Grumman Duck

 

John's latest build is a Grumman Duck seaplane. This model is being built to a scale of 1/4.6 to suit the power output of its Fiala 85cc 4 stroke engine and to ensure it is not to big to fly from the local lake. Design of the model started in mid 2023 and the first wood parts were cut on  the teams CNC machines in late 2023. A big design feature of the Duck is its complicated retracting undercarriage which involved a lot of head scratching to mimic the full size. To check the design, a 3D model of the undercarriage was printed to check the geometry before machining of the metal parts is commenced. It is intended to operate the retracts by hydraulic pistons and pumps to get a scale retraction.

Starting the wing construction whilst still working on the detail design of the fuselage on the computer

Top wing center section framed up

Tailplane and elevators under construction.

Starting to frame up one fuselage side

Partially sheeting one side of the fuz before lifting it from the bench

Addind the second side fuz frames whilst ensuring everything remains straight and true.

A jig was used to hold the top wing centre section at the correct incidence whilst making the cabane struts.

Tricky convex curves to sheet on the lower fuz.

Preparing the top wings to align with the center section.

Checking top wing alignment.

Cabane strut wirework all finished. This will eventually be sheeted in balsa. Top fuz sheeting also added.

Carving the lower wing wing root fairings.

Checking the tailplane and fin alignment prior to glueing into position.

3D printed model of the prototype undercarriage for the Duck. Used to check geometry and clearences.

Working on the CAD design for the undercarriage

Main retract formers being assembled before construction of the float starts.