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The PBY-2 model was powered by two Max .10 Shenuerle engines, but they just wouldn't quite "hake it" to get the model off the water. Yes, a couple of .15s would, but I didn't have the time to make the modifications. So, the model hung up on display.
Time went by, and finally I had all projects under control. But the PBY hung there - sort of leering at me. It was time to do something about it.
I had heard a lot about the power potential increase when you modify a glow engine to pure compression ignition – or "diesel" if you wish. So, I called Bob Davis, head honcho of Davis Diesel Development, and told him my problem. Yes, I could go to .15 engines, but the model only had 2 ounce tanks, and a glow engine with .15 displacement wouldn't run very long. Also, installing larger tanks meant a major modification.
"Try a .10 diesel head," Bob said. "You'll get about the same power – if not more – than a .15 glow engine."
So I did. And Bob was right - Suffice it to say at this time that, using the same 7x6 Master Airscrew props which were on the flying boat, the rpms increased from 11,500 to 13,500! I was convinced.
It came up on the step after a fifteen foot run, planed for another twenty to twenty five feet, and lifted off perfectly. As a matter of fact, the two Max .10s with their diesel heads were far more power than required for scale like flight.