Originally Posted by Osprey
I think the key thing here is the fastest current is not on the surface, the surface water is being slowed by that same wind and friction with the air. The faster current is 2-3 layers down, the 16 is catching more of the quicker current while the 14 is probably riding higher in slower water. Think of the river like a tube, everything on the outsides is slowing the current (bottom, banks, air) and the middle of the tube doesn't have anything to slow it down. Each layer of water from the sides in is moving a bit differently.
I think it's called a "laminar" flow. A little more speed a few inches under. It's why those swimmers go zipping by. Seems like 15 / 20 years ago, alot of the 14's had smaller tubes and wrap floors, sat a little lower and tracked awesome. It's been breed out of a lot of them with larger tubes and self bailers, with an emphasis on responsiveness.
A responsive boat is great in the whitewater, but I'll take a good tracker in the wind any day.