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Mounted my wings on the fuselage. Yay! But my wings sweep forward 1/8"

K

KitfoxJoe

Active Member
Hi all
Ok mounted my wings. my rear spares are all the way against the fuse. and yes I used a flush 1/8" rivet above where the rear spare is. So no interference with rivets. But my wings sweep forward 1/8". I am thinking the only way to remove the sweep is to take the wings off and file the rear spare down say 1/32 or 1/16. But before I do that I wanted some feed back. So, is it ok to file the rear spare? Thanks Joe
 
Yes it's okay to do that. Just go slowly because it won't take much filing at all. There was another thread along these lines not too long ago if you want to do a search.

BTW, 1/8" sweep is within Van's tolerances. But you can get as close to spot on as you'd like. Just keep in mind the potential damage that might happen if you're going in and out with the wing bolts repeatedly.
 
Be careful. Removing 1/8 inch off the rear spare = 1 inch of sweep at the outboard end of wing. Larry
 
1/32"

You'll probably only need about 1/32" removed from each drag spar. That should bring them into alignment. Very common issue that is easy to fix.
 
I find it difficult to believe that 1/8 th of an inch forward sweep would make any detectable difference. The end of the wing is, what, 9 foot out from the fuse?
 
I trimmed mine a bit, as suggested, and my little bit of forward sweep was corrected easily.
 
The number one concern in this area is the edge distance of the bolt hole on both the rear wing spar and the fuselage attach points. With that in mind you can remove material from either part as long as this edge distance is not compromised. There is one bolt in this location to allow for some movement between the wing and the fuselage. If the rear spar is filed so perfectly that it is completely tight against the fuselage then this can become a pinch point by not allowing that slight movement between the wing and the fuselage.
 
1/8" sweep problem??

Complete the airplane and go fly, it is not a problem.

If you are looking to build a perfect airplane, have fun. An OAT change could effect the measurement that much, for sure it would change the length of your metal tape measure.

A long time ago a FAA inspector told me he had seen Cessna's coming off the line with wing dimensions off by an inch. It is not big deal for small aircraft.
 
I think Vans says within 1/4" is good enough. But I'm a perfectionist and made sure I had the edge distance buffer, then trimmed a bit off the aft spar and got mine within 1/32".
 
I'd leave well enough alone...you'll never know it.
Click to expand...

Plus 1 - I thought the instructions indicated that a forward sweep wasn't a big deal as long as both sides were similar.

There is a fix for gumming up the rear spar, but it ain't pretty. So, me, if the 1/8 was constant on each side, I'd live with it.

Dan
 
Been there done that

My RV-7A has less than 1/16" sweep but I had to cut the rear spare to acheive this.

I recently helped another builder with his RV-7 wings. In order to achieve close to zero sweep we had to cut down the rear spar on the wing and the rear spar attach on the fuselage. We had the wings on and off several time to get the job done. Use two of the 1/4 Bolts (only partially in to pin the wing and a few temporary bolts (hardware store bolts) in the other holes. Tighten the temp bolts. Not issue with edge distances at all.

Just be careful to identify where to remove the material and build some drill jigs to drill the rear spar holes, finish the holes with a reamer.
 
Thank you for all your input

Well it sounds like the concensus is within specs move on. So that's what I will do. Now I only have 9,998 things to do. Man I'm getting close. LOL Thanks all. Joe
 
Lemmingman said:
If you haven't seen it, look at this:
http://www.vansaircraft.com/pdf/Wing_ Incidence.pdf

I had forward sweep as well.
Click to expand...

That about settles it :)

Now check the forward sweep! Hang 2 plumb bobs on each wing, one at the tip and one at the root (tank area). Then stretch a single long string across the front of the these four plumb bobs. If there is no or minimal (get real, less than 1⁄2?) sweep fore or aft, then move on to #4 below.
 
aft spar

In doing some research on aft spar loading it appears upon abrupt pitch up maneuver the lift vector shifts forward putting a forward load on the wing and tensile load on the aft spar. This wing forward load is significantly higher than the normal aft loading from wing drag in level flight and the upwards loading when the flap is deployed. Therefore, mind the aft spar wing attachment edge hole distance on the drawing.
 
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fwd sweep

in case you had still not decided on a repair for your forward swept wings, i thought i would chime in with my experience of same and my repair.
you said your wings were mounted - which means your rear spar is not only filed "per plans" but the hole, to bolt it to the fuselage, has been drilled and filled with said bolt, per plans, am I right? if so, it matters not how you file the in-board aspect of the spar doubler and reinforcer plates because it's position is now fixed by the placement of the hole.
I removed and replaced the rear spar doubler and reinforcer by drilling out rivets and replacing them with cherry max rivets when the new, properly cut and properly drilled (i.e. we mounted the wing on the main spar, moved for and aft for sweep, moved up a titch for angle of incidence and then drilled using the previously drilled holes in the fuselage tines [my made up term, can't remember exactly what they're called]) as templates and voila! no forward sweep.
would i do it again? well, if i could have drilled out the initial rivets better, maybe.
but i did it out of obsession with perfection and while i have no more forward sweep i'll always wonder about my repair.
retrospect has me preferring a sound evaluation of the aerodynamic implication of 1/8" forward sweep before cutting metal.
good luck
jrh md
n377cp, kwvi
 
Forward sweep isn't a problem up to at least 1/2" per Van's. It also isnt a big deal if one wing has a bit and the other not, at least it wasn't for me. Vans built my QB fuselage center section out of square. It was impossible to square both wings. The best compromise was one wing 1/2" forward sweep and the other none. She is true and fast. It just isn't a big deal.
 
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