Designed and built by Mr Vernon W. Oldershaw of Bakersfield,bCalifornia, in 15 months for a cost of $4,000, as a development of the O-2 but for Open Class competition, the O-3 featured a longer span of higher aspect ratio and a retractable gear.
The O-3 is of all-wood construction with cantilever shoulder wings and a V-tail; the wings have a spruce spar and plywood ribs and skins, with wooden ailerons and air brakes on the trailing edges. The ellipitcal-section fuselage is built up from plywood bulkheads, the front portion from the nose to the wing trailing edge having a glassfibre outer shell and the remainder being plywood-covered. The tail surfaces, which are slightly swept back, are of similar construction to the wings. There is a retractable rubber-sprung monowheel and a tailskid. The pilot sits under a one-piece flush-fitting cockpit canopy.
The original O-3 single-seat sailplane made its first flight in June 1967. One was flown in several Nationals and made a flight of 694 km./ 431 miles. Two O-3’s were built, and both were subsequently motorized. A two-cylinder, in-line, two-cycle Yamaha snowmobile engine was mounted inside the fuselage behind the wing spar driving a pylon-mounted wooden pusher propeller via belts.
Oldershaw began to develop a retractable powerplant installation which was added to a second O-3 completed in 1975, the engine being used primarily for take-off and climb to soaring height. It is a 31 hp Yamaha Snowmobile SW433 two-stroke 'flat twin' driving a two-blade fixed-pitch wooden pusher propeller, the pylon mounted propeller retracting forwards into the fuselage behind closed doors to lie over the engine, which is behind the cockpit. There is a single aluminium fuel tank in the fuselage of 2.5 US gallons capacity.
Wing span: 16.46 m / 54 ft
Span: 55 ft 0 in
Height: 4 ft 8 in
Wing area: 125.0 sqft
Aspect ratio: 24.1
Empty weight: 780 lb
Max weight: 1,000 lb
Max speed: 125 mph (in smooth air, power off)
Max cruising speed: 95 mph (power on)
Min sinking speed: 2.30 ft/sec at 55 mph
Best glide ratio: 37:1 at 68 mph
Take-off run: 900 ft
Range with max fuel: 50 miles