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The gap isn't normal, and the wing imbalance could be from many other sources. How bad is it? Something trimming out can't solve, when I fly switching fuel between left and right wing I always end up with one heavier than the other and need to trim to get level.

I'd look at the flap retraction separately.
 
No, not normal.

Rigging is never “one and done”. The best process I’ve found is:
- Get the flaps all the way up, with left and right perfectly matched.
- Once the flaps are up, clamp the left aileron trailing edge with trailing edge of the flap. Now compare how the right aileron trailing edge lines up with the right flap trailing edge.
- If there is a difference, first corrective action is to adjust the aileron push tubes so they do match.
- Go fly. Take more data.

If you still have a problem you need to check:
- Any twist in a flap?
- Any twist in an aileron?
- Are the aileron symmetric with the top wing skin trailing edge (inboard and outboard)?
- Do the ailerons have the same height to an extension of the top skin (as in using a straight edge across the skin to aileron with the aileron clamped to the raise flap? Again compare the two ailerons at both inboard and outboard locations.

Whatever you do defer any aileron trailing edge squeezing until you check the more common causes for a heavy wing. Consider aileron squeezing as a very fine adjustment to a good rigging, not a fix to a bad rigging.

Carl
 
I would check the rigging first, per the manual.

Pull the wing tips
Use the end wing rib tooling holes to line up the aileron trailing edge (see plans for the tooling hole fixture (sheet 12A)),
Use the bellcrank fixture to check or set the pushrod lengths.
Once the ailerons are rigged, then you set the flaps to match the ailerons.

(and hope the wingtips line up with the ailerons!)

After that, if you still have a heavy wing, Van's has an article on the Vans website that tells how to check and correct. (for the pre-punched wings, you basically squeeze the light wing aileron TE (just a little!) as the aileron hinge brackets aren't builder drilled anymore.)

Good luck. I'm about to do this exercise with a fellow 8 owner with a heavy wing.
 
The gap at the flap/fuse intersection should be very small in the range of 1/32" measurements. You can close up the gaps by adjusting the flap pushrod length from each side. The flaps were probably removed for painting and the reassembly was probably not done correctly. This is an easy fix so do this first.

Work one thing at a time and recheck.
 
Don't squeeze down the ailerons! It's not a true fix - it just adds additional out-of-trim aerodynamics into the airframe.
 
I would check the rigging first, per the manual.

Pull the wing tips
Use the end wing rib tooling holes to line up the aileron trailing edge (see plans for the tooling hole fixture (sheet 12A)),
Use the bellcrank fixture to check or set the pushrod lengths.
Once the ailerons are rigged, then you set the flaps to match the ailerons.

(and hope the wingtips line up with the ailerons!)

After that, if you still have a heavy wing, Van's has an article on the Vans website that tells how to check and correct. (for the pre-punched wings, you basically squeeze the light wing aileron TE (just a little!) as the aileron hinge brackets aren't builder drilled anymore.)

Good luck. I'm about to do this exercise with a fellow 8 owner with a heavy wing.

You can purchase undrilled A-406 aileron hinge brackets from Vans. Had to do this on friends RV a little while ago. Slot the drilled ones first to find the location needed to correct the heaviness then drill the undrilled bracket to the new hole location.
 
The ailerons should be aligned using the tool holes drilled in the outer ribs. There is a drawing for this particular item.
On my RV8, after the ailerons are mounted and aligned, I fitted the flap and aligned it to the trailing edge of the aileron. Then the flap/fuse intersection plates are fitted and riveted to the fuselage. When the flaps are remounted after moving or reassembly, the flap/fuse intersection plates should serve as the alignment guide to ensure everything is back to where it was. This assumes all the parts are straight at the start.
 
The ailerons should be aligned using the tool holes drilled in the outer ribs. There is a drawing for this particular item.
On my RV8, after the ailerons are mounted and aligned, I fitted the flap and aligned it to the trailing edge of the aileron. Then the flap/fuse intersection plates are fitted and riveted to the fuselage. When the flaps are remounted after moving or reassembly, the flap/fuse intersection plates should serve as the alignment guide to ensure everything is back to where it was. This assumes all the parts are straight at the start.
Yep - this is what Van’s says to do, however….

The “align with the tool holes” or “use the aileron bell crank jig” to set the ailerons is, in my opinion, a good starting point. I do not consider this to be a complete rigging process.

In particular, I would not be surprised if the current flap low problem reported by the OP is a result of setting the ailerons rigging then aligning the flap trailing edge to the aileron trailing edge, but never doing final checks. I recommend always rigging the flaps fully up (and identical left and right) then working out from that. I personally know of one RV that had a heavy wing for years. One flap was 1/4” lower than the other. Once properly rigged the heavy wing was gone.

I offer careful measurement using straight edges the wings to determine flap and aileron mounting height should not be overlooked. This is how you find the notorious “one end of the aileron is lower in the breeze than the other”. I refer back to the post on no hole aileron brackets as the cure.

Side note. Back before prepunched everything Van’s wing shipping crate came with a full size wing cross section drawing on the crate plywood. Careful cutting transformed this drawing into a very good aileron and flap rigging jigs. I kept these from my first build and still find use for them on other RVs.

Carl
 
Next time I go to my hangar, I want to look at something I didn't pay close enough attention to yesterday:

I'm curious if the aileron/flap/wintip trailing edges are all lined up with the flaps adjusted in the current slightly extended position.

If so, just trying to visualize it sitting here, that'll mean that with the flap-up postion being readjusted, and the ailerons adjusted to align, then the aileron trailing edges might be slightly above the wingtip trailing edges. Hmmmm.....
Believe it or not you don’t have to fret about the wing tip alignment. The consensus is it doesn’t have much effect. It’s seems like it is almost always related to the aileron alignment to the wing. Check the aileron alignment to the wing tooling holes and the hinge alignment first.
 
I would follow the company advice on how to fix a heavy wing, in the order described:


If all of that doesn’t fix it, then you’ll have to get creative, but I would follow the Vans directions first.
 
I would not squeeze the trailing edge. My last 8 that I owned had someone do that to it before I got it. Dramatically heavier roll forces than any other RV.
 
While totally inapplicable to an RV8 heavy wing I thought you all might find it interesting. On my Mooney M20E if you have a heavy wing the maintenance manual says to bend the trailing edge of the opposite elevator down; heavy right wing, bend the trailing edge of the left elevator down.
 
YIKES!

I think I’ll pass on bending the elevator.
I just finished this process. I had a pretty heavy left wing on my first flight - such as you let go of stick and you’ll be at 60 degrees of bank in few seconds. Vans, Carl and others are spot on and using bits from all these resources helped on my recently flown RV-8. For me, I made sure my flaps were up against the stops as Carl mentions. Then checked tooling holes with laser levels - all good. I didn’t do the fuel thing as vans suggests - it’s not necessary in my opinion.

When diagnosing the left heavy wing and reading everything it quickly became apparent standing in front of the left wing looking at my left aileron that the aileron was sitting slightly high as compared to the upper wing surface. So I slotted (elongated the 4 holes) in both brackets in the left aileron. I shifted the bracket 3/32” which lowered the aileron by this amount. To my surprise this small amount resulted in a heavy right wing. But I knew I was on the right track so I about halved the correction and it’s pretty good. I did buy the new brackets but not sure if I’ll install them anytime soon. I simply put some torque marker on the bracket to monitor any movement which I doubt will ever happen. I made a reference line for removal when needed.

Mark
 
YIKES!

I think I’ll pass on bending the elevator.
Agree. The two elevator designs are not the same. The RV has the folded trailing edge. The Mooney has the flat sharp pinched rivet trailing edge and this is why it can be bent. Here is a picture of the Mooney elevator. Needless to say, don't try and bend the Vans elevator.
 

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I did the same thing on my RV6 with a heavy left wing, except I only slotted the outboard aileron bracket. The outboard bracket can be removed without disturbing the inboard aileron connection at all. I used a small bench with pillows to support the aileron near its flying position while the bracket was off for slotting. It took longer to remove and then reinstall the wingtip than it did to modify the bracket. Slotting that bracket lowered the outboard end of the aileron about 1/16”, and that was enough for me.
 
I would not squeeze the trailing edge. My last 8 that I owned had someone do that to it before I got it. Dramatically heavier roll forces than any other RV.
There may be a misunderstanding about this technique. The goal is for the aileron top and bottom surfaces to be flat from the leading to the trailing edge. Often they don't come out that way when built and are somewhat convex or less frequently concave along some or all of the aileron. Squeezing the trailing edge gently and carefully only where it's convex will flatten it out. Similarly, bonking the TE with a rubber mallet pushes out a concave surface. This is documented in Van's literature somewhere, and not long after my first flight I spent a couple of hours with Dick VanGrunsven's brother Jerry making sure mine are as flat as could be. The result for me was curing a heavy wing and very light stick forces overall.
 
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