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post #2 of Old 02-24-2013
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Re: End Plate Effect

End plate effect is about making the outer end of a foil (wing) more efficient. End plates are typically associated with keels. End plates offer theoretical advantages in two ways. First is the minimization of loss of pressure difference between one side of the keel at the keel tip and the other is in reducing tip vortex and therefore reducing drag.

In a heeled boat, the pressure differential at the bottom of the keel is reduced by water slipping off the tip (bottom) of the keel. This reduced pressure makes a proportion of the lower keel area less effective. The end plate caps the bottom of the keel directing water aft so by adding a plate at the end of the keel the pressure cannot 'leak' as much.

But also, as a boat makes leeway water slips off of the high-pressure side of the keel to the low-pressure side of the keel and creates a turbulent swirl know as a tip vortex. This mass of swirling water is towed behind the keel creating drag. The longer the keel, the bigger the vortex, the greater the drag.

The end plate reduces both the pressure drop and reduces the size of the vortex. These are also related to the reasons that a deep-high aspect keel is more efficient than a shallower fuller length keel. It is rare to see a boat with a true end plate, but it is very common to see newer boats with bulbs, Scheel keels and so-called wing keels, all of which do two things, lower the center of gravity of the ballast in the keel, and provide an endplate for the keel. At typically designed, none of these act as wings.

I hope this is helpful,

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Curmudgeon at Large- and rhinestone in the rough, sailing my Farr 11.6 on the Chesapeake Bay

Last edited by Jeff_H; 02-25-2013 at 08:56 AM.
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