Woodspring gliding club at Weston-Super-Mare had a T-21 with a canopy. During a launch one day, one side flew off and got trapped between the strut and the fuselage. The other side remained attached which caused all the crud in the bottom of the cockpit to be sucked off the floor and into P1’s eyes. An interesting circuit ensued, trying to see and at the same time not lose the errant canopy.