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Old Feb 23, 2002, 11:11 AM
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Kings Park, New York, USA
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Differential Elevon on Flying wing?

Anybody ever fool with differential Elevon on a flying wing?

Does it help out with adverse yaw?

What does it do to flight? What rates have you fooled with?

On my newest project Zagi E3C I think I need all the help I can get to counter P-Factor created by the 3/4 HP 14.5x14 combo.

Ron Parigoris
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Old Feb 23, 2002, 11:50 AM
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Sparky Paul's Avatar
Palmdale, CA
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Could you add ALL the information to this question..
such as your experience with this exact setup in full-scale??
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Old Feb 23, 2002, 12:10 PM
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Boulder, CO USA
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Sounds like Ron is building today Cool. I'm recovering my original Zagi today and am planning on using my 6AXS for the Tx for the rudder tip experiment. I have no clue what to use for the rates. Hopefully someone can post some info.
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Old Feb 23, 2002, 02:35 PM
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Kings Park, New York, USA
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Hey Sparkey Paul

Hey Sparkey Paul

Thx for the help out on elevon design.

I ended making a 19% elevon area that follows the wing. I cut the center of the trail edge on the wing a bit to make it thicker so the elevon taper would more be in line with the airfoil.
TE is thick in the center of the wing and thin at the tip. I laminated 1/8 bass to Balsa to make the elevon. So now I have a proper taper elevon that is 2.75 wide at the center and 1.75 wide at the tip.

I weighed the elevon prior to thinning it, and found the balance point, that should equate to 50% area. This is where the horn will go.

So this is going to be a Zagi 48 inch 3C. I am going to thin the thickness of the wing a bit. Installing an Aveox 1015 2Y with 4.4 to 1 and Castle 55 amp ESC and a 14.5x14 Rudy Freudenthaler prop. Batteries are 16 zapped CP1700SCR cells. Using a Hobbico Gyro for pitch that can be controlled in flight to set gain.

I am using the quick stick design so i can switch power units in under a minute.

Other sticks will be a Soaring only battery stick for very high winds with a wicked duration, and a hundred MPH attempt with a 10 cell zapped and selected RC2400SCR pack and 2 Promax 4011s with 4.7x4.7, or 4.75x4 or 5x3 props.

Anyway doing the torquey aveox first, and I need to counter torque from it, and at slow speed compensate for P-Factor.

Hense the question about using differential elevon to help out a bit of overcoming P-Factor.

The Aveox has a slower than 80 mph pitch speed, but torque is a problem. The Twin Promax has not much torque, but will have over a hundred MPH Pitch Speed, so flutter on that one is a concern.

If P factor is a real problem, I can probably add an extra tail to the center, and if I really had to I could add a rudder that is controllable. It is only going to be at slow speeds the worst, and i could live with flying sideways till the airspeed builds, that should not be that long.

Or of course practice rolling a few times at launch, will make sure the the expensive cars are upwind to prevent me from hitting the ground ;-)

Thanks for your help.
Ron Parigoris
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Old Feb 23, 2002, 04:00 PM
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Chesapeake, VA
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I'm not sure if you mean the same thing I think you mean when you say "differential elevon"... Do you mean simply moving each elevon up more than down when it's used as an aileron? The standard zagi/razor/etc design uses differential elevon movement by default... The mechanical servo link acts to pull up more than it pushes down, even with equal throw. With a computer radio, you can set it even moreso. I have it set on my FMA Razor so downward movement is about half the upward movement. As far as I can tell, there's no affect on flight other than reducing adverse yaw
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Old Feb 23, 2002, 07:35 PM
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Kings Park, New York, USA
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Silly Me

OK I should have used my brain a bit more before posting.

On ailerons yes differential will help preventing adverse yaw.

Not with a flying wing!!!!!!

You can create differential elevon by having standard motion and giving a bit of up elevator!!!!!!


If my JR allows differential in mix mode, it would only have the effect of pitching when you roll.

Silly me I thought have thought about it more.

Thx for the help guys.

Ron Parigoris
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Old Feb 24, 2002, 11:15 AM
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Chesapeake, VA
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Oh, I see your point! Never thought of it as aileron & elevator mixed... The % differential would be a lot more important than with a conventional plane. Nevertheless, the same physics that create adverse yaw are also creating flap/spoiler movments on conventional wings. So the lowered aileron on a flyingwing would be in a higher pressure airstream than the raised aileron, so the net effect would be approximately neutral elevator in a properly mixed plane. Leaving the ailerons without differential would impart a slight down elevator, I'd imagine.

Either way, I've never had a problem with pitching on my wing in banks & still have to add elevator to turn. Good luck!
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Old Feb 24, 2002, 12:24 PM
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This is from an old issue of R/C Soaring Digest, by the "The Wing is the Thing" guys..
They did this on a plank, but it might work on a ZAGI, which isn't far from a plank...
.
They discuss differential ailerons on a swept wing.. but in the August '92 issue which I don't have.
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Old Feb 24, 2002, 10:04 PM
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Hey Sparkey Paul

Hey Sparkey Paul

Very interesting, hinge the elevons at the bottom.

I reread the blurb on #2 and #3, and don't seem to quite get the whole picture.

#2 says Yaw reduced, does that mean adverse Yaw is reduced, or ability to yaw (skid)is reduced?

#2 also says that there is no drag increase with elevator. Does this mean that there is no drag increase with up elevator? Does it mean #3 has a drag increase with up elevator?

#3 Kind of sounds like it is best at countering adverse Yaw (inducing a skid), is that correct?

Sorry for the hundred questions. If it is what I think, I will try the bottom hinge and use some Gap seal on the top

Ron Parigoris
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Old Feb 24, 2002, 10:14 PM
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The article says.."When flying in a straight line, alternating left and right aileron input did not produce rolling motion. Rather the wing would simple oscillate around the yaw axis... hinge the elevon from the top surface.. the yawing motion is reducecd but not eliminated... up elevator is no longer accompanied by the increased drag of the control surface protruding into the airflow (Frise action)."
"#3 ..yaw response to alternating aileron input has been nearly entirely eliminated, roll control is very precise.."
.
I was flying my ZAGI today, and yaw with aileron is a given. It wiggles in yaw when turning, and recovering from turning. How much of this is due to the flexible Lexan tiplets.. I intend to put some styrofoam plates out there to see what stiffer surfaces do.
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