International Measurement System

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The International Measurement System (IMS) is a system of handicapping sailboats for the purpose of racing that replaced the earlier International Offshore Rule (IOR) system in the early 1990s. It is managed by the Offshore Racing Congress (ORC). [1] In the sailing world it is usually referred to simply as 'IMS'.

Handicap forms for sailing vessels in sailing races have varied throughout history, and they also vary by country, and by sailing organisation. Sailing handicap standards exist internationally, nationally, and within individual sailing clubs.

The International Offshore Rule (IOR) was a measurement rule for racing sailboats. The IOR evolved from the Cruising Club of America (CCA) rule for racer/cruisers and the Royal Ocean Racing Club (RORC) rule.

The Offshore Racing Congress (ORC) is an international body for the sport of competitive sailing and is responsible for the establishment and maintenance of rating and classification standards used to define offshore, that is marine as opposed to inland, yacht racing handicap categories.

Synopsis

IMS was the first yacht racing rule developed around the central idea of a Velocity prediction program (VPP). The VPP was a complex computer program that integrated continuous hullform information in order to predict a given boat's speed potential in a given wind velocity. Details on the VPP were openly available to the yachting community, in contrast to the earlier IOR system. Designers and boat owners much preferred this as they were able to design new yachts to maximise performance under the rule with a degree of certainty they had not enjoyed under the IOR rule. IMS is generally believed to have made significant leaps of progress forward from the IOR rule it displaced in terms of fairness and accuracy.

A velocity prediction program (VPP) is a program which solves for the performance of a sailing yacht in various wind conditions by balancing hull and sail forces. VPPs are used by yacht designers, boat builders, model testers, sailors, sailmakers, also America's Cup teams, to predict the performance of a sailboat before it has been built or prior to major modifications.

IMS racing declined seriously in the early 2000s. A raft of new technology developments in yacht design led to a situation where the very largest and most expensive yachts were able to gain a significant technology advantage which the rule was less able to account for. Smaller yacht owners began to feel unfairly disadvantaged under the rule and between 2003 and 2007 much handicap racing around the world changed to using the newer IRC rule.

However, an improved, revised version of IMS was developed over the years 2006-2008, and known as the Offshore Racing Congress (ORC) rule. As of 2008 some major sailing clubs around the world considered replacing IRC with ORC in their club activities, heralding a return to the IMS system in a more modern form.

The Offshore Racing Congress Rule is a system of handicapping sailboats for the purpose of racing. It is managed by the Offshore Racing Congress (ORC) and is usually referred to in the sailing community simply as "ORC". ORC is an enhanced version of the earlier IMS handicapping system that was used globally from the early 1990s to the early 2000s.

Notes

  1. "ORC Offshore Racing Congress - World leader in rating technology". Orc.org. Retrieved 2012-09-14.

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