On Tue, 31 Mar 2009 16:05:39 -0700, Mark Borgerson
wrote:

Until you get into the classes like the America's Cup yachts, with
their tilting keels, doesn't a fixed keel improve windward
performance?

The problem arises when you sail in an area with a lot of shallow
water. The swing keel is a compromise but it will give you better
performance than a shallow fixed keel.