Location: Sunnyvale, CA Is the center of flotation in line vertically with the center of gravity?
Location: Japan The centre of floataion, CF or CoF, is the centre of gravity of all the area, or centroid, about the waterplane of a ship.
The Centre of Flotation is the centre of the area of the waterplane - a section taken horizontally through the boat at the waterline.
Location: Alliston, Ontario, Canada The center of buoyancy (CoB) is determined by the underwater shape of the hull.
Let's define the useful term Metacenter; when the boat is upright the CoB is on the centerline of a symmetrical hull. The greater the vertical distance between the CoG and the Metacenter the more stable the boat. Imagine a nice perfectly round dry log floating high in the water; its CoG, CoB and metacenter are all on the axis and the log has neutral stability so it will roll helplessly if disturbed.
It should be noted that the relationship between the metacenter and CoF is usually maintained on for small heeling angles.
Returning to the mystical pivot point mentioned at * above, that the boat rotates about as it heels. Originally Posted by fferhani Most definitions of the center of flotation say that it is the center of gravity: this definition, this one, and this one. A vessel is nothing but a bunch of opinions and compromises held together by the faith of the builders and engineers that they did it correctly.
I just want to understand key concepts in sail boat and motor boat engineering because I went on a day sailing trip last month with friends and found boat engineering very interesting.

Originally Posted by Ad Hoc The centre of floataion, CF or CoF, is the centre of gravity of all the area, or centroid, about the waterplane of a ship. Location: Sunnyvale, CA OK so it seems pretty clear that the center of flotation is the center of the waterline area.
Does anybody understands why the center of the waterline area should have those properties?
Importantly a vessel trims dynamically around the CFPlane CG arm and statically around the CG CB arm. You easily can easily conceive some shapes that would lead to extremes of this principle for example some ULDB sled racing sailboats.
Location: Iowa Because the Center of Flotation, being only a slice of the hull with no depth does not account for the volume of water that it occupies whereas the Center of buoyancy, which includes volume, does. Mini kayak or kneeboard construction » Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Search this Thread Advanced Search Similar Threads Thread Thread Starter Forum Replies Last Post Center of gravity in Rhino?
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Or put another way, if they're not, the vessel will always trim to bring them back into line.
When the boat heels slightly the CoB shifts to one side, and a vertical line through it will cross the centerline at the metacenter. Do not be tempted to think of metacenter and CoG as the pivot and bob of a pendulum; the boat does not pivot about its metacenter *. The slight variations in spelling and grammar enhance its individual character and beauty and are in no way to be considered flaws or defects.

Right now I am reading the fourth edition of Ted Brewer's Understanding Boat Design, which I checked out from the library.
The CoF is not always inline with CoG, it varies with hull shape, on the water line, in plane view.
You might expect it to rotate about the CoB when it’s in the water, but that ignores the effect of its own mass which is centered at the CoG. The first three references you give have little or nothing to do with yacht design or naval architecture.
Looking at the profile of THIS shape you will see that the center of flotation of the profile is significantly forward of the center of flotation of the triangle. The center of buoyancy is the culmination of all this and will be forward of the plain center of flotation of the triangle. The point along the waterline where this shift will occur coincides with the center of flotation which is fixed. The center of buoyancy shifts with the center of gravity to support the hull at the new trim angle.