Hi there.
After approx 20 years absence, I'm back in the control line business. Made me a couple of planes last winter (Legacy 40 and Accentor, both from Brodak). The Legacy is no longer with us, as the bellcrank came rushing out trough the wing during a flight! Suspended bellcranks for me in the future! The Accentor works fine as a trainer.
I've now a Starduster from RSM on the building board, and have with great interest followed Fred Cesquim's building of the same, and got some tips on the building process. Thanks to Fred.
One topic however I've been working on, is to get the hinges as frictionless as possible. Having your plane on a slack line in a poor wingover, friction in the hinges is not what you want to fight against while recovering. All the hinges on the marked to day, have some amount of friction between the two parts. Not much, but when you add up the number of hinges in a stunter, it begins to count. So, after some thinking and trying, I came up with a solution I would like to shear (or maybe it's already invented, making me the goof of the year!). But anyhow, here is what I did:
* Starting with a Robart hinge, I drilled out the the rivet the hinge is pivoting round. Took care not to drill into the plastic part.
* With the two parts separated, I trimmed the edges, to make a flush design.
* I then cut an approx 1" long piece out of a 1.5mm (approx 1/16") carbon fiber rod. This rod fits exactly into the holes on the Robart hinge, and the hinge pivoted with no friction, and with no slack. (Take care to cut the number of rods you need to the same length). I don't know if a rod of 1/16" will fit in as well as the 1.5mm rod. But as we use the metric system here in Norway, 1.5 mm is what we get, and it worked fine.
* Next thing is to make grooves in the flap and elevator to fit in the rod and space for the pivot point of the Robart hinge.
* Epoxy in place the rod, taking good care not to get any glue into the places it shouldn't be. I tried to pull off the hinge after the glue had dried, but I wrecked the bals wood around it. So, it sticks well enough. But as an extra precaution you can glue som silkspan over the rods when covering.
* Mounting the flap/elevator to the wing and stab is standard procedure drilling a hole the Robart hinge can be glued into.
Take a look at the pictures attached, they show the procedure.
Happy landings to you all!
Roy