Builders' Forum Archives
Re: Weather Cocking Thoug
Posted by Dave Houser on Jul 29, 2006
I have done a lot of modifications and trimming to my kayak to reduce weathercocking. It also seems to be one of my pet BB subjects. Here is my take on the physics of a kayak in a crosswind that I have posted several times:
If you picture you in your kayak crosswise to the wind, there is an area presented to the wind that creates drag, a force applied by the wind. That drag force pushes you and the kayak sideways. The sideways movement of the hull through the water, whether you are moving forward or not, creates a lateral resistance force on the side of the hull pushing opposite in direction to the wind. Both of these forces can be represented as point forces acting at their respective centroids. If the centroids line up vertically with each other your kayak will not tend to turn (yaw). Now then, if your kayak is "weather cocking" the wind force is behind the lateral hull resistance force and a moment (rotation force) is created that will rotate the bow of the kayak into the wind.
So how can you reduce this weathercocking tendency? 1- Put less front keel in the water, 2- more aft keel in the water, 3- put more wind area (deck and exposed side) forward and/or 4-less wind area aft. Adding ballast aft or moving the paddler aft will do all four and thus reduce weathercocking.
Adding an adjustable skeg allows you to trim the kayak for the current wind (and wave) conditions so it will weathercock, be wind neutral or will leecock depending on the extension of the skeg. And you can also add a rudder, but note that having a rudder up in the wind makes a kayak weathercock more and thus a crosswind will dictate its use. Adding a fixed skeg trimmed to size to make the kayak wind neutral will add a lot of tracking. I have found that I like having a kayak that is very close to being wind neutral without a skeg or rudder. I always find a way to test paddle any kayak I am building in a crosswind to locate the cockpit and seat. Before installing the coaming and cutting out the cockpit hole full size. Waves and following seas also affect tracking so a good sweeping stroke, edging, off center paddle holding or even stern rudder and bow rudder are necessary skills.
In Response to: Re: Weather Cocking Thoug by Kurt Maurer on Jul 29, 2006