The pilot of the unregistered and unlicensed experimental homebuilt requested a high speed taxi test from the ATCT controllers with an option to takeoff for closed traffic. Witnesses said the aircraft became airborne after about a 150 foot ground roll and entered a steep climb. The pilot then reported to ATCT that 'I've just lost a rudder pedal.' The aircraft then fell off on a wing and entered a steep nose down spin or spiral to ground impact. Earlier in the day, an airline pilot who also holds an A & P mechanic's certificate talked to the pilot and looked over the aircraft. The pilot told the witness that the aircraft had not flown in two or three years. The witness said he saw many discrepancies on the aircraft as he watched the pilot work on the rudder cables in the rear seat area. Some items noted by the witness were: 1) rudder cables not routed correctly on the pulleys in the cockpit area, 2) rear cockpit right rudder pedal was collapsed on the floor, and 3) rudder cables connected to the winglet rudders with bungee cords which were tied together. The witness said he recommended to the pilot that it not be flown. FAA inspectors examined the aircraft and reported that control system continuity could not be established due to cockpit impact damage.