Garys Sikorsky

Garys's SIKORSKY S-39

The Sikorsky S-39 was an American light amphibious aircraft produced by Sikorsky Aircraft during the early 1930s.

The S-39 was a smaller, single-engine version of their twin engined S-38. This model is based on those flown by Varney Air ferries around the San Francisco Bay area.

This model is scaled approximately at 1:18 giving a wingspan of 900mm. It is built from Depron foam sheet over 3D printed frames with wings and tail plane also Depron. Further 3D printed parts are the nose cone, motor nacelle, struts and float bases.

The plane was designed using CAD software which enabled the creation of files for the 3D printer.

The fuselage was built up by positioning the plastic frames on an aluminium 'spine' to hold them in the correct position and alignment, then sheeted with 3mm Depron. The spine is removed after assembly.

The wings are cut to shape from 6mm Depron, then heat formed in a custom oven to achieve the camber. The tailplane assembly is 3mm Depron. This is joined to the wing by two composite booms of balsa and carbon fibre strip.

This aircraft has a unique design where the fuselage (hull) hangs from the wing / empennage assembly by a (large) number of struts. This allowed me to place all the RC hardware (Rx, ESC, servos etc) on the wing (under the centre section) as a complete assembly. When the fuselage is attached, the battery is the only electrical part in the fuselage, the power leads going up to the wing through a hollow alloy streamline section.

A pair of undercarriage struts can be screwed on for hard surface use.

This model flies well off the water and is quite stable in flight, preferring fairly calm weather. Landing is another matter, and considerable care is required to achieve a smooth 'no bounce' landing.

Watch the You Tube video for more information