A PLT OF AN EXPERIMENTAL ACFT MAY HAVE ENTERED CLT CLASS B AIRSPACE WHILE ON A XCOUNTRY FLT. THE PLT WAS FLYING ABOVE A CLOUD LAYER AND DID NOT NOTICE HIS PROX TO CLASS B AIRSPACE UNTIL THE CLOUDS BEGAN TO CLR.

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I WAS OPERATING A SMALL EXPERIMENTAL ACFT ON A VFR XCOUNTRY FLT. MY PROJECTED COURSE WAS TO PASS TO THE E OF CHARLOTTE CLASS B AIRSPACE ON A SOUTHERLY HDG. THE WX WAS GOOD VFR BUT THERE WAS A BROKEN CLOUD LAYER AT ABOUT 6000 FT MSL AND THE VISIBILITY WAS ONLY ABOUT 10 MI. THE CLOUD LAYER BEGAN TO THIN AND THEN IT ENDED COMPLETELY AND THE VISIBILITY SUDDENLY IMPROVED TO 60 MI OR BETTER. IT WAS AT THIS POINT THAT I DISCOVERED THAT I WAS CLOSER TO CHARLOTTE THAN I HAD ANTICIPATED. BEING AT 8500 FT; I THOUGHT I WAS ABOVE THE CLASS B AIRSPACE. I CONSULTED THE WAC CHART I WAS USING BUT DISCOVERED THAT THE FLOOR AND CEILING HEIGHTS FOR CLASS B AIRSPACE ARE NOT INCLUDED ON THE CHART. AFTER SEVERAL MINS I CONSULTED THE CHARLOTTE SECTIONAL CHART AND DISCOVERED THAT THE CEILING OF CLASS B AIRSPACE AT CHARLOTTE WAS 10000 FT MSL. I IMMEDIATELY CLBED TO 10500 FT MSL TO STAY ABOVE IT. I WAS UNABLE TO DETERMINE EXACTLY WHERE I WAS LATERALLY IN RELATION TO CLASS B AIRSPACE PRIOR TO MY CLBING TO 10500 FT AND I MAY HAVE BEEN IN CLASS B AIRSPACE FOR A SHORT TIME. I WAS NOT IN COMS WITH ANY ATC FACILITY. THE ACFT WAS EQUIPPED WITH AND WAS USING MODE C ALT RPTING XPONDER. I SIGHTED NO OTHER ACFT AND THERE WAS NO TFC CONFLICT. FLYING VFR USING VISUAL REFS TO REMAIN CLR OF CLASS B AIRSPACE IS JUST TOO INEXACT. TO BE SAFE YOU JUST ABOUT HAVE TO HAVE A GPS WITH A MOVING MAP DISPLAY.