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Old Nov 18, 2012, 02:16 PM
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United States, VA, Forest
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Rudder Question

Thought I would post here instead of vintage since it applies mostly small planes. On designs like most of Ken Willardís small stuff, the rudder is angled. This works fine if you are going to be using some type of pulse or escapement utilizing a u shaped wire over the rudder, but if you are using a servo with a pushrod, it creates a problem. The angled rudder causes the pushrod to bind. If you made the rudder the same area but made it vertical, would this cause a flying problem? In other words, is there any advantage to angling the rudder?

John
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Old Nov 18, 2012, 02:52 PM
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John, angled rudder hinge line gives a slight 'up' elevator effect when the rudder is deflected. I know what you mean by pushrod binding with this setup. I helped the condition by using a fairly long run of music wire, unsupported, to the rudder horn. Flexible enough to bend with the angled travel, stiff enough to handle air loads.
Hope this helps!

John
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Old Nov 18, 2012, 09:39 PM
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IMO Rudders on this size models are a waste of a servo.
Aileron and elevator are Far preferable.. If you want / can use positive control that is.
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Old Nov 18, 2012, 11:41 PM
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Quote:
Originally Posted by Bare View Post
IMO Rudders on this size models are a waste of a servo.
Aileron and elevator are Far preferable.. If you want / can use positive control that is.
Yea, but when it's single channel, kinda hard to do just ailerons.

John
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Old Nov 21, 2012, 05:23 PM
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I'm wondering if you simply mount a slightly recessed micro servo in the fuselage say at the top near the front tip of the rudder, run a direct music wire pushrod with "V" bend for adjustment would work. It would keep the pushrod reasonably short. You could slightly over-drill the pushrod horn, so there is a very slight amount of slop to eliminate binding. This may not be necessary since with a smaller diameter music wire would have some flex so it would twist slightly without binding. YMMV.
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Old Nov 21, 2012, 07:34 PM
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I hear what you are saying, but a short rod as you describe would flex/bend less than one running the length of the fuse. Think I will just try on my next one to have the rudder vertical and see what happens. Thanks!

John

PS. May even try mounting the servo on a plate like a actuator and putting the horn into a recess on the tourque rod like an actuator would work. Should work the same way except it will be proportional.
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Old Nov 21, 2012, 08:12 PM
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I have flown a couple like this, including a TF Schoolmaster. I installed a ball link on the rudder horn, which was easy and completely solved the problem.

Jim
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Old Nov 21, 2012, 08:54 PM
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There's more than one way to skin a cat. I guess it just depends how ingenious one wants to get. Ball link makes sense. One could use the original RO torque rod and mount servo in a manner to move it similar to the old RO escapements or magnetic pulse actuators. One could maneuver a flex link to alignment is more true. Use pull-pull cables. Mount servo below rudder to directly torque it.

I've use the pushrod through the back fuselage plate's torque rod hole, bent up and forward to the nylon control horn ala Carl Goldberg style. (See OuterZone Goldberg 1/2-A Skylane plan servo detail found on: http://www.outerzone.co.uk/plan_details.asp?ID=868

That probably provides the longest pushrod and is more tolerant to flexing.
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