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Angle of incidence KitFox IV horizontal tail

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Posted

Does anyone know the factory angle of incidence for the horizontal tail of a Model IV.  We're doing some repair work....

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Posted

I would be interested in this too. I am putting KF wings on an Avid fuse, but when I went to measure some local Kitfoxes, they had the all moving HS. The angle of an Avid doesn't really help because the wing airfoil and angle are all different.

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Posted (edited)

The Kitfox Model 4 horizontal stab is adjustable with 3 holes on the front mount.  I drilled the top hole with the front of the stab as high as it can go.  That made the  hole 1/4 inch below the bottom of the vertical fin. The other two holes are 7/16 inch center to center from the hole above them.

 

The manual says most fly best in the top hole.  I made the first flight with the stab in the top hole.  It took one finger slight back pressure to fly level in the top hole.  I moved it down to the middle hole and it took very slight forward pressure for level flight.  I left it there as the design is to trim with flaperons.  Everything you load in the plane moves the CG back And flaperons trim the nose down.

 

I calibrated my smart level for zero degrees on the cabin floor which is the leveling point for the Kitfoxes.  The middle hole is 2.8 degrees down.  Top hole is 1.5 degrees down.  I can't check the bottom hole but suspect the same increase in down incidence.

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Edited by tcj

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Posted

Thanks tcj. This is really helpful.

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Posted

Thanks TCJ.  Exactly what we needed!

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Posted (edited)

I made those measurements kind of in a hurry last night.  I leveled the plane carefully and took them again this morning.  I edited my post above with the new readings.  It doesn't change the outcome really as they are small differences and the stab is adjustable.  The new readings for my plane are the top hole gives 1.5 degrees down and the middle hole gives 2.8 degrees down.

 

For what its worth my model 4 has a relatively forward CG.  I also have a nose tank and don't often put fuel in the wing tank so that makes the loaded CG usually about 12.25 inches.  You might consider the probable CG your plane will have and build accordingly.  Some Model 4s have as much as 3 to 3.5 degrees down incidence on the horizontal.  In any case drilling the top hole as high as possible gives you the option for a more rearward CG.

 

I looked in the book also to refresh my memory.  The book says drill the top hole as high as possible and space the other two holes 1/4 inch apart.  I can't remember why I spaced mine 7/16 apart but anyhow you can see the results.

Edited by tcj

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Posted (edited)

tjc,

      What is your wing incidence?  Or, from spar to spar?

EDMO

Edited by Ed In Missouri
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Posted

Ed, I can't check the incidence of the spars with the fabric on.  I checked it on the number 2 rib from trailing edge to the low point the level touches a few inches behind the front spar...this looks to be the thickest part of the wing too.  I got 0.2 degrees down. (minus 0.2 degrees).  This wing is nearly flat on bottom, just about 1/4 inch under camber.

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Posted

I was working on my plane today and noticed the wing spar to fuselage attach bolts stick down past the bottom profile of the wing.  These make an easy place to put my smart level to measure the incidence of the spars at the root end.  I put the level on them and it measured 0.2 degrees down.  I think it is no coincidence this is the same angle of incidence I measured on the bottom of the wing.

 

These measurements probably have some margin of error.  Probably a couple tenths of a degree.  It has me thinking the incidence of the wing may be zero.

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Posted

I am sure I need to relocate my single-point horizontal stabilizer fitting - when spring comes I will make all new measurements.

EDMO

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