PLT OF SAILPLANE ENCOUNTERS SEVERAL COMMERCIAL ACFT IN CLOSE PROX TO HIS LOCATION WHILE PRACTICING THERMALLING NEAR CO15.

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A GLIDER TRANSITION PLT AND I WERE IN A BLANIK L-13 GLIDER AT 11000-13000 FT DIRECTLY OVER KELLY AIR PARK (CO15) NEAR ELBERT; CO; OR WITHIN 1 NM OF IT. CO15 IS LOCATED APPROX 6 NM DIRECTLY S OF THE DENVER CLASS B AIRSPACE. EARLY THAT DAY; A MEMBER OF OUR GLIDER CLUB HAD CALLED COS APCH BY RADIO TO INFORM THEM OF HVY GLIDER ACTIVITY IN THE VICINITY OF CO15 ANTICIPATED THROUGH THE DAY. WE HAD A SERIES OF ENCOUNTERS OF MINIMAL SEPARATION BTWN OUR GLIDER AND AIRLINERS ON A NORTHERLY HDG APPEARING TO BE FLYING FROM COS TO DEN. THE FLT LASTED 1.8 HRS. AT THE TIME OF THE TFC CONFLICTS; THE ORIENTATION PLT WAS PRACTICING THERMALLING; IN THE 11000-13000 FT MSL ALT BLOCK WITHIN 3 NM OF CO15. THE AIRLINERS APPEARED TO BE COMING OVER CO15 AT 12000 FT MSL CONSISTENTLY. THERE WERE A TOTAL OF 5 AIRLINERS THAT PASSED BY US IN A 15 MIN PERIOD; 3 IN ABOUT 5 MINS. ALL APPEARED TO COME FROM COS; OR AT LEAST THEY WERE IN A LINE BTWN COS AND DEN. 2 AIRLINERS APPEARED TO BE LESS THAN 1 MI FROM US AND LESS THAN 500 FT VERT SEPARATION. 3 OF THE AIRLINERS APPEARED TO BE WITHIN ABOUT 1/4 - 1/2 MI OF US. THE ONLY ONE THAT SAW US WAS AN A319/320(?) THAT WE BELIEVED WE COULD SEE HEADS IN THE WINDOWS. IT WAS PROBABLY LESS THAN 1/4 MI FROM US AND LESS THAN 100 FT ABOVE US. IT BANKED TO THE R FROM ITS NORTHERLY HDG AS WE WERE DEFINITELY CLOSE TO IT AND SLIGHTLY OFF TO THE L AT THE SAME ALT. I HAD MY HANDHELD RADIO WITH ME IN ADDITION TO THE ACFT RADIO. I PROBABLY SHOULD HAVE CALLED DEN APCH; WHICH I BELIEVE I HAVE PROGRAMMED IN; BUT WAS BUSY IN THE SEE AND AVOID MODE TRYING TO FIND CLR AIRSPACE TO OPERATE IN WITHOUT GETTING INTO MASSIVE SINK.