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Old Jul 18, 2001, 08:45 AM
Isaiah 40:31
rc capo's Avatar
West Palm Beach, FL
Joined Jun 2000
689 Posts
Fork Tailed Linkage

Does anyone have any good idea's or diagrams for fork tailed linkage, like on a P-38.

I have a twin boom free flight that I am converting to rc electric and want the rudders and elevator to work...of course.

Model Aviation had a P-38 electric featured a few years ago, I must have thrown that issue out.

Thanks

RC
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Old Jul 18, 2001, 02:31 PM
Balsa Flies Better!
Stamford, CT
Joined Oct 2000
6,712 Posts
What I've seen is one servo to the elevator and either one servo one rudder or an external hookup using ball links or something similar to the second rudder. I plan on using this trick on a P-38- didn't want to add yet another servo to the poor airplane.

Sam
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Old Jul 18, 2001, 03:40 PM
ὅπερ ἔδει δεῖξαι
Gerald's Avatar
Joined May 2000
3,335 Posts
In my P38 I used one servo with two flexible snakes. I didn't want to mention this because I'm not entirely satisfied with it as there's a lot of friction. There is one servo in the tail end of each boom, one for elevator and one for rudders. The rudder linkage has one relatively straight short run to the near rudder and a longer run to the far rudder following a tortuous path through the inside of the horizontal stab. Everything is fully hidden inside the frame and flying surfaces including the horns. It remains to be seen how well this works. I had to use a stronger (heavier)servo because of the friction. Fortunately the rudders won't see much actual use in flight.

Here's a drawing of it.

P38 Rudder linkage

This one has a 40" span and its pretty cramped at that.

[This message has been edited by Gerald (edited 07-18-2001).]
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Old Jul 18, 2001, 04:12 PM
Isaiah 40:31
rc capo's Avatar
West Palm Beach, FL
Joined Jun 2000
689 Posts
I'm sorry, I forgot to mention this little devil has a wing span of 27".

rc
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Old Jul 18, 2001, 11:13 PM
Registered User
Oscoda, Michigan / Mississippi State University
Joined May 2000
153 Posts
It may not be scale, but you could put the elevator servo in the center cockpit pod, and run very fine pull-pull cables out of the rear of the cockpit pod to the center of the elevator. You probably wouldn't notice them in flight, and it would be a very light, direct, and solid linkage.
For the rudder I would probably put the servo in the center pod as well, and use bellcranks in the wing to engine pod joint area to get the linkage out to the rudders through the booms.
Or, you could just run one direct pushrod to one rudder, and connect the rudders through an internal linkage in the horizontal stab. This would be the lightest setup. You would just need to bury a connecting rod between the rudders in the stab.

-MarkVZ-
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Old Jul 19, 2001, 05:02 AM
Gambler-AG DLG Designer
Allan Wright's Avatar
Lee, NH, USA
Joined Jun 2001
5,185 Posts
You can see how I did it when I converted the Thistle to RC.

<A HREF="http://pease1.sr.unh.edu/aew/rc/thistle/">http://pease1.sr.unh.edu/aew/rc/thistle/</A>

Al
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