elevator horn?

Most of the elevator horns I have seen have three holes in them spaced at about 1/4 inch. I would like to have a finer adjustment on the flap-to-elevator ratio. Would drilling two more hole spaced evenly between the existing holes giving about 1/8 inch spacing weaken the control horn? There isn't room in the narrow aft end of the fuselage for a slider type control horn.

Ron,

I'd be suspect about the strength and/or durability of a horn with ~1/16" holes drilled 1/8" apart. PERFECTLY located, that leaves only 1/16" between holes; any 'drift' of the drill gives one side or the other a smaller 'land' between them. Ever hear of 'tear on the dotted line'? <g>

I remember somewhere seeing a sort of screw pedestal type of horn among RC (ugh) goodies. The pushrod connects to a tab off a barrel threaded onto a rod -- like certain aileron links.

THAT geometry also needs to be considered: the pushrod connect point is at the hole in the tab. Surface response geometry depends on the surface hinge, and the pushrod connect, points (and other things.) RCers use deliberate offset to get aileron differential throw to reduce adverse yaw.

We don't need/want/allow that for flaps or elevators!

Anyway, the item I have in mind bolts to the surface like a usual nylon horn. Instead of a flat plate rising to the pushrod, a threaded rod with locknut rises. The tab barrel (usually self-threading) is run down the thread to the desired position. Almost infinitely trimmable IF you can get to it.

Another type of aileron link has a pushrod tab that straddles a wheel collar on the horn rod riser. Again, consider geometry carefully, and find a way to gain access to the setscrew. Also near-infinitely adjustable, a bit wider than the threaded barrel type above, and needs access only to the wheel collar setscrew and whatever range of travel you need.

Luck!

How bid of a plane? On my Bear, I slightly widened the tail to allow for the slider horn and ball link. Sure glad I did. Don't think I would have ever sorted out the trim without the adjustables in the rear.

>How bid of a plane? On my Bear, I slightly widened the tail
>to allow for the slider horn and ball link. Sure glad I
>did.

I have changed my designs to also allow more room for the ball link.

Don't think I would have ever sorted out the trim
>without the adjustables in the rear.

A slider in the rear is mandatory, I think. The flap to elevator ratio is possibly one of the most critical adjustments on the plane, and can effect all of the other trim features, most especially the tip weight.

One to one ratio simply means nothing to me. It takes what it takes. It certainly is easier than making new flaps or changing the CG to unheard of numbers.

LAST EDITED ON Aug-20-04 AT 08:00 AM (CDT)
 
>A slider in the rear is mandatory, I think. The flap to
>elevator ratio is possibly one of the most critical
>adjustments on the plane, and can effect all of the other
>trim features, most especially the tip weight.
>
>One to one ratio simply means nothing to me. It takes what
>it takes. It certainly is easier than making new flaps or
>changing the CG to unheard of numbers.

I think you're right about the flap/elevator ratio. I can see how flap/elevator ratio, CG, and lead out position all interact. But would you elaborate a bit about the interactions with tip weight?

I didn't make the mods to this airpalne to incorporate a slider in the tail because it would require major surgery and this airplane is about learning about the engine, not so much about learning about flap/elevator ratios. I do have a very simplistic "trinary" (equal, less than, greater than) system.

The red wing you see in the background of the picture <edit: in the "Too Simple" thread> is project about learning about flap/elevator ratios and is adjustable in every way I can think of. But that's another story...

LAST EDITED ON Aug-19-04 AT 05:45 PM (CDT)
 
I still have about 50 of the adjustable control horn setups like Lou describes above. These are left over from Ukey production. E-mail me for prices etc.
Joe

I use Tom Morris' double eared slider horn. I like having 2 arms with the ball link in between. Very solid and easy to adjust.