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I've chosen an airfoil for the wing, now i'm confused weather i should do the same for tail or just attach a flat piece of wood as tail. I'm going for conventional tail design. This is my first ever plane so sorry for the dumb question.

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closed as off-topic by fooot, Ralph J, KorvinStarmast, xxavier, Sean Apr 10 at 20:46

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "This question does not appear to be about aviation, within the scope defined in the help center." – Ralph J, KorvinStarmast, xxavier
If this question can be reworded to fit the rules in the help center, please edit the question.

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    $\begingroup$ Related: How does an aircraft tailplane work? $\endgroup$ – ymb1 Apr 10 at 16:16
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    $\begingroup$ How big is the plane? How much tail up or down force you need to counter the wing? $\endgroup$ – CrossRoads Apr 10 at 16:52
  • $\begingroup$ @CrossRoads it's a small trainer plane. wing is 1m*0.3m and it has a pitch down momemt of 0.03 at the angle of attack at which it will fly. Moment arm between CG and tail is 1m which means the counter force needed from tail is 0.03N. Correct me if I've calculated it wrong $\endgroup$ – ssmalik Apr 11 at 4:42
  • $\begingroup$ and yeah it's supposed to be a 1.7kg plane $\endgroup$ – ssmalik Apr 11 at 4:50
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A flat piece of wood with rounded edges will work fine.

The tail's job of producing downforce doesn't require the lift coefficients or angle of attack range required of the main wing, so the actual airfoil shape is not that important especially at low speeds, even more so under the low Reynolds numbers ("thick" air) that RC airplanes work at.

In fact most fabric light aircraft get by with what is effectively a flat surface wind deflector, like this Super Cub.

Cub Tail

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  • $\begingroup$ sorry didn't see your answer while answering, anyway, nice example too. $\endgroup$ – qq jkztd Apr 10 at 17:39
  • $\begingroup$ No worries. The more the merrier! $\endgroup$ – John K Apr 10 at 17:41
  • $\begingroup$ @John K nice picture! Notice the tail surfaces are flat plate as you say. They are also low aspect ratio (the vertical is half a delta) because they require a GREATER angle of attack range than the wing. The wing should stall first. But it is great that you show these flat plates are fine even on full scale aircraft. $\endgroup$ – Robert DiGiovanni Apr 10 at 17:44
  • $\begingroup$ Flat tail surfaces need to be larger than those with a proper airfoil, because the maximum possible lift coefficient is lower. This is not needed to trim the aircraft, but in manoeuvring those limits can count indeed. $\endgroup$ – Peter Kämpf Apr 10 at 18:00
  • $\begingroup$ The Zenith 701's flat topped cambered tail is probably one of the best examples of that point taken to the extreme, in order to get adequate tail power at the 701's crazy low speed. The drag of the thing was not such a big deal in an airplane that can only cruise at 80 or so. $\endgroup$ – John K Apr 10 at 20:36
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Flat plate will be adequate as most r/c planes are overpowered and do not require perfect efficiency to enjoy. Much more important are the proportions of wing, Hstab, elevator, and elevator throw. Finer points can come later. See what other planes similar to your build have.

If it is your first plane, you may be far better off buying a ready to fly. Gain some experience. There are so many variables it is best to start with an easy trainer and hook up with an instructor or somebody with experience. These can be found at local radio control flying clubs.

In the mean time, you can build simple gliders and experiment with designs. As in the early days of flight, the thin undercambered wing will give amazingly slow glides.

Also, check out R/C Groups on the web.

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A flat piece of wood is technically not an airfoil due to the lack of curvature, but it may help to think of it as an airfoil with a very, very bad lift:drag ratio. The tail needs a certain amount of lift to stabilize the plane, so the more drag you incur in getting that lift, the more power you will need to overcome it. But the tail is small compared to the wing, so its overall effect on efficiency is also small.

Is it better for you to add a little more power every time your plane flies or to add a lot more effort once while building it? Only you can answer that.

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  • $\begingroup$ that's right but my plane is supposed to be just 1.7kg, with wing dimensions of 1m*0.3m only. Very little counter force will be needed from the tail. Would i still need to make tail out of an airfoil? $\endgroup$ – ssmalik Apr 11 at 5:30
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Some full scale aircrafts with humans in them also have one flat airfoil as horizontal and vertical stabilizer. For instance : Laser 230 aerobatic aircraft.

enter image description here (source)

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