PAGE
REVISION:
DATE:
VAN'S AIRCRAFT, INC.
05-11
RV-ALL
2
04/15/13
Scenario B: Both skins already in place:
With the skins and wedge prepared as described in scenario A, insert the
wedge between the skins. Use several clecos to hold the wedge to one of the skins and maintain alignment.
Peel the backing from the side that corresponds to the un-clecoed skin, clecoing and pressing the skin
in place on down the length of the TE. See Scenario A for the remainder of the process for the second skin.
Now for the riveting. Trailing edges are riveted with "double-flush" rivets. These are standard rivets, but instead of setting the
shop head on a flat surface, it is set in a dimple and ends up flush with the skin surface. However, a
double flush rivet will not look the same on both sides. The factory flush head will set almost perfectly flat.
The finished shop head will be flush with the skin, but it will not fill the dimple completely. This
has been described as "an acorn sitting in a dimple." Do not fall into the trap of trying
to use a longer rivet to "fill the hole." Rivets used in this manner will bend over
instead of setting properly and the force involved in trying to drive more rivet
material flush into the dimple will cause puckering and waviness.
Place blocks on either side of the back riveting plate,
to allow the control surface to lie flat as it slides
over the plate (Note, because RV rudders vary
in cord and thickness from top to bottom,
the skins are not entirely flat so they can
not be laid flat on a table. Instead, position
the rudder so that only the aft couple of inches
are on the back riveting plate and spacers.
Then place shims under the spar as needed.)
Weight the control surface down to the work
surface so it remains straight while riveting.
Starting at the MIDDLE of the control surface, to
minimize pillowing, back rivet about every tenth rivet
just enough to lock everything in place. Do not set the
rivets all the way yet. Continue with the remaining rivets
by doing one rivet midway between others that have already
been done, and working back and forth along the trailing edge
until all are initially set.
TRAILING EDGE (AEX WEDGE)
FIGURE 3: DOUBLE-SIDED TAPE
5.8 RIVETED TRAILING EDGES
Control surfaces with riveted trailing edges have a wedge shaped filler piece whose cross-section and degree of pre-fabrication
may vary. Whether or not the part comes pre-drilled it will need holes and these holes will need machine countersinking in order
to receive a dimpled skin. A simple method of accomplishing this is detailed below. Some set up time is required but with a little
planning ahead a number of these pieces may be done at one sitting resulting in a big time savings.
To avoid confusion the wedge shaped filler piece will be referred to here as "wedge" and the trailing edge in general as "TE." Use
scrap aluminum strips that are thinner than the max. thickness of the wedge to be countersunk. Cut a small V-shaped notch into
one strip to prevent interference with the countersink cutter pilot. Position the strips so that the foot of the countersink cage
contacts the top face of the wedge squarely (flush) and the countersink pilot aligns with the centerline of the hole pattern. Attach
a piece of safety wire or string between the countersink cage and the post of the drill press so that the cage does not spin. Use a
low speed setting on the drill press. See Figure 1.
FIGURE 1: GUIDE AND CUTTER SETUP
FIGURE 2: COUNTERSINKING WEDGE
Building a truly straight TE is one of the more difficult things to do in aircraft construction. To help keep the TE straight we advise
adhering or bonding the components together before setting the rivets. Use of double-sided adhesive tape makes it possible to
keep the wedge aligned all the way through the TE build process. We recommend 3M tape product number F9460PC VHB for this
purpose. In the past fuel tank sealant has been used on RVs for this application.
To apply the tape, prep all surfaces to be bonded with isopropyl alcohol, wipe them down and wait until the excess liquid has
evaporated. Apply a continuous piece of tape to both sides of the wedge as shown in Figure 3. Avoid touching the adhesive since
skin oils can degrade its effectiveness over time. Allow the tape to bond 15-20 minutes before proceeding further.
At this point there are several possible scenarios one may encounter involving the bonding of riveted TEs, but two predominate.
They are (A) when one skin will be rolled into place onto another and (B) whenever both skins are already in place at the time the
wedge is to be installed.
Scenario A: One skin rolled into place on another.
Once the adhesive on the wedge has had a chance to bond (see above) remove one protective strip from the surface of the tape
and adhere the wedge first to the control surface skin that will remain flat. Insert a small number of clecos from the outer skin
surface, poking them through both tapes and the remaining protective strip, to aid in aligning the wedge. Use finger pressure to
compress the joint and bond the entire length of the wedge to the skin.
Lay the opposite skin onto the wedge using the clecos as a guide. Install enough clecos to the opposite skin to ensure the skin will
maintain its correct alignment and then roll the skin back as described in the construction manual. Follow the process described in
the manual for completing all of the internal structure riveting. Lower the upper skin when complete. Keep the control surface TE
on a flat surface. Use a straight board and small weights to hold the TE straight. Lift the un-bounded skin slightly and begin
progressively pulling the backing from the tape. Once the backing is started the skin can stay close to the wedge while pulling the
backing out from between. As clecos are encountered remove them before pulling the backing past to avoid tearing. Once the
backing is fully removed apply finger pressure along the entire length of the wedge to get a good bond to the second skin. Insert
rivets into the TE holes with the manufactured heads oriented up (on a rudder it's builder's choice). The double-sided tape covering
the holes should keep the rivets in place though it might be necessary to apply an additional strip of regular tape.