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Jan 13, 2020, 12:26 PM
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Thank you for your replies. I have a Futaba 10J and a Spectrum DX6.
Michael
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Jan 14, 2020, 03:12 AM
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tspeer's Avatar
Quote:
Originally Posted by cessna180j
I have built several profile prop in slot foam jets. I would like to build a Gripen with working canards. I need some help figuring out how to set up their functions. I understand to control pitch ,elevons move in opposite directions and in roll they move in the same direction. But how do you achieve this.
Thank you for your help.
Michael
Don't use canards for roll control - only pitch. Do all the roll control with the elevons. The reason is downwash from the canards affects the wing. In pitch, positive lift on the canard lifts the nose, which is ahead of the c.g. Downwash from the canard decreases the lift on the wing, which is behind the c.g. Both effects act to pitch the plane up.

But when using differential canard deflection for roll, the lift from a canard and the lift induced by downwash on the wing are acting in opposite directions on the same side of the c.g. So they fight each other. It can even lead to control reversal if the wing effect is greater than the direct effect of the canard.

As for how to implement pitch control with the canards, it's done with mixing in the transmitter. Mix the elevator with the canard using a change of sign so they move in opposite directions. Of course, if the control horns are on opposite sides of the canard and wing (say, the horn is below the canard and above the wing elevons) then you don't need the change of sign.

That assumes you are using separate servos for the canard and elevon. You can mechanically link the canard to an inboard elevator so they're driven by the same servo, just like the control line pilots link the flaps and elevators together. You'll want to use separate ailerons outboard of the elevators for roll control.
Jan 14, 2020, 12:01 PM
Registered User
Thank you for the very informative information regarding the proper canard elevon set up. I intend on using individual servos for each control surface. I will do a mock-up and attempt the proper mixing with my Futaba 10J.
Michael
Jan 15, 2020, 12:43 PM
Registered User
Just did a mock up of elevons and canards on my Futaba 10J. The elevons , just the selection in the transmitter. For the canards , using 1 servo, I just mixed the elevator channel to aux. 7 which the canards are on and put the selection on a switch. Now I have elevons as they should be and the canards moving in unison only up and down. Also canard travel can be set with the transmitter and can be switched on or off.
Michael
Jan 15, 2020, 07:54 PM
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JureZ's Avatar
Quote:
Originally Posted by cessna180j
Just did a mock up of elevons and canards on my Futaba 10J. The elevons , just the selection in the transmitter. For the canards , using 1 servo, I just mixed the elevator channel to aux. 7 which the canards are on and put the selection on a switch. Now I have elevons as they should be and the canards moving in unison only up and down. Also canard travel can be set with the transmitter and can be switched on or off.
Michael

check the following:

canard up , elevons down
canard down, elevons up


you could have the elevons work as tailerons (without elevator input effect)
Jan 15, 2020, 10:03 PM
Registered User
Thank you , I have it set up the way you stated. Probably did not make myself clear.
Michael


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