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If I understand it correctly, the usual configuration with tandem wings is that the front wing has ailerons - controls the roll. And the rear wing (a bit smaller than the front one) has elevators and rudder to control the pitch and yaw respectively. Am I right? Or are there any mistakes in my understanding?

my design

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    $\begingroup$ Can you give us a bit of background? Are you designing an RC model? Why canard? Some particular characteristics you want to achieve? $\endgroup$
    – sophit
    Feb 7, 2023 at 21:21
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    $\begingroup$ For real tandem wings the rear wing is exactly the same size (not smaller) than the front. But yes, that's where you put the elevators. It's exactly the same logic for canards where the rear wings is also where you put the elevators (though they're normally configured as elevons - elevator+ailerons) $\endgroup$
    – slebetman
    Feb 8, 2023 at 7:03
  • $\begingroup$ @sophit Yes, it will be an RC trainer. Though I decided to make the wings straight (picture updated), to make it easier to build. $\endgroup$
    – Mark
    Feb 8, 2023 at 15:25
  • $\begingroup$ Yes, I have. Though I am still trying to put the wings more apart = more stability, but I need my payload in front. Gotta find the sweet spot :). $\endgroup$
    – Mark
    Feb 8, 2023 at 16:39
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    $\begingroup$ There are many good answers here about tandem wing configuration, like this one or this one. Read especially carefully the comments of @PeterKämpf 🖖 P.s.: I clean up a bit my comments. $\endgroup$
    – sophit
    Feb 9, 2023 at 6:22

2 Answers 2

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I think your assumption, that the rear wing is a little bit smaller than the on in front is not necessarily true.

There might be tandem wing planes with that constellation, but in some papers I found, the wing size differs between different models. The papers [1] and [2].

In addition some images depicting the mentioned:

enter image description here

enter image description here

In the case of the Miles M.35 Libellula, featured in the photographs above, the control surface arrangement was as follows: the front wing had flaps outboard and elevators (for pitch control) inboard. The rear wing had flaps inboard and ailerons (for roll control) outboard. Also, as can be clearly seen in the photos, the rear wing had vertical fins with rudders (for yaw control). (From page 18 of first cited source.)

If the front and rear wings have appreciably different span, it is logical to put the ailerons (roll control surfaces) on whichever wing has the larger span, and the M.35 followed this practice.

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    $\begingroup$ Thank you very much for your answer, I will put the ailerons on the bigger one. So there is no problem in putting elevators on the smaller one in the image I have added to my question, I plan to use the front wing with ailerons and the rear wing with elevators. I think that is matching in what you have suggested. Thank you once again. $\endgroup$
    – Mark
    Feb 7, 2023 at 19:21
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Many tandem-wing airplanes have a rudder (for yaw control) and vertical fin on the fuselage, not on the tips of the rear wing. The former is arguably more "usual" configuration. Examples: Rutan "Quickie", "Flying Flea". See also the concept design pictured in the first image, and described in the second cited source, of this related answer to the present question.

On the "Quickie", the front surface wing had full-span control surfaces that functioned as elevators. The rear wing had ailerons, mounted inboard.

On the (rather unusual) "Flying Flea", the entire front wing pivoted up and down for pitch control. Roll control was accomplished solely by the rudder, via aerodynamic coupling between yaw (or more properly slip) and roll, thanks to the generous dihedral of the front wing, as well as the high-mounted position of the front wing.

With a tandem-wing aircraft, it makes intuitive sense that you would want the control surfaces to move in such a way as to immediately increase, not decrease, the lift of one of the surfaces to create a nose-up pitch torque, and this only works if the elevators (pitch control surfaces) are on the front wing. However, many of the older "free-flight" model airplanes did have very large tails with lifting airfoils. There have likely been some aircraft, in model form if not in full-scale form, that could arguably be described as "tandem wing" aircraft, with the rear "wing" not too much smaller than the front wing, that had the ailerons in the front and the elevators in the rear. In general, it makes sense to put the ailerons on whichever wing has the greater span, although the inboard position of the ailerons on the Rutan "Quickie" seems to challenge this logic.

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  • $\begingroup$ To "quiet flyer".......So, would you suggest to make the front wing smaller, or the rear wing smaller? And as you have said " In general, it makes sense to put the ailerons on whichever wing has the greater span", I will put ailerons on the big one and elevators on the smaller one. I have edited my answer and added a picture of my plane, I will be glad to hear any suggestions, as you clearly aren't new to this topic :). Thank you sincerely for your time. $\endgroup$
    – Mark
    Feb 7, 2023 at 19:03
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    $\begingroup$ @Mark -- I need to be careful about getting involved in conversations in comments-- Stack Exchange policies discourage that. If you gather 20 reputations points you'll be able to post in "chat" rooms and maybe we could discuss some more. But honestly I don't think I have a great deal more to add-- I don't actually design airplanes, either full-scale or model... $\endgroup$ Feb 8, 2023 at 0:57
  • $\begingroup$ The quickie's front surface was elevator only. The Rutan tandems didn't have flaps. $\endgroup$
    – John K
    Feb 8, 2023 at 4:15
  • $\begingroup$ @JohnK -- that makes sense. Apparently there is an error in the wikipedia article, in the section titled "configuration". en.wikipedia.org/wiki/Rutan_Quickie#Configuration $\endgroup$ Feb 8, 2023 at 13:15

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