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RADIO CONTROL NEWS
Thirty-five years ago I won my first control-line contest with a Drone Diesel powered ukie. Ever since then. I've wondered why the diesel has never reached the high popularity levels here as it did in Europe. The drone was powerful even though difficult to start and a bit messy with exhaust. It was cheap to operate and it turned a very hefty prop. But, it died after a short period of popularity (primarily on the East Coast) and with it sent the production of any American diesel as glow ignition, two-cycle engines became "the way to go."
A diesel, better said as "compression ignition" is a very simple internal combustion engine. All that's required for running is appropriate fuel (usually kerosene, oil, and ether) and a good flip. An electrical source, ignition components and glow plugs aren't needed.
In any event, I rediscovered diesels a number of years ago as I tried to make my Eyelash design into a full-fledged multi-channel bird. Eyelash was a 1/2A version of the Eyeball, an in-line (engine thrust wing-stabilizer) design for pattern. Power was a typical .049 Cox engine and it wasn't until I tried a Davis Diesel conversion of this engine that I made the project work. In this case, a conversion of a popular glow engine to diesel operation made an overweight idea viable.
If you haven't been looking, "Davis Diesel*" is a company that provides heads that will make almost any Schnuerle glow engine into a diesel. Such conversion involves no more than a replacement of heads on a given engine and a different kind of fuel (a change of fuel lines is also needed). The heads range from .049 all the way to the new Super-Tigre 2500 and 3000.
A few years ago. I converted an O.S. .61 FSR to diesel operation in an effort to make an overweight Skybolt perform. The airplane, as a result of far too much paint, flew like a log. With the Davis head, I was able to increase the propeller size by 3 inches while retaining the same pitch and it all worked. The airplane became a better flyer and I won a number of meets with it after the change.
Basically, when you install a Davis diesel head, your engine gains the ability to turn larger props, frequently in sizes that would be impossible with glow. Fuel requirements are substantially reduced and noise goes way down (a factor I had missed in my first experiences with Davis diesels).
I like all the advantages in diesel operation, but I believe the noise reduction is the one that any modeler ought to look at. Frankly, the noise level drops to that of four-cycle engines. Of course this is exhaust noise-prop noise remains as it would with any engine turning any given rpm. The noise reduction apparently comes from the fuel burn pattern of a diesel engine-such an engine simply doesn't have the explosive exhaust note of a methanol-fueled engine. In addition to that, a dieselized engine can use a very restrictive muffler without much power loss, which further reduces noise.
I've recently been flying a Davis dieselized ST 2500 in a Midwest Stik design. The engine conversion proved capable on any reasonable prop, easily matching glow operation. And it did that at lower fuel costs and substantially lowered noise levels.
Is the diesel a perfect answer to our power problems? No, nothing is. They are a bit more difficult to start but, when the technique is learned, they become as easy as most engines. An electric starter snaps them right off. They also tend to exhaust more oil than glow. This can be solved by using a long tube to route exhaust away from the airplane. Actually, more recent fuel formulations with reduced oil and clean-burning kerosene have reduced the mess in diesel operation.
A Davis Diesel converted "60" would make a near perfect powerplant for Turnaround pattern. The engine can turn a large. high-pitched propeller and should meet FAI noise level restrictions. Certainly the diesel remains a fertile area for experimentation; it will be interesting to see who becomes a winner with this type of engine.