C172 FLIGHT INSTRUCTOR REPORTS NMAC AT SMALL TOWER CONTROLLED ARPT WITH BE36 AS BOTH ACFT ARE TOLD TO GO AROUND TO AVOID A DEPARTING G109. A SECOND CONFLICT OCCURS BETWEEN THESE TWO ACFT BEFORE THEY CAN SAFELY LAND.

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WORKING WITH 2 CFI APPLICANTS; 1 FLYING GETTING FAMILIAR WITH OPERATING THE ACFT FROM THE R SEAT; THE OTHER WAS AN OBSERVER. WE WERE ESTABLISHED ON ABOUT 2 MI FINAL WHEN THE TWR CLRED A MOTOR-GLIDER (GROB 109B) FOR IMMEDIATE TKOF IN FRONT OF US. AN IMMEDIATE TKOF IN THE GROB DOES TAKE LONGER THAN MOST ACFT; AND THIS ALERTED US TO THE INITIAL POSSIBILITY OF NEEDING TO DO A GAR. AT ABOUT THIS SAME TIME; A BONANZA; ALSO ON THE TWR FREQ RPTED ON FINAL BEHIND US; AND WAS TOLD TO FOLLOW US; ALTHOUGH HE DID NOT HAVE US IN SIGHT YET. TWR DID ALERT HIM TO THE TIGHT SPACING. WHEN WE WERE DOWN TO ABOUT 1 MI FINAL; THE BONANZA RPTED US IN SIGHT; AND THAT THE SPACING WAS TIGHT. AS A RESULT THE TWR TOLD US TO GO AROUND; WITH THE INTENTION OF THAT INCREASING THE SPACING BTWN US; AND ALSO THE GLIDER AND BONANZA. HOWEVER; IMMEDIATELY AFTER THAT THE BONANZA RPTED IT WAS GOING AROUND DUE TO LACK OF SPACING BTWN US AND HIM (BONANZA). THE TWR TOLD THE BONANZA TO KEEP 'IT ON THE L SIDE OF THE RWY' AND WE CONTINUED STRAIGHT OUT ON THE UPWIND; KEEPING THE GLIDER IN SIGHT. TWR THEN REQUESTED THE BONANZA TO TURN TO THE L DOWNWIND; IN WHICH I SUSPECT HE DELAYED HIS ACTION. BASED UPON RADIO COMS; OUR MOST LIKELY TARGET FOR COLLISION AVOIDANCE WAS QUICKLY BECOMING THE MOTOR-GLIDER; WHICH WE WERE OVERTAKING. I EXPLAINED TO THE STUDENT FLYING; THAT ONE OF THE BEST WAYS TO MAINTAIN SEPARATION FROM THE MOTOR-GLIDER IN THIS TYPE OF SCENARIO WAS TO TRANSITION TO A VX CLB. VX FOR THE C172R AND VY FOR THE GROB ARE ABOUT THE SAME SPD; BUT THE ANGLE OF CLB IS MUCH GREATER FOR THE C172R; SO IN DOING THAT WE WOULD MAINTAIN THE LATERAL SEPARATION AS IT EXISTED AND GREATLY INCREASE THE VERT SEPARATION. THANKFULLY; MY STUDENT DELAYED OR WAS SLOW IN TRANSITIONING; AND JUST AFTER THAT EXPLANATION THE BONANZA FLEW DIRECTLY OVER US AT ABOUT 75 FT. THE TIS-A SYS INDICATED THE BONANZA AS +100 FT WHEN WE FIRST SAW HIM; AND AT ZERO FT (SAME ALT) IMMEDIATELY THEREAFTER. AT THIS MOMENT THE TWR REPEATED THE INSTRUCTION FOR THE BONANZA TO TURN L; WHICH INCREASED THE SEPARATION TO SAFE LIMITS. IF WE HAD TRANSITIONED TO THE VX CLB IT WOULD HAVE BEEN MUCH CLOSER; OR A COLLISION. NORMALLY THIS WOULD BE THE END OF THE SITUATION; BUT IT REAPPEARED JUST A MIN OR TWO LATER. AFTER THIS EVENT; THE BONANZA HAD ENTERED L DOWNWIND FOR RWY 32 AND WE HAD ENTERED R DOWNWIND. TWR RPTED THE TFC FOR US TO FOLLOW AS THAT SAME BONANZA; WHO WAS THEN ESTABLISHED ON THE L BASE LEG. THE BONANZA COULD NOT FIND OR SEE HIS TFC TO FOLLOW; SO HE MAINTAINED ALT AND OVERSHOT THE FINAL. HE THEN DECIDED TO TURN FINAL/UPWIND OR WHATEVER AT TFC PATTERN ALT DIRECTLY INTO THE R DOWNWIND. I NOTICED THIS; AND THE STRONG POSSIBILITY OF A DEVELOPING HEAD-ON COLLISION; SO I TOOK CTL OF THE ACFT AND IMMEDIATELY STARTED A L 180 DEG TURN TO AVOID THE ONCOMING TFC. TWR ALSO NOTED AND TRIED TO GET THE BONANZA TURNED AWAY TO THE E; WHICH TOOK A MOMENT OR TWO. AFTER THIS; WE HAD TO RE-COORDINATE WITH TWR TO GET REESTABLISHED AND LAND.