When you fly giant scale aircraft you have a choice of engines and power systems. When it comes to aircraft with round engine cowlings however, nothing beats the sound and performance of a radial engine.
Most giant-scale airplanes feature an engine box built into the fuselage and secured at multiple points for strength. The Hangar 9 De Havilland Beaver is no different. The length of the Saito 33R3 radial engine (with the included mount) is longer than that of the recommended Evolution gas engine, so the position of the engine box has to be adjusted. I measured the Saito’s length from 1/4 inch behind the propeller to the engine mount. I then installed the cowl using that same distance. I marked this dimension with a pencil on the inside of the cowl. This showed the new location for the firewall. I then cut away the excess material from the front of the engine-box structure so that the engine (attached to the firewall) could slip into position. A Dremel Moto-Tool and a cut-off wheel did the job. A sanding block smooths the edges nicely.
I made a firewall template (including the engine mount bolt hole pattern) and worked out the positions for the throttle arm, carburetor venturi, and the fuel and vent lines. I then fabricated the new firewall, laminated together using three layers of 1/8-inch plywood using 30-minute Zap epoxy…
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