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  #1  
Old 10-13-2008, 03:47 AM
chris mitchell chris mitchell is offline
 
Join Date: Jul 2006
Location: near Harrogate, England
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Default Rigging ailerons and flaps

This post is a bit long and a bit complex - I've tried hard to explain where I have got to so I hope its not confusing! I'm feeling uncertain about how to proceed, so please read on and give me the benefit of the accumulated VAF experience!

I spent the weekend rigging the ailerons and flaps. Previously, when building the wings, I had set the aileron pushrod length with the aileron locked in the neutral position and the bellcrank also locked. For the former I used an aluminum strip appropriately drilled and attached to the tool holes in the outermost rib, with a bolt through it that sat tightly in the trailing edge radius of the aileron. For the latter I used the Vans template. So far so good.

Now that the wings are on, I mounted the ailerons and flaps, again set the ailerons in the neutral position and set the bellcrank. I attached the flaps (after trimming the upper surface to match the fuselage) and the flap pushrods (after enlarging the holes that the pushrods run through. Then, before drilling any holes for the flap fairings, I thought I would check that the ailerons and flaps on the left sat at the same angle as the ailerons and flaps on the right.

Leveled fuselage along and across top longerons, rechecked incidence and both wings are at identical incidence within 0.1 of a degree (using a digital angle meter). I then put the meter on the top surface of the outboard part of the right aileron - 10.6 degrees, and inboard 10.8 degrees. The right flap not surprisingly as I had aligned its trailing edge with that of the adjacent aileron - was 10.8 degrees. On the left side the outboard aileron measurement was 10.3, inboard 10.2 and the flap 10.2 degrees ie all slightly less than the right.

Taken at face value, the implications of these measurements to me are that:

In flight the aircraft will try to roll to the left (right aileron down in comparison to left average 10.7 versus 10.15 ie 0.55 degrees different)
The left aileron has a slight twist (0.1)
The right aileron has slightly more twist (0.2)

Given the uncertainties in any measurement process - even the leveling process is subject to + or - 0.1 degree (smallest calibration on the meter), then all the individual measurements also; and the inaccuracies of building a handmade aircraft, - are these figures acceptable? Has anyone else gone through this exercise (surely you all have?). My inclination is to go back and adjust and tweak until everything is as identical as I can make it - after all I got the wings to come out as identically as I can measure. But in practice would I notice the control stick deflection need to take out these minute differences? If I toured the hangar checking all the production aircraft, would they even come close to these sorts of differences?

As ever, many thanks in advance.

Chris

RV8, final assembly......
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  #2  
Old 10-13-2008, 04:36 AM
pierre smith's Avatar
pierre smith pierre smith is offline
 
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Default Yes......

.....to answer your question, Chris, the figures are acceptable. Heck, we simply aligned our ailerons with the wingtip and clamped them with a carpenter's rubber tipped clamp and then matched the flaps to them, clamping to the ailerons, never checking the exact angles of either. Guess what? The airplane flew hands-off straight and level first time out.

Part of your phase-1 is tweaking all this stuff until you get her to fly and handle to your satisfaction. Attention to detail is OK, but don't let one or two tenths of a degree worry you.

Regards,
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  #3  
Old 10-13-2008, 07:00 AM
Rockyjs Rockyjs is offline
 
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Chris,
I agree with Pierre. I've got about 58 hours on my RV-7 and am still tweaking things. I have gone back and made similar measurements to yours and there are so many variations that I gave up. My plane flies great! Build on and see how it handles, then make small adjustments and refly.
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  #4  
Old 10-13-2008, 08:23 AM
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jthocker jthocker is offline
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Location: Cincinnati, Ohio
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Chris
Your procedures were exactly correct.
Lock the outboard end of the aileron with the template, lock the bellcrank with the pre-set push tube, center your sticks, then adjust the long push rods. Like Pierre said, now lock the ouboard ends of the flaps to the ailerons and then adjust the overhanging flap skin to the fuselage( bend up, or joggle down). Then I install the wingtips. Put the flaps up, lock the ailerons to the flaps, and adjust the wingtips so that the trailing edge aligns with the outboard aileron trailing edge.

IF YOU DO IT THIS WAY, YOUR AIRPLANE WILL FLY STRAIGHT WITH THE STICK IN THE NEUTRAL POSITION. ALL THE CONTROL SURFACES AND THE WINGTIPS WILL BE ALIGNED.
THERE MAY BE SOME WING HEAVINESS BUT THAT USUALLY CAN BE CORRECTED BY SQUEEZING THE AILERON TRAILING EDGE.

This prodedure has worked for me on 6 planes now.
The digital level is great for leveling the plane and maybe for setting the incidence angle. Otherwise it will only frusrate you.
If someone has managed to build contol surfaces without some slight twist or curve in at least one of them, my hat is off to you. The aeronautical engineers out there can debate this all they want, but these steps have worked for me and I have never adjusted the rod end bearings of any of the control surfaces after the initial control rigging.
The aileron squeeze/or unsqueeze has always worked to make the plane fly hands off.
I would throw my digital level away, but it comes in handy for other things.
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  #5  
Old 10-13-2008, 04:00 PM
Finley Atherton Finley Atherton is offline
 
Join Date: Nov 2005
Location: AUSTRALIA
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Chris,

Rig it as others have suggested by aligning everything with the wing tip. If you find you have a heavy wing you could try playing around with the rigging by setting the aileron and flap at their "average" positions and see if it helps. My logic could be faulty, but this is how I see it. For the right wing, the 10.6 degrees you measured at the wing tip would be correct (I assumed you used the wing tip aileron alignment tool). The inboard tip of the aileron is 10.8 so the average is 10.7 degrees. In essence the aileron is sitting 0.1 degree lower than it should be. Adjust the outboard tip of the aileron up so it measures 10.5 and this will make the average incidence of the aileron equal the correct 10.6 degrees (as measured by the wing tip aileron alignment tool). Do a similar adjustment for the flap so that it's average incidence also equals 10.6 degrees.
A complicating factor would be any wing twist present. In theory, to get it perfect, I assume that the average alignment of the aileron and flap should be measured against the average incidence of the wing rather than just at the wing tip.

Fin
9A Flying

Last edited by Finley Atherton : 10-14-2008 at 02:49 PM.
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  #6  
Old 09-10-2017, 08:00 PM
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flyenforfun flyenforfun is offline
 
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Default

Question: which aileron do you squeeze? The light or the heavy one? My light Alaron looks perfect the left heavy aileron looks like it needs to be squeezed in tightened up a bit
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  #7  
Old 09-11-2017, 04:21 AM
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Larry DeCamp Larry DeCamp is offline
 
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Location: Clinton, Indiana
Posts: 501
Default Aileron trailing edge

The thinner the trailing edge, the less effective, and control stick force increases in my experience. Thicker is better.
In respose to the OP, as said by many, perfect wings, flaps and tips are unlikely. Perfectly aligned fairings and pants are not likely. I have found tiny Gurney flaps for rudder and aileron trim to VERY effective and aesthetically acceptable. YMMV
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  #8  
Old 09-11-2017, 05:14 AM
Robert Anglin Robert Anglin is offline
 
Join Date: Mar 2008
Location: houston, texas
Posts: 700
Default Van's web page.

Quote:
Originally Posted by flyenforfun View Post
Question: which aileron do you squeeze? The light or the heavy one? My light Alaron looks perfect the left heavy aileron looks like it needs to be squeezed in tightened up a bit
If you go to Van's home page and dig though the that to find their two or three page "Heavy wing" Q&A work sheet, then use that as you guide you will find it will tell you most everything you would want to know and how to go about fixing it. The only suggestion I have is to do it in the order they lay-out.
Hope this helps, Yours, R.E.A. III #80888
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  #9  
Old 09-11-2017, 05:48 AM
flyenforfun's Avatar
flyenforfun flyenforfun is offline
 
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Location: Wilmington DE
Posts: 320
Default

Quote:
Originally Posted by chris mitchell View Post
This post is a bit long and a bit complex - I've tried hard to explain where I have got to so I hope its not confusing! I'm feeling uncertain about how to proceed, so please read on and give me the benefit of the accumulated VAF experience!

I spent the weekend rigging the ailerons and flaps. Previously, when building the wings, I had set the aileron pushrod length with the aileron locked in the neutral position and the bellcrank also locked. For the former I used an aluminum strip appropriately drilled and attached to the tool holes in the outermost rib, with a bolt through it that sat tightly in the trailing edge radius of the aileron. For the latter I used the Vans template. So far so good.

Now that the wings are on, I mounted the ailerons and flaps, again set the ailerons in the neutral position and set the bellcrank. I attached the flaps (after trimming the upper surface to match the fuselage) and the flap pushrods (after enlarging the holes that the pushrods run through. Then, before drilling any holes for the flap fairings, I thought I would check that the ailerons and flaps on the left sat at the same angle as the ailerons and flaps on the right.

Leveled fuselage along and across top longerons, rechecked incidence and both wings are at identical incidence within 0.1 of a degree (using a digital angle meter). I then put the meter on the top surface of the outboard part of the right aileron - 10.6 degrees, and inboard 10.8 degrees. The right flap not surprisingly as I had aligned its trailing edge with that of the adjacent aileron - was 10.8 degrees. On the left side the outboard aileron measurement was 10.3, inboard 10.2 and the flap 10.2 degrees ie all slightly less than the right.

Taken at face value, the implications of these measurements to me are that:

In flight the aircraft will try to roll to the left (right aileron down in comparison to left average 10.7 versus 10.15 ie 0.55 degrees different)
The left aileron has a slight twist (0.1)
The right aileron has slightly more twist (0.2)

Given the uncertainties in any measurement process - even the leveling process is subject to + or - 0.1 degree (smallest calibration on the meter), then all the individual measurements also; and the inaccuracies of building a handmade aircraft, - are these figures acceptable? Has anyone else gone through this exercise (surely you all have?). My inclination is to go back and adjust and tweak until everything is as identical as I can make it - after all I got the wings to come out as identically as I can measure. But in practice would I notice the control stick deflection need to take out these minute differences? If I toured the hangar checking all the production aircraft, would they even come close to these sorts of differences?

As ever, many thanks in advance.

Chris

RV8, final assembly......
Chris, just out of curiosity do you have a different Pitot tube then the stock Pitot tube that you fabricate the vans kit?
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  #10  
Old 09-11-2017, 11:36 AM
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JonJay JonJay is offline
 
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Quote:
Originally Posted by Larry DeCamp View Post
The thinner the trailing edge, the less effective, and control stick force increases in my experience. Thicker is better.
I would only comment that keeping the trailing edge radius "per plans"
is best. Not thinner, not thicker. This will give you the designed control feel and responsivness.
Most adjustments need to be made as a result of the transitioning to the trailing edge not being done correctly. The "bulbous" transition is a common one.

Squeezing a trailing edge should be a last resort as most issues are found elsewhere.
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