Cal's Evals » WALLER TC 670

Release Date: 11/14/2004

Waller TC 670 Trailer Catamaran


The TC 670 is the smallest of a family of multihulls designed by Mike Waller. It is a multi-chine catamaran; built from plywood and epoxy-fiberglass. The following figures show this boat in comparison with the average values of four other catamarans with length overall between 20 and 23 feet listed on the Multihull Dynamics, Inc. website.


Displacement: 1.06 tons [0.99 tons]


Length Overall: 22.00 feet [22.05]


Length at Waterline: 21.00 feet [20.79 feet]


Beam Overall: 8.10 Feet [11.55 feet]


Sail Area (Main plus jib): 248 sq. ft. [248 sq. ft.]


Displacement-Length Ratio: 56.96 [54.79]


Sail Area–Displacement Ratio: 22.37 [24.18]


Beam between hull centerlines: 5.77 ft. [9.12 ft.]


Base Speed: 7.6 knots [7.72 knots]


Texel Rating: 139 [135]


Bruce Number: 1.19 [1.23]


Stability Speed: 12.10 knots



The numbers show that the TC 670 is pretty much average for this small data set except for its very narrow beam overall and beam at the hull centerlines. The other boats for comparison are the Tomcat 6.2, the Maine Cat 22, the Hirondelle 23 and the K-Kat 23.


The narrow beam, clearly selected so that the boat can be hauled on a trailer without disassembly of the hulls, has the direct effect of lowering stability speed, the beam wind speed at which the windward hull can be expected to lift out of the water, to nearly two and one-half knots below average, or 16%. The designer provides Hobie-style "wings" for hiking out to allow sailing in higher speed winds. While this provision may be satisfactory for daytime sailing under moderate conditions, my Hobie 18 experience says that it is NOT the answer for night sailing or heavy weather.


The TC 670 has a single centerboard and a centerline rudder, sleeps two in a double berth and can sleep two children in a cockpit under a boom tent.


More information can be obtained for this and other Mike Waller designs on Mikes website at



Calvin H. Markwood
Engineering Analyst
Multihull Dynamics, Inc.

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