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wing aft spar alignment

J

jacksel

Well Known Member
Is it normal to have to take considerable material off the RV-7 QB wing rear spar tab to properly interface it to the same RV-7 QB fuselage?

I installed the wings initially using 7/16 bolts. When I clecoed in the wing root fairing in place the gap got considerably wider moving aft on the forward surface. Using the leading edge plumb bob technique described in the plans, the wings seemed to have a slight forward sweep.
 
I've helped rig the wings on two 7's and I think we had to file down the rear spar on one to make it eliminate some forward sweep as well. Just don't go crazy, as it doesn't take much filing at the wing root to make the wing tip sweep back. You don't want to lose the edge distance on the mounting hole.
 
Not sure what "considerable" means and can not speak for the 7 QB directly but I do know it is not unusual for the rear spar to hit the fuselage side and have to be trimmed some.
What is absolutely critical is maintaining edge distances around the rear spar bolt.
I believe Vans allows up to 1/2" of forward sweep regardless.
I would make a quick call to them if you don't get a solid answer here.

(Typing while Dave was answering. On my 6 wings I built to plans,and on two QB 8's I was helping with, some trimming was required. I have some forward sweep on my 6. No adverse affects.)
 
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Root Fairing ?

The rear spar will usually take a little trimming on a 7 but you do not want to put the root fairing on and then drill the rear spar. Most of the root fairings have to be pulled into position and are tight to seal well. That by itself could pull the spar out slightly and cause some forward sweep.

Set the wing up per Vans instructions and you might have to file the spar just the slightest bit. I also seem to remember that it hits a rivet that can be filed instead of the spar....but that part is a little fuzzy :) That was 7 years ago.

Leave the root fairing off while setting the wing up. You can always make it fit later but fitting the wing incidence with no influence from the fairing is more important. Be very careful with the edge distance on the rear spar.
 
Thanks guys.....I'm going to remove the wing, trim the tab slightly, and re-install and check again.....jacksel
 
Two things need to be trimmed.

The rear spar of the wing needs to be trimmed per the plans.
One thing to check on the quick build fuselage: on mine they used a 470 rivet just above the rear spar carrythrough that hit the wing rear spar at the top edge. I had to file a very small notch in the top of the rear wing spar to clear the rivet head.

Then on the rear spar carrythrough in the fuselage, the front bar only will hit the flange of the wing rib and not let you fully seat the rear spar into the carrythrough.
You have to file a 1/16" taper on the FORWARD bar of the rear spar carrythrough. By taper, I mean 1/16" off the top of the forward bar that tapers to 0" at the bottom. This is because of the dihedral in the wing.

Before doing any trimming, study the pieces that I have mentioned so you fully understand what I am trying to say. I do not have any pictures so I am trying to verbally describe this. I may not have been clear so be very careful. I learned these tips from several peoples build sites, so maybe you can research those on the web. Your plane may be different so don't take this as gospel.
 
I did a slow build wing but had a QB fuselage. the drawing for the rear spar cut in the first lans is pretty good but like a couple of folks hace stated you might have a rivet on the fuselage to file the spar a little. I would set the plumg bobs back on the front wing. at least in 4 places and eliminate any sweep to the wing. It is done easily enough. measure and re measure forget the wing root it is not time for that. after measuring and you think your right take a 15 minute break and then measure again. you do not want to screw this hole up!

Jack
 
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