Technical » Classifying Multihulls

Release Date: 7/23/2006

When viewing, shopping, admiring multihull sailboats, it is easy to become enthralled with the prospect of high performance - meaning speed. Sailing past another boat is probably one of the primitive urges of man. However, many multihull sailboats are really not designed for racing or even sailing particularly fast. They have other features that make them attractive to sailors, probably the most noteworthy being sailing nearly level and enjoying the comparatively large deck surfaces.

Charles E. Kanter, in his book "Cruising in Catamarans", does a great job bring all of this into perspective under the same title as this writing, "Classifying Multihulls." He makes an analogy of automobiles with sailboats to define five classes of sailboats and then describes each class briefly. He has given Multihull Dynamics Inc. permission to summarize them on our site.

The classes of sailboats and the analogy with motor vehicles is as follows:

Automobiles

Sailboats

  1. Grand Prix Racing Car
  1. Experimental/High Performance
  1. Sports Car
  1. Racing
  1. Coupe
  1. Racing/Sport Cruiser
  1. Sedan
  1. Cruising/Racing
  1. Station Wagon
  1. Cruising
  1. Van & RV
  1. Residential/Utility

Kanter's Class Descriptions:

  1. Experimental/High Performance - "Means the sole reason for the boats" existence is to go as fast as it is possible to make a sailboat go. For catamarans, Lwl/Bh greater than 15 are expected.

  1. Racing -High performance is still a goal but there are more compromises in the design to facilitate production and the creation of class or level racing. For catamarans, Lwl/Bh of 12-15 are expected.

  1. Racing/Sport Cruiser- Purpose for the design is to achieve maximum performance and/or to conform to class rules. Some amenities exist, with the addition of a head and galley allowing you to use the word "cruising" in the description of the vessel. For Catamarans, Lwl/Bh ratios of 10-12 are expected.

  1. Cruising/Racing - Compromises in the performance potential of a given design exist to add amenities. A partial rule of thumb is: if a boat has a center-board or dagger boards it is probably class 3 or 4. If a fixed keel or keels, probably class 4 or 5. For catamarans, Lwl/Bh of 9-11 are expected.

  1. Cruising- Attention to living in its design priorities defines a cruising boat. Lwl/Bh of 7-10 are expected.

  1. Residential/Utility- This is a catch-all category to include all those floating multihulls that do not fit into any of the five categories above. There are many creative, useful, entertaining vessels floating around that satisfy the requirements and dreams of their owners. There is no criticism implied or intended unless someone ventures beyond safe limits with such a vessel. Kanter says "If it looks like a summer cottage with a mast stuck on it, it will probably will sail like a summer cottage with a mast stuck on it! " some of those summer cottages with a mast stuck on do sail quite well.

In Kanter's book, he places a number of boats he describes in it's appropriate class. There is no attempt to do this on the Multihull Dynamics, Inc. website. Use these categories to keep your judgments of various multihull sailboats in perspective - very few RVs are used for racing.

Calvin H. Markwood
Engineering Analyst
Multihull Dynamics, Inc.

Contact Cal: multihull.analysis@comcast.net

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