Mr. George Pereira built the single-seat flying boat GP2 Osprey 1,
later known as the X-28A (US Navy 158766) in 1970. He started on the
design and construction of a two-seat amphibian development in
January 1972. Powered by a Franklin Sport the GP3 Osprey 2 (N3GP)
made the first flight from water in April 1973, the aircraft becoming
airborne after a take-off run of less than 800 ft (244 m).
The Osprey 2 had an unusual form of hull construction when after
completing the all-wood fuselage structure and installing the
controls the undersurface was given a deep coating of polyurethane
foam. To produce the needed hull form the foam layer was sculptured
and then protected by several layers of glass-fibre cloth bonded with
resin; after that it was polished and painted. This resulted in a
light smooth but extremely strong structure, with good shock
resisting characteristics.
The wingtip floats were constructed in the same manner as the
aircraft hull; the wings aft of the main spar were fabric covered.
The landing gear was manually operated; the engine was mounted on a
steel tube pylon structure bolted to the wing truss.
After the initial flights from water the plane was tested from land
and during the subsequent test flights a slight buffet aft of the
cabin was observed. This occurred with retracted landing gear at a
speed of 120 mph (193 kmh); and there was also an unacceptable high
noise level.
To counter this a modification was made in early 1974 by lengthening
the cabin by 7 in (0.18 m) and a Lycoming O-320 was installed in a
new cowling. Also the vertical tail was altered by enlarging the fin
above the tail plane, flight-testing was resumed and completed
satisfactorily during 1974.
Through Osprey Aircraft the design plans and kits came available to
the amateur constructors and over 500 have been built and flown. The
Osprey 2 designer received an award from the publication
"Mechanics Illustrated".