jeep -- this is becomming a marathon & I'm not going to say any more after this post -- some of the commentary & examples have been entirely irrelevant, or just plain silly. I am more than aware of the reasons why multi-blade props are used in various circumstances. I spent many years doing research in fluid dynamics & have written more than a hundred scientific publications in the field. I also have a lifetime of both FS & modelling flight behind me. Don't teach me to suck eggs -- I know how to do it very well.

If what you have claimed is true, there is a reason for it -- and it isn't because three-blade props are more efficient -- they aren't. Your story clearly indicates that your engine was significantly underproped with the 14-6 2-b. However, that doesn't explain the 9700 rpm with both props --- what is your explanation? I would have thought that you would be more curious about the "why" of your observation -- it is anomalous and you clearly don't see the significance of that anomaly. I doubt very much if you have a magic engine/prop/airframe combo. That is why I have personal reservations about it. You should also be wondering why the big guns in the modelling world don't use multi-blade props in performance applications -- they certainly are not ignorant of the dynamics of flight & the appropriate application of multi-blade propellers.