Originally Posted by MTK
A 13x8 apc sport? Really? that's the prop I've used on my YS63. The CRV engine may be trully this anemic, I don't know....let me suggest a couple things to get a lower reliable idle....higher nitro, 20-25% heli blend. A hotter plug such as an OS F. The hotter fuel will produce a better top end too. It sounds to me like your CG may be fine...be careful moving it aft, especially if the model is heavy for its wing area. A 60 size warbird with maybe 650 squares shouldn't weigh more than about 8 1/2 pounds for decent flight envelope, and 6 1/2 pounds is far better. If it's heavier and the CG is moved aft, it's a recipe for a crash on the landing. Come to think of it, if the CG is moved too far foreward, the same crashed landing may result. In both cases the wing stalls.
Appreciate the reply, that RCV91 is a good reliable engine, but trust me, it's just not nearly as strong as a YS or OS, never was really; I chose this engine because it is heavier than other 90 size 4-Strokers and I needed nose weight to balance; your right, I also used a 13 x 8 on a YS63 that I had; the fuel would be a good idea, but the Manufacturer of RCV Engines doesn't recommend anything higher that 10 to 15% and I have been running exactly that without any problems, the Low idle I can get is smooth and reliable, and like I had said previously, never had a problem landing with a 3 Bladed Prop but the prop would not pull the plane with any balls, the 13 X 8 does the job, I just can't seem to get it slow enough for a decent landing unless there is at least a 5 mph wind in the plane's face, Also, like I mentioned I believe the CG changed from when I originally built rthe plane because I changed the Air Valve and Placement and the CG was off, more Nose Heavy then when I originally balanced it.
Anyways, I will try the plane with the changes I made, the shift of CG slightly more AFT will be manageable, I can move it forward if need be, but the change was slight, it may not even be enough to affect anything, we shall see.