The Rutan style smaller wings canards you see today are designed for
aerodynamic efficiency and speed and not for load carrying capacity.
Some of the canard efficiency (and turbulence advantage) is that both
the canard and main wing is lifting, whereas in conventional aircraft
the tail is actually pushing down. The canard flies just like other
wings - obeys the same law of physics - but current canard wing designs
are for higher stall speeds to stall before the main wing, a flight
safety feature. That means the landing/takeoff speed is limited by the
relatively high stall speed of the small canard wing. Canard aircraft
are generally more CG sensitive and the canard stall speed is dependent
on the CG position - means longer takeoff for front CG and shorter for
aft CG. By contrast the conventional design has the CG near lift center
of main wing which carries most of the load and essentially dictates
the stall speed - considerably lower for the large wing. It is possible
to design a canard with large wings and lower stall speeds suitable for
water landing. It would probably look something like the Wright
brothers design with the canard way out up front to minimize the canard
wing CG position dependency. But why bother.
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SQ2000 canard: http://www.abri.com/sq2000