ORIGINAL: shakes268
Bill,
I have the 85" QQ Yak, DA-50 spinning a Mej 23x8 prop. Elevator throws are about 55 degrees. Rudder is around the same throw as well. I am slightly behind the aft recommended CG point (still flies great).
I tried different entries. First few times was the stall turn entry - got it on its side, reversed rudder input, full down and it tries to enter then rolls on its back and does a gorgeous flat spin.
Tried with a downline tumble entry which seemed to be more successful (downline, sticks upper left then slide out of the aileron) - spun 2 or 3 times and rolls over into an inverted flat spin.
Shakes,
It sounds like you have enough throw and possibly power depending on the weight of the plane. A Da50 will get a 15 to 16 pound plane going but once around 17lbs or higher that is a lot of mass to get moving. You could try getting more throw but I do not think it will help. It could also be a matter of timing on you part. You are getting into it but you may be hitting it before the tail starts coming around.
Try going in from a downline roll. Kick the sticks into the flat spin once you get rolling pretty good, (blender) position and immediately neutralize the airlerons.
In the video I posted above, I make a reference to a section about 2/3rds into the video, at that point he is rolling straight down, enters into the blender but neutralizes the airlerons just before it starts to flatten into the flatspin, at this point he has all kinds of momentum for the KE spin. Watch carefully and you will see this happen but it happens very quickly
Power is everything on this maneuver on a Yak. On my two Yak examples, both are right around 17 and 18 pounds respectively the 17lb one has a tuned pipe on it's DA50 so it's putting out more power than a canister or pitts muffler.
The second one is 18lbs but has a 58cc on a pitts so it's brute power getting the maneuver started
I once ran into this on my Cap, I could get two or 3 turns before it would fall out. That was a 14lb plane with a Fuji 43. Now I stuffed a DA50 into it at 14.5lbs and with my throttle curve I'm at 1/4 throttle doing KE and watefalls.