Rudder reactions

[Temptation]

	Quote: Originally Posted by Baron
	A trip strip is basically a fence to 'trip' or turbulate the flow, so it was a little artificial ridge on the top of the turtledeck. I do not know how high of a fence George used. This did not eliminate the coupling, but it reduced it enough to take notice to fuse cross-section as a contribution to pitch coupling. It's cool to experiment with that type of thing, but I think multi-point mixing works well enough for most everyone that just wants to fly - Cap 232s are sweet competition planes once the mixes and thrustline are set. -Baron

Baron, thanks for the explanation. I appreciate it. I think I will stick with the mixes as you suggested.

Thanks again,

Mike Darr

[ScottZ]

I have a 33% H9 Cap 232 and noticed that it does require more mixing and tweaking than other designs. In my setup I gave the motor about 4 degrees right thrust and about 1 degree upthrust .This seems to work for 3D only cause this setup changes pitching with throttle changes. This works for me cause it lessens the elevator mixing in KE and reduces the constant up elevator in hovering. You can also do this by mounting the gas tank on top of the wing tube. I leave the CG right where the manufacturer recommends since the CG on this Cap is very critical. If you don't spend some time tweaking a Cap you probably won't like it but once you get it where you like it the Cap can be a 3D animal!!!!!!!!!!!!!!!!!!

[heydick]

Here's a question for you trim guru's.
On a plane like this that has inherent pitch coupling to the belly, what would happen if you moved the CG foward and dialed in a few degrees of reflex on the ailerons. Would that help reduce the amount of mixing required to hold straight KE while at the same time keep your inverted flight performance the same?

[Black Bird]

	Quote: Originally Posted by heydick
	Here's a question for you trim guru's. On a plane like this that has inherent pitch coupling to the belly, what would happen if you moved the CG foward and dialed in a few degrees of reflex on the ailerons. Would that help reduce the amount of mixing required to hold straight KE while at the same time keep your inverted flight performance the same?

This plane has inherent pitch coupling to the belly. Mixing only reduces the amount of control inputs needed to sustain a flight condition. Your double edge sword can only be yeilded by the pilot. The pilot will always be the ultimate trim.

[Shawn Berkheimer]

	Quote: Originally Posted by heydick
	Here's a question for you trim guru's. On a plane like this that has inherent pitch coupling to the belly, what would happen if you moved the CG foward and dialed in a few degrees of reflex on the ailerons. Would that help reduce the amount of mixing required to hold straight KE while at the same time keep your inverted flight performance the same?

This is pretty much what I would do except I would leave the ailerons alone. with a more forward CG the airplane will require a small amout of up trim ( in relation to where it is now ). This up trim will help compensate while in the knife position.

Shawn

[JoeAirPort]

	Quote: Originally Posted by Shawn Berkheimer
	This is pretty much what I would do except I would leave the ailerons alone. with a more forward CG the airplane will require a small amout of up trim ( in relation to where it is now ). This up trim will help compensate while in the knife position. Shawn

So you say to move the CG forward and decrease the rudder to elevator mixing for knife edge flight, right? Won't the elevator end up in the same position as the more aft CG and the higher rudder to elevator mixing during knife edge? Not sure if you gain anything of that's the case. Now if his CG is too aft anyway, I see why it would be better to move it forward. Too aft and it climbs in a head wind, also balloons on landing. No fun.

[Shawn Berkheimer]

	Quote: Originally Posted by JoeAirPort
	So you say to move the CG forward and decrease the rudder to elevator mixing for knife edge flight, right? Won't the elevator end up in the same position as the more aft CG and the higher rudder to elevator mixing during knife edge? Not sure if you gain anything of that's the case. Now if his CG is too aft anyway, I see why it would be better to move it forward. Too aft and it climbs in a head wind, also balloons on landing. No fun.

My guess is that on the trim flight the airplane wanted to climb and down trim was required. The airplane has to fly at a positive AOA just enough to counteract gravity. This is really the only constant. When you move the CG forward the elevator will need to be trimmed once again but this time with up trim. When the airplane is on it's side and the wing is not supporting the weight of the airplane this up trim will help keep the airplane from tucking to the gear.


Shawn

[JimC-MD]

Hi Shawn, it was good talking to you on the phone the other day.

Let's see.

The plane needed two clicks of down on the maiden, on a 9303 with the trim steps set to one. It held 45's very nicely and only needed a breath of down inverted. It still needed up pressure in a hover. So I am sure the CG was a tad aft for some folks taste but it flew nicely. I have since found a resolution to the problem.

One a cold afternoon I zipped out to the field to try for a quick flight or two. The wind was a strong quartering cross at 15-20 mph. I took off climbing out steeply and banking at a 45 when I flamed out. (stupid me) I thought "no sweat" and proceeded to bring the plane around an abbreviated pattern (due to low altitude). When I entered the downwind/crosswind turn in the wind picked up and started to blow the plane out of the sky, I leveled the wings, got the nose down, found level and landed it...... It rolled to a very low rock retaining wall, struck it with the CF prop and tore the nose off of the airplane.

So I now have the opportunity to correct the cg with glue!

Actually, I will be giving this plane to my brother in law. The damage is very light, he wants a bigger plane, and needs to learn some building skills. This will be a good project for him because he does not need to worry about wrinkling it, I took care of that already!

[JoeAirPort]

	Quote: Originally Posted by Shawn Berkheimer
	My guess is that on the trim flight the airplane wanted to climb and down trim was required. The airplane has to fly at a positive AOA just enough to counteract gravity. This is really the only constant. When you move the CG forward the elevator will need to be trimmed once again but this time with up trim. When the airplane is on it's side and the wing is not supporting the weight of the airplane this up trim will help keep the airplane from tucking to the gear. Shawn

Oh ok, I was thinking the elevator would need more down trim with a forward CG (DUH!!). I was thinking backwards. So if we want these aft CG's for 3D, we have to live with the pitch-to-belly in a knife edge. That explains why many of mine needed so much up elevator in a knife edge.

Sorry to hear about the flameout rough landing.

[toprudder]

I flew a Great Planes Cap 21 years ago (early 90s) and actually did fairly well flying it in pattern (Masters class).

I had just enough throw in the elevator to fly the pattern and perform snap rolls and spins. I had very little throw in the elevator as a result. I never had a problem with it snapping unless commanded, due to the very small amount of throw. Most others that I saw flying Caps back then had too much throw and they would typically stall the plane on landing approach. The fact that this plane had a short fuselage and high-aspect ratio wings made the situation worse. I believe the Cap 232 is different in this respect, the wings are lower aspect and the fuselage is longer.

I had 33% mix between rudder and elevator on mine. It would hold a knife-edge beautifully with that mix. However, it acted funny when making small rudder corrections in other areas. I suggest you select your mix not on what it takes to knife-edge, but what it takes to keep from pitching up/down in level flight when making small rudder corrections. Learn to live with whatever is left when flying knife-edge. If you have a programmable mix curve on your radio, you can experiment with that as well, since pitch coupling is usually non-linear.

IMHO, trying to move the CG and change the thrustline to correct rudder-pitch coupling is just going to screw up other aspects of flight. Pick your thrust angle changes based on uplines, pick your CG on upright/inverted elevator changes (I believe you should always have to hold just a little down while inverted) and use a throttle to elevator mix to correct downline problems if needed.

Of course, this is what I would do if I were flying in pattern or IMAC. If you want to do 3D, then the changes you make should be tailored to that type of flying.

Just my 2CW.

Bob R.