A C172 INSTRUCTOR AND STUDENT; DEPARTING SPG; ENTERED CLASS B AIRSPACE WITHOUT A CLRNC.

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WHEN READY FOR DEP; WE WERE ASKED WHERE WE WERE HEADED; AND WE RESPONDED WITH A REQUEST FOR DEP TOWARD DELAND. I THEN MADE THE INCORRECT ASSUMPTION THAT THE TWR CTLR WAS COORDINATING A DEP HDOF WITH TPA APCH; SO AS TO TRANSITION BACK TOWARD TPA INTL (THE WAY WE CAME IN) AND RECEIVE CLASS B CLRNC WITH THEM ONCE AIRBORNE. APPARENTLY; NO SUCH COORD WAS REALLY TAKING PLACE AND; THEREFORE; WHEN TOLD TO 'MAKE A L TURN FOR AN EBOUND DEP;' WE DIDN'T REALIZE THAT TPA APCH WAS NOT EXPECTING OUR DEP AND SUBSEQUENT REQUEST FOR A CLASS B CLRNC. ADDING TO OUR CONFUSION IS THE WAY THAT THE CLASS B/CLASS D OVERLAP IS CHARTED ON THE SECTIONAL CHART. WE HAPPENED TO BE USING A (CURRENT) TERMINAL VFR CHART FOR THE TAMPA/ORLANDO AREA; WITH THE LARGER SCALE MAKING IT MUCH EASIER TO READ. ACCORDING TO THOSE CHARTS; THE WHITTED CLASS D AIRSPACE IS SEGREGATED INTO 2 OVERLYING CLASS B 'ZONES.' W OF AND ABOVE THE ARPT; THE CLASS B IS CHARTED AS 100/30. E OF AND ABOVE THE ARPT; THE CLASS C IS CHARTED AS 100/12. HOWEVER; THE SEGMENTED BLUE LINE THAT DEPICTS CLASS D AIRSPACE HAS A [15] BRACKET AROUND THE ENTIRE ZONE. THEREFORE; E OF THE ARPT; THERE IS AN OVERLAP WHERE WE WERE -- AT 1400 FT MSL. ACCORDING TO THE CLASS D SEGMENTED CIRCLE AND [15] BRACKET; WE SHOULD HAVE STILL BEEN IN CLASS D AIRSPACE. ACCORDING TO THE 100/12 NOTATION; WE WOULD ALSO BE IN THE CHARTED CLASS B AREA. AT ABOUT XA30; WHEN REACHING 1400 FT; THE WHITTED TWR INFORMED US (PER TWR RADAR; I PRESUME) THAT WE WERE IN CLASS B AIRSPACE; AND HE INFORMED US THAT CLASS B STARTED AT 1200 FT; AND WE WERE AT 1500 FT AND; THEREFORE; IN VIOLATION. HE THEN CALLED OUT BONANZA TFC TO US; MY STUDENT RPTED IT IN SIGHT; AND I TOOK THE CTLS AND DSNDED TO AN ALT OF 900 FT MSL TO EXIT THE CLASS B AIRSPACE. SUBSEQUENT TO THIS; WE EXITED WHITTED'S CLASS D TO THE E OF 900 FT MSL; STAYING CLR OF MACDILL'S CLASS D AIRSPACE PER GPS; CALLED TPA APCH AND ASKED FOR CLASS B CLRNC AND FLT FOLLOWING TO DELAND. THEY GAVE US A XPONDER CODE; TOLD US TO STAY CLR OF CLASS B (WE WERE BY THIS POINT); AND THEN LATER GAVE US RADAR CONTACT; 'CLRNC TO OPERATE IN THE CLASS B AIRSPACE;' AND PERMISSION TO RESUME OWN NAV DIRECT DELAND; AND ALT AT OUR DISCRETION. THE REST OF THE FLT CONTINUED WITHOUT INCIDENT. MY WHOLE CONFUSION SURROUNDING THE INCIDENT INVOLVES THE WAY THAT WHITTED'S CLASS D AND CLASS B OVERLAP AREAS ARE CHARTED ON SECTIONALS AND TERMINAL VFR CHARTS. IT WOULD APPEAR TO ME AT FIRST GLANCE THAT WHITTED'S CLASS AIRSPACE GOES UP TO 1500 FT OMNI-DIRECTIONAL OUT TO THE PUBLISHED 4 MI RADIUS LIMIT. I'M STILL NOT SURE WHY; AT 1400 FT MSL; YOU ARE STILL CONSIDERED IN CLASS B AIRSPACE; WITH THE WAY THAT IT IS CHARTED. THEREFORE; IT WOULD LEAD PEOPLE (LIKE MYSELF) TO THE CONCLUSION THAT THE CLASS D CIRCLE TAKES PRECEDENCE OVER THE OVERLAPPING CLASS B; WHEN BOTH ARE CHARTED IN THE SAME AREA. AFTER ALL; WE FIGURE MACDILL'S AIRSPACE WOULDN'T MAKE MUCH SENSE. IF EVERYTHING OVER MACDILL IS CLASS B ABOVE 1200 FT; THEN WHY CHART [26] FOR THE WHOLE AREA? AFTER REALIZING OUR VIOLATION; WE WERE QUICK TO EXIT THE CLASS B AIRSPACE; PROMPT TO COMPLY WITH TWR INSTRUCTIONS; AND COMPLETED THE FLT SAFELY. HOWEVER; WE WERE STILL UNCLR AS TO THE CHARTING OF THOSE 2 AIRSPACE LIMITS. WOULD CHANGING THE CHARTING HELP ANYBODY ELSE TO AVOID AN AIRSPACE INCURSION? PERHAPS THE WHOLE REST OF THE AVIATION WORLD KNOWS THIS CHARTING POLICY ALREADY; AND I JUST HAVEN'T LEARNED IT YET. HOWEVER; IN TALKING TO ENOUGH PEOPLE AFTER THIS FLT; I THINK THERE IS WIDESPREAD CONFUSION.