szempruw

W2 Rib already had some notches in it if one were going to put in one servo controlling both flaps with a bell crank. I transferred these holes to W3 Rib and decided this was good spot for the servo linkage.

I took a WAG at flap throw thinking I would have 7/16 - 15/16" of servo throw on the control arm and an arm length of 5/8" to 11/16" which would allow final adjustments once the servo was installed for real. The drilled horn hole will be slightly ahead of the hinge pin to minimize vertical travel of the connected linkage. I easily get 40 deg flaps with this setup. Careful not to get too short an arm since you can get more throw than you bargained for. I drilled the arm closer to 9/16" by mistake. Still plenty of adjustment, especially if you add in servo travel limits by the radio.

I planned the horn's location and made some G10 ribs and cut them to fit the balsa laminate. I epoxy glued them to some extra balsa ribs. Maybe over-kill, but I thought it would be easier to glue them to the sheeting. The spacing between the G10 accounts for the 4-40 swivel assembly.

The pics show the near completed flap, trailing edge sanded down to accept the sheeting. I just have to layer on the top sheeting. The front shows the swivel rod sticking out an oval shaped hole. I used a lock nut and epoxy for the swivel screw as there is no good way, short of surgery, to access this connection after sheeting. My friend says it is robust and will outlast the plane! I hope he's right. What we do for scale appearances!

I'm happy with the results so far. It was an easy build, a blend of Pica's design and a more scale like finish. I now have 3 hinge points and an easily removable flap. And in case you are wondering, I'll either use a little L bent into the end of the music wire captured by the large nylon L bracket or I'll drill a guide hole in the L bracket to hold a CF rod. Either way, the flap can be glassed, finished and re-installed at will, a nice feature.