Dear, Dont you think the coefficient of moment around the aerodynamic center of the wing and airfoil is different. Cause the airfoil coefficient of moment is too small compared to the wing which can be seen in the xflr5. Can you please make a video on seeing the value of coefficient of moment of the wing using xflr5 cause there is not even one.
Sry I really don’t want to annoy you but I have another question 😅 So Im currently calculating a plane but my problem is that I don’t know how I should include the cm of the horizontal stabilizer...if I add it to the moment of the main wing it gets smaler, so I should make the tail smaler, but than the moment of the tail is different etc....so how can I calculate that? (Sry for my bad english, I Hape you know what i mean)
Since the moment of the horizontal tail is small compared to the moment of the wing and the moment between the CG and the aerodynamic center combined, you can ignore the moment of the horizontal tail. Like you say it does contribute some moment but it is small and can be safely ignored unless you have a very large horizontal tail (nearly as large as the main wing).
Use a Symmetrical airfoil for the stabilizer surfaces and it will have Zero moment when aligned in trail at high speed where moment actually matters. Moment caused by large control surface deflection results in a moment in the direction of the desired control, at least in the case of conventional, aft-tail placement. So pulling-up causes the elevator trailing edge to deflect upward, causing it to assume a negative camber shape, which generates a positive (nose up) moment on the horizontal stabilizer, which tends to "lift" the fuselage in the direction of the intended pull-up. None of this is measurable in flight testing, because its a ver small torque force, and because the lever arm from CG to tail is so large that the pitching moment is educed to a tiny force at the CG.
For structural considerations the moment of the wing at cruise is pretty small compared to other conditions like Va at n1 (maneuvering speed at maximum G). But I would calculate the moment at cruise so that I could determine the Horizontal tail incidence.
Thanks that is a very simple explanation, makes it easy to understand!
Dear, Dont you think the coefficient of moment around the aerodynamic center of the wing and airfoil is different. Cause the airfoil coefficient of moment is too small compared to the wing which can be seen in the xflr5. Can you please make a video on seeing the value of coefficient of moment of the wing using xflr5 cause there is not even one.
Where does CP come in this equation ?
Sry I really don’t want to annoy you but I have another question 😅
So Im currently calculating a plane but my problem is that I don’t know how I should include the cm of the horizontal stabilizer...if I add it to the moment of the main wing it gets smaler, so I should make the tail smaler, but than the moment of the tail is different etc....so how can I calculate that?
(Sry for my bad english, I Hape you know what i mean)
Since the moment of the horizontal tail is small compared to the moment of the wing and the moment between the CG and the aerodynamic center combined, you can ignore the moment of the horizontal tail. Like you say it does contribute some moment but it is small and can be safely ignored unless you have a very large horizontal tail (nearly as large as the main wing).
Ultralight Airplane Workshop, Ok thanks
Use a Symmetrical airfoil for the stabilizer surfaces and it will have Zero moment when aligned in trail at high speed where moment actually matters.
Moment caused by large control surface deflection results in a moment in the direction of the desired control, at least in the case of conventional, aft-tail placement.
So pulling-up causes the elevator trailing edge to deflect upward, causing it to assume a negative camber shape, which generates a positive (nose up) moment on the horizontal stabilizer, which tends to "lift" the fuselage in the direction of the intended pull-up.
None of this is measurable in flight testing, because its a ver small torque force, and because the lever arm from CG to tail is so large that the pitching moment is educed to a tiny force at the CG.
Why didnt you also calculate the moment in regular cruise condition?
For structural considerations the moment of the wing at cruise is pretty small compared to other conditions like Va at n1 (maneuvering speed at maximum G). But I would calculate the moment at cruise so that I could determine the Horizontal tail incidence.