Quote:
Originally Posted by McGillicuddy
. . . I think where maybe it gets tricky is that the finer casting makes more complexity available to the shape thus they can use more cup or rake in a similar geometry to improve the desired performance characteristics. Between that and the added weight varying models may or may not prove harder to turn. . .
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Gillie, that's a good observation. Whenever we improved our blade casting technology at Pratt, I never knew any engineer that didn't want to introduce more complex cooling schemes and 3-D aero designs that made the parts even harder to make! I'm sure prop designers are no different!
One other thing the could make the stainless props harder to turn is that the stronger material will hold it's shape better under load, where the aluminum props will tend to flatten out and lose pitch or cup. I think the Comprop folks that make the composite props actually claim that as an advantage, i.e. the prop flattens out to provide less pitch and allow engine to rev further up into power band when getting on plane. However that might be a good example of the old saying about fixing a problem, "If you can't FIX it, FEATURE it!" Bottom line is that prop design is so complex that you can't generalize . . . the reduced drag of thinner blades can easily be offset by subtle tweaks in blade shape, profile, rake, etc.! Denny