A PA28 CFI ENCOUNTERS BUILDUPS DURING A VFR FLT AND IN TURNING AND DSNDING TO AVOID THE CLOUDS HE INADVERTENTLY ENTERED THE CLASS C AIRSPACE OF BDL; CT.

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DEPARTING THE MASSACHUSETTS AREA; I CLBED TO 4500 FT MSL HDG W TO CLR THE WINDSOR LOCKS CLASS C AIRSPACE AND A SCATTERED LAYER OF CUMULUS IN 3-4 MI VISIBILITY WITH HAZE. WHILE CRUISING AT 4500 FT; I REALIZED TOO LATE THAT THE CLOUDS WERE BUILDING TO THE W AND AS I APCHED THE WINDSOR LOCKS AREA; A CLOUD APPEARED AHEAD AND BUILDING SO I DECIDED TO DSND AND TURN S TO AVOID THE CLOUD AND THE WINDSOR LOCKS CLASS C AIRSPACE AS WELL AS THE BRAINERD CLASS D AIRSPACE THAT SITS JUST S OF WINDSOR LOCKS. WITH 2 MOVING MAP GPS'S (PORTABLES) RUNNING; I FELT CONFIDENT IN THE INFO ON THE SCREENS AND THAT I HAD AVOIDED THE AIRSPACE WITH THE DSCNT AND TURN UNTIL 1 GPS INDICATED I WAS ONLY 'NEAR' THE AIRSPACE AND 1 INDICATED I WAS 'IN' THE AIRSPACE. I DIDN'T REALIZE HOW CLOSE I WAS TO THE BOUNDARY DURING THE DSCNT AND WITH THE DOUBT IN MY MIND NOW OF WHETHER OR NOT I ENTERED THE CLASS C OR D AIRSPACE (OR BOTH) I AM FILING THIS RPT. I FEEL AS THOUGH I FELL INTO THE TRAP OF RELYING TOO HEAVILY ON THE 'COCKPIT GADGETS.' THERE WOULD HAVE BEEN LITTLE OR NO PROB HAD I JUST ESTABLISHED COMS WITH WINDSOR LOCKS PRIOR TO OVERFLT. THE VISIBILITY WAS A FACTOR BUT VISIBILITIES OF 3-5 MI IN HAZE ARE COMMON IN THE AREA AND I SHOULD HAVE PLANNED A BETTER ALT OR JUST USED THE RADIO SOONER TO PREVENT THE POSSIBLE INCURSION. MY CONCERN IS THAT I HOPE I DIDN'T CAUSE A TFC CONFLICT ALONG THE EDGE OF THE AIRSPACE AS I DSNDED AND CERTAINLY I HOPE I DIDN'T GET INTO THE AIRSPACE BUT I'M NOT SURE SINCE I HAD CONFLICTING MESSAGES FROM THE GPS'S. THE CONDITIONS CHANGED RAPIDLY WITH THE SCATTERED LAYER BUILDING FASTER THAN I THOUGHT IT WOULD. AS A RESULT; THE ALT WAS NOT HIGH ENOUGH TO STAY ABOVE THE BUILDING CUMULUS. HOPEFULLY; NEXT TIME I WILL PLAN BETTER FOR THE CONDITIONS AND USE THE RADIO EVEN FOR AN EXPECTED OVERFLT.