Technical » Texel Rating: Multihull Handicap System

Release Date: 4/7/2006

About the Texel Rating

Texel Rating is a system which allows different multihulls to race against each other. This system is originally developed by Nico Boon for the biggest cat-race in the world, the Ronde om Texel (the Texel Round) in The Netherlands. Later this system was extended to sea-going catamarans and trimarans.

 

An excellent presentation on the Texel Rating may be found at the website www.texelrating.org. You can get information on this rating system by clicking on the Royal Dutch Yachting Union logo. See especially the writing Why Texel Rating by Nico Boon.

 

The form of the rating equation used in the Multihull Dynamics, Inc. website is a very basic one that gives an approximation of the actual rating that is useful to compare one boat against another. The formal rating equation includes extensive hull and sail measurements and includes correction factors for spinnakers, genoas, screechers, keels and propellers. Considering the specification data used on this website, i.e., data that is readily available in sailing magazines and websites, and considering that different users of this site may or may not be interested in applying the corrections, this site includes only the catamaran correction and does not go into the detailed sail plan and hull measurements.

 

The MDI site uses the equation, TR = 100 /(0.99*(Lwl)^0.3*(0.88*SA)^0.4/(D)^0.3)*K, where K is a correction for catamarans, based on the equation, K = 1/(0.19*(0.88*SA)^0.4/D^0.36+0.91) if greater than 1 (otherwise 1).

 

***The Europeans are using a different exponent for displacement in the formula that results in a 20 - 25% higher value.

 

(Note: These equations require metric specification inputs, i.e., meters, square meters and kilograms.)

 

The catamaran correction K given above is approximately one percent for racing cats and from four to six percent for the cruising cats. Nico Boon explains In 2000, Erik Lerouge in France started to introduce a correction for cats as well as trimarans. The maximum difference between the two was about 5.6 %. Very fast and light catamarans only were considered to be equal to trimarans with the same dimensions. Why? Cabin trimarans have less wetted surface, generally sail a bit better, hard on the wind, can tack faster than catamarans.

 

When used as a rating system for a race, the elapsed time for each boat is divided by its Texel Rating and multiplied by 100 to obtain the corrected time. Lowest corrected time wins the Corrected Time trophy. Lowest elapsed time wins the First to Finish trophy.

 

You can find the detailed Texel Rating equations for beach cats and cruising multihulls on the Texel Rating website. Clicking on the logo for the Dutch Catamaran and Trimaran Club will show the specifications needed and the formulas used for cruising multihulls. It can be seen that precise measurements of numerous hull and sail parameters, plus information on propellers and keels (fixed, centerboard, low-aspect ratio, etc.) can be taken into account for these calculations. There is also the adjustment to catamarans mentioned above to make them compete more fairly with trimarans. Nico Boon states that different countries either use or do not use these correction factors.

 

 

Cal Markwood