ORIGINAL: KenLitko
Well, in a way we are discussing compressibility effects. Saying that we are at a low mach number (below about .3) can be used to say that we are dealing with low speed (incompressible) flow... which was my point.
As far as the magnitude of C_L goes, think of it this way... say that we have a model designed for flight at 100 mph (flight C_L). Below this we can maintain altitude by increasing C_L, above this we can maintain altitude by decreasing C_L. So to say that induced drag goes down as speed goes up is a common way of looking at induced drag and speed's effect on it.
You can extend the argument to situations where there is a momentary high C_L (turns, etc...), but we are talking about racing (thinking flat-out speed). OTOH... that exemplifies the point.... if there will be a lot of turning (high C_L maneuvering), induced drag will be an even more important factor.... because we will be losing speed in those turns due to induced drag, not parasite drag.
No, compressibility is in no way involved. You have not explained how you determined that induced drag predominates below 200 mph.
Induced drag would be more important if turns were involved, but still not the most important. Profile drag also increases in turns.
banktoturn