Rotaryphile

I set up all my conventional layout aircraft with 0-0-0 wing incidence, stab incidence, and thrust offset. I regard any need for thrust offset as an admission of design deficiency. When an aircraft is inverted, downthrust becomes upthrust, and right thrust becomes left thrust; a rather odd setup.

The last thing that a full-out aerobatic aircraft needs is pitch stability. Pitch stability causes the nose to drop when airspeed decreases, and to rise when airspeed increases, making aerobatic line holding more difficult. With zero pitch stability, with hands off the controls, the nose tends to stay nailed to the same angle. This requires a far more aft CG; not too far ahead of the absolute aft limit where the aircraft becomes dynamically unstable in pitch.

My preceding incidence/thrust recommendations apply only to aerobatic aircraft. A free flight or R/C trainer-type canard would need greater incidence in the canard stab, a CG location that is well ahead of its neutral stability location, and probably some nose-lowering thrust offset.

Canards are frequently claimed to be safer, because the canard stab tends to stall before the main wing, causing the nose to drop, thus retaining a safe airspeed. In reality, exactly the same thing can be achieved with a conventional tractor layout, simply by locating the CG well ahead, so that the stab is unable to produce sufficient download to force the wing into a stall. The trade off, of course, is increased landing speed. A canard's stab supplies an up force at landing speed, and thus does not fight the wing, so that a canard with a forward CG location could have a slightly lower stall speed than a tractor layout would provide.

Canard homebuilt aircraft seem to suffer at least as high an accident rate as those with tractor layouts. In a tractor layout, the heavy parts hit the ground first in a crash, and the nose, which needs to carry the weight of the engine, is much stronger. In a canard, the pilot may be crushed and chewed up by a rear-mounted engine and propeller.

My experiments seemed to indicate little, if any, aerodynamic advantage to a canard configuration. My canard gliders produced no better sink rate than my conventional tractor gliders did. With so much fuselage side area is ahead of the CG, canards also need far greater vertical stabilizer area than tractors need, causing higher drag.