Confusion after mounting wings...

After a 4 month forced hiatus, I got back to the plane today. I got it moved into the driveway and fit the wings. I was planning to get wing incidence set and such, but never made it that far.

The wings went on easily enough with some Tractor Supply 7/16" bolts. A really quick measurement from the tip of the outboard aileron bracket to the rear of the fuse showed about 3/16" difference between the wings.

We setup the plumbobs and it was clear that the wings both had some slight forward sweep. However I dont understand how to get rid of it. The rear spar attach might have 1/16" before it touches the round headed rivet. We wiggled...pushed and cursed at it and could not get the wing to move even a mm. With those main spar bolts in there I have no idea how it is supposed to move at all. The instructions don't make it any easier.

Equate these distances at the same time checking that the wings have no forward or aft sweep

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It then proceeds to tell you how to check with plumb lines. Then we get this confusing sentance:

Mark this position with a vertical line at the rear spar attach, on both rear spar and center section.

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What am I marking? Why? I can under stand the rear spar, but why am I marking the center section...it's already bolted to the wings? I've read ahead and in the next 3 pages this mark is never mentioned again. Is this a line that tells me where to drill the hole? What is this line telling me on the center section?

I guess the line is a moot point until I can figure out how to adjust the wing to make the distance from the tips to the tail equal and remove any sweep from the wings.

Any guidance or ideas you might have had would be most helpful.

FAQ on Vans...

I don't know if this will help. But there's a document on the Vans FAQ page that gives more detailed instructions for setting the wing incidence. It's been a few years since I did this. But I remember finding this useful.

http://www.vansaircraft.com/pdf/Wing_ Incidence.pdf

Michael-

It sounds like your rear spar attach bars may be slightly too long at either the fuselage or the wing. You may need to file them a bit so that you can pull the forward sweep out of the wings. This shouldn't effect edge distance if your wing sweep is correct. Hope this helps.

I hung my wings a few weeks ago. I too had forward sweep of almost 1/4" and found the rivet just above the rear spar fork was holding the rear wing spar out. We shaved the head of this rivet off on both sides as a quick fix and leading edge went into almost perfect alignment. Just make sure that you don't have any rivet heads holding the rear spar out. If you're not touching the rivet, I'd take a screwdriver and gently pry the rear spar fork apart just to see if it is holding you out as well.

Also check the rear spar fork (from the fuselage) and ensure that it's not interfering with the flange on the inboard rib of the wing. If it is, you'll have to shorten it a touch.

Lemmingman said:

Then we get this confusing sentance:

What am I marking? Why? I can under stand the rear spar, but why am I marking the center section...it's already bolted to the wings? I've read ahead and in the next 3 pages this mark is never mentioned again. Is this a line that tells me where to drill the hole? What is this line telling me on the center section?
I guess the line is a moot point until I can figure out how to adjust the wing to make the distance from the tips to the tail equal and remove any sweep from the wings.
Any guidance or ideas you might have had would be most helpful.

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I think you might be misreading "center section" to mean the main spar. I believe this refers to the rear spar carry-through in the fuselage.

One thing that RV7A Flyer reminded me of, was that you might want to put a radius on the top corners of the rear spar carry through fork. It can interfere with the root rib because of the wing dihedral.

It's the top rivet

drone_pilot said:

I hung my wings a few weeks ago. I too had forward sweep of almost 1/4" and found the rivet just above the rear spar fork was holding the rear wing spar out. We shaved the head of this rivet off on both sides as a quick fix and leading edge went into almost perfect alignment. Just make sure that you don't have any rivet heads holding the rear spar out. If you're not touching the rivet, I'd take a screwdriver and gently pry the rear spar fork apart just to see if it is holding you out as well.

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Though it has been 5 yrs since I installed my wings it was the top rivet as mentioned that is the problem. I temp installed the bolts, checked the sweep and saw the interference. I removed the temp bolts, pulled the wings out just a few inchs and cut the corner of the rear spar tab to clear the rivet. Temp installed the wing, sweep was within 1/16" of an inch and set the incidence angle, drilled the rear spar, drilled the bottom skin overlap to the wing and fit the wing root strip (don't recall the exact name of the part). Then pulled the wings and cleaned up the corner cut on the rear spar tab.

I left a 1/4" gap between the root strip and the fuselage. The rubber seal fits great without any glue required and I have not had any problems with it with over 3 yrs and 220+ hours of flying.

Depending on exactly where you installed your flap (spanwise) you may need to trim the inboard side of the flap skin to provide clearance with the fuselage side skin. You might also need to swap out the some of the AN470 rivets on the inboard flap reinforcement plate with AN426 rivets to prevent interference. I have a 5/16" gap between the flap skin and fuselage side skin and it works great.

I haven't yet plugged my wings in (within a few months I hope), so I'm not completely sure what you have interfering with what. What I do remember is that the plans (Dwg 38, I think) shows a trim of the inboard ends of the rear spar doublers. Did you do that?

Miles,
Even if you follow the plans to the exact letter, it is likely that you will have interference on one 470 round head rivet that hits the top of the wing rear spar and also interference of the top edges of the fuselage center sections of the rear spar against the wing rib (or something, I can't remember). It will give you a fraction of an inch forward sweep.

You will be well within the John Deere alignment tolerances even with the interference, so don't bother calling Oregon.

Slight rounding of the top edges of the rear spar center sections and the rear wing spars makes everything fit perfectly.

I believe there is a guide/section in the plan that suggest how much to cut/shave from the rear spar tab that will give you plenty of room to set the incident just right. It is very little that needs to be removed.

Michael Burbidge said:

I don't know if this will help. But there's a document on the Vans FAQ page that gives more detailed instructions for setting the wing incidence. It's been a few years since I did this. But I remember finding this useful.

http://www.vansaircraft.com/pdf/Wing_ Incidence.pdf

Michael-

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Thanks for pointing me to this. It will be most helpful. It is much more descriptive than the instructions.

RV7A Flyer said:

Also check the rear spar fork (from the fuselage) and ensure that it's not interfering with the flange on the inboard rib of the wing. If it is, you'll have to shorten it a touch.

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Now this I did not check. I was so focused on the rear spar itself I couldn't tell you if the fork was touching or not. I look at that this weekend.

Mel said:

I think you might be misreading "center section" to mean the main spar. I believe this refers to the rear spar carry-through in the fuselage.

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Thanks Mel. I think you're right. I was reading it too literally.

longranger said:

I haven't yet plugged my wings in (within a few months I hope), so I'm not completely sure what you have interfering with what. What I do remember is that the plans (Dwg 38, I think) shows a trim of the inboard ends of the rear spar doublers. Did you do that?

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This is to plan. I measured from the outboard line of rivets to the edge of the spar and it was spot on. Fortunately I didn't try to trim anymore off.

rzbill said:

Miles,
Even if you follow the plans to the exact letter, it is likely that you will have interference on one 470 round head rivet that hits the top of the wing rear spar and also interference of the top edges of the fuselage center sections of the rear spar against the wing rib (or something, I can't remember). It will give you a fraction of an inch forward sweep.

You will be well within the John Deere alignment tolerances even with the interference, so don't bother calling Oregon.

Slight rounding of the top edges of the rear spar center sections and the rear wing spars makes everything fit perfectly.

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Thanks for the info, Bill. Is that interfering rivet one to which I might still have access so it might be switched to a -426 countersunk rivet? Anyone have a photo pointing out the offending rivet?

-426 Rivet

longranger said:

Thanks for the info, Bill. Is that interfering rivet one to which I might still have access so it might be switched to a -426 countersunk rivet? Anyone have a photo pointing out the offending rivet?

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That is exactly what I did when building - I used a -426 rivet in this location since it was well known that the -470 rivet could sometimes be an issue. It is the one directly above and closest to the rear spar attach point.

It has been over three years since I did my wing fit up and I honestly can't remember if using the -426 actually saved me some grief or not. I do remember that I was able to get the wings to 0 sweep with no problems.