So that different boats from different lengths and benefits can compete in equality of conditions and regata can have interest, coefficients settle down correctors. This way, perhaps although a quick boat enters first position, is gained by another boat with smaller benefits, but than it has run and it has arrived very well at goal after other regateros boats. The objective is that the most capable equipment gains the race and not the fastest boat.

   Without these adjustments, the most extreme boats always would be the winners. For it compensated time is used `', according to which the real time until the arrival it is fit by `Rating' of each boat. This solution entails the lottery of the changing conditions of the meteo. For example good wind can blow in the morning until the quickest boats enter, and soon to fall the conditions of wind leaving to the boats of smaller benefits nailed in the sea. On the contrary, a race that perhaps begins with a weak mañanera breeze, raises of wind to push with determination the boats that by Rating would enter later.

   The compensated time can calculate like the real time multiplied by the type of Rating that is applied, or like the real time to which a Rating multiplied by the miles of regata is reduced to him, or as a combination of both forms.

   The great question is in like fitting the Rating according to each boat, from the results obtained in many regatas previous. It is necessary to predict the benefits of the boat of possible the most loyal and honest form. If a boat arrives systematically in last position independent of the crew sails who it is necessary to improve its Rating to him. This way empirical PHRF (Performance Handicap Racing Fleet) very used in the United States, or also by Rating IR2000 calculates published by the RORC, or the Handicap of France.

   The other form to create a Rating without leaning in experiences of previous races, consists of being based on mathematical models that consider many parameters of the boat, on which it will depend his behavior and aptitudes for navigation; It is famous IMS (Internacional Measuring System) for which has been developed a computer science model that allows its calculation in all the conditions of wind.

   The races at the high level prefer to be based based on more general laws of the hydrodynamics and aoerodinámica being left margin to the naval architects, to be able to foment the technological innovation. In order to calculate this type of Ratings the terminal velocity of the boat by means of physical laws will be considered: As a example we can comment that the terminal velocity of a sailboat with the maximum of wind that can support, will be a function by the squared root of the length of floatation. Nevertheless, with loose winds its theoretical speed will depend on the resistance of its helmet to the advance and on the surface of candles.

   The naval architects for competition boats will look for the hypotheses more favorable than they allow to always make fast boats but within the fulfillment of the Rating.  `Looks for failure' not anticipated by the designers of the Rating as in fact it became for the design of the PenDuik III that brutally gained when exploding the hollows noncontemplated by the equation of the calculation of Rating for schooners that were considered slow.

   For example the Rating (expressed dimensionally in units metric) and simplified for a sailboat of the America Glass, whose length of floatation is L, with S squared meters of lifting candle, and a displacement of D tons, comes expressed by the equation:

  The constructor must play with these data so that the result is equal to 24 (meters). Coefficient 0.679 is calculated so that the looked for result agrees with total the maximum length of a America Glass, that is to say 24 meters. If we do numbers considering that move 25 tons, that the length of floatation is of about 18 meters, and that have 300 meters squared of empopadas candles in fitted and 500 in, the result will be near 24.

   Rating IOR (Internacional Offshore Rating) also considers security aspects to force that the boats are more stable and safe during navigation the following calculation of the IOR that was used during the decade of the Eighties, and knowing that L is the length of floatation, S the surface of candles, B is the maximum sleeve (masterful frame), D is the depth of the helmet, DC the openwork, FC the freeboard, EPF the factor of the motor and of the helix, CGF the stability factor, MAF the factor of movable appendices, is of the following expressed way:

   At heart it has been tried simply to apply a formula, but to define each one of the measures exactly to introduce for lack much Literature. As a example, the definition of the Rating for a America Glass occupies almost 50 pages.

   The naval designers tend to prefer that some restrictive rules like a length limit are applied, a minimum value of stability or surface of candle, being left freedom for the other aspects of the naval design. They are known like `box rules' that is applied in regatas like Transpac 52 or Open 60. In these cases the boats compete in real time and leave many more possibilities to the innovation and the technological advances.