### Technical » The Texel rating and its development since 1984

**Release Date:**2/22/2011

The

Updated 14 February 2011

The Texel rating formula has been used in the

As a consequence the Texel Race organization, supported by the national sailing authority in

A formula has been developed of the general form:

Texel Rating TR = 100 / (c * RL ^ p * RSA ^ q / RW ^ r * various factors.

RL, RSA and RW being the rated areas, calculated using the measured data of the length, the sail area and the weight. The extra factors are multipliers, the rating committees consider to have a substantial influence on the performance.

The unchanged powers for RL and RSA have been 0.3 and 0.4 respectively. The power for RW had been fixed at

For multihulls all over the world there are now three handicap systems using the basic Texel rating formula described above Since 1997 its main formula is used in the Australian OMR rule, for racing with around 170 multihulls, mainly on the East coast of Queensland. In the same year 1997 the French started to use the same TR formula in their Multi 2000 rule. With more than 110 multihulls on the rating list. Technical advisor there is the well-known designer Erik Lerouge. That rule organization now is in the hands of the national sailing

In both rules, naturally, you find the TR formula used in

The rating committees wish to harmonize the rules towards one rule for all multihulls, as far as possible. The Dutch rating committee as step 1, decided to return in 2010 to our formula used between 1993 and 2002. At the same time we will start using the same constant of 1 as in the OMR and the Multi 2000 rule. This lowering of the constant factor from 1.15 to 1, only determines the level of the rating numbers, not their relative differences.

Our formula then becomes: TR = 100 / (rl ^0.3 * rsa ^ 0.4 / rw ^ 0.325). The constant 1 could be left out of the formula.

OMR and Multi2000 prefer to use a TCF, a time correction factor, so their basic formula is even simpler: TCF = rl ^0.3 * rsa ^ 0.4 / rw ^ 0.325.

The correction factors for elements considered to influence the performance of the designs in the

The correction factor P for boats with various kinds of propellers. Finally the correction factor Q for designs with NO efficient dagger boards or centre boards. This factor based on the ratio draft / RL (rated length). For details about the Dutch version of the rating rule, see the formulas in the text of the rule on www.texelrating.org, in the section for cabin multihulls.

The consequence of the announced changes in the basic Dutch formula are that heavy, relatively slow multihulls get a TR number, that is relatively higher than the one used before. The maximum difference between the fastest and the slowest designs will be around 10 % more then with the formula used from 2002 2009.

Another consequence of the change in the power for RW and the constant factor is, that the formula predicting Vb (boat speed) from Vt (true wind speed) had to be changed too. This formula now becomes Vb = 164 * Vt ^ 0.75 / TR.

In the Dutch version of the rule, TR numbers as well as TCF numbers have been published for years on the lists with the rating numbers. In these lists all the data of the boats for which they have been calculated can be studied. The lists can be downloaded as Excel files. See the website for them too. There are lists for measured boats and a longer list for unmeasured designs. The data for these boats have been found in designer brochures, on the internet, etc.

To complete the picture of the three rules, it is necessary to explain that in

Apart from this return to an older version of the basic TR formula, some changes have been made which have to do with the rating of screachers. These sails can be defined as narrow spinnakers, with ratios of mid girth length (smgscr) divided by the foot length (sfscr) less than 0.75. They tend to be near 0.50 now, or even a bit lower, because of hollow parts in de luff and the leech of these sails.

In

In case owners use both spinnaker and screacher, rsascr is reduced to the arbitrary 0.06 * msascr. After the 2010 season, the effects of all the changes in 2010 naturally will be evaluated.. The rating committee decided that there is no need in 2011 to change this method. In