: When I was playing around trying to design a special purpose kayak (for duck
: hunting) I measured my CG in a paddling position by sitting on a plank on
: top of a dowel creating a fulcrum. I discovered my CG was approximately 12
: inches forward from my back (with waders and wading boots on).

: While reading a kayak review in Sea Kayaker Magazine I noted with interest
: the location of their paddler's CG in a footnote that read "*Fixed
: "Paddler" weight has its center of gravity located 10"
: above the lowest part of the seat and 10" forward of the seat at
: back. The "cargo's" center of gravity coincides with the kayak's
: approximated center of gravity."

: By definition the CG of the kayak and all of its contents has to be directly
: over the center of buoyancy. If it does not the bow will move up or down
: changing the location of the center of buoyancy so CB is under the total
: CG. So if your plans show the location of the design CG or CB your back
: should be 10" behind that location. Add at least 3" to allow for
: leaning back while rolling before locating the back of the cockpit.

: However I found in my Yare I needed to move the seat back from the location
: on the plans to avoid weather vaning so I am enlarging my coaming (and
: cockpit opening) 2-1/2" to the rear (to avoid adding ballast in the
: aft compartment).

: A previous related post I made on leecocking might help: If you picture
: yourself seated 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 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 "leecocking" the
: wind force is in front of the lateral hull resistance force and a moment
: (rotation force) is created that will rotate the bow of the kayak
: downwind. So how can you reduce this leecocking tendency? Two ways. 1- Put
: more front keel in the water and/or less aft keel which will move the
: lateral center of resistance of the water on the hull forward. 2- Put more
: wind area (deck) aft and/or less forward which will move the wind drag
: aft. Adding ballast in front or moving the paddler forward will lower the
: front keel, raise the aft keel, lower the front deck and raise the aft
: deck, all help move the two centroids toward each other. Putting a sail on
: the rear deck (rudder in the up position) will help. Putting the rudder in
: the water or adding a skeg will make it worse (unless you have enough
: forward motion to create large enough lateral hydraulic forces, just don't
: stop paddling). Adding or removing keel or deck are not easy to do on a
: finished kayak. So I would first move the paddler forward and then add
: forward ballast if additional trim is needed.

: Sea conditions and forward motion of the kayak also affect weather vaning or
: lee cocking of a kayak so being able to move the seat forward or back to
: trim the boat I think is a nice feature. My foam seat is attached with
: Velcro and the seat back adjusts with buckles in the supporting webbing so
: when I finish my coaming enlargement I hope I have enough seat movement to
: trim the kayak and still be able to lean back. Time will tell.

: Hope this at least provides some amusement.

What a great post dave. you should put this in the wikiwikie thingie.