As always, the best place to get started is by reviewing the prints and assembly instructions.
The RV-9A Rudder incorporates internal stiffeners and flush skin rivets to provide clean air
flow over this flight control surface. As I was building, I wondered how fast a Cessna 172
might fly if it were to use this same technology. Below, the stiffeners were cut, using tin
ships, from pre-drilled, pre-marked 90 degree angle sections. The cutting activity
was performed while Vivian and I watched TV one evening. However, the final sanding
and Scotch Brighting processes was performed in our shop. Fluting can also be done
while watching you favorite TV program.
Here, we are back riveting using our three position C-Frame table. The only
trick here is to Cleco every other hole, tape the rivets into place and raise the C-Frame
height using a 1/4" piece of plywood under it to account for the Cleco height on the
face down side. Once the first set of rivets is done, the Clecos and plywood piece
are removed, and the second set of rivets is taped into place and riveted. Even though
this is not the suggested reviting method, we were very happy with the results.
We are now fitting the Rudder skeleton and counterbalance arms to the skins and match
drilling them to the two Rudder skins.
After everything is match drilled, deburred, dimpled and a thin coating of epoxy
primer is applied, we are now ready for the final assembly. Before riviting, I'm
supporting the Rudder Horn with one of the Horizontal jig cradles in order to better
align the assembly and sight the trailing edge using my laser plumb bob.
We are installing the Rudder Counterbalance Weight after countersinking the weight
so that it will fit into the dimple on the rib side. It is a good idea to order #10 and #6 screw
dimple and countersink sets for the Rudder and Elevators.
After being satisfied with the alignment, we first set the trailing edge rivets using
a flat squeeze set. Once the rivets were set, they then need to be double flushed
into final place because both sides are dimpled and countersunk. Using a bench
sander and an old Scotch Bright wheel, I machined an angle onto one of the flat
sets matching the angle of the trailing edge. Remember not to use sanding
belts or Schotch Bright wheels on aluminum after contacting steel. I alternated
every other rivet to provide a symmetric look and aerodynamic profile. Again,
this is not the recommended method, but we were more comfortable with it.
The final step, using a one inch steel pipe, was to bend the leading edge into
a rounded shape. Most of the fun was making the trip to the home improvement
store to find a steel pipe. The rivets are pop style rivets, so the riveting is
the easy part of this step. However, my hands were a little sore after this activity.
After 77.5 hours and a little fiberglass tip work, we have ourselves a very nice
RV-9A Rudder indeed. A high speed Dremmel tool with cutting attachments is
almost a requirement in order to trim the upper and lower pieces of fiberglass into
their final shape. You can almost imagine the entire aircraft attached to this fine
looking rudder.
