John Haas' 1/48th Ki-64 'Rob' Completed!

Expert craftsman John Haas has now finished his 1/48th scale Kawasaki Ki-64 'Rob' project and here it is. Previous in-progress instalments can be found here, here, here and here. John concluded that although the model had not been easy to build he was pleased with the result. He hopes that blog readers will enjoy these images of the model and find inspiration as to what is possible with old school woodcraft.

A most interesting concept, the Ki-64 explored performance with twin engines mounted in tandem driving two contra-rotating propellers and cooled by a vapour-phase steam condensing system. The rear engine drove the variable pitch front propeller via an extension shaft passing above the cockpit floor between the pilot's legs whilst the forward engine drove the rear fixed pitch propeller. Each engine could be operated separately and it was envisaged that for cruising the forward engine could be shut down with the aircraft flying satisfactorily on its rear engine and front propeller alone.

The cooling system, which was designed to reduce the drag and vulnerability associated with conventional externally mounted radiators, operated with a flash steam generator-centrifugal separator  with a pressurised liquid coolant. The generated steam was circulated through 130 sq ft of wing panels and the condensed water pumped under high pressure into two 18 gal wing leading edge supply tanks by ejector type venturi pumps using the engines as a source of power. 98% of the pumped water was re-circulated and only 2% flashed into steam. There was also an auxiliary top-up water tank in the rear fuselage. For these reasons the designers believed that the coolant system was actually less vulnerable to damage during combat (and not more vulnerable as some sources have suggested) since any loss of coolant through leakage should be adequately compensated by the amount of excess water available in the supply tanks and auxiliary tank. In a post-war report on the system the Kawasaki designers Takeo Doi and J Kitano stated that:-

"As the vaporised water is small compared to the circulating water  it will be apparent that it is not vital if the wing is punctured by gunfire or by missiles."  

Comparison of Ki-64 to Ki-61 Hien 'Tony' ~ same scale

The port wing condenser panels and supply tank served the front engine whilst the starboard panels and tank served the rear engine. Prior to installing the system on the Ki-64 it was tested and improved using a modified Ki-61 with the conventional under fuselage radiator removed (cue unique modelling subject) which made 35 flights from October 1942 until the end of 1943. Once installed in the Ki-64 only five test flights were made before an emergency landing following an in-flight engine fire wrecked the aircraft. Plans to test the system in extreme cold weather conditions using methanol instead of water were never achieved. A disadvantage of the system was the lack of space available for fuel tankage and consequently the Ki-64 would have had a relatively short range of 620 miles. Had it been developed into operational service external drop tanks would probably have been used to extend its flight time. The cooling system was considered to be of sufficient merit by the US Air Technical Intelligence Group which evaluated it post-war as to warrant further study at that time.  

With very special thanks to John Haas for sharing a unique and fascinating project with Aviation of Japan.

Image credit: All photos © 2015 John Haas