Don't forget about the RV Speed Range!
Guys,
My partner in the RV-8 was adamant about having a fixed pitch prop. I had to convince him that the constant speed was a GOOD idea. This is how I explained it.
For a Super Cub or other conventional light aircraft like a Citabria etc, a fixed pitch prop works fine. The reason for that is that the speed range of these aircraft is only from, say, 40 knots to 100 knots. That is 60 knots of airborne operational speed.
The RV on the other hand, operates from 55 knots to 175 knots. The airborne operational speed range is 120 knots. Twice as much as a "normal" light aircraft. It becomes obvious then, that no fixed pitch propellor will be able to be anywhere near efficient throughout the RV speed range, and only at one cruise speed.
My partner said he understood this but I could tell, he was still not convinced.
Then, we went flying in a friends fixed pitch RV-4. I told him, "Notice the RPM during the takeoff roll" "Hmmmmm. Only 2350 on takeoff." I said "Yeah, guess what that works out to for horsepower?"
We looked it up and it came to around 125 hp out of the 150 available. So then I asked him, "How much horsepower would be available for takeoff from a 4000 foot elevation airstrip?" The answer was obvious and he decided that maybe a constant speed prop might be a good thing.
During the same RV-4 flight we bumped the speed up to 175 mph indicated. The RPM was nudging 2600 at this point. It was obvious the airplane wanted to go faster but the engine RPM was getting into the limiting range.
The big trade-off with the fixed pitch propellor is takeoff performance vs. high speed cruise performance, and on the RV, the trade-off is aggravated by the large operational speed range
So, I guess my point is, that if you want to exploit the true potential of your RV, then get a constant speed propellor.
If you will be happy with limited takeoff and climb performance and good, high RPM cruise performance, then, get a fixed pitch propellor.
If you do get a fixed pitch propellor, and choose a wood prop, be prepared to throttle back to 2000 RPM in any kind of rain. Sad, but true, the rain will eat a wood prop on a speedy RV. However 2000 RPM and 110 knots will keep your leading edges OK.
Hope this will help with your choice.
Cheers, Pete