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Old Nov 13, 2001, 11:01 PM
high-speed freak
opualuan's Avatar
San Jose, CA
Joined Sep 2001
3,863 Posts
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
Electric Coolhunter
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United States, TX, Fort Worth
Joined Jun 2000
14,634 Posts
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
Ascended Master
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Palmdale, CA
Joined Oct 2000
13,499 Posts
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.
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Old Nov 14, 2001, 11:10 AM
Almost a Pilot
Mauilvr's Avatar
NorCal
Joined Oct 2001
3,760 Posts
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.
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Old Nov 14, 2001, 11:34 AM
Registered User
max z's Avatar
The Netherlands, ZH, Boskoop
Joined Mar 2001
1,150 Posts
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) .
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Old Nov 15, 2001, 12:18 PM
Registered User
San Fransisco,Ca,Usa
Joined Aug 2001
86 Posts
OOOO.......
Max z please tell us more about the "Paddle".
PRETTY PLEASE
Thomas
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Old Nov 15, 2001, 02:17 PM
pfg
Registered User
Vancouver, BC, Canada
Joined Feb 2001
446 Posts
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.
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Old Nov 15, 2001, 05:27 PM
high-speed freak
opualuan's Avatar
San Jose, CA
Joined Sep 2001
3,863 Posts
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?
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Old Nov 15, 2001, 10:37 PM
Almost a Pilot
Mauilvr's Avatar
NorCal
Joined Oct 2001
3,760 Posts
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)
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Old Nov 16, 2001, 04:26 PM
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The Netherlands, ZH, Boskoop
Joined Mar 2001
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Thomas, just follow the link I gave and all will be revealed.

Max.
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