How to start the RCV
Brian, et. all:
Well I braved the 48 degree temps and the 15-20 mph winds to get a flight in today on the H-9 P-51 and the RCV 90.
Before I get into the details let me offer a few thoughts. I, like many others, wanted to try to find an engine that could turn a three or four blade prop for some of my scale planes. I have been flying the H-9 P-51 with a YS 91 and a Graupner 14x7 three blade prop. With the combo, I was turning 9000 rpm on the ground and the model flew extremely well. Having flown a lot of different types of planes (BVM Aggressors (199 mph), 120" span A-10 (86 mph), Patriot with YS 45/pipe (144 mph), etc.) I beleive that I have a firly good feel for the approximate speed of a model. HAving said this, I would estimate that the speed of the P-51/YS combo was in the 105-110 mph range. I have about 20 flights on the YS 91 H-9 combo so I am fairly comfortable with the combo and I have a good feel for the speeds of the model in different wind conditions.
The RCv 90 that I flew today has just a tad under 2 hours of bench running time on it. The last 30 minutes of running time was with a Zinger 18" x 10" two blade prop. I tacked this combo at 5250 rpm on the test stand. I was using an OS F type plug, Powermaster 10% fuel with 18% oil. This fuel met the RCV requirements relative to castor/synthetic content and percentages. I installed the 4 blade Zinger 16"x10" prop on the RCV 90 and got it all cranked up and tacked. Boy the four blades sure looked neat on the front of the model! The engine turned this prop at 4900 rpm. I could lean the engine about another 100 rpm but it really fell off after that and I was reluctant to lean it too much on the ground. Static thrust felt pretty good. I could idle the engine down to about 1700 rpm. It was a little rough below this setting so I probably needed to adjust the bottom end a little but I left it as it was since it idled smoothly and transitioned pretty crisply to full throttle.
The take off was pretty smooth and took a little right aileron (could be wind or torque) immediately after breaking ground. Interestingly enough, I don't remember putting any right rudder into it for take off (like I had to do with the YS 91). Climb out was a little slower than the YS. I flew the plane for about 8-9 minutes and tried rolls, loops, dives and climbs. The plane seems to be noticably slower than the YS. The upwind passes were slower than with the YS. I would guess that the downwind passes were just a little slower that the YS combo upwind passes. I would estimate the model to be flying in the 65-70 mph range upwind and about 85 mph downwind. I don't think that I really expected the RCV to be as fast as the YS but I was hoping it would be close but it was not to be. With the YS 91 and the Graupner the model would do really large loops (maybe 200 ft in diameter) from level flight. With the RCV, the model would loop from level flight but they were fairly small loops (maybe 100 ft dia.). The other thing I noticed was that the model didn't have very much vertical (thought the bigger prop might give me more than the YS). One aspect that I fully expceted to happen on landing did. When you throttle the four blade prop back the model really bleeds speed in a hurry. It takes about 3-4 seconds for the speed to fall off, but when it does, it does so quickly.
Having said all of the above, let me say that I haven't given up on the RCV. I am going to try the 16x10 three blade prop this week ( I am going to a fly in and will et a chance to try it out). I beleive that what others have said in the various RCV threads is correct. That is that if you want to fly at a "scale like speed" then the RCV is probably a good choice. However, I am of the belief that if you want to go fas, you need to turn some RPM. Now that I have set the P-51 up so that I can easily change between engines at teh field, I will put somemore time on both combos and get back to all of you.
It was not and is not my intention to malign an engine or a manufacturer here, so please beleive me when I say that all of the above info was presented to help people make an informed decsision. If the RCV doesn't work out on the P-51, I will put it in my Top Flite Beechcraft Bonanza or their Stinson Reliant. I WILL find a good match for the engine. I am not going to abandon the unit. It is an exceptional work of art and it runs really well. I just need to find the right plane for it.
Hope this has been informative. Also, I am having trouble getting my photos of the combo sized correctly so that I can attach them. If someone wants to resize them for me let me know and I will e-mail them to you for posting.
Later,
Ed