Author Topic: Tailgroup alignment  (Read 572 times)

Tim Lunceford

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Tailgroup alignment
« on: December 10, 2018, 05:43:41 PM »
I have been fussing with the Cadet to get it as straight as possible.  I knew that the tail was tilted with the left side being lower than the right in relation to the wing.  Previously I had lower the right wing by 1/2 degree to get the incidence the same on both wings to level the wings in flight.  That help some but did not totally cure the problem.  As a long time RC pattern flyer I am really aware of how much better an airplane flies if it is straight.  Meaning that I am still unhappy with the trim of the airplane.  It turns out that the horizontal stab is not only tilted but also angled.  The right side is 1 inch closer to the trailing edge of the wing than the left.  The only solution that I have come up with is to reset the tail on the longerons.  To do this would require drilling new holes in the longerons.  Anyone have a better ideas?   Tim

Bill Poynter

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Re: Tailgroup alignment
« Reply #1 on: December 10, 2018, 09:10:16 PM »
Have you determined that the horizontal stab spar is actually out of square with the fuselage?  Try running a chalk line from the fuselage sides next to the cabin to the stab spar to check for squareness at the spar. 

Tim Lunceford

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Re: Tailgroup alignment
« Reply #2 on: December 11, 2018, 12:11:47 PM »
That is the process that I used.  When this Cadet was restored the top longerons were replaced at the rear of the fuselage due to rot in that area.   

Keith U.

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Re: Tailgroup alignment
« Reply #3 on: December 16, 2018, 08:51:13 PM »
Tim,
How did you change the incidence in the wing?  I am left wing heavy and really want to get to fly hands off.  I rigged and fussed with control rigging, its gotta be the incidence, not sure how to proceed.  thanks   Keith

Tim Lunceford

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Re: Tailgroup alignment
« Reply #4 on: December 17, 2018, 07:54:04 PM »
Keith,  the first thing I did was blocked up the fuselage with the top longeron level.  I purchased five digital levels from Home Depot and used double face tape to attach the levels to the bottom of the wings at the
 roots and at the tips.  This showed me that the wings were one degree different.  It also showed that the individual wing had some twist in them.

I decided to lower the right wing 1/2 degree to start.  To accomplish this I removed the rear spar fittings on the right side. Calculated the amount that the rear spar had to move down to change the incidence.  Next step was to machine a bushing with the inside diamieter of the spar bolt.  The spar fitting were drilled slightly over size.  I elongated the holes in the spar fitting to get the proper distance in the spar plates and welded the bushings in.



Keith U.

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Re: Tailgroup alignment
« Reply #5 on: December 18, 2018, 12:37:24 PM »
Thanks Tim, that sounds reasonable, might fly it another season before I get to it.  I am sure that changing the incidence would fix it.  Nothing is simple about this fix though...