Among the attractions at this year?s Royal Yachting Association Sailboat and Windsurf Show at Alexandra Place in London (March 4-5) are three new trapeze dinghies ? the RS800, the Stealth Catamaran, and the Laser Vortex. The RS800 is a double-trapeze dinghy being billed as ?perfect for couples or those overawed by the 49er.? The Stealth Catamaran, which like the RS800 also carries an asymmetrical spinnaker, is a 20-foot, double-handed craft with a carbon fiber mast and bowpole. And the Laser Vortex, a single-handed, trapeze dinghy, is designed with a tunnel hull for speed and stability. Though these vessels won?t be immediately marketed in the U.S., trapeze devotees can always check them out online for vicarious thrills (www.rya.org).