J Hallock,
Actually, you're going to find that experimenting with 3-bladers on models is a pretty small little box. There aren't usually many 3-bladers in the hobby shops, or only one or two. The biggest hobby shop in my area happens to have about 5 different sizes, and that's also 5 props total. It won't be easy. There are a couple of small-shop custom prop makers that are around but they're mail order and I can't remember seeing one of them advertising for awhile now. I'd like to suggest that if you plan to be somewhat rigorous in your testing that you look around for a Prather Pitch Gauge. There actually might also be other pitch gauges out there, but I know and use this one and it's a jewel. And after using it for a very short while it'll be fairly obvious that there is a lot more to a prop than the diameter/pitch markings on the sucker and those very often aren't correct for all the props from the same box, and often isn't correct from one blade to the blade on the other side of the hub.

speedster1919,
And merry Christmas to you. BTW, in WWII, the Corsair and P-47 were already faster than just about anything they flew against. But they didn't climb as fast as some. In fact, the designers were working hard to cure that problem. Before the P-47 got it's 4-blade, almost everything with guns in the wings could outclimb that hulk. After it got the 4, it could even outclimb the Spitfire. The design change was really an attempt to get more blade area working and to keep the prop tips under mach speed. They wanted climb and speed but really wanted climb BAD!
And an interesting little tidbit about efficiency of props.... The c/l speed boys have used ONE BLADED props for years and years and years. Can you guess why?