canard installation

[Spyros]

Fellow builders,

 

I’m a Long-Ez builder from Greece and am going to install the canard in my fuselage: as I’m not an engineer I hope someone of you knowledged guys will be available to enlighten me on this topic.

may you explain to me the reason why the new performance canard is installed with more incidence then the GU?

What if the new canard is installed at the same incidence of the GU?

How does a canard incidence variation affect the behaviour of the main wing?

Thanks

[longezdave]

I can only say that I installed my Roncz canard per plans and it stalls and performs as advertised. I certainly would not recommend using a lower incidence, because it will change the stall characteristics.

 

Good luck with it.

 

Dave Adams

Long EZ N83DT

[Lynn Erickson]

Fellow builders,

 

I’m a Long-Ez builder from Greece and am going to install the canard in my fuselage: as I’m not an engineer I hope someone of you knowledged guys will be available to enlighten me on this topic.

may you explain to me the reason why the new performance canard is installed with more incidence then the GU?

What if the new canard is installed at the same incidence of the GU?

How does a canard incidence variation affect the behaviour of the main wing?

Thanks

Install it the way the Roncz plans says. how do you know what the angle of incidence is? the only line you are given in the plans is a level line to use for building. the canard level line should be level to the longerons. if you install the roncz with less incidence it will fly but the take off will be longer. at lower incidence it will need faster airspeed to get enough lift to take off.

[Spodman]

I have read also that the Roncz stalls at a higher angle than the GU (which sorta contradicts what my instructor beat into me about stall angles...) I expect installing the Roncz at the same incidence as the GU would make it more likely your wing will stall before the canard: Not good:scared:

[Marc Zeitlin]

may you explain to me the reason why the new performance canard is installed with more incidence then the GU?

As Lynn points out, since you don't know where the "Zero Lift Line" is for either the GU or Roncz canard, you (or anyone) have no clue what the relative angle of incidence of the two airfoils is - all you have is the "Level Line". Since the shape of the airfoils is different, you can't make the claim that one incidence angle is higher than the other. You don't even know if they're different.

 

What if the new canard is installed at the same incidence of the GU? How does a canard incidence variation affect the behaviour of the main wing?

Folks seem to be concentrating on the stall behavior of the aircraft with canard incidence angle, and there certainly is some effect there - there have been numerous discussions on the COZY mailing list in the past (an archive search will turn them up) regarding canard incidence angle effects on stall behavior. Depending on other characteristics of the airplane, lowering the canard incidence angle MAY make the plane more susceptible to deeps stalls, although a small incidence angle change will probably not have much effect in this area.

 

With respect to rotation on takeoff, lowering the incidence angle will require more elevator deflection to be able to rotate at the same IAS, but that creates more drag, so the takeoff roll might be a bit longer. If you attempt to rotate at speeds close to the stall speed, you might not be able to because the extra deflection of the elevator will cause the canard to stall (on the ground, at the ground incidence angle) at a higher speed that it otherwise would, so you'd have to go faster to get above that stall speed.

 

However, the more important effect, in my mind, besides these two, is the fact that the canard needs to be at a higher incidence angle than the main wings in order for the aircraft to have positive pitch stability. Lowering the canard incidence angle can easily make the aircraft unstable in pitch, and that's a very bad thing. The front wing on EVERY aircraft, canard or conventional, needs to be at a higher AOA than the rear wing. Lowering the canard incidence angle might make this relationship incorrect, so you'd lose some or all of the pitch stability of the aircraft. Numerous folks have mounted their canards at too low an angle, found that their planes were not pitch stable, and had to increase the canard incidence in order to correct the problem.

 

There's a reason that the canard incidence angle was set where it is - much testing was done to determine the correct angle. Why do you think you'd want to change it?