I've recently been trying to perform waterfalls and elevators with my aeroworks 90-120 yak. My waterfalls aren't very tight and my elevators don't drop straight down. My cg is slightly tailheavy and my 3d rates on my elevator control surface is everything i can get. My engine idles around 2100 rpm with a 17x6 prop. Do I have a cg problem? Should I be more tail heavy or nose heavy for these maneuvers?

Tailheavy. Keep moving cg back a little each time and then fly it to see how it performs.

how much throw r u abe to get do u know the degrees?

Dont know the degrees, but the control surface can not physically move any further up or down. Deflection each direction is 3 3/8 inches.

Use engine bursts to keep the tail down, but not too much to keep it stalled in elevators, and to do tighter waterfalls enter the maneuver from a hover , absolutly not moving or slightly tailsliding, then add full down and full throttle, also, don´t use too much aileron, but rudder corrections may help also to make it tight

Daniel

Try some different props.Some may laugh at me,but they can make a huge difference,how the thrust is used effectively at low rpm.The sink rate is adjusted by small blips of throttle.

Where you get on and off the throttle is very important to get tight waterfalls. The CG needs to be pretty far back and if you can measure the throw in degrees it should be at least 45 degs. I would think you have that much if you are maxed out because my AeroWorks Extra 260 60/90 size will get that much. It does great waterfalls as does my nephews AW Extra 260 50cc. All of the AW stuff I have been around will do good WF's so IMHO it's just a matter of getting the setup and technique right. Good luck.

Edited to add: I forgot the mention that it sounds like your CG is still too far forward if you are having trouble getting it to do a decent Elevator. The elevator surface needs to be able to hit 45 degs for that too and that's where it should be as you are descending. Full up and just enough throttle to keep the plane level in pitch. Remember as you move the CG aft it's gonna get harder to land.

A spoileron mix will also help if you don't want to get the CG to far back.

David

I forgot about that one Dave, that helps too.

With elevators heading into the wind makes them drop straight down.

i also have that yak and last year i had a saito 150 with a vess 17/6 prop on it, cg was slight down pressure inverted. the waterfalls were ok almost like what you described and i have about 50degree's elevator travel. this year the only thing i changed was the motor and prop. went with a mld 28 gasser and a vess 18/6 and the waterfalls were almost like it was on a pivot. i really believe the bigger prop made all the improvement. what motor and prop combo do you have?

120 ax and 17x6 prop

you could try the other suggestions but with my experiance and it's limited but the 18" prop and the fast spool up on the gasser really made a difference. and some planes will waterfall better than others too.
how is the wing rock doing the elevators? i havn't done alot of elevators, alot of flat spins and blenders and waterfalls and KE stuff. i get some wing rock and i don't like it to much so i am going to try to cut back some weight.

During elevators, there is alot of wing rocking, more than during harriers. Dry weight of the airplane is 9lb 10 oz.

I would say again to try a spoileron mix. Even with the CG way back some planes wont do it. An example would be a Funtana50X. This is the first plane I got to do an elev. Because of wing rock and other factors I'm sure, the only way it will do one is with spoilerons. Doing them inverted also helps with the wing rock if you have not tried that. Maybe the rudder being in clean air helps. Anyway I posted a few pics of the mix in action.

David