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 Post subject: Aileron Rigging
PostPosted: Wed Aug 05, 2009 20:12 
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Joined: Mon Jan 30, 2006 23:16
Posts: 574
Location: Ash Flat, AR
After a few exercises of making adjustments in the wrong direction I finally got my wing wash in/out under control. I had a very heavy RH wing.

I actually adjusted it so far that it went to the opposite wing, but that is all nice and neutral now.

Back in the early part of the year I consulted this wise board about the book spec of 40 lbs for the aileron idler cable. After adjusting to this it seemed much too tight to me, to the point of making the ailerons a bit hard to move.

So, I relaxed the tension till it felt comfortable and let it go at that. This took it back to just about the same feel as when I started.

The result was that the RH aileron drooped a bit but that helped me when that wing was heavy.

Now I notice that the ailerons are perfectly aligned at neutral in cruise but misaligned on the ground?? The stick may be slightly to the right but very little so that is a non issue to me.

This makes me think the Champ is trying to tell me the aileron idler cable is too loose and is adjusting itself in flight!!

My inclination it to re-tighten the cable at least a little bit to see how it goes.

What do you Champ guys/experts think about this?

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Gus Causbie
Ash Flat, AR
N83564, 7AC-2235, A65-8


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 Post subject:
PostPosted: Wed Aug 05, 2009 20:35 
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Joined: Wed Dec 08, 2004 16:49
Posts: 2176
Location: San Martin, California
Gus,
I would center the stick and adjust the cables with enough tension to keep the ailerons neutral on the ground and in flight. This isn"t as easy as it sounds. There is a bunch of hocus-pocus about drooping ailerons, I think it adds drag. After your satisfied with the stick location and aileron locations safety them up and you"re done. Any rigging to fix a heavy wing should be done with the struts. I shorten the heavy wing to make it fly more. Some people are concerned with "tip stall" caused by shortening a strut. I haven't had any issues with this method but I do stay within my Mach number restrictions.
Paul

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Mailing Adress : Paul Agaliotis 2060 E. San Martin, San Martin,Calif. 95046


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 Post subject:
PostPosted: Thu Aug 06, 2009 14:48 
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Joined: Mon Jan 30, 2006 23:16
Posts: 574
Location: Ash Flat, AR
Paul,

I'm sure I will have to adjust the side turnbuckles before this is over to get the stick centered. Unfortunately the rebuilder enclosed the cabin sides with large riveted in Al panels. I will either have to drill out the rivets or cut a hole at the turnbuckles, a real pain.

My understanding of wingtip wash in/out is they both need to have less angle of incidence than the rest of the wing to keep the ailerons flying during a stall approach but different so there is no heavy wing and no need for left rudder in cruise.

When this is all correct right rudder is required in climb, there will be no skidding or turning at cruise and left rudder will be required in a high speed descent.

While I was trying to balance the wings it became obvious to me that the tips could be adjusted enough so that they probably wouldn't provide adequate lift for those short takeoffs I love. On the other hand, if adjusted too much the other way, cruise would be reduced.

I remember going through this a few years ago when I replaced the control cables in my Navion and it wasn't much fun!

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Gus Causbie
Ash Flat, AR
N83564, 7AC-2235, A65-8


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 Post subject:
PostPosted: Thu Aug 06, 2009 19:09 
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Joined: Sat Feb 07, 2009 20:57
Posts: 83
Location: Whiteville, North Carolina
Gus,
I have a problem similar in nature in that at climb out I do need a little right rudder and a little less at cruise. At cruise both wings will remain level but have to have just a touch of right rudder. Is this something a rudder tab could solve or just let it be

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Joey from the coast of the Carolinas


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 Post subject:
PostPosted: Fri Aug 07, 2009 12:26 
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Joined: Fri Aug 15, 2008 12:03
Posts: 302
Location: Madison, Wisconsin
My understanding is that the wing "should" have ZERO washin or washout. I believe this is measured from the bottom of the rib just inside where the struts meet the wing compared to the root rib.

However if there is a heavy wing I suppose you have to determine if it is improper aileron rigging or if an adjustment to the wing rear strut is needed.

If a wing strut adjustment I always understood you should shorten the rear strut on the light wing (lowering its AOA and thus reducing its lift). This if anything may put a small amount of washout into the wing and thus keep the tip flying into the stall a bit longer.

I also was told and maybe it is mumbo-jumbo, that on the ground with the control centered, BOTH ailerons should droop very slightly from the trailing edge by the same amount. The theory being is that the aileron hing play will take this out by wind loads during flight.

I am interested in this thread because on my chief, in level flight I have to hold a very light right rudder pressure and slight left aileron. So far I've just lived with this slight variation. But I have to believe this can be rigged and/or trimmed out but have been hesitant to start changing things and have to keep brining out an IA to make the small adjustement(s).


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 Post subject:
PostPosted: Fri Aug 07, 2009 13:31 
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Joined: Wed Dec 08, 2004 16:49
Posts: 2176
Location: San Martin, California
Shortening the rear strut will increase the AOA reletive to the longitudinal axis. Set it up flat just as you described and fly it. I shorten the strut on the heavy wing. This assumes that the tail is also rigged correctly. I have rigged some wings that were way out of rig because they were trying to compensate for a mis-rigged tail.
I'm headed out in a few hours to assemble and rig John Rodkey's Chief. He can let you know how it works.
Paul

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Mailing Adress : Paul Agaliotis 2060 E. San Martin, San Martin,Calif. 95046


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 Post subject:
PostPosted: Fri Aug 07, 2009 13:56 
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Joined: Fri Aug 15, 2008 12:03
Posts: 302
Location: Madison, Wisconsin
Paul. You are right. You lengthen the rear strut on the light wing to reduce AOA and its lift.

I re-read my previous post about 3 times before I submitted it, and I STILL got it reverse on the wing strut adjustment.


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 Post subject:
PostPosted: Fri Aug 07, 2009 16:54 
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Joined: Mon Jan 30, 2006 23:16
Posts: 574
Location: Ash Flat, AR
ff,

You wrote about it, I actually made the adjustment in the wrong direction and it took a lot of muscle to keep the wings level. It was so obvious that I could see it in flight but not on the ground.

Your Chief right strut probably doesn't need to be lengthened more than a couple of turns of the strut fork. I way overdid mine the first two times!

I was thinking that the long aileron hinge had something to do with my ailerons trailing correctly in flight even though they are off centered at rest. I haven't yet gotten into the manual section on rigging since we are preparing for a long trip to the NW, this will all have to wait until we return.

Right now I also need a slight bit of right rudder at cruise to center the ball and the left wing is a tad light, but not much, so I'm getting there. It really bugs me to cruise in a skid even if it is slight!!

Wash in/out is only at the wing tips and, I assume, is not affected by the strut adjustment since it moves the whole wing. At first I thought I was adjusting WI/O but it became obvious to me that the whole wing was moving. As far as I know all light prop airplanes have a slight bit of WI/O at the tips to make it fly straight in cruise. The vertical stabilizer is also offset a bit to the right for the same reason. Right rudder on climb is normal as is a slight bit of left rudder in descending at speeds above cruise.

I don't think the wing adjustment affects AOA, angle of incidence is what we are fooling with.

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Gus Causbie
Ash Flat, AR
N83564, 7AC-2235, A65-8


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 Post subject:
PostPosted: Mon Aug 10, 2009 08:41 
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Joined: Fri Aug 15, 2008 12:03
Posts: 302
Location: Madison, Wisconsin
My understanding is a bit different. I understood washout to be where the tip is slightly lower AOA so that it remains flying while the root is stalled. And it usually results in allowing the aileron's to be useful all the way into the stall.

I think you are right about adjusting the rear strut. It does move the whole wing. Well sort of. Since it is fixed at the root any change will result is some twist.

In my case for rigging, if I let go of the controls it will SLOWLY enter a right turn. If I have an adjustment made, I would do it in 1/2 turn increments. It is not far out of rig so I assume to go at it very slowly. I tried bending the rudder trim tab. And this takes out the pressure on the right rudder but it still wants to bank a bit. This is what makes me think I should lengthen the rear strut 1/2 turn and see what the results are.

I understood that only an A&P should make this change. I suppose because it is very sensitive as you pointed out.


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