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This is what I gleaned from that R/C forum's thread on canards. I hope it helps others interested in designing these unique gliders.
> First of all, there is a great online tool for determining a canard's CG -- "Canard Center of Gravity Calculator" located here: https://rcplanes.000webhostapp.com/cg_canard.htm
> Regarding canard angle of attack: "The canard wing must stall first to keep the main wing flying. A canard’s positive AOA makes sure that the canard lifts the front of the plane before the rear wing does it's part. With increased speed, the canard raises the nose and this gives a positive AOA to the rear wing which then does its job. In other words, because the smaller canard wing will stall before the larger aft main wing and drop, it keeps the main wing from stalling and losing all lift.
> Canard incidence: generally, a 3.5° incidence works well. Less incidence is needed on fast and/or short nosed models. If the CG is closer to the glider's front, some positive incidence in the canard wing will help. I'm assuming the reverse is true (less or no incidence) if the glider is tail-heavy.
If your glider has already been built and tends to pitch up excessively or loop, then the issue may be too much incidence.
> Canard size: The area of the canard should generally be 30% of the main wing area.
If the area of the canard wing is too small, it will stall as the plane slows during climb out and the nose will drop, causing a gain in speed and the cycle repeats. This will result in a “hopping” movement as the glider stalls and recovers repeatedly. If this is the case, or the CG is too far forward, increasing the canard size by more than 30% will help.
> Canard wings with a small aspect ratio (ratio of the span to the mean chord of an airfoil) will stall faster.
> Regarding canard airfoils: If the chord is less than 5", sanding in an airfoil doesn't make a difference. What makes more of a difference is that case is incidence angle. If the chord is 5" and over, airfoiling the canard may help performance.
> Dihedral: Swept back leading edges on both the main wing and canard wing acts as dihedral (I’ve seen several swept-wing canard gliders that don’t rely on dihedral but have the wings mounted flat).
> Rudders should be located aft of the CG. The closer it is to the CG, the more area is needed.
