Adding Rudder Trim to a Flying RV-10
Added 11/4/2007 - 288 Flight HoursThis is my personal documenation written during my preparation and execution of installing Vic's rudder trim mod onto my flying RV-10. It is a bit unnerving to have to do this task and cut a painted rudder, so I prepared well for it. I would strongly suggest that even if you don't plan during your build to install rudder trim that you at least pull 2 wires into your rudder for the trim so adding it at a later date doesn't involve accessing the tailcone. I had to stuff my daughters and wife all the way back into the tail during this upgrade to pull and secure wires, that would have been nice to have done during the initial build.
The douber and access plate used are available from Van's as VA-195C and VA-195D, which are the doubler and hatch cover used for the stall warning system on the wings. From Vic's photos, you can see he used a Ray Allen servo p/n T2-7A.
Rudder Trim Installation Steps
- Remove rudder (Letting rudder hang from
the ceiling or shop crane but stay connected via cables is workable)
- Drill hole for trim servo wire and pull wire into Tailcone and Rudder
- Note: If your rudder bottom fairing
is permanently installed you will likely have to run the trim servo
wire up the leading edge of the rudder and enter through one of the
many large lightening holes.
- Cut hinge to 11" length
- Drill small hole in bottom of hinge
length (this hole is for safety wire to keep hinge pin in place)
- Measure and mark hole location:
- Vic's Hole Location is: Measure for access hole 17 3/4" up from bottom of rudder to fairing seam, Servo center 10 1/4" from the rear of rudder, and 21 1/2 from bottom of rudder. Access cover is 4 1/2" back from leading edge of rudder spar.
- Tim's Hole Location is: Measure 3.2" from inside of center hinge cutout on rudder / Measure 7" to doubler plate top corner perpendicular to vertical edge of doubler to trailing edge / Measure 7.8" to doubler plate bottom corner perpendicular to vertical edge of doubler to trailing edge / Measure 21.5" from forward bottom corner of doubler plate to lower edge of skin at rudder fairing / Measure 20 7/8" from aft bottom corner of doubler plate to lower edge of skin at rudder fairing.
- LOCATION NOTE: While the location of the servo isn't ultra critical, there are factors to consider. First, mounting it in the locations above allows you to use the previously un-used shaft that comes with the Aileron Trim package. Next, although Van's approves of the rudder balance with the mod unofficially (at least that's what they told Vic), it might be a good idea to keep the servo towards the leading edge of the rudder for control surface balance reasons.
- Additional Note: You may notice from my photos that the doubler was rotated after the initial marking. I looked at the cover plate and noticed that one side of the cover plate had 3 screws and the opposite sides have 2 screws. I decided it best to have more screws on the side that is into the airflow. The doubler holes are symmetrical though so rotation isn't a problem if you drilled first like I did.
- Match drill doubler outer rivets to Rudder, and mark cover plate screw holes
- Drill and cleco 4 cover plate screw
holes and attach cover plate
to rudder without doubler. Trace cover plate outline onto rudder
for cutting.
- Cut acces hole in rudder to undersize
of cover plate, then
file and sand hole to final size, occasionally test fitting doubler and
plate to ensure straight edges.
- Dimple doubler screw holes and install
nutplates on doubler plate. (I used K1100-06 nutplates)
- Drill and countersink holes for rivets
into doubler plate. Countersinking is used to prevent skin
stretch on rudder.
- Lay servo onto cover plate and orient hole locations so pushrod is perpendicular to trailing edge, mark holes, drill, and dimple.
- Note that servo pushrod is not centered on servo.
- Draw line perpendicular to Trailing
Edge to servo location where
pushrod travels
- Countersink MAC servo holes and install temporary screws to hold servo on cover plate
- Position hinge centered on pushrod line
- Drill rivets on trailing edge in location of hinge
- Match drill hinge to trailing edge
- Locate pass-through hole for pushrod no closer than 1 hinge rivet spacing from hinge line
- Drill hole and test fit actuator
rod. Elongate hole as
necessary, allowing for covering by rudder exit fairing
- Trim rudder pushrod fairing and test fit over hole
- Cut L-Tabs for hinge for servo actuation lever arm. 2.5" long each, and bend at 1"
- Rivet L-Tab lever arms to hinge in center of hinge length, on non-eyelit side
- Cut or adjust pushrod to required length for neutral tab with servo in center position
- Install all hardware with clecos and temporary screws and test operation with 9V battery.
- Paint all parts, rivet, install
hardware, and then paint rivet
heads (Squeeze rivets gently so you
don't stretch the skin and cause oil-canning)
- Complete switch wiring
- Verify hinge pin is secured with safety
wire
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