Control movement.

I'm building a Sterling Ruffy from a Sterling kit. The flaps move 20 degrees up and down but the elevator moves 20 degrees up and down also. I don't think it is enough elevator movement. I have 3 hole horns on flap and elevator with the bell crank pushrod in the top hole and the elevator push rod in the middle hole of the flap horn and the hole closest to the pivot on the elevator. No binding. Is this enough throw? I have a two ended heim joint I can install in the top hole on the flap horn and run both push rods off it. 1000 times easier than drilling another hole as things are kinda permanent, What do you think?

Perry try the heim joints and see what uou get for travel. I try to get about 35 degrees in both flap and elev, usually this is enough.
Keep me informed....

If it's not too late, I would prefer to get move throw out of the bellcrank, rather than do tricks with the horns. A system with all the hole inboard has more stress on the joints than one with all the holes outboard. Also, a system with all the hols inboard is defeated by a small amount of slop.

'Fraid I don't know the details, but Ted Fancher spent some time sorting out the best ratios on this design. (For his liking).

Perry,

My personal appproach is to try to make the recommended angles match my comfortable range of handle 'throw.' THEN, I try to make sure the surfaces can move further: if needed it's there. If more turns out to be needed in general, that's something that adjustable handle line separation can nail. And, vice versa...

Free motion of the bellcrank, pushrods, horns and hinges is important. So, I go for free, not sloppy, motion greater than the recommended angles. No hanging up on structure, or binding on anything, anywhere. If the recommended angles prove the best, the margin doesn't matter. You simply won't be using it...

It may happen that a freak gust disturbs the model's attitude and 'takes away' all or most of the line pull. If the linkages are free enough, even when there's no detectable pull, you may be able to save some control using the line drag alone.

I found some bind as the elevator moved up or down the hinges rotated the elevator into the stab. I mashed the wood down and got more travel but still not enough. I bit the bullet and put the elevator pushrod in the top hole of the flap horn and the bell crank pushrod in the second hole. Still not perfect but better. That is the best I could come up with and closed the fuse. up. I kinda think it will work.

Is not the elevator horn affixed to the stab with a brass bearing of some sort? If not, a lot of motion is being transfered to movement of the horn rather than rotation of the horn. Very bad, and makes for a system that will have a short life.
Chris...