ARF Nobler Flaps

I flew my ARF Nobler for the first time this week. After a few tweaks of the flap and engine setting, I was able to do my first pattern on the third flight.

I definitly notice un-equal turn ratio doing inside versus outside. This was worst in the outside square. In fact I almost hit the ground on it.

I know this is caused by non having an offset in the stock flap horn that came with the ARF.

I was going to put a Tom Morris Offset Horn, but notice their was not enough room because it would hit the wing mounts.

So without doing a major modification of the horn, is their a simple solution to fixing this problem?

Can I bias the flap do have a little for up (which is give the model more down) at the neutral setting? Or would this cause a problem on level flight?

Bill:

I would wager that far more National and World Championships have been achieved using standard, 90 degree horns, ala Nobler O.E. than the newfangled Tom Morris devices or similar.

My bet is that you can follow "normal" trim tactics to equalize turns....adjust the flap to elevator pushrod, etc. Incidence seems to get out of whack on these, too...

Try normal trim before you tear stuff apart.

See Ya

Herman,

Adjusting the length of the elevator pushrod will fix the unequal turn. If it won't grove in level flight after the adjustment try opening up the hole in the elevator a couple of drill sizes to add a little slop. This did wonders on my Nobler.. You can cut an access hole under the stab to get to the elevator horn, just cover it with Monokote when finished. I didn't even put the wood back in.

Bob,
I talk to a few other people about this. Wouldn't it be better to bias the bellcrank to have more travel in the down direction, rather that just adjusting the elevator pushrod. If I only adjust the elevator pushrod, then there will a differential incidence in the relation of the flap to elevator.

By biasing the bellcrank, it does the change the incidence. For example if I shorten the flap pushrod, then I should extend the elevator pushrod. Does this seem logical?

Without getting into allot of explaining, just shorten the elevator pushrod until it turns the same both directions. Don't worry about the flaps or bellcrank they will take care of themselves.

You are compensating for an incidence problem, my Nobler had the same problem because I didn't check it as close as I do when I actually build. My elevator hangs down enough to be obvious when the flaps are level but it now groves and turns the same in both directions.

I've never seen an ARF Nobler so I gotta ask. Are you absolutely sure the pushrod is not bending?

LAST EDITED ON Mar-21-04 AT 01:06 AM (CDT)
 
Usually the pushrod does not bend on down control, because it is being pulled, not pushed.

Standard Disclaimer:
Caution use at your own risk, results may vary, I am not a professional. I need to rely on smart people for their idea's, I don't have any of my own.

Dito, on the elevator control rod. It is hard to get a pushrod to bend while under tension.

Tom Morris control horns do work and they work quit well. I believe unless the stock bellcrank is changed along with the operational hardware, I don't believe you will gain anything from the swap.

I changed out the stock bellcrank, the flap horn wire. I used a 3 1/2" Tom Morris bell crank, threaded rod and two clevises for the flap control.

I sounds as if there is a slight difference between the up and down movement of the elevator. The tapered design of the ARF Nobler elevator makes it hard to adjust level with with the naked eye.
I used modified line levels on both the flap and the elevator horns to find level, and adjusted accordingly.

My ARF flew right off the board without any trim problems. (check your elevator throw to the flap throw in both directions.

Does your airplane grove around the circle or does it hunt?