the pilot's failure to maintain an adequate airspeed margin while performing a return to runway maneuver, which led to a stall and spin. Factors in the accident were: 1) the deteriorated condition of the glider towrope, which resulted in towrope failure during a critical phase of the tow; 2) the duct tape covering over the abraided portion of the failed rope end that made inspection of the rope difficult; and, 3) the gusty winds and turbulence.