Model 2 adverse yaw?

[herman pahls]

I have hundreds of hours on my model 2 Kitfox.
The first 14 years with a Rotax 532 (C.G. was near the rear of envelope).
The last 2 years with a Jabiru 2200 (C.G is near the front of the envelope).
I like flying behind the Jabiru engine but find that in windy and gusty conditions coordinated turns are almost impossible and therefore dangerous. The 532 seemed to have much less adverse yaw (much easier to keep the ball centered). I am tempted to reinstall the 532 to determine if this is all in my head.
I added 4 pounds to the tail to move the CG more to the middle and still do not like how it flys.
I started flying a Piper Pacer 3 years ago and coodinated turns are a non issue.
When I found this model 2 kit in a barn 17 years ago I was advised to hold out for a model 4 because of differential aileron action on the improved model 4 controls.
I would like opinions from the undercambered Avid and kitfox flyers about what I am experienceing and is there a fix.
Are the model 4's handling vastly improved?
Thanks Herman Pahls Oregon 541 404 6464

[SkySteve]

Herman,
I fly a model I with a 912, 80 HP. I cut the vertical off, replaced it with a model IV vertical & rudder. Huge difference in a good way.

[rogerh12]

My model 2 with a 582 engine had horrible adverse yaw. People seem surpised when I say that, but I'm glad someone agrees with me. Maybe it was because of the heavier engine, I don't know. All I know is it was bad.
Now I have a model 4, for the reasons you mentioned before (but it's now flying yet)

Roger

[jiott]

I believe the Model 2 did not have aileron/flaperon differential. The differential (less down than up travel) makes a big difference in reducing adverse yaw because the drag on the outside wing is reduced in comparison to the inside wing. I don't know, but maybe the Model 2 flaperon linkage could be modified to provide differential.

Jim

[Av8r3400]

I believe the I-III flapperon mixer is virtually a direct copy of the Avid Flyer units. There is a modified part offered by Airdale that adds an amount of 'differential' to the aileron control. The part is something like F-7a or similar. Brett would know off the top of his head. This may help your situation.

Additionally, is there built in vertical stabilizer offset in the early Kitfoxes? If so, wouldn't this be in the opposite direction when going from a two stroke to a four stroke Jabaru (Prop rotation direction). Could this be part of your problem?

[toekh]

I have about 100 hours in my Kitfox 2 behind Jabiru. There is no weight added when they did the conversion from Rotax 532 to the Jabiru engine. The start battery is placed about 3 feet behind the seat. I have wing tanks.
I have very little adverse yaw, almost none. When some of my buddies try to fly my plane, almost everyone of them overdo the rudder movement. In the other hand I have to push right rudder a little bit constant to fly in a straight course.
One of my friends formerly owned an Avid Flyer, similar to my plane. He also had a Jabiru engine in his plane. He was able to trim his aircraft flying hands off in every plan and his method was changing the engine angel with some shims in the engine mount.
Must say that I love the Jabiru engine, even if it takes a few more feet’s to go off the ground compared to a Rotax 532/582. In the other hand it sounds like a real airplane and burn 2-2,5 gph at 55 kt. And it looks like a jewel

[dholly]

I believe the I-III flapperon mixer is virtually a direct copy of the Avid Flyer units. There is a modified part offered by Airdale that adds an amount of 'differential' to the aileron control. The part is something like F-7a or similar. Brett would know off the top of his head. This may help your situation.

Looking at my KF-III mixer, I do not believe these parts are directly interchangeable. The Avid mixer differential mod consisted of:

- replacing (2) existing p/n F7 bellcranks with (2) new p/n F7a bellcranks (the new bellcranks have noticeably more curve, as seen in the attached comparison).

- replacing (2) p/n F37 straight ~2-1/2" long threaded-end rods with (2) new p/n F37a bent ~5" long threaded-end tube rods.

I've also attached a pic of the (unpainted) F7a and F37a modification parts installed in my old Mk-IV mixer.

[FoxDB]

I have been interested in the differential flaperon mod by Airdale for my Kitfox 1. I have not checked to see if the Airdale parts would fit the Kitfox Mixer. If not I am planning to do a CAD layout to investigate the motion. I have Raven drawing that detail the Kitfox/Raven parts. I just need info on the Airdale parts. If anyone has additional info on this please post.
Thanks Dave

[herman pahls]

I want to thank those who responded with possiblities why replacing the Rotax 532 with a Jabiru 2200 would induce more adverse yaw on my Model 2 Kitfox.
I recently spoke with Joey who posts on this forum ( Avid flyer with 582 and E-box) regarding what he feels may be off with my Model 2's rigging now that a Jabiru has replaced the 532.
Since I had just flown the Kitfox I was reminded that the flaperon forces are much higher with the Jabiru than with the 532.
The flaperons have a very effortless feeling when checking control freedom at run-up.
Joey mentioned that flaperon reflex can cause higher aileron stick forces.
With the 532 I adjusted pitch trim with the flaperon lever.
With the Jabiru the flaperon lever is all the way down to trim which would give more up on the trailing edge of the flaperons than what I flew with the 532 for years.
So is more flaperon reflex when the trailing edge is higher?
The Jabiru added 30#'s bringing the empty weight to 520 #'s which moved the CG forward versus the CG of the 532 which was towards the rear.
The 532 and Jabiru CG's were or are in the envelope.
The only other change made when installing the Jabiru was going to 1 inch unfaired lift struts from the original 3/4 faired lift struts.
Some of you questioned Vertical fin offset and wing twist as possible issues.
Any further ideas why I no longer enjoy or feel comfortable flying this Kitfox ( especially in gusty wind or turbulence) with the much higher flaperon forces and the almost impossible ability to keep the ball centered in turns?
Thanks Herman Pahls Oregon 541 404 6464

[cap01]

herman , i think there is something to that vertical stab offset . i have a very early model IV 1050 with a 912ul , thats right at the change from III to IV . i have the same problem with the ball . i have over 300 hrs on it and havent mastered it yet , just live with it and havent spun in yet . i pretty much eliminated a rigging problem and even installed a rudder trim tab which helped a little . appears to be more pronounced when banking to the left where the ball takes off to the right . ive flown speedsters that dont do that . the idea of replacing the tail sounds good if a person had one .