From a purely structural/mechanical point of view, is there any reason not to install two ball links - - one for the flap pushrod and one for the elevator pushrod - - on opposite sides of the flap horn but through the same hole in the flap horn?

Aside from purely structural/mechanical considerations, are there reasons - - controls geometry particularly - - not to do this?

Your comments and suggestions will be greatly appreciated.

Wynn:

Thank you for your response.  I have not built a flapped stunter since the Veco Chief I built when I was a teenager with no coach and no clue.  (Miraculously, the Chief flew pretty well, I thought.)  That was a very long time ago and little has changed since then.  So, I don't have the knowledge or the experience to doubt what you say.  Therefore, please take the following as nothing more than a question or a plea to dispel a small bit of my ignorance.

I asked the original question because it seemed to me that if the moment arms of the bellcrank, flap horn, and elevator horn were all the same I would get 1:1 flap:elevator deflection.  Less flap deflection relative to elevator deflection, if appropriate, could be achieved by changing the hole in the elevator horn.  What am I missing?  Is there something else about control system geometry about which I don't know enough to even ask?

Any help you are willing to give me will be most welcome.

Wynn:

Thank you for your response.  I have not built a flapped stunter since the Veco Chief I built when I was a teenager with no coach and no clue.  (Miraculously, the Chief flew pretty well, I thought.)  That was a very long time ago and little has changed since then.  So, I don't have the knowledge or the experience to doubt what you say.  Therefore, please take the following as nothing more than a question or a plea to dispel a small bit of my ignorance.

I asked the original question because it seemed to me that if the moment arms of the bellcrank, flap horn, and elevator horn were all the same I would get 1:1 flap:elevator deflection.  Less flap deflection relative to elevator deflection, if appropriate, could be achieved by changing the hole in the elevator horn.  What am I missing?  Is there something else about control system geometry about which I don't know enough to even ask?

Any help you are willing to give me will be most welcome.

Peter,

Your throws will be the same with your described setup. Its true you can change the flap/elevator differential by changing the pushrod on the elevator. But remember that this will also effect the elevator travel in relationship to the handle angular displacement. This may or may not work out for you, I always try to set my up so I can adjust the flap travel while leaving the elevator travel alone just to keep the relationship between eleveator and handle. It may not be important, but that's the way I do it, it just sortof establishes a baseline I can relate to.

Your point is valid.  But most other hookup schemes apply the same twisting action.  The real fix is to use one of the double horns that box the output device between two arms.  Most people get by by using a really heavy duty horn that overwhelms your (well founded) concern.

I do it quite a bit now to get the surfaces to move according to what I want.  In fact on my King Sweep if you look at the pictures on the related thread you will see one bolt with ball link on each side of the flap horn.