I made a two-wing jig on one set of posts. This means that the two wing
skeletons balance each other (more or less), so there should be less strain
on the cross-arm braces. On the other hand, the cross-arms need to be much
longer to allow working room between the wings, so the braces need to be
stronger... who knows? My cross-arms are 46" long 2"x2"x1/8" angle steel
(actually a couple of old bed rails), and I made the upper braces from
the same material. My lower cross-arms were from the same angle, 42" long.
They were actually slightly too long, so I ended up having to cut slots
in them too to allow the skins to fit properly. You don't want them protruding
past the outer edge of the rear spar.
To make it easier to get between the wings, I put the braces on the upper cross-arms above the arms rather than below. This didn't affect the stability of the jig, but was pointless -- the distance between the spars, and therefore the cross-arms, is only a couple of feet... no way am I going to fit between them. My upper cross-arms are about 54" (about nipple height on me) from the floor, so the lower ones will only be about three feet above the ground, and I'll have to duck through this space :-(. To minimise the ducking and diving, I'll skin the underside of the far wing before rivetting ribs and rear spar to the near one. If I did it again, I'd mount the upper cross-arms 6" (or even a foot) higher. Also, I'm building in a single garage, with the workbench going down one side... I have adequate room between the wings, but not really enough on one side.
On reflection, I think the ideal jig would be set up on 3 posts in an A-configuration. Put the root ends of both wings at the apex of the A (not sure whether it'd be better to have the upper or lower surface inside the A). Put a work-bench at the cross-bar of the A. As with the empennage jig, the posts aren't really important. What is important is to get the cross-arms in the right place and firm, and to have access to both sides of the wings.
I see no reason why the cross-arm should extend beyond the edges of the spars, but if you do it that way: Mark McGee <FMark40@aol.com> suggested to the RV-list: I installed anti-head-gashing units on my wing jig angles. The angles are 1 1/2 inch steel angle. The ends are nicely protected with tennis balls. Just cut an L shaped slot and slip them over the ends of the angles. They are soft and brightly coloured and will prevent those unsightly head wounds.
Justice suggests to mount #14 rib web 1/8" further inboard than plans call for. This is probably a bad idea -- I advise that you *think* about this real hard.
IF YOU BUILD THE SKELETON TO MATCH THE SKIN, YOU'LL GET A PERFECT WING. Therefore, start by taking a wing skin and clamp it to the main spar and mark where the rib rivet lines are on both sides of the spar. Now you have just saved yourself a lot of grief worrying about locating ribs and angles. And you can save a lot of time dispensing with all those measurements. Also, mark centrelines on all your rib flanges. Be generous in marking centrelines!
There's no need to set things up in the jig yet. You may find it convenient
to work with the spars on the jig, but, if I did it all again, I'd do all
of this step on the workbench.
RV-List message posted by: "Scott A. Jordan" <SAJ_SLJ@compuserve.com>:
When drilling the W-409 nose ribs to the main spar the directions say to use
032 material to keep the rib centred on the spar. Since I didn't
have any .032 scrap handy I used .020. I didn't notice it until after
I drilled a few ribs that they were sagging, the .020 wasn't strong enough
to hold the rib up.
My approach was to get rib #1 in place first... mark a centreline on its attach angle; with the aid of a bright light and/or a torch, this was visible through the 3/16" bolt holes in the spar. I used two bushings (3/16" OD, 3/32" ID) to protect the spar whilst drilling. Drill the first hole, then leave the bushing in place and put a 3/32" cleco through the angle into the bushing to keep that end aligned properly. Then drill the second hole through the bushing. Finally remove, the angle from the spar and drill these holes out to 3/16". Bolt the angle to the spar (hardware bolts, wing nuts) clamp rib 1 to it, and drill rib 1 to the angle and to the spar.
Now clamp the top skin to the spar (it's convenient to clamp it to the top of the tank flange with sidegrip clecos) and rib 1, making sure that the first line of holes aligns with the centreline of rib 1. Now you can mark the positions of ribs 2-7 through the holes onto the spar. Remove the skin and use a set square to extend the dots down to the edge of the spar. Repeat this using the bottom skin, so that you have rib centrelines marked both on the top and bottom of the main spar. When attaching each rib, align the rib flange centrelines with the lines on the spar. You *will* want these ribs to be accurately placed relative to the skin. A couple of mine were a little off, which caused problems when dimpling and then when riveting the skin on. Especially where the holes were a little too close to the rib web, and especially near where the ribs attach to the spar.
For ribs 2-7, first, drill the rib to the angle. Then cleco the angle to the rib and drill the angle to the spar as above. As a double-check, you should be able to see the angle centreline through the 3/16" holes. Clamp the rib in place, drill it to the spar, and remove.
A similar process will apply to ribs 8-14: get the first one (rib 10, 11, or 12, since they are bolted through the flange and there's not a lot of leeway) in the right place, then use the skin to ensure that all the other ribs are positioned correctly relative to this one. Check that rib 8 is exactly 10" from rib 7. NOTE: There is a single hole in both the inboard skins which corresponds with a hole in the outboard skins. This hole is the front one of the splice line outboard of rib 8. It seems to me that it would be good to identify this point *before* drilling ribs to spars, so that it can be used to ensure proper alignment of ribs 8-14 with ribs 1-7. I didn't realise this until after I'd drilled both sets of ribs to the spars.
Ribs 10-12: These are different from ribs 1-8 because the main rib will be bolted to the spar. Mark centrelines on the main rib flange, drill rib to spar using light as above. Bolt main rib to spar, then drill #40 through the pilot holes into the spar. Cleco through these holes to hold the pre-drilled nose rib on. Remove the main rib, clamp the reinforcement angle to the spar and nose rib, and back-drill it to the spar. Bolt the angle and main rib on, and drill #30 through the #40 holes. For ribs 11 and 12, continue these holes through the angle, separate, and drill these holes out to 3/16" or more to allow blind riveting.
Ribs 13-14: These are riveted directly to the spar, and not bolted. Clamp main rib in place, drill pilot holes #40, cleco on nose rib, drill holes out to #30.
SK32 in the manual is the Bible. It shows the two spars and the exact locations of the rib webs. Use this VERY CAREFULLY to double check all your other measurements. Since this is the only way to mark the rib positions on the rear spar, be sure that your main spar rib locations agree.
After attaching the tip ribs, remove any excess spar flange that extends beyond the ribs. This will interfere with the fibreglass tip... you need at least 1/2" of skin everywhere outboard of the tip rib for the tip to attach to.
Ribs 1-2 have 3 holes to attach to the rear spar; the outer holes which are back-drilled through the spar and one centre one. This one needs to align with the space between the stiffeners in the spar, about 1 1/4" from the lower hole. This hole needs to be continued through the doubler and the doubler drilled out to 3/16". A pop-rivet will go here to attach the rib to the spar, with its tail between the spar and doubler.
Rib 3 will also have 3 holes, but don't drill the centre one just yet, since it depends on the flap brace.
Ribs 4-5 have 4 holes. Again, leave the inner two until the flap brace has been figured out.
Ribs 6-13 have 4 holes, which are already drilled. Note that ribs 6-9 have the second-to-top hole dimpled, and ribs 10-13 have the bottom hole dimpled. Be sure which is top and bottom of the spar before dimpling!
Rib 14 is attached by 4 flush rivets... you will need to countersink
the W607F doubler for this. WC's suggestion that this could be dimpled
doesn't make sense to me. I couldn't use my countersink cage on the hole
nearest the flange, so I just put the 1/8" pilot CS cutter in my hand deburring
tool and carefully used that to form the countersink, checking often with
a 426-4 rivet to see whether I was done yet. Note that rib 14's holes should
not be dimpled! 
In about 5 ribs (out of 28) I had to remove one of the clecos from the rear spar in order to slightly (about 1/8") twist the rib to keep rivets reasonably centred as I drilled down the skin from the spar. If I were to do it again, I would C-clamp the rear spar to the ribs until skins were drilled to ribs, then drill thru rear spar with angle drill. This would be a problem only in the inboard ribs (maybe) where they go thru the rear spar 1/8 strips.
I found rib 5's front flange to be at a slightly different angle to ribs 1-4, possibly because it's the opposite facing rib. This made clecoing it to the rear spar problematic. On the other wing, I've riveted ribs 5-14 to the rear spar first. This I did out of the jig (riveting ribs to rear spar on the first wing was quite difficult). Then I'll attach ribs 5 and 14 to the main spar first, then cleco the rest of these ribs to the main spar. Then it'll be ribs 4, 3, 2, 1, attaching each rib in turn to both spars, rather than attaching all ribs to the main spar, and then all ribs to the rear spar.
WC suggests 4-8 and 4-6 rivets to attach ribs 1-5 to the rear spar... I found these to be slightly too short... I cut some 4-11 rivets down to about 4-9 for ribs 1 and 2, and used 4-7 rivets for ribs 3-5. The rest of the ribs were attached to the rear spar by 4-5 rivets.
Although WC says to attach ribs 1-5 at first by the outer holes only, I see no reason why the pop-rivets in ribs 1 and 2 shouldn't be installed at the same time. In fact, it seems like a real good idea to insert the pop-rivet in rib 2 before attaching rib 1.
Note that these pop-rivets need a corresponding 3/16" hole drilled in the rear spar doubler to allow room for their tails. This isn't shown on the plans, nor mentioned by WC or FJ in their notes. I did find a message from FJ in the RV-list archive saying this was needed.
From the RV-list: With the spar not in the jig but resting with the flange vertically on sawhorses or whatever I drilled one side of the leading edge skin where it attached to the spar (not the ribs.) This makes it easier to get the skin drilled to the spar without the spar drooping which it will do in the jig. I also drilled the top row of rivets where the skins meet at the spar. With the skins resting on the horizontal ribs it is easier to get an expert fit than trying to wrestle the skin in place in the jig.
I then placed the spar and rib assembly in the jig and with the skin clecoed along the spar it will have less tendency to droop and require less support in the middle to get a straight spar.
WC says to set the jig up level, then mark the skin butt-line on. I found the butt-line useful for checking the straightness of the spar whilst levelling the jig, so suggest that that gets done first.
Marking the butt-line... the SK-32E shows a technique to get a line 1" from the main spar web using a dial micrometer. What I did (not having a dial micrometer) was to put my set-square on the web (outboard of all the stiffeners) so that it protrudes over the edge. Then put a ruler against that and mark down one inch. Then take the set square and line it up against the bottom of the flange and with the mark. Mark on the set-square where the mark is. Now go to various places on the spar and mark off your set-square. Note that there are slight differences in the width of the spar flanges from one side of the spar to the other.
To level the spar, I used a water level made from a piece of garden hose with
some clear tubes (the barrels of a couple of ballpoint pens) RTV-ed into
the ends. Clamp and tape one end to the spar so that it exactly lines up
with the butt-line (reference end). Note that some water will dribble out
of here from time to time. Clamp and tape the other end (variable end)
to the other end of the spar, so that there's about an inch of clear tube
above and below the butt-line. Make up some coloured water (a teaspoon of
food colouring in a litre or two of water), and fill the hose. At the variable
end, if the water line is below the butt-line you need to lower the spar
slightly. Conversely, if the water line is higher, you'll need to raise
that end of the spar. Simple! Each time you adjust the spar, you'll probably
need to add a little water to the hosepipe. At the same time use a spirit
level to make sure that the spar is level cross-wise.
To get the spar straight also isn't difficult. Stretch a taut line along the main spar flange, aligning each end with the butt-line. You can then easily see much sag there is in the middle of the spar (about 1/8" to 3/16" for me). You don't need a jack at all. I easily lifted the skeleton by hand, and inserted a 4x2 prop, plus some shims to get it exactly right, under rib 9. No problem.
I have come to the conclusion that Orndorff's order of wing construction may be best. Here's why: since the leading edge and tank skins are curved, adjustments are more problematic that filing a flat piece. Thus, if these can be mounted first, the hard part is over. GO mentions in the tank construction portion of the video about running a taut string along the spar as a straightness measure. Use a thick thread and just bring your LE and tank skins to this line and you will be right on. I had not run the thread previously and as a result there was about a 1/16" taper over the wing. With the main skins already done, there's no turning back now so I have to file the skins--including tank LE portion where it buts against the LE outboard. No big deal but time consuming and knowing my wing ain't exactly right-on.
RV-List message posted by: Thomas Gummo <tg1965@linkline.com>: The plumb bobs like to swing in the breeze. This makes aligning the wings difficult. You put a can under each plumb bob and lengthen the cord to allow the plumb bob to hang into the can without touching anywhere. Next, fill the can until the plumb bob is about half under water. You could also use oil for better damping.
Make sure you get the right skins in the right places! The lower outboard skins have the inspection hole cut-out, and are different L and R. The lower inboard skins have only every second "rib 1" hole pre-drilled. There are two sheets of .025 * 13" * 27" al sheet for the wingwalk doublers.
As at the tip end upper cross-arm, I needed to cut a small slot in the lower root-end cross-arm to allow the skin to fit. I guess my jig posts weren't quite far enough apart.
Here's a tip: You cleco your main wing skins on, look through the holes, only to find the little black line is not centred. You reach through, move the rib a little...but by the time you're ready to drill, one or more ribs have moved.
Prior to clecoing on your skins, drill the hole through the spar
and the rib flange while you can see the alignment. Then, when you
cleco the skin in place, the cleco will hold the rib in place, and each
rib will retain its general alignment. Any adjustment to find the
centreline mark should be minimal.
The wingwalk doubler butts up against the rear of the main spar flange.
It certainly doesn't go on top of the main spar flange. Note that CS4-4
pop rivets attach ribs 2-4 to the upper inboard skin, through the doubler,
so those holes will need to be drilled and dimpled/countersunk #30.
When deburring these holes (and there's a helluva lot of deburring to do!) note that the doubler will be countersunk so you don't need to deburr the outside of the doubler. Do yourself a favour. Write on the top surface of the inboard four (five?) ribs, "Do not dimple." The wingwalk doubler goes between these ribs and the top skin and since the doubler is countersunk, no need to dimple ribs or spar flanges under doubler. However, I was not entirely happy with the wingwalk countersinking results, as this sheet is .025. I think that if you want to avoid dimpling the three layers in question, it would be best to countersink the .032 skin.
With my Avery handsqueezer, I could dimple most of the spar and rib holes. There wasn't sufficient clearance to do those on the spar adjacent to the bolts. My visegrip hand-dimpler (with a bit ground off one side of the dimple dies) managed most of these. I tidied up all these holes with a countersink.
A quick tip I came up with last night to peel that darned protective
plastic off of your wing skins, at least the flat skins. Peel about
3 inches in one uniform piece, peeling lengthwise, then wrap about a 4
foot broomstick around it. Lay the skin down on a carpeted floor and just
roll the stick about 1 inch at a time, kind of like opening a sardine can
with a key. It comes off in one nice neat piece.
Save yourself a nostalgic trip back to the days of Plane Geometry and make a notation on the inspection cover drawing (either 19a or 21) that the radius for the cover itself is 1 3/4 inches. Couldn't find anywhere so I messed with it until I had a paper template that fit. I can't believe this is not on the plans.
As noted by WC, pretty much ignore the dimensions given in the plans and sketches for the inspection hatch covers. Measure to fit to cover the hole! Note that rib 9 is NOT in the middle of the inspection hole, and place the nut-plates accordingly. I incorrectly decided that the plans had been sloppily drawn, and placed the rear nutplates equidistantly -- one of them is too close to rib 9, and I've now got a tricky joggling problem to fit the nutplate between the rib and skin :-(
I drilled the nutplate holes 5/32", then used a screw through the hole to hold the nutplate aligned whilst I drilled the #41 rivet holes.
Use your deburring tool to countersink the 3/32" attach holes of the nutplates so that they fit flat against the dimples in the spar or skin. Dimpling the 5/32" (#19) screw holes probably requires a 5/32" dimple die, but might be possible by using the nutplate as a female die and a cut-down CS screw as a male die. I haven't tried this yet.
Spent most of today fooling with the bellcrank gussets (W425s) FJ has some notes (6,7) under this heading and when I checked, I don't believe it is necessary to do what he suggests. You might want to pencil in a note to yourself there. What you want to do is position the lower wing skin and see if the gusset would really get in the way of the inspection plate ring. Mine was clear by 1/8".
Be careful in measurements on this or any other assembly where attachments will be made from many directions and edge distances will be critical. You will see what I mean when you line up the W425 braces on the rib/assembly. Don't get too hasty in drilling holes in pieces (e.g. W425) that will attach to (in this case) three different surfaces. Go ahead and make a light centre-punch where you think the hole will be and you can drill in situ without fear of drill wandering. If you have to move it slightly, you won't have a useless hole to deal with.
Note that the outboard flange on the W425 is quite small... it's difficult to get two 1/8" holes in it and still maintain proper edge distance. My W425s didn't have this flange bent, presumably so you can bend it exactly to fit between the ribs. Even when bent right back at the corner, my W425s were too long... double-check those before bending that flange, in case you need to shorten the other two flanges.
Make a note under FJ's item #8. This one bugged me because it called for practically dismantling the skeleton. What I did was just remove the outer rib beyond each side of the 2-rib gusset assembly from the main spar only. Just leaned it back an inch or two at the top so my rivet gun would fit it. I have a double offset 1/8 set but I think I could have done it just as well with a straight long one. In fact if a straight set would not have gotten the two rivets closest to the top skin, I would have removed the skin in that area or used pop rivets before I would go thru all that rigmarole FJ proposed.
Rather than make the brackets shown in SK-36, I attached them to a 6"x2"
on the floor under the jig. The 6"x2" was then braced to the rear spar
and the jig bottom arm by a couple of 4"x2"s placed vertically. By crossing
the straps between the rear spar and floor, the straps hold the LE skin
down nicely against the spar.
RV-List message posted by: WPAerial@aol.com: I found putting telephone books under cargo straps work really well when cinching up wing or fuselage skins. The books take the form of the skin.
Fit the skin before rolling the edges. On my R wing, the LE skin overlaps both the top and bottom main skins. So it would have been better to *not* roll either edge so that the LE skin can slip over the main skin; rolling down the edge hinders that. Best to leave edge-rolling until after the LE skin has been drilled to the skeleton, but before dimpling. Conversely, you may want to roll the LE skin top edge first to stop it slipping over the main skin.
Alternatively: Use a piece of duct tape to tape a 4"x4"x4" block (one per strap) against the rear spar (to simply hold it in place, or you'll need an extra set of hands), where the strap will run, then put the strap on around the wing. The block protects the free trailing edge of the skin from the strap when it is tightened.
I couldn't get the LE skins to line up with both the top and bottom main skins. There always seemed to be a 1/16" to 1/8" gap at the bottom join, especially at the tip end. In the end, I lined up the top join and drilled and clecoed the skin to the spar, then tightened down the straps to get the bottom edge to line up. That worked fine on my R wing. On my L wing, that was a mistake... it meant that the curve of the skin didn't quite match neatly with the curve of the ribs, and had to be pulled into place by the straps. It also meant that all the spare metal on the LE skin had to be taken off the bottom edge, which might lead to edge distance problems.
If it becomes necessary to shave a few thousandths (or more) off a large wing skin, tape it to the side of your workbench, drill thru 6-8 rivet holes into the bench edge and use clecos to hold the skin firm and fast as you work that edge with the vixen file. Leave the clecos in for temporary fastening to the skeleton to check, then pop 'em back into the workbench for final shaving.
ammeterj@home.com (John Ammeter) wrote to the RV-list: Use a wide felt tip marker (one that will make a mark about 1/16" wide) to mark a line down the middle of the rib flange. As you drill thru the skin stop and see if the line is centred, left of centre or right of centre. You can't move that hole but you CAN move the next hole. Keep 'moving' the holes as you drill and you'll be within 1/16" of the centreline all the way down the rib.
Another method that works is to hold a steel nail in the middle of the flange and, using a stud finder, locate the place to drill the hole. You'll only have to do this for the first hole since the line on the rib will work for the rest of the holes.
smcdaniels@juno.com (SCOTT R MCDANIELS) wrote to the RV-list: A couple very important steps is to be sure you get the ribs as straight as they can be when straightening/fluting, and be sure that all of the flanges are exactly 90 deg. Straightening the ribs seems to be a simple thing but it is difficult to tell when you have it just right because of the curve in the flanges. Use a flat table top, etc., and double... no triple check them. Be very picky at the forward most portion of the ribs. And check all of the flanges with a small square.
I like to mark the centre lines with a very fine line of a bright colour (red). The fine line makes it possible to know exactly what the rib position is relative to the hole (not just that it is close because I see line colour). Having it "close" for 1 or even a couple holes will be ok, but it shows that a trend is started and sooner or later it will bite you.
I drill the top side of the leading edge ribs without strapping down the skin. I start at the main spar working back and forth on all ribs moving up a couple holes at a time. When I have about 3 holes left to drill at the top (leading edge) I then strap down the skin and continue drilling over the top and then down towards the main spar on the bottom side. If the ribs are not lining up you can unstrap and move/massage the ribs into position. If they are close then I use a small pick with a very sharp point on it to move the rib by poking through the holes and moving it were it needs to be.
Don't press too hard when drilling the front-most holes on the LE skin... these go into a separate 'tongue' from the rest of the flange. This is easily bent.
The only real trouble I had with tanks was a result of an error with leading edge installation. The LE is very easy but here's what happened: I followed somebody's instructions to leave plastic on inside of LE skins. What I didn't do was notice that the plastic bunched-up at the very front, particularly on the inboard end. Net result was that since tank overlaps the inboard LE assembly, this threw off the tanks maybe 3/32". Doesn't sound like much, but it is critical. Take a look at the relationship of rivet holes, nut plate holes, flange radii, etc- on the tanks and you will appreciate the import of this error. The net result is that I made it work, but instructions should caution folks in this regard.
Be sure you have the correct distance on the main spar flange to accommodate the tank attachment nutplates if you are installing the inboard skins before the tanks. It's easy to trim skins either way but there isn't a lot of freeboard for those nutplates.
I didn't use the threaded-rod technique shown on the video. Since the skins are pre-drilled, it's simply a matter of lining up the centrelines of the ribs with the pre-punched holes. Like the main ribs, there was a bit of pushing and pulling needed to keep things lined up, especially whilst drilling the top rib flanges.
For cosmetic reasons, you should be careful to line up the spar rivet holes of the LE skin with the corresponding rivet holes on the main skin. Easiest way to do this is probably to use a square to draw a line at right angles across the spar flange through the main skin attachment hole.
It's not at all clear from the plans... the W-623 flange strip (mine were actually 36.5" x 1.5" x .032"... precut and included in the wing kit) goes round the LE in front of the main spar, between nose rib 8A and the skin. It extends inboard of the LE skin to provide a "flange" for the tank to attach to. It's easier to deburr the edges and corners of the strip before bending. To form the W-623 to shape, I used one of the 8A ribs held in a vise, and clecoed the strip in place. After that, it still needed a bit of hand manipulation to get it to stay in the right shape.
Mike Thompson wrote:
When riveting the LE skin to the W-623 flange strip, ensure that
you leave plenty of W-623 sticking out for the tank to screw onto. Check
the distance from the edge of the tank skin to the screw holes along the
outboard edge. This edge will butt against the LE skin, and there should
be enough W-623 sticking out for the screws and rivets to go into it without
violating edge distance requirements. I think that the W-623 is ONLY JUST
wide enough -- if you have any protruding outboard from the edge of the
rib 8A flange, you won't have enough inboard.
Even though the manual specifies the attach strip have 1/2 inch showing outside the leading edge skin to accommodate the fuel tank nutplates, note that in drawing 18a the distance between the edge of the tank skin and the pre-drilled holes is 3/8th of an inch. This obviously will not leave proper edge distance for the nutplates. Rivet the tank attach strip with 3/4 inch showing. After assembling the tank but before drilling the skins, trim the attach strip as needed based on the distance from the edge of your tank skin and your outboard tank rib. Trim the attach strip as necessary to allow the leading edge skins to meet.
I didn't like WC's suggested technique for drilling the flange strip
(place flange strip between skin and rib flange; drill, hoping rib is correctly
aligned). What I did instead was to drill the LE skin to the skeleton (ribs
9-14 only) with the flange strip in place round rib 8A. Then, remove the
flange strip and drill the skin to rib 8A. Finally, remove the skin and
back-drill through rib 8A into the flange strip. For this, you'll need to
mark the flange strip "centreline" on the inside of the flange strip. 
I cogitated for a while on whether to dimple or countersink the W-623
flange strip. I countersunk, and now wish I'd dimpled. The .032" metal
really isn't thick enough for countersinking.
Drilling the 7/16" pitot hole through the L skin and spar flange should
be done as follows: drill a pilot #41 (or so) hole from inside the flange
through both flange and skin. Then drill both skin and flange out to 7/16"
from the outside.
Don't forget to drill holes for the tie-down brackets.
Before riveting, use GO's technique of stretching a line across all the rib flanges... many of mine got a little out of square during the drilling and dimpling steps.
If it becomes necessary to shave a few thousandths (or more) off a large wing skin, tape it to the side of your workbench, drill thru 6-8 rivet holes into the bench edge and use clecos to hold the skin firm and fast as you work that edge with the vixen file. Leave the clecos in for temporary fastening to the skeleton to check, then pop 'em back into the workbench for final shaving.
I just used my standard bucking bar and ordinary (i.e. non-swivel) flush
rivet set. No particular problems, so long as you ensure that the gun is
perpendicular when you start, and don't allow it to "walk". Also used my
normal rectangular bucking bar... no problem. I knew my extra-long arms
would be useful for something other than changing light bulbs :-) 
Attaching the LE to the spar was awkward but doable. Or it would have
been, except that I'd riveted the bellcrank gussets on first :-(. That
turned an awkward job into a damn near impossible one. Just to make matters
worse, I'd permanently attached my wiring conduit in the LE first, in such
a way that it interfered with inserting the bolts, and got in the way of
bucking the topmost rib-spar rivets in ribs 9, 13, and 14. 
When riveting the LE skin to the W-623 flange strip, ensure that you leave plenty of W-623 sticking out for the tank to screw onto. Check the distance from the edge of the tank skin to the screw holes along the outboard edge. This edge will butt against the LE skin, and their should be enough W-623 sticking out for the screws and rivets to go into it without violating edge distance requirements. I think that the W-623 is ONLY JUST wide enough -- if you have any protruding outboard from the edge of the rib 8A flange, you won't have enough inboard.
If you don't already have a 1/8 rivet set that is double offset, get one. You'll need it for the bellcrank installation and riveting the #14 and #13 ribs to the spar.
Bob Haan <bobh@cdac.com> wrote to the RV-list: Several people asked me to elaborate regarding the large back riveting jig for wing top skins:
This apparatus is a 16 pound steel bucking bar about 3 X 3 X 12 inches that is balanced by a 16 pound counter weight. The 3 X 3 end is polished. The long axis of the bucking bar hangs on a rope in a horizontal orientation so that the 3 X 3 end can be centred on the rivet to be set. This rope runs up from the centre of the bucking bar through an overhead pulley, through a second overhead pulley and then down to the counter weight. The two overhead pulleys are attached to a car that travels below an overhead rail that runs the length of the wings.
The rope, pulleys and counter weight allow the bucking bar to be positioned on the wing top skin vertically. The travelling car allows the bucking bar to be positioned on the wing top skin horizontally.
I nailed two horizontal 2X4s to the outsides of the vertical 4X4s of the wing jigs about 7 feet up. I placed the rail the car with the pulleys travels on on top of these 2X4s and clamped it in place so that the bucking bar swung and travelled just in front of the top skin.
My wife positioned the counter balanced bucking bar and I back riveted. The unusual weight and size of this bucking bar gave excellent results.