SECTION 7
RV-8/8A
7-3
8s7-1r11 06/13/11
PREPARING THE WING RIBS
You will save time if you set up and prepare all the ribs for both wings at the same time.
Begin preparing the ribs by deburring the edges of the flanges and lightening holes. A small Scotchbrite wheel
mounted in a die grinder prepares the inside edges of the holes quickly and easily. Pay particular attention to the
forward parts of the leading edge ribs. Remove all bumps around the notches to insure that the skin fits well.
Wing ribs come in seven flavors. Part numbers are marked on the ribs at the factory, but if you cleaned them off by
mistake, they may still be identified:
x
There are three types of main ribs, W-710, W-711 and W-712. At first glance they look identical, but they are
not. W-710 is 0.032" thick. W-711 and W-712 are 0.025" thick. W-712 is slightly longer than W-711 and the
7/16" dia. hole near the front flange for the pitot tube line is omitted.
x
There are two different leading edge ribs: W-408-1 and W-709. The W-408-1 rib is slightly (0.032”) undersized
around the perimeter to accommodate the W-423 joint plate, is 0.032" thick, and does not have holes in the
curved flange.
x
Tank ribs differ in thickness and hole pattern. T-703 ribs, used on the ends of the tanks, are 0.032" thick. The
internal T-704 ribs are 0.025" and have a pattern of large holes to allow the fuel to run from one bay to another.
The holes in the upper side are for venting air, and are located at the high point of the tank in a three-point
attitude and in cruise flight. DON'T CONFUSE LEADING EDGE AND TANK RIBS. They look much the same,
but the tank ribs are shorter.
Ribs may be either "left" (suffix L, i.e.: W-709-L) or "right" (suffix R, i.e.: W-709-R). You may identify the "hand" of a
rib by holding it with the leading edge away from you with the flange closest to the tooling holes toward the floor. If
the flange is on your left, the rib is an "-L", if it is on the right, it is an "-R".
Adjust rib flanges 90
q
to the web using hand seamers.
The forming process leaves ribs bowed, particularly the leading edge ribs. Straighten the webs with fluting pliers.
Place the center of each flute at the midpoint between the prepunched holes. Use a straightedge or holes in a wing
skin to check for straightness of the line of rivet holes. The straighter the parts, the better they will fit.
Make provisions for running stall warning system wires (left wing only) and, if you intend to install them, wingtip
position lights, strobes or landing lights. Drill holes in the ribs for grommets, or conduit sold in VAN'S
ACCESSORIES CATALOG. Opening up the tooling holes works well. Be careful not to interfere with the pitot line
or control systems. Leave the tooling hole in the outboard tip rib undrilled for now. The smaller hole is useful for
aligning the aileron. The 7/16" hole in the inboard ribs of the left wing get plastic grommets for routing the pitot tube line.
ASSEMBLING THE WING SKELETON
MAIN RIB/SPAR ASSEMBLY
Cleco the W-710, W-711 and W-712 ribs to the main and rear spars. Be sure the proper ribs are in the right
locations and that wire and pitot tube routings are aligned. The ribs do not have all their flanges facing the same
way.
Drill the holes attaching the ribs to the spars to full size. Most of the ribs simply fit to the spar without modification,
but the rear flanges of the three inboard W-711 ribs require two new rivet holes . Drill these, using the holes in the
spar as guides. The holes left unused in the rib are simply abandoned.
Remove the ribs and do the necessary deburring and priming.
Reassemble the ribs and spars with clecoes.
Put protective tape on the W-706B/D spar flange bars to prevent bucking bar damage when installing the top and
bottom most rivets. Rivet the main ribs to the front and rear spar, EXCEPT for the outboard W-712 rib, which is
riveted to the rear spar, but not the main spar. Place the manufactured head of the rivet on the rib flange (side with
thinnest material), to prevent distorting the parts.
WING STAND
Although the matched-hole process eliminates the need for the traditional wing jig, mounting the wing in a stand will
make it easier to build. A stand allows access to both sides of the wing and makes it easy to take measurements
and assure the wing is straight. The wing has no washout, twist or taper.
RV-8/8A
SECTION 7
7-4
8s7-1r11 06/13/11
The stand (shown on DWG 12A) is simple; two vertical posts run from floor to ceiling. Horizontal arms of steel angle
or wood, bolted to the posts, support the main spar. The size of the posts and arms is not important, but they must
be sufficiently strong and rigid to support the wing.
Clamp or bolt the wing skeleton to the horizontal arms of the jig. To provide a mounting point on the outboard end
of the wing, drill and bolt a temporary 5" long piece of aluminum angle, parallel to the spar web, to the outboard rib
with 3/16" bolts. The small additional holes in the ribs will not compromise strength.
The center of the skeleton will sag toward the floor when it is mounted in the stand. To make installing and
removing the skins easier, support the skeleton in the middle. Run a fishing line along the rivet holes in the main
spar. Then adjust the middle of the skeleton with a 4x4 wood block and shims, screw jack, etc., (almost anything
that will remain stable works) placed under a rib. Raise the skeleton just enough to bring the rivet holes even with
the fishing line along the length of the spar.
FITTING THE WING SKINS
Wing skins are pre-punched with pilot holes for the ribs and spars. The vinyl can be left in place when fitting and
drilling the main wing skins to prevent scratches (except on the inside of the leading edge and tank skins, where the
vinyl should be removed before fitting.) Remove the vinyl before dimpling to prevent pounding trapped drill shavings
into the skin with the dimple die.
FITTING THE WING WALK DOUBLERS
The wings have doublers under the main skin next to the cabin sidewall to add strength and help support the loads
imposed by people entering and leaving the airplane. Make the wing walk doubler (DWG 17A) from AS3-025x9
3/8x26. Lay W-702 on a bench and slip the doubler underneath it. The doublers nearly butt against the aft edge of
the main spar channel and overhang the rear spar by about an inch. Align the inboard edges and set the forward
edge of the doubler 9/16" aft of the forward edge of the skin. Using the skin as a guide, drill all the holes for each rib
in the wing-walk doubler.
FITTING THE MAIN SKINS
Cleco the forward row of holes in W-702 and W-703 skins to the matching holes in the main spar. Cleco the W702
and W-703 skins in place using a cleco in every fourth hole.
Don't forget to insert the doubler between the ribs and the W-702 skin. The main skins overlap at the eighth rib from
the root. The outboard skin should fit on top of the inboard one.
Gently pull ribs into position if the matched holes do not align with the skin holes. Drill all the holes to final size.
Start drilling in the upper middle of the panel and work down and out toward the edges, work out any slack as you go.
Move the clecoes down one hole (into the drilled holes) and drill all the remaining holes.
Draw a couple of lines on the main skins that intersect at the center of the hole for the tiedown eye.
Remove the bottom main skins before fitting the leading edge and tank skins. Leave the top skins clecoed.
LEADING EDGE ASSEMBLY
BUILDING THE CRADLE
Construct a cradle as shown on DWG 12A to hold the tank and leading edge during construction. Don't waste time
making the cradle perfect, since it simply holds the leading edge, and has no bearing on alignment. Use a W-709
rib to trace the shape. Pad the surfaces of the cradle to prevent skin scratches.
FITTING THE LEADING EDGE
Remove the vinyl from the inside surface of the W-701 leading edge skin.
Modify the W-701-L leading edge skin for the stall warning assembly. Complete OP46-02 Steps 1-4 and OP46-03
Steps 1-5.
Place the W-701 leading edge skin in the cradle. The ribs are much easier to install with it pre-bent to shape in the cradle.
Cleco the W-709 ribs into the W-701 Leading Edge Skin. The rear flange hole patterns of the two W-709 ribs just
outboard of the tiedown do not match the hole pattern on the spar. In this case, use the spar as a guide to drill the
ribs and abandon the unused holes in the rib.
