When I get to altitude and bring it back to flight idle, I feed in full up elevator and my airplanes like to porpus. My 1/4 scale and my profile airplanes, the planes will pitch up and stall, drop the nose and pitch up again, stall drop the nose over and over. Is this an indication of not enough aft CG or not enough elevator throw or both? I don't get it. I do have 45* throw on my full rate elevators and the CG is already pretty far aft. Do I need more of each?

u should have enough as some birds will do it wiht less throws....

Sounds like CG is to far forward. It is also often necessary to add a slight bit of power which helps to keep the tail down. When the airplane is in the elevator, both wings are stalled. The airplane can then drop the nose and if it is allowed to do that, it will gain forward velocity and the wings will start to fly again, this often manifests itself in wing rock and can be alleviated with a little power to bring the nose up, slow the decent and bring the wings back into a stalled condition.

I think your main problem is that when doing an elevator you do not "feed in" the elevator. You pull full deflection and hold. Feeding in the elevator promotes flying on the edge of stall, where most planes will have a tendancy to porpus or snap. Same generally applies to a harrier.


Of course if your cg is not far enough aft, it will be impossible to do an elevator, you won't have enough elevator authority to keep the wing fully stalled. My judge for the correct CG is to perform a 45* inverted climb at about 1/2 power (enough to sustain the climb without accelerating). Let go of the elevator, the climb angle should slowly diminish (I would say the plane should return to level flight after about 2-3 seconds.)

I agree it makes for a cleaner elevator if you pull full up elevator fast (very slow air speed of course). Some times I even give a quick down elevator and then full up to snap it into a harrier or elevator (many 3D people do this actually). I had a few planes that did what yours was doing not matter what I did. I don't believe it was for lack of elevator throw or CG. It was a fun fly profile and the wing was too stable (square wing tips). It totally bummed me out that it did this and I finally sold it. I started out with a Funtana 40 and that thing did the most awesome elevators, especially inverted. But it had the tappered wings and was very unstable (hence the sudden snap and many crashes). But it couldn't harrier too well...not in these thumbs anyway. It would rock like crazy.

If you want to mix spoilerons in. It will help a bunch.

David

Few planes will do it well at idle unless the CG is way back. A couple clicks of throttle and you may find it settles in nicely.

Thanks, it will be a few days before I can get back out to experiment. Now I have also wondered about mixing in spoilerons like daveopam mentioned. How much do you mix in? Or should I say, how much do you start with? I have a Mojo 40 that's a blast to fly, but this is one of the airplanes I can't even get to do the elevator yet. Would I start with like 1/2" of up throw on the ailerons with full up elevator or what? Thanks for your help.

for starters, try mixing 50% spoileron with elevator on a switch. Using spoilerons will enable even the most stubborn planes.
check to be sure the plane will fly out of the maneuver without switching the switch back. You don't want to be reaching for a switch while you're that close to the ground (especially if the wings are rocking a bit).

What you have is an airplane telling you it has a c/g perfect for stable flight. It's doing what it's supposed to do. The c/g is too far forward, move it back. If the c/g is set correctly, or close to the neutarl point, the nose should pitch up and stay there at flight idle and low rate elevator as the plane stalss straight ahead. The quality of the maneuver will be effected by vertical speed, forward speed, balance, power levels, and control surface deflections. No one thing makes it happen perfectly.