Pitch Coupling Effects IMAC maneuvers
 

I have a H9 Sukhoi and love it to death so far. The CG is just slightly rearward of where "precision" flying is called for and it pitches pretty hard to the belly during knife-edge. With a rud-elev mix, I have slowly found that sweet spot where it does KE perfectly with half low-rate rudder. Since then I have another problem, when I do an axial roll with rudder I get some departure in the tail. When flying straight and level, rudder deflection gives me some ballooning as well. I think it hurts me a little on hammers and I see it really well on landings but nothing too hard to correct. Why is my pitch coupling different for KE and level flight? Do I need to run my CG forward?

Pitch Coupling Effects IMAC maneuvers
 

sounds like the awnser is yes

Pitch Coupling Effects IMAC maneuvers
 

I put my mixes on a switch so I could use them only when needed. This was for knife edge, and vertical lines both up and down.

Pitch Coupling Effects IMAC maneuvers
 

I have the same problem but I still want to move my CG farther AFT. How do people have a permanent rudder-elevator mix and still not have problems with other maneuvers?

Pitch Coupling Effects IMAC maneuvers
 

do you have a point mix of just a straight mix. I am playing with the point mixes so I can leave them on all the time.

Pitch Coupling Effects IMAC maneuvers
 

Geistware,

Why do you still want to move the CG aft? If it is for better 3D, you might consider doing this in some sort of "removable" manner so that your plane doesn't require switchable mixing during the flight.

I have all of my rudder mixed out all of the time. But my plane is setup with small throws and a "normal" sequence CG. It is very pure throughout the entire range of attitudes. You probably need a plane with very little mixing to start with.

Ken

Pitch Coupling Effects IMAC maneuvers
 

I'm running a straight mix on a JR-10X, Rudd-to-Ail/Elev. It's a one-stop-shop for KE fixes. Because the hook to the wheels is more pronounced than other planes I have, (they balanced slightly nose heavy), I was hoping there is a fix in balancing but don't know which way to go fore/aft. I love 3D but IMAC sequences come first. Maybe I do need a multi-point mix instead with less elev at smaller rudder deflections to get through the rolls and landings.

Pitch Coupling Effects IMAC maneuvers
 

patient

Pitch Coupling Effects IMAC maneuvers
 

I have the same problem on an Ultimate, at low rates I can mix out pitch couple with rudder, but at high rates I need a different mix. So I have tried a multipoint mix (futaba ff9 5 point mix) which works in some situations like knife edge, but its completely wrong for stall turns.

The solution is to have the mix on a switch, so you just use it when you need it. Ideally if IMAC is your thing, get an airplane with a symetrical setup where rudder is pure.

Pitch Coupling Effects IMAC maneuvers
 

I downloaded this and printed it out last year and found it to be a great help in my setup. Although it is written for a JR 10 series radio, the mixing ideas can be used for any high-end computer radio. There is some information in the article about KE mixing that I think you will find useful.

http://horizon.hobbyshopnow.com/articles/1169.asp

Ken

been there done that
 

http://www.rcuniverse.com/showthread...hreadid=182788

Boys,

try this thread. I have learned alot since then and have been through two more airplanes. what I have learned to do is set the plane up to be "predictable" and fly it from there. I try and find the happy medium between upline and knife edge coupling and learn to fly the plane. this is not to say that I dont spend time trimming - not by any means! some planes come in trim better than others of course. my radiocraft extra trims in very solid to rudder mix corrections. although my stadacher does some weird stuff depending on airspeed and rudder deflection.

by all means set the plane mixes and leave them on! again we are striving for the purest flight characteristics to rudder imput. if you are a sport flyer that likes to do the occasional knife edge across the field then a mix on a switch might not hamper you. If you are flying precision manuvers then correct the plane as best you can and leave the mix there.

personally I do not like to flip switches. be it a switch for knife edge or snaps or rolls or whatever. when you start to fly more complex manuvers and sequences your focus should be on your flying presentation within the sequence, IMO. things can get a little rushed in the upper class sequences of advanced and unlimited (I fly advanced) and you could get bitten in an unknown if you loose focus on your switches. ive seen many a flyer (and you know who you are!) fly a snap on a roller rate or vice versa. as crazy as it may seem to some, I dont flip any switches when I fly. I set my plane up to snap well and fly it from there. I have a higher roll rate than some like but I fly on 30% expo or so on the ailerons. I manager through the rollers ok like this, I have tried a roller condition switch but keep going back to my way :rolleyes: . the rest of the sequene feels pretty natural to me with this set up.

hope some of this helps

Hubbb

Pitch Coupling Effects IMAC maneuvers
 

Geistware,
If an aircraft has a tendency to pitch to the belly during knife edge with the application of rudder, this tendency will remain the same regardless of the attitude of the aircraft. It is for this reason that most fliers find the proper rudder/elevator mix and leave it on all the time.

Pitch Coupling Effects IMAC maneuvers
 

I would like to leave it on and may use a less than optimal mix but the reason I like a aft CG is that when I roll inverted, I do not like to add elevator to compensate. All the planes I have owned have been set up so that the plane flew straight inverted or right side up. I just don't seem to be able to mix it out.

I am using a point mix but may start with a regular mix.