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Old Nov 13, 2001, 11:01 PM
opualuan is offline
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high-speed freak
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inverted v-tail


I am trying to mix the tail in a scratch-built plane... yes, I searched, but I didn't find anything even though I'm sure I've seen this before...

it's an inverted v-tail. I was going to use elevon mixing, but that doesn't make sense. elevator up= both up. elevator down= both down. the rudder mixing I don't get. when viewing from behind the plane, should right rudder= right-up left-down, or just right up, or just left down? I'm very confused, as I know the control setup is workable, but I don't understand how the vectors should all add up...

plus, I have a jr xf421ex piece o' junk... am I going to need a v-tail mixer to mix this kind of v-tail?

any help appreciated!
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Old Nov 13, 2001, 11:48 PM
Thomas B is offline
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opualuan, you have the tail movement directions correct. If you are doing a three channel model with rudder, elevator and throttle, no ailerons, you can indeed use aileron mixing to do what you are talking about.

If you are doing a 4 channel model, you will need more mixing options.
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Old Nov 14, 2001, 10:33 AM
Sparky Paul is offline
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On the inverted vee, right rudder command is left surface down, right surface up.. the opposite of a conventional vee.
Elevon mix should be capable of doing this.. if there's no ailerons. Then you need P-Mix.. or the JR equivalent.
Old Nov 14, 2001, 11:10 AM
Mauilvr is offline
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Sparky Paul didn't give himself the credit he deserves - check out his web pages listed to see his Inverted V Tail Camera Plane.
A very cool, well thought out design complete with aerial photos.
Old Nov 14, 2001, 11:34 AM
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Opualuan it is very simple, use Delta mixing. The rudders will work exactly as ailerons would, which is why I designed my Paddle that way (see www.rbckits.com) .
Old Nov 15, 2001, 12:18 PM
Thomas vogel is offline
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OOOO.......
Max z please tell us more about the "Paddle".
PRETTY PLEASE
Thomas
Old Nov 15, 2001, 02:17 PM
pfg is offline
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you can also use v-tail mixing. i dont have the tx here with me to look at but i think i had to have the correct servo (and it did mater) on each surface. i thought servo reversing could take care of it but it didnt - its an easy fix though, you just swap the servos at the receiver.
Old Nov 15, 2001, 05:27 PM
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ok... I haven't ever received an email from ezone telling me there were replies to this thread... thanks for all your suggestions, I was worried that the wrong tail mixing was going to get me into a trouble spot...

another question specific to this model: 7-10oz wingloading, 36" span, 4" chord, 1f^2 wing area, very thin flat-bottom airfoil (1/4" at its thickest). currently the tail sections are 2" wide and control surfaces ar 1/2" wide, length of tail from boom to center is 8", tails joined at 45 degrees. the plane is being equipped to travel FAST. is this tail and control surface area sufficient? I know I could decrease the tail joint angle (tails are at 45 degees from horizontal), but this kinda ruins the design...

any thoughts?
Old Nov 15, 2001, 10:37 PM
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opualuan:
I just found this info yesterday on ezone, but can't remember where (short term memory loss???).
It may help answer your questions:

Horizontal and vertical tail volume coefficients:

Vh = (stab_area/wing_area) * (stab_arm/wing_chord)

Vv = (rudd_area/wing_area) * (rudd_arm/wing_span )

"stab_arm" and "rudd_arm" are measured from the CG to the quarter-chord point of each tail surface. Eyeballing the quarter-chord point locations is OK.

Typical ranges for RC gliders are:

Vh = 0.30 .. 0.50
Vv = 0.01 .. 0.03 (up to 0.05 for some DLG's)
Old Nov 16, 2001, 04:26 PM
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Thomas, just follow the link I gave and all will be revealed.

Max.


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