Ah yes, the Sigma - whatever happened to that? The BRM of gliding I think.
It came to Alberta and was rebuilt with slotted flaps by Dave Marsden. I don't know where it is now. I'll make some enquiries.
The hydraulically actuated flaps increased the wing area to 177 square feet (an increase of 35%), lowering the wing loading and stalling speed (37 knots), allowing the desired tight circling when thermalling.[3] The hydraulic pressure needed to move the flaps was provided by the pilot pumping on the rudder pedals, this proving to be tiring, not to mention that moving the flaps in flight was found to be almost impossible due to bending in the wings. Performance testing revealed a disappointing[4] best L/D of 41:1 and the project was wound up in 1977.[1]
The group offered the Sigma up to further development by other parties, selecting a proposal by David Marsden a professor of mechanical engineering at the University of Alberta (on sabbatical at Cranfield Institute of Technology and a glider pilot holding records with his own glider designs such as the Marsden Gemini).[5]
The aircraft was moved to Canada in 1979 by Marsden, modified with a new flap system, conventional ailerons in lieu of outboard flap sections and the tail parachute was removed from the rudder. Despite the glide ratio only increasing to 47:1, its good climb rate made it competitive with contemporary Open Class gliders of the time, breaking the US 300 km triangle record in 1997 at 151 km/h (82 kn).[1]
https://en.wikipedia.org/wiki/Operation_Sigma_Sigma