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Offset Vertical Stabilizer

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Posted (edited)

I would like to center the vertical stabilizer (remove offset) on my C Model for installing a four stroke CW rotation engine Jabiru or 912 Rotax. Don't think i want trim tabs to make up for it.  Also, not sure about shiming the motor mount to compensate.

Any tips would be greatly appreciated!

First has anyone done it?

Second is it worth it 

Edited by Jumpingjack

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Posted


I did it to my kitfox it was super easy.

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Posted

Or shim mt

 

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Posted

So I ran two string lines from the VS to estimate where shiming the mount would need to be , one sting is centerline and the other is parallel with the offset VS.

I don't have an engine or mount so I used two strips of plywood and extended 23 inches, from firewall to guesstimate prop flang location, and come up with    4.92 in from center to offset. That looks to be the amount need to shim to be inline with the VS.

I think centering the VS would reduce drag.

Learning stuff here,  any thoughts appreciated.

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Posted

I doubt that you would have to offset the mount that much to over come the VS being at an angle, I'm sure the fuselage has some effect on where the plane points, but if seems the easiest thing to do would be to move the VS to being centered.  Then maybe all you will end up needing is a small trim tab.  And it's anybody's guess which side of the rudder you will be putting it on. The Avid MK IV had the VS centered, and lots of them (most probably to start with) were fitted with a 582.  (Left hand prop.)   Mine was, and I went to a Jabiru engine (right hand prop) and never gave the VS a thought.  I did have a factory built motor mount though.  Never shimmed it and I do have a trim tab on the rudder, and it flys just fine.  Little over an hour this evening in fact...  :-)  JImChuk

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Posted


I did it to my kitfox it was super easy.

So, I just cut the forward tube and the two brace tubes, center and reweld?

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Posted

I doubt that you would have to offset the mount that much to over come the VS being at an angle, I'm sure the fuselage has some effect on where the plane points, but if seems the easiest thing to do would be to move the VS to being centered.  Then maybe all you will end up needing is a small trim tab.  And it's anybody's guess which side of the rudder you will be putting it on. The Avid MK IV had the VS centered, and lots of them (most probably to start with) were fitted with a 582.  (Left hand prop.)   Mine was, and I went to a Jabiru engine (right hand prop) and never gave the VS a thought.  I did have a factory built motor mount though.  Never shimmed it and I do have a trim tab on the rudder, and it flys just fine.  Little over an hour this evening in fact...  :-)  JImChuk

JimChuk,

I guess I'm looking for a member with a C model that has done the mod, and running a Jab or 912, before and after results. And was the effort worth it.

I also want to upgrade tail feathers to MK IV while I'm at it.  

Thanks, Jumpingjack

 

 

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Posted

I do know that one guy had a B model and installed a Jabiru engine on the plane and left the VS as it was because the plane was covered and all he did was add a trim tab to the rudder.  He flew that plane for well over 1000 hrs before a mishap that wrecked the plane.  I would center the VS myself and adjust from there if needed.  YMMV.. JImChuk

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