An interesting question is this: WHY would the original designers have added such elaborate "lightening" holes at all? I mean, why bother to lighten this prop retention plate at all? What why would saving some pound or two of weight UP FRONT matter? Certainly these hub plates would have been difficult to manufacture and would have to be properly balanced. So why bother? In the world of RC WWI modeling, we almost always need MORE weight up front. We can even by "heavy hubs" for planes like the Cub or the Corsair.

Why would WWI engine designer's have wanted to save weight? Perhaps it had to do with minimizing the "total propeller weight" -- but given that this metal flange is closely centered on the drive shaft it's impact would seem to be minimal. Folks back then WERE however concerned with engine weight. In fact, airplanes look the way they do precisely because engines were "too darn heavy" so designed had to extend these weird appendages "out the back" to balance the dang thing. I remember reading about Anthony Fokker solving a CG problem on one of his prototypes by having his technicians weld a couple more inches of length into the tail tubing.

So were the "lightening holes" in the prop retention plate (what I've been calling the "hub") actually about "saving weight up front" so not to need to add additional weight on the tail? This sounds crazy from an RC perspective but then we have these darn "underweight and overpowered" model engines to work with.

Anyway, it's an interesting question to ponder as I drill the 25 holes in the Mercedes 180 "hub." [sm=50_50.gif]