The Piaggio 136 Royal Gull is a twin engined amphibian aircraft designed in Italy and later built under license in the USA. It features a gull wing, twin pusher engines, flaps and retracting undercarriage. Span was 13.53 m.

Details are available by searching Wikipedia and Google images (among others).

The model to be built is at 1:7 scale, giving it a wingspan of 1930 mm (76"), fuselage length of 1542 mm (60.75") and a tailplane span of 700 mm (27.5"). Wing and tailplane will be removable for transport or storage.

Design goals are for the model to be:
- radio controlled using 7 channels
- able to operate from land or water
- electric powered
- close to scale appearance
- lightweight
- to include flaps and retracts
- to have stable flight characteristics
- be easy to transport and assemble, with minimum of connections
- have a duration in excess of 5 minutes, ideally 10 minutes
- have easy flight battery replacement
- have differential throttle control to give good steering control on the water.

A free-flight plan of the Piaggio is available, but I could not find an RC version so decided to design my own. My plan was drawn up in drafting film (remember that?) then copied onto many A3 paper sheets to build up a working plan. Modifications and corrections can then easily be made onto the film.

The design follows the principles used by Ivan Pettigrew for his very successful range of electric powered seaplane models, for which plans...Continue Reading