With the rudder complete according to the plans, it’s time for me to venture off into experimental land for the first time in the build. A lot of other 10 builders are putting an electric rudder trim in and I want to do the same thing. There are some great write ups on other’s build sites that I borrowed most of the ideas from and then just tweaked to make my own.
I started by laying out where the trim tab will be on the rudder. I didn’t want to add any structure outside of the rudder, so I’ll be cutting a tab out and hinging it. I choose the vertical mid point between two ribs for the location. I then measured out the tab based on very scientific eyeballing and comparing to others. I made sure to keep it centered and spaced evenly between the ribs and also to keep the hinge line perpendicular to the air flow. Once copied to the other skin, it’s time to break out the Dremel and start stressing about making the cuts right. It wasn’t nearly as bad as I thought it would be.
The hinge was next coming from a stick of piano hinge from Aircraft Spruce cut to size. A main goal is to make it as drag resistant as possible, so I put the hing on the left inner skin which allows more movement to the right and a minimal gap when it is trimmed to the right (which is where it will spend most of its life).
Next step was to create a mounting arm for the servo rod. I started with a piece of manila folder to get the shape close. This is where all my experience with RC models really paid off, as the system is very similar to any RC plane or helicopter set up. I then cut two pieces of aluminum trim to the curved shape and bent the tabs in opposite directions to mount onto the trim tab. Again, to minimize drag and maximize coolness factors, I cut a slit for the servo arm to slide through so I could have the mounting tabs inside of the tab.
Rather than have an inspection panel with the servo mounted to it, I used another idea of having a piece of aluminum trim mounted to the hinge which serves as a base for the servo. This way, I can remove the entire trim tab system, servo and all, from the rudder for maintenance using a minimum number of screws. It’s also a little cleaner looking in my opinion.
A rudder cable fairing finishes it off, again mounted from the inside and finished with a little micro and epoxy to smooth things out and cover the rivets.
I trimmed a couple pieces of left over Styrofoam from the elevator trim tabs to epoxy in and keep the shape / provide structure for the tab. I finished it off with a little micro to seal it all up. The leading edge (non-hinged) was bent inward to create clearance for travel.
Overall, I’m very happy with the end result and it was a pretty easy project once all thought out. I’ll hook up the wiring connector later in the build. I did test it and get a pretty fair amount of travel. Based on other’s I saw at Oshkosh, this will be more than enough trim power for the 10 even during full power climbs.
