GRUMMAN AA5B PLT ON VISUAL TO RWY 15L AT SBA RPTS CONFLICT WITH ACFT TURNING FINAL FOR RWY 15R. AFTER RPTR QUERIES TWR; TWR RECLRS INTRUDER TO LAND RWY 15R AND BOTH ACFT LAND SAFELY.

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I WAS ON A VFR FLT TO SBA WITH MY WIFE; WHO IS ALSO A PVT PLT. I WAS FLYING THE ACFT FROM THE L SEAT. I ENTERED THE AREA FROM THE E. SHORTLY AFTER BEING HANDED OFF FROM SANTA BARBARA APCH TO THE LCL CTLR; I WAS INSTRUCTED TO ENTER A L DOWNWIND FOR RWY 15L. I WAS AT PATTERN ALT (1000 FT AGL). WHILE I WAS TURNING FROM DOWNWIND TO BASE; THE CTLR CAUTIONED ME THAT THERE WOULD BE ANOTHER ACFT ON OPPOSITE BASE FOR RWY 15R (HE MADE A SIMILAR CAUTIONARY STATEMENT TO THE OTHER ACFT). EVENTUALLY WE MADE CONTACT WITH THE TFC AND CONTINUED THE TURN FROM BASE TO FINAL. THE OTHER ACFT; AS IT ROLLED FROM BASE TO FINAL; TRANSGRESSED ONTO THE FINAL FOR RWY 15L DIRECTLY ABOVE ME. I COULD NOT SEE IT AT THIS POINT; BUT MY WIFE COULD (THE CANOPY OF OUR ACFT; A GRUMMAN AA5B; AFFORDS EXCELLENT VISIBILITY IN THE UPWARD DIRECTION). I PREPARED FOR AN EVASIVE MANEUVER -- WHICH WOULD HAVE BEEN A BREAK OFF INTO A L TURN AND REJOIN THE PATTERN -- WHICH XMITTED THE SITUATION TO THE TWR. THE TWR THEN EMPHATICALLY INSTRUCTED THE ACFT ABOVE ME THAT HE WAS CLRED TO LAND ON RWY 15R. THAT ACFT ACKNOWLEDGED AND SIDESTEPPED BACK TO THAT FINAL APCH COURSE. THE STRESS OF THE SITUATION RESULTED IN A FASTER-THAN IDEAL LNDG (I HAD TO QUICKLY SHIFT FROM AN ANTICIPATED GAR TO A LNDG CONFIGN). AS A GENERAL OBSERVATION; THIS CTLR WAS OVERLOADED AND DID NOT HAVE GOOD SITUATIONAL AWARENESS OF THE TFC FLOW INTO AND OUT OF THIS ARPT. IT WAS A BUSY DAY; WITH SIMULTANEOUS OPS ON RWYS 15R; 15L; AND 25. HE WAS ASKING NUMEROUS ACFT TO EXECUTE 360 DEG TURNS IN THE AIR TO MAINTAIN SPACING. WHILE I AM NOT AN AIR TFC CTLR; I DO BELIEVE THIS IS AN INEFFICIENT AND INEFFECTIVE WAY TO MAINTAIN TFC SEPARATION AT A BUSY ARPT. OTHER CTLRS AT SBA (AND OTHER ARPTS FOR THAT MATTER) CAN DO A BETTER JOB WITH MORE TFC; SO I SUSPECT THIS WAS A TRAINEE. IF SO; A SUPVR SHOULD HAVE INTERVENED SOONER.