“Thread drift... Rod , you mean that you could make the MCR01 go even faster than 138kts if you wanted to? Seriously impressive....”
The short answer is yes, but it is not as simple as that…
There are no figures on how to set up my kit built C/S prop on my airframe. This means I have to adjust and test, adjust and test. I have the fine pitch stop where I want it but the coarse pitch stop is too fine to achieve best performance, especially at altitude. In order to adjust and test I need a day, which is very smooth (no nasty bumps), as the aircraft does 152kn TAS (3000ft) flat out, and if I move the coarse pitch stop it will go faster (by an unknown amount). This brings up the other problem, the VNE is 162kn, which is ok, but the rough air speed is 128kn. There are certainly conditions, say above a broken layer, or on a still evening when it would be perfectly safe to cruse at 140kn plus, but it has its down sides.
My aircraft is an MCR01 Club, which has a bigger wing than an MCR01 Sportster. A well sorted sportster will cruse at 160kn (but has 30kg less useful load and needs more runway). To do this it uses a special “high speed” blade on the PV50 prop hub. I have the standard blades, but am now getting into the speed band where the “high speed” blades would be more efficient. There is no danger of my blades failing, but I am loosing performance. The importer would love to see what would happen if I fitted the high speed blades, but unless he loans me £700 worth of blades to try I am unlikely to find out!!
I am also getting 15lph (mogas) and I suspect that getting an extra 7 or 8kn would push the fuel burn up to 18lph+. I will probably have another play at some point, but I am having too much fun flying her long distance to go back to development right now. Over the winter I may upgrade the glass HSI to a full “synthetic vision” big screen system and maybe tweak the prop some more as well or I may just keep flying her as much as possible…
Rod1