Control Horn Bushings

[Motorman]

Got the Morris flap horn. The two brass clips get glued into the trailing edge but what holds the brass tubing from sliding out? Do you solder it to the clips before gluing?

Thanks,
MM

[Don Jenkins]

I have Tom's controls in 5 of my planes and they work extremely well.  I epoxy the bearing tubes to the clips when I epoxy the clips into the trailing edge of the wing.  I also put a touch of thin oil (3-in-one) on the horn wire to keep the bearings free from the epoxy.  This seems to work for me, but I am sure there are other thoughts on the matter.

Don

[Motorman]

My pushrod is angled too. I guess the bellcrank attachment comes out on the right. Does anyone bend the horn wire so the flap horn comes out on the right? Seems it would keep the pushrod straighter. Does it matter?

MM

[Brett Buck]

My pushrod is angled too. I guess the bellcrank attachment comes out on the right. Does anyone bend the horn wire so the flap horn comes out on the right? Seems it would keep the pushrod straighter. Does it matter?

     You mean, put the flap horn off-center?  If so, yes it does matter some. If you have a short side and a long side, the long side flexes more than the short side, causing rolling torques.

     You can correct for geometry of the pushrod other ways, like putting the bellcrank itself off-center. It's a non-trivial geometry problem to come up with the perfect set of alignments but you can get it close enough by making sure everything meets at 90 degree angles and adjusting the length of the flap pushrod until it measures even travel rates in the +-10 degree range.

     Brett

[Eric Viglione]

Got the Morris flap horn. The two brass clips get glued into the trailing edge but what holds the brass tubing from sliding out? Do you solder it to the clips before gluing?

Thanks,
MM

This is an old pic from Starfire #2 I built for 2010, but I still do it this way. Use carbon tow strands to hold horns into trailing edge. Tack in place and pull tight with a tiny amount of CA (don't want to attack the foam underneath) then epoxy in place. Nothing worse than control slop here, when the horn gets pushed away from the trailing edge. I also use tiny 1/16th ply 1/4" square stops laminated to the inside of the fuse to stop the horn from moving further out.