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Old Nov 25, 2012, 11:56 PM
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The 'Wack, BC, Canada
Joined Oct 2002
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Well, for a "fix" of this sort to work it needs to be doing something that fixes an existing problem. It also mentioned that it worked best on higher values of "advance ratio".

Higher advance ratios on a prop used in a wind tunnel setup suggests higher angles of attack for the blades and that suggests that perhaps the blades were at a high enough angle that the forward surfaces were suffering from some amount of separation bubble formation or even to the point where the blade was stalled. A stalled blade will still produce thrust but it does so with a high drag penalty. The notches act as a turbulator to generate a turbulent boundry layer which could be working to reduce the size of the separation bubble or even to delay the final full stall condition. Not to say that ANY of this is the answer for you. It's all just possibilities since we simply can't see what the blades were doing in his testing and what the airflow was like.

So the notches didn't help on the APC prop. Likely because the prop was not suffering from poor airflow issues in your case. So adding the notches did nothing since there was nothing that the effect of the notches "fixed".

Your blog also mentions that the prop was operating in a rather high ambient airspeed. So likely the angle of attack at the blades was low. Again a recipe for a smooth airflow over the blades which had nothing that needed "fixing" by the notch effect.
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