Primer on unstayed rigs, particularly for day boats and beach cruisers. Includes a discussion of reefing and some tips on sailing a cat ketch.
Sponberg has designed over 60 different cat ketch or other free-standing rigs. His site contains lots of information on why free-standing masts and wing masts make sense, and how they are designed and built.
Good descriptions of successful unstayed rigs on the author's 52-foot performance cruiser and Bruce Schwab's Open 60 round-the-world racer.