So I’m reading The Art of Kayaking by Nigel Foster, and in particular the section on steering. He notes that the bow has a lot of water pressure on it (when underway) and the stern not so much. As such, it is typically the stern that wanders (e.g., during weathercocking). He then states that “neither a rudder at the bow nor a paddle stroke at the bow is sufficient to steer a boat or kayak when it wanders off course” and that “all correction strokes need to be made at the stern, noting also that this is why a rudder is invariably placed at the stern of a boat, not the bow.”
This implied, if not explicit, rationale for this sounds dubious to me. Except in the special case of a bow jam, the paddle blade does not contact the boat at all. With both the bow and the stern rudder, the paddle exerts torque on the paddler who makes contact with the boat and thereby turns it. The torque on your body is the same irrespective of the position of the paddle blade (bow or stern), and so too is the point of contact with the boat (your hips, so more or less the middle of the boat). It seems like the effect on your boat should be the same as well.
As an aside, looking up stuff on the net as to why a rudder is placed at the rear of a boat, I saw several reasons, none of which had to do with pressure differentials at the bow vs stern (although I can’t say I did an exhaustive search). If my logic is flawed, I welcome a counter-argument. I just want to make sure I understand it correctly. As an empirical matter though, I feel I get at least as much turn radius out of a bow rudder as I do with a stern rudder.