On 10-May-2004, "riverman" wrote:

But then the question was posed about canard wings on aircraft, which are
basically rudders on front. They don't destabilize the airflow.

Destabilizing the airflow isn't the issue. Destabilizing the aircraft is!

A pilot can't control a plane with a canard. You need fly-by-wire (i.e. a
computer to control the canard). Humans can't react fast enough. The Wright
brothers had a forward horizontal stabilizer on their first aircraft and it
quickly disappeared from aircraft design until small, fast computers came
around. (ditto forward-swept wings, negative dihedral [with exceptions - the
F4 comes to mind; not sure on its avionics.]). Aircraft that had these
characteristics were usually termed "widowmakers".

So lets toss that around here, too.....just why ARE the rudders on the back
of boats? Anyone ever experimented with a front-rudder?

If you put the rudder on the front, the kayak will not have good directional
stability, as any deflection of the rudder will result in the forces on the
rudder increasing and the deflection increasing (i.e. it "runs away"). The
paddler will have to be very quick to react to any deviation from the intended
course. If the rudder (or skeg) is on the stern, a deviation in course results
in an increase in the force on the rudder and it moves _back_ to the initial
course - it is self-correcting.

Take a skegged kayak and paddle it backwards with the skeg deployed. You'll
see the effect quite quickly. Alternatively, trim a kayak with a heavy load
forward pushing the bow down. It will be harder to control (track) than a
kayak trimmed heavy in the stern.

BTW - there are a few folks that hypothesize that the baidarka's flexibility
and bifurcated bow allowed for the paddler to twist the baidarka and use the
lower part of the bow as a forward rudder. However, modern materials make
baidarkas too stiff to reproduce the effect - sealskin is a lot more stretchy
than painted/coated cotton, nylon or polyester.

Mike