One leftover task from fitting the wings was installing the control stops that limit aileron travel. The plans call for riveting aluminum blocks to the inboard aileron hinge brackets on each wing, and these blocks serve as stops hitting against the steel hinge points bolted to each aileron.

But other builders have a more elegant solution. Turns out a small Delrin spacer, fitted where an aluminum spacer normally goes on those steel hinge points, make a perfect control stop. All that’s needed is some Delrin rod stock of the appropriate diameter, cut to the appropriate width, with a 5/16″ hole drilled in the center to accommodate an aluminum bushing to protect the spacer from wear. When the aileron is at its maximum up travel, the Delrin spacer hits against the top of the aileron hinge bracket.

To me this is a much better solution than having the steel hinge point banging against an aluminum block. Some trial and error is required to find the right spacer diameter – the larger the spacer diameter, the smaller the aileron travel – but checking out other builders’ websites who’ve done this, 3/4″ seems to be a common diameter and that size worked for me as well.

Because I’m an obsessive-compulsive engineer, the spacers had to be precise. As I am wont to do, I threw money at the problem and had a local machine shop bore the holes in the middle of each spacer.  Joe at Coastal Milling Works in Medford MA is happy to take on small milling and machining jobs for a very reasonable cost. After spending too much time trying to center-drill some test spacers, I decided to hand the job to Joe and he handed me back ten perfectly-drilled spacers. If you’re in the Boston area and need some small machining work done for your project, go to Coastal – you’ll be glad you did.

Here’s the finished spacer, and it’ll go just to the left of the rod-end bearing and washer in the picture above. This little diversion came out very well…much better than the plans aileron stops.

I have a few extra spacers…if you’re contemplating this approach and are interested, let me know.