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  #1  
Old 04-12-2020, 08:18 PM
Bart Bart is offline
 
Join Date: Jan 2008
Location: Pecan Plantation (0TX1)
Posts: 195
Default Wing Tip Alignment Tolerance Question

I've see this question floating around all the forums and have ignored most of the discussions until today. After having re-read many of the "mismatched wing tip" threads I wanted to ask the -14 crowd about tolerances.

Both my tips are 1/4 inch above the aileron and flap reflex position. The rigging on everything has been near perfect until today. In fact it wasn't until the nut plate installation was finished that I noticed both tips were slightly (1/4 inch) above the flap/aileron line.

I'm torn about cutting the TE open and creating the perfect alignment over seeing what the actual flight conditions might show with my 1/4 inch off alignment. Since both are nearly identical my gut is saying leave alone until we see what happens in flight...but I'd like to hear what other folks have experienced.
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  #2  
Old 04-12-2020, 08:26 PM
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DanH DanH is online now
 
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Tip trailing edge high or low seems to have almost no effect. I even taped a great big tab to the trailing edge of a tip once just to see what happened. Zip.
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  #3  
Old 04-12-2020, 08:33 PM
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emsvitil emsvitil is offline
 
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Location: SoCal
Posts: 494
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Make a little wing (tip) fence to go there so it looks like that's the way it's supposed to be..............

Fence would also stop any weird airflow thru the gap between the aileron and tip.
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  #4  
Old 04-12-2020, 11:14 PM
JDeanda JDeanda is offline
 
Join Date: Apr 2013
Location: Ventura, CA
Posts: 234
Default Tips

Adding a tab to a wingtip and deflecting it up (to roll the airplane toward that side) is not nearly as effective as adding one on the other side, deflected down, to raise that wing. Our RV-6 , not built by me, has a bit of wash-in on the right wing. We ran out of right aileron trim at high cruise speed. I added an old/ timey deHavilland tab to the underside of the left wing and got the rigging closer. It’s just a piece of 1/4” round arrow shaft taped under the trailing edge, parallel to the trailing edge. Adding one on top of the right tip did nothing. I finally put a stronger spring in the aileron trim system and now we can just get it to fly straight at higher speeds. Using fuel out if the left tank helps, too.

Last edited by JDeanda : 04-13-2020 at 09:22 AM.
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  #5  
Old 04-13-2020, 05:57 AM
RV6-KPTW RV6-KPTW is online now
 
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Location: Sebastian Fl X26
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Splitting the trailing ends and adjusting to be more visually appealing is very easy.
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  #6  
Old 04-13-2020, 07:03 AM
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Carl Froehlich Carl Froehlich is offline
 
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Bart,

I assume you are not yet flying, so before you start cutting wing tip trailing edges I recommend some careful measurements to make sure your rigging really is correct. This cannot be done until the wings are on the airplane. For example:
- Are the flaps all the way up? For the RV-10 and 14 this is easier than the previous planes, but should not be glossed over. Take a straight edge across the length of the flaps, is each flap the same over the length and are both flaps the same? You are looking for flap twist and that each flap comes up flush with the fuselage.
- With the flaps up and the elevator clamped in the trail position, do the ailerons line up perfectly with the flaps? For the RV-10 and RV-14 you must clamp the elevator in the neutral position first as any deflection will pull on the aileron push tubes.
- If good, then do the same straight edge on the ailerons that you did with the flaps.
- Finally, with the ailerons softly clamped to the flaps, measure the gap between the leading edge of the aileron and the wing skin. Again across the length of the aileron to make sure it is constant, and both ailerons are the same. On many RVs a heavy wing is caused by an aileron hinge point being too high or too low. Easy to fix if it is.

For builders who have not yet fitted the wingtips, recommend deferring this until final assembly, and after the above checks are done. The little aluminum gig that comes with the kit that it tells you to use is ok for getting stuff in the ballpark, but not for perfect before you drill mounting holes in the wingtip.

Carl
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  #7  
Old 04-13-2020, 07:41 AM
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kbalch kbalch is offline
 
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Quote:
Originally Posted by Carl Froehlich View Post
- Are the flaps all the way up? For the RV-10 and 14 this is easier than the previous planes, but should not be glossed over. Take a straight edge across the length of the flaps, is each flap the same over the length and are both flaps the same? You are looking for flap twist and that each flap comes up flush with the fuselage.
- With the flaps up and the elevator clamped in the trail position, do the ailerons line up perfectly with the flaps? For the RV-10 and RV-14 you must clamp the elevator in the neutral position first as any deflection will pull on the aileron push tubes.
My understanding is that, on the -14 at least, the ailerons are meant to match the flaps at 0 degrees, not when the flaps are fully up (-3 degrees). Do I have that wrong?
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  #8  
Old 04-13-2020, 07:51 AM
Bart Bart is offline
 
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Carl,

Thanks for the advice. Wings are attached, I should've noted that. I did recheck the flaps, aileron, and overall alignment. They are very satisfactory. They were QB flight controls and Van's did a great job putting those together. The wing tip aileron gap is 3/10th's, they are about 3/100's difference between both ailerons/wingtips with the elevator neutral position and flap reflex /aileron alignment lightly clamped. No visible twist using a straightedge. My question is...do I need to continue troubleshooting or leave it and see what happens in flight?
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  #9  
Old 04-13-2020, 08:26 AM
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rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by kbalch View Post
My understanding is that, on the -14 at least, the ailerons are meant to match the flaps at 0 degrees, not when the flaps are fully up (-3 degrees). Do I have that wrong?
Yes, you have it wrong.
The ailerons are technically always at a - 3 degree reflex (when neutral) for cruise flight (where the airplane spends the majority of its flight time).
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Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

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  #10  
Old 04-13-2020, 08:28 AM
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rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by Bart View Post
Carl,

Thanks for the advice. Wings are attached, I should've noted that. I did recheck the flaps, aileron, and overall alignment. They are very satisfactory. They were QB flight controls and Van's did a great job putting those together. The wing tip aileron gap is 3/10th's, they are about 3/100's difference between both ailerons/wingtips with the elevator neutral position and flap reflex /aileron alignment lightly clamped. No visible twist using a straightedge. My question is...do I need to continue troubleshooting or leave it and see what happens in flight?
As Dan already said, the position of the wing tip trailing edge (unless grossly off) has pretty much zero influence on the roll trim.
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Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

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Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
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