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  #1  
Old 02-17-2018, 04:33 PM
efitzgerald efitzgerald is offline
 
Join Date: Jul 2016
Location: Dryden, MI
Posts: 32
Default Wing Incidence Problem

I temporarily mounted the wings.

After making relief notches to clear a rivet at the top of the rear spar stubs, the sweep and triangulation is less than 1/16" off.

But when I check the incidence with the rear spars lined up to the bottom of the flange:

The left wing is 0.2 degrees high on the trailing end at the tip.
The left wing is 0.1 degrees high on the trailing end at the root.
The right wing is 0.0 degrees at the root
The right wing is 0.1 degrees low on the trailing end at the tip.

The best I could do was to lower the stub of the the left wing spar approximately 3/32""

The left wing is 0.1 degrees high on the trailing end at the tip.
The left wing is 0.0 degrees at the root
The right wing is 0.0 degrees at the root
The right wing is 0.1 degrees low on the trailing end at the tip.

So it appears that there is some twist to the wings. Also the flap / fuselage interface is not going to the same on both side as the left is slightly lower. Edge distance is not a problem, there is lots of room. This is a quickbuild kit, the quality seems to be good other than a lot of scuffs and scratches.

What are you recommendations?

Thanks,
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  #2  
Old 02-17-2018, 04:38 PM
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9GT 9GT is offline
 
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Location: Southern Michigan
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Default

One tenth of one degree is pretty good IMHO. You would not even see that with an old fashioned bubble level used by builders pre digital age.
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  #3  
Old 02-17-2018, 04:54 PM
efitzgerald efitzgerald is offline
 
Join Date: Jul 2016
Location: Dryden, MI
Posts: 32
Default

I am not a fan of digital protractors / levels (I am using a Mitutoyo Pro 360). But all of my semi precision / precision levels are useless for this (they are too accurate). When I check with a 6" torpedo level, the bubble is touching the line on the left tip. The root ends looks good and you can see only a very small deflection on the right tip.

The instructions and guides from Vans don't list a tolerance for incidence, they only state that it must be the same. The biggest irritation is that the distance between the flap skin to the fuselage will not be the same on both sides of the fuselage.
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  #4  
Old 02-17-2018, 05:01 PM
engineerorange engineerorange is offline
 
Join Date: Apr 2008
Location: Catawba, NC
Posts: 161
Default

One of my wings had about .2 degrees of twist. I set the incedence in the center of the wing and guess what, it flies straight and level with the ball centered. A tenth of a degree is nothing. One of my flap skins also has about a 1/8-3/16 joggle to meet the bottom of the fuselage.
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  #5  
Old 02-17-2018, 05:44 PM
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wirejock wirejock is offline
 
Join Date: Oct 2005
Location: Estes Park, CO
Posts: 2,903
Default Incidence

I seem to remember this in a search. Basically the consensus was make them both the same at the measurement point in the plans. I did ask about sweep and was told make them the same. A call to Vans would be prudent before drilling the rear spar holes.
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Larry Larson
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  #6  
Old 02-17-2018, 05:58 PM
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Mel Mel is offline
 
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To quote an old saying, "BUILD ON!" Your errors are WELL within build tolerance.
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  #7  
Old 02-17-2018, 06:43 PM
rv7charlie rv7charlie is online now
 
Join Date: May 2006
Location: Pocahontas MS
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Well...shucks. I was going to tell him I'd take it off his hands......


;-)
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  #8  
Old 02-18-2018, 09:52 AM
efitzgerald efitzgerald is offline
 
Join Date: Jul 2016
Location: Dryden, MI
Posts: 32
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I drilled to #30 to check everything out before final drilling. Wing incidence angles are still 0.1 high on the left, 0.0 on the roots and 0.1 low on the right end.

After trimming the flaps and bending the overlap up a small amount on both sides it looks really good.

Thanks for the input. This is one of those areas that are so easy to waste lots of time second guessing everything.
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  #9  
Old 02-18-2018, 12:17 PM
Pat Stewart Pat Stewart is offline
 
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Location: Granbury Texas
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You could call vans but I think I can tell you what they will say "Thats pretty darn good". As Mel said, build on.
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  #10  
Old 02-19-2018, 12:37 PM
RV7 To Go RV7 To Go is offline
 
Join Date: May 2011
Location: Ontario, Canada
Posts: 91
Default Incidence

As memory serves, which it doesn't always, I think the manual, or possibly on a drawing, it states the incidence should be +.5 degrees. I believe the manual also states that the most important thing is that they are both the same.

I bought a 4 which flew fine but had a heavy left wing. I went through the Vans trouble shooting instructions starting with the wing incidence. Found one wing had a 1.2 degree washout and the other had .5 degrees washin. Both were zero at the root. The rear bolts had already been enlarged to 3/8" so I could not change the incidence and wasn't about to build new wings. The light aileron trailing edge had already been squeezed so no joy there. I adjusted the outer aileron bracket on the heavy wing 3/32" and the heavy wing issue was gone. The plane flew with centre aileron trim and a centred ball. It didn't have any weird tendancies through the flight envelope.

Bottom line is you are well within tolerance. Build on as others have said.

Al
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