Kitfox IV rudder & vertical tail size increase question

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Posted

So I have a Kitfox IV 1050 powered by a Rotax 582. It flies very well except for yaw which I'd describe as manageable but tiring. It would certainly be a drag on any trip of significant time.  

I've read that the Kitfox IV 1200 had the height of the vertical tail and the rudder increased by 10 inches to help with the yaw stability. I am contemplating making changes to my vertical stabilizer and rudder this winter. This brings up a few questions.

1. Does this mod "solve" the yaw stability issues?

2. With the increased height was there an increase in wall thickness of the tail post or rudder post?

3. Is there a "better" mod to help with the yaw stability?

 

Thanks in advance,

John Brannen

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Posted

When you said manageable, but tiring, I was thinking you meant it pulls to one side.  Maybe not, but if that's what you meant, how about a trim tab on the rudder.  Easy to do, and you could go further later if it doesn't do what you need.  JImChuk

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Posted

No. What I mean is the airplane has what I would describe as neutral to slightly negative yaw stability.  Keeping the ball centered requires constant pilot input, especially when there is any turbulence. Flying a cross country of any distance with this type of stability would be tiring and in my view unnecessary if it can be corrected. That is my goal.

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Posted

I added a considerable amount of area to the vertical and horizontal tail of my plane during the rebuild.  It tracks very nicely and does not run out of elevator or rudder at low speed. 

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Posted

I've seen your airplane and I'm thinking of doing similar, by just making a new rudder with a counterbalance and squaring off the top front of the vertical. Doing it this way I wouldn't have to  mess with the fabric on the fuselage as long as the post for the vertical stabilizer is strong enough to handle the taller rudder. 

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Posted

Good timing on this thread.  I made a new rudder for my KF2 that is slightly larger than the KF4-1200 rudder and I'm about to weld up the new vertical stab.  I was considering leaving the cross pieces which would greatly reduce the area of the stab but I think I would be better served to cut the cross pieces out and extend the front tube forward as well as up.

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Posted (edited)

Well I went out flying yesterday and flew over to a friends strip. He has a Kitfox IV 1200 whereas mine is a Kitfox IV 1050. Here is where you can't believe the internet. Everything I read online said that the KF IV 1200 tail is 10" taller than the KF IV 1050. IT ISN'T!!! I checked the two airplanes and it is 53" - 47" = 6" taller. The rudder is 2" wider as well.

So I've decided that I will make a new rudder for my airplane to try out. So that I don't have to modify the vertical stabilizer or fuselage, I will make all of the changes to only the rudder with the new rudder having an aerodynamic counterbalance to achieve the taller height. I'm thinking I will make it about 8" taller and 3" wider that the stock 1050. This will be very much like @Av8r3400 did on his "Mangy Fox" and will be a bit larger than the 1200 rudder as well.

 

Edited by 109jb
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Posted

Well I went out flying yesterday and flew over to a friends strip. He has a Kitfox IV 1200 whereas mine is a Kitfox IV 1050. Here is where you can't believe the internet. Everything I read online said that the KF IV 1200 tail is 10" taller than the KF IV 1050. IT ISN'T!!! I checked the two airplanes and it is 53" - 47" = 6" taller. The rudder is 2" wider as well.

So I've decided that I will make a new rudder for my airplane to try out. So that I don't have to modify the vertical stabilizer or fuselage, I will make all of the changes to only the rudder with the new rudder having an aerodynamic counterbalance to achieve the taller height. I'm thinking I will make it about 8" taller and 3" wider that the stock 1050. This will be very much like @Av8r3400 did on his "Mangy Fox" and will be a bit larger than the 1200 rudder as well.

 

Any chance you got around to making the change with a new rudder and have flown it? 

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Posted

Well I went out flying yesterday and flew over to a friends strip. He has a Kitfox IV 1200 whereas mine is a Kitfox IV 1050. Here is where you can't believe the internet. Everything I read online said that the KF IV 1200 tail is 10" taller than the KF IV 1050. IT ISN'T!!! I checked the two airplanes and it is 53" - 47" = 6" taller. The rudder is 2" wider as well.

So I've decided that I will make a new rudder for my airplane to try out. So that I don't have to modify the vertical stabilizer or fuselage, I will make all of the changes to only the rudder with the new rudder having an aerodynamic counterbalance to achieve the taller height. I'm thinking I will make it about 8" taller and 3" wider that the stock 1050. This will be very much like @Av8r3400 did on his "Mangy Fox" and will be a bit larger than the 1200 rudder as well.

 

Any chance you got around to making the change with a new rudder and have flown it? 

Not yet.  I have been very busy with other stuff and the airplane is 30 minutes away from me. On top of that it is in a gravel floor hangar that I have to cart my tools out to each time I want to work on it.  All that has slowed the progress of the things I want to get done on the airplane.  The good news is that after being on a waiting list a hangar at the airport 10 minutes from me came available.  I will need to get the airplane moved over and then outfit a bit with tools and then I can get to work. The rudder mod is toward the top of the list of things  I want to do but isn't quite at the top of the list. First on the list is to revamp the engine cooling system, then a tailwheel fix, then the rudder enlargement.

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Posted

 

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Posted

Hey Larry, I just got done watching your video and I really enjoyed it. Very informative, and nice to see a little more detail on your super nice Kitfox. Keep it up:BC:

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