND LEG. I CONTINUED TO FLY THE PATTERN EXPLAINING THE PROCS AS WE WERE FLYING. I NEVER HEARD THE MERLIN STATE ON THE CTAF THAT HE WAS CLEAR OF THE RWY. ON FINAL I CONDUCTED MY FINAL CHECKS AND LOOKED FOR THE MERLIN ON THE PARALLEL TXWY BUT COULD NOT FIND HIM AND JUST ASSUMED THAT HE HAD ALREADY PULLED IN BETWEEN THE HANGARS. I LANDED THE AIRPLANE ON THE RWY AND PREPARED TO TAKE OFF AGAIN. AS I WAS APPLYING POWER I NOTICED THAT THE MERLIN'S TAIL WAS STILL STICKING OUT INTO THE RWY AT THE DEPARTURE END. I KEPT THE POWER AT IDLE BUT CONTINUED TO ROLL DOWN THE RWY. I ASKED THE MERLIN PLT ON THE CTAF WHETHER HE WAS GOING TO MOVE; AND HE REPLIED THAT HE WAS DISABLED AND WOULD NEED A TUG. I SLOWED OUR ACFT AND THEN MADE A 180 DEG TURN ON THE RWY AND EXITED ON THE NEXT TXWY. I THEN TAXIED TO THE OTHER RWY TO CONTINUE OUR TRAINING AND TOOK OFF ON RWY 29. WITHIN A FEW MINS THE MERLIN WAS TOWED OFF THE RWY AND MY STUDENT AND I SWITCHED BACK TO RWY 36. FLYING THE NEXT FINAL; I LOOKED HARD AT THE DEP END OF THE RWY TO FIGURE OUT WHY I DID NOT SEE THE MERLIN. ALL I CAN RATIONALIZE IS THAT THE COLOR OF THE MERLIN CLOSELY MATCHED THAT OF THE THRESHOLD MARKINGS FOR RWY 18 AND DUE TO THIS CLUTTER IT WAS HARD TO MAKE OUT THE ACFT.