They are. I have never had to replace them myself but looked into replacement before even installing them. If you do a search you can find the posts on how to do it. Basically you drill the flange off the hinge pin to get the hinge apart. Cut the hinge flat to the surface and then use the drill jig again to drill the center of the hinge. Sometimes that is enough to get the hinge out. If not I have also read of using copper tubing just a hair smaller then the hinge and cutting a piece 4 inches long. On one end you file some slots into the end just 1/16" into the tubing. 4 or 6 slots work as cutting teeth and you put that into a drill (or use by hand) and slowly cut into the hinge. As you get the majority of it out the smaller pieces should come out. If you butcher all those (and I could I'm sure then I have also read about drilling out the hinge with a bigger drill bit then the hinge but the same size as some wood dowel. You glue in the wood dowel into the hole and let dry and then use the drill jig again to redrill for the new hinge. Even more ways with some searching but after many flights on different planes I still have not had to do it. I'm sure i will some time (From a crash) but I'm not concerned about doing it.

I have also read some guys have made a removable rudder using the Robarts. They drill out the hinge pin and replace with a piece of piano wire. That way they can remove the wire and remove the rudder for transport.