IMS The I nternational M easurement S ystem (IMS) Version 1.0

IMS The International Measurement System (IMS)Version 1.0 www.orc.org

The history • In 1812 , seven years after Lord Nelsons Battle of Trafalgar, there were about 50 yachts in England that started to engage themselves in yacht racing, as there were few new battles to look forward to. • In 1827, at the Cowes Regatta, Royal Yacht Club awarded three winners prizes in a handicap system, where the class limits were 75 respectively 45 tonnes. The Ton-system was based upon Royal Customs system to estimate how big volume merchant ships were to pay tax for, • In 1843, the Royal Yacht Squadron started to use a handicap system that was based upon a system that used a time comparison that was based upon sec/ton. The division in classes was crude, but here are the first structured handicap lists to be found. • In 1845-47, New York Yacht Club (NYYC) developed a handicap system • None of these systems still used neither displacement or sail area!! • In 1882, the Sewanahaka Yacht Club (New York) adopted a rule that also included sail area. This rule was dominant for 20 years ! www.orc.org

The structure of handicap systems • A handicap system is usually built up by ; • A rating factor for each boats performance, e g ; • a multiplying factor , like LYS-factor of 1.018 or • a performance value like sailed time per nautical mile like GPH=535,9 sec/Nm • and • A number of different ways to compare - score - these , like • Time-on-Time (ToT) • Time-on-Distance (ToD) • Performance Line Scoring (PLS) • Performance Curve Scoring (PCS) • Rating systems can to various part be based upon design factors (measured or estimated), on subjective estimates or combinations of these. • Some rules have secret formulas to avoid so called ”rule-cheating”. www.orc.org

Examples of handicap systems • EmpiricalEstimated(!) number boats 2004/5 • LYS (SWE/NOR) 12.000 • Portsmouth Yard Stick (UK and others) 12.000 • Design-based • Danish Handicap (DH) (DK) 6.000 • ORC CLUB 4.800 • IMS 3.700 • Design-based + empirical • Performance Handicap Fleet (PRFH) (US) 20.000 • IRM/IRC (former Channel/CHS) (UK/FRA) 6.500 www.orc.org

The IMS system www.orc.org

The background • Development started in the early 70´s as ”The Irving Pratt Project” at Massachusetts Institute of Technology, USA. • In 1976 US Offshore Committee adopted the system as a base for a new Measurement Handicapping System (MHS) • In 1985 ORC adopted the system as a parallel alternative to the International Offshore Rule (IOR). In 1992/94 the last IOR races were run. • In the 90´s a number of subclasses have developed, like Maxi, IMS 600 etc.Initially both Racer and Racer/Cruiser classes, from mid 90´s yacht designs have generally been adopted to race in the Racer/Cruiser class • In 1993/94 the ILC classes were introduced to replace the IOR level classes. www.orc.org

IMS Targets • Based upon transparent and scientific concept • Encourage to build Dual Purpose boats • Shall evaluate actual wind conditions • Shall work against “rule-cheating” • Develop IMS as a living system, prepared to adapt to new trends • Shall be able to use boat at World Championship aswell as at the local Sunday Club race • Shall give credit to age www.orc.org

IMS main components • A method to measure a boat ; • With a hull measuring machine • In water (stability and displacement) as well as rigg complexity, sails and specific materials • A checklist for certain data and factors • 2.A Velocity Prediction Program (VPP) • - At different wind speeds and angles • 3. Predictions of max speed at different race courses • - Windward/Leeward, Circular etc as well as Inshore/Offshore • 4. Establishing comparative scoring at different principles; • - General Purpose Handicap (GPH) • - Time on Time (ToT) or Time on Distance (ToD) • - Performance Curve Scoring (PCS) • - Performance Line Corrected Time (PLC) • 4. Calculation of race data in e g the ALTURA or VELUM computer software www.orc.org

IMS most important publications • International Measurement System (IMS) • IMS Regulations • ORC Championship Rules (”Green Book”) • IMS Guide for Race Committees and others Race Management Scoring Software Package • Formulations of the IMS • Designer IMS Velocity Prediction Program(VPP) • ISAF Special Regulations www.orc.org

The Velocity Prediction Program (VPP) • Based on a ”Lines Processing Program” (LPP) where the boats hydrostatic data are being calculated based upon the measurers data. • LPP is in the next step used as an input to the Velocity Prediction Program (VPP), then added with the effects of the appropriate sails at different wind speed and angles. Influences of “Dynamic allowance” as well as special features like movable ballast are also implemented. • The boats calculated performance is then described in a certificate and an optional polar-diagram. • Evaluation and review of various components influence is continuously made by the ORC Technical Committee (ITC). www.orc.org

Measurement principles • Partly by measuring a number of data like ; • Hull profile, mast arrangements etc • Sails • Propeller arrangements • Stability etc • Partly by compliance check of IMS Regulations, e g • Accommodation space, • Kitchen facilities etc • Needs 4-5 hours for a full measurement plus additional 8-12 hours if no hull offset data file exists. Hull measurement cost is depending on size. Measurers have to be ORC authorised.Cost can be estimated by national rating offices. • The VPP is annually reviewed by the Technical Committee and all boat data are again processed in a computer, before a new certificate is issued. www.orc.org

The certificate´s most important contents • Theoretical max speed in different wind speed and directions • Optimum beat angle, gybe angles as well as VMG at beat and reach • Allowed crew weight (max/min) and allowed sails and sizes • Comprehensive forecasts for certain race configurations in different wind-speeds; • Windward/Leeward • Circular Random • Ocean Course • Simplified rating data for Time-on-Time etc • Extra heavy equipment like radar, wooden deck is specified (and compensated) www.orc.org

Different applications within IMS of the rating data www.orc.org

General Purpose Handicap (GPH) • Stated in sec/Nm in the certificate, represents the typical speed in a set of typical circumstances. • Based upon averaged Circular Random sailing in 8 and 12 knots wind • Primarily intended for; • Separation in sub-classes (bands) • Base for simplified rating like Time-on-Distance or Time-on-Time www.orc.org

Time-on-Distance (ToT) Implies that the forecast e g 580,3 sec/Nm (e g GPH in the certificate) of each boat is multiplied with the total distance of the course, which gives a fix allowance for each boat on this course. These individual allowances are used for direct summary of actual sailed time. Example from a race of 80 Nm; DELTA 580 sec/Nm fastest boat, no extra allowance 0 min allowance ECHO 610 sec/Nm 610-580= 30sec/NM 30 x 80NM= 40min allowance FOX 595 sec/Nm 595-580= 15 sec/Nm 15 x 80Nm= 20min allowance Results 1. FOX Sailed time 40:15 - corr 20 min = 39:55 hrs 2. ECHO Sailed time 40:50 - corr 40 min = 40:10 hrs 3. DELTA Sailed time 40:15 - corr 0 min = 40:15 hrs Advantages; Can be calculated in advance, same factor disregarding race distance and wind conditions. Crews have a clear evaluation opportunity. Disadvantages ; May give credit/discredit to some boats in light or rough weather. Not to be used with tide, due to difficulties to establish the real course length. www.orc.org

Time-on-Time (ToT) Implies that a rating factor, e g TMF in the certificate, is used for direct comparison of sailed time, without any special regard to distance. Example; ALFA TMF = 1,00 and sailed time 60 min BRAVO TMF = 1,05 and sailed time 55 min CHARLIE TMF = 0,95 and sailed time 60 min (A slow boat will have a low TMF factor !) After correction 1. CHARLIE Corr tid 0,95 x 60 = 0.57:00 2. BRAVO Corr tid 1,05 x 55 = 0.57:45 3. ALFA Corr tid 1,00 x 60 = 1.00:00 Advantages; Same factor disregarding race distance and wind conditions. Easy to handle in simple handheld calculator. Disadvantages ; May give credit/discredit to some boats in light or rough weather. www.orc.org

Performance Line Scoring (PLS) • Based upon the principle to combine ToT and ToD advantages/disadvantages • Varies the scoring compared to the course length and the actual elapsed time, thereby giving consideration to the windspeed. Can roughly give about the same accuracy as Performance Curve Scoring, but can be calculated on a palm-sized computer. • Is based upon the formula; PLS = (PLT x Elapsed Time) - (PLD x Distance) • PLT is a factor found in the certificate • PLT Offshore is based upon Ocean Course and has a typical value of 0,8-0,9 • PLT Inshore is based upon Olympic Course and has a typical value of 0,9-1,1 • PLD is also a factor from the certificate • PLD Offshore is based upon Ocean Course and varies within 50-100 sec/Nm? ? • PLD Inshore is based upon Olympic Course and varies within 2-300 sec/Nm? • Advantages; Same rating factors disregarding race distance and wind conditions. Requires no sophisticated computer. • Disadvantages ; May give some credit/discredit to some boats in light or rough weather, but should be better than ToT and ToD. www.orc.org

Performance Curve Scoring (PCS) • Performance Curve Scoring means that you ; • First calculate the average time in sec/Nm that each boat, e g ALFA, has used to sail around the race course. • Then you compare this performance with the boats own theoretical best performance on the same race course. This is then established in a graph with values for average time/Nm and for windspeed. Data for this graph is to be found in the certificate. This gives the “Implied Wind” for the performance the boat has made during the race (The wind that would have prevailed for a 100 % performing boat and crew). • 3. Finally you compare the performance of ALFA with the so called ”Scratch-boat” and thereafter you calculate the time that ALFA would have used if they had been sailing the scratchboat . This is the adjusted ALFA time. www.orc.org

The Scratch-boat can be ; The theoretically fastest boat in the race (usually) or A theoretical boat, e g a 100 ft boat represented by an appropriate GPH-value Please note that the Scratch-boat only is used as a theoretical model and that the actual scratchboat of the race will have to measure his real performance against the theoretical performance as everyone else ! ! The Scratchboat www.orc.org

Example of Performance Curve Scoring . For each boat, a theoretical Performance Curve is established, where the boats theoretical speed at 6, 8, 10 knots of wind for the actual race course is displayed. Example of a ”Heavy wind boat” 800 sec Example; At 6 knots windspeed, boat Charlie should sail with an average speed of about 800 sec/Nm, providing the crew made no mistakes and used the right sails. Example of a ”Light wind boat” that starts moving at very little wind, however gains little additional speed from 9-10 knots of wind www.orc.org

Example of crossing Performance curves Example of a more extreme ”Heavy wind boat” that needs much wind to get going even at low speed Some boats can vary considerably in performance in light and strong winds compared to more conventional competitors. Performance Curve Scoring honours this special performance and give them appropriate rating . This is however not possible in the more simple scoring methods like TMF and GPH, only in PCS and partly in PLS. Boats Example of a ”Light wind Boat” www.orc.org

Example of ”Implied Wind” Ex of ”Implied Wind” and adjusted time for s/y ALFA compared to the ”SCRATCH-boat” Situation The race track layout and distance is decided by the Race Committee. Furthermore is decided which boat will be the ”Scratch-boat”. The boats ratings in expected seconds/Nm are put in the diagram. Total distance 80 Nm. METHOD; 1. ALFA has sailed the race course with an average of 900 sek/Nm. The graph then shows that ALFA has sailed like if it had been blowing 7,0 knots/sec. This is ALFA´s ”Implied Wind” ! 2. We then look at what this performance of Implied Wind=7,0 kn/sec had meant if the same crew had sailed the Scratch-boat?? It would have given a speed of 600 sec/Nm. 3. ALFA´s adjusted time will then be 80 Nm x 600=48.000 sec, which is 13:20:00 hrs 900 600 7,0 www.orc.org

Summary Performance Curve Scoring • Through comparing your own sailed time with the theoretical best performance of your boat, you will receive your own performance expressed as a theoretically used wind or ”Implied Wind”. • You do not have to measure the windspeed, but it may be done and implemented to provide even more accuracy! • The corrected time for each boat in the result list will represent the time that the actual crew would have used sailing the scratch-boat , with a similar performance as they sailed in their own boat • The Performance Curve is specific for each special kind of race course and each individual boat. Needs a PC-computer to do the scoring. www.orc.org

Intends to increase the accuracy in the speed predictions by considering the winds natural variation over a period of time. Rationale ; An anemometer registers the altogether value of windspeed ant time to an average. In reality has this been built up by a series of observations with both higher and lower wind-speeds than the average. As the Performance Curve is not symmetrical around the average wind, it is possible to get increased accuracy by estimating a series of predictions close to the average windspeed. The impact of these are calculated as follows ; 23,58 % of the observed average value (from the anemometer) 19,8 % of the speed predictions for +/- 2 knots of the average wind 11,73 % of the speed predictions for +/- 4 knots etc 4,89 % of the speed predictions for +/- 6 knots 1,79 % of the speed predictions for +/- 8 knots Adding the wind averaging makes the boats rated around 3 % faster. The wind averaging is only added in the “Selected courses” WindAveraging www.orc.org

Gives compensation for those parts of the sailing where the boat is not moving in stable and straight conditions, such as during a tack. Is based upon seven different design-variable factor like ; Beat compensation Downwind compensation Length/volume compensation etc Further details can be found in IMS Regulations Appendix 8. Typical DA-value is 0,2-0,4 % and may max be 1,5% The specific value of DA for each boat is found in the certificate. It his however implemented with increasing age as follows; Boats in Cruising/Racing are always given full allowance. Racing boats are given no allowance during the first three years, thereafter 20 % During the fourth year, additional 40 % during the fifth year etc until full DA from the eight year. DA is automatically added in the certificate data´s Dynamic Allowance (DA) www.orc.org

Gives possibility to give credit and appropriate rating for older boats. Is calculated from year of building up to actual year of certificate. Gives allowance of 0,05 % annually up to 20 years, when the total age allowance will be max 1,00 %. Age Allowance is automatically implemented in the certificate. Age Allowance www.orc.org

Scoring options Scoring options for the Race Committee www.orc.org

Scoring can be used by the Race Committee in any of these options: Time-on-Distance Handicap , implying sailed time adjusted with distance multiplied by GPH according to certificate Time-on-Time Handicap , implying sailed time multiplied with TMF according to certificate Performance Line Scoring , implying sailed time adjusted with PLT and PLD according to certificate Three Windspeed Scoring, implying Time on Time, but expanded to also take a rough windspeed band in consideration when sailing Windward/Leeward Circular Random Fixed Courses Windward/Leeward (with actual wind or PCS) Circular Random (with actual wind or PCS) Non-spinnaker Course (with actual wind or PCS) Ocean Course(always with PCS) Constructed Course with specified tracks, where final results is calculated with either actual winddirections or actual winddirections and windspeeds or comparison with Performance Curve Scoring (PCS) Scoring options for the Race Committee www.orc.org

TripleNumber scoring Introduced by the Netherlands in the early 2000´s • Offers three different time multiplying factors in three windspeeds • 6-9 knots called Low Range • 9-14 knots called Med Range • 14-20 knots called High Range • The IMS certificate gives time multiplying factors (TMF) for • Windward/Leeward • Circular Random www.orc.org

In the certificate, the times are presented in sec/Nm for a race course that would be ; 0,5 Nm beat (at the optimum ”Beat Angle”) 0,5 Nm downwind (at the optimum ”Gybe Angle”) Example Windward/Leeward Wind Start/Finish www.orc.org

Based upon to calculate which time the boat needs to sail a circular race course with the total distance of 1,o Nm with a constant wind from same direction The certificate shows sec/Nm for various wind speeds Is regarded to imply around 25% beat and 75 % open winds Circular Random Wind www.orc.org

Non-spinnaker Course May be used at local/club races without spinnakers www.orc.org

Can only be used with Performance Scoring (PCS) Aims to allow fair scoring to boats that have sailed an long offshore course with the boats spread out over large areas with varying conditions. Originally developed for Newport-Bermuda race conditions. Contents: 30% Windward/Leeward and 70 % Circular Random at 6 knots 20 % WW/LW and 80 % Circular Random at 8 knots 10 % WW/LW and 90 % Circular Random at 10 knots 100 % Circular Random at 12 knots 80 % Circular Random, 5 % beat 52 degr,10 % 90 degr, 5 % 135 degr at 14 knots 60 % Circular Random, 10 % beat 52 degr, 20 % 90 degr and 10 % 135 degr at 16 knot 20 % Circular Random, 20 % beat 52 degr, 40 % 90 degr and 20 % 135 degr at 20 knot Advantages; Requires nowind assessment by the Race Committee. Is regarded to give a better fairness at longer races that not are circular, where the competitors are spread out, and wind conditions are much varying over large areas Disadvantages Will not give best fairness at constant very light or strong wind conditions, especially if the wind remains blowing from a dominant direction. Ocean for PCS www.orc.org

The Race Committee decides the race course distances and bearings The Race Committee can then decide if they want to use ; only a wind direction for each leg or use both wind direction and wind speed for each leg Wind data can also be obtained by averaging the boats wind reports Evaluation of different competing boats are then made by using Performance Curve Scoring (PCS) Constructed Course 3,0Nm/45 degr Wind 90 gr/8 knots 2,8Nm/200 degr • Advantages • Most exact evaluation of each leg • Gives the Race Committee possibility • to provide fair scoring it the race • has to be shortened Disadvantages - Wind data estimates can be controversial 1,2 Nm/ 300 degr 0,7Nm/250 degr S/F www.orc.org

State of the art • ORC recommendation for the most accurate scoring; • Constructed Course with • Performance Curve Scoring (ORC 2004 Guide For Race Committees) www.orc.org

ORC Club ORC Club is a simplified version of IMS, based upon the same VPP, however using fewer inputs; • Only about 25 measured data are needed, can be supplied by the owner, no official measurers are needed • Offers scoring with ToT, ToD and PLS. Local software or hand held calculator can be used. • Primarily intended for local use, not for championships or major international events. • Racing together with IMS boats is possible www.orc.org

Computer software • ORC offers these options; • VPP can be purchased on ORC website, primarily to be used by designers. • The scoring software ALTURA to be used Race Committees can be downloaded from ORC website free of charge, so can the manual. Based on DOS.. • The scoring software VELUM to be used by Race Committees can be purchased at ORC webpage at agreement with the supplier. Based on Windows. • Both scoring softwares offers English, Spanish, Italian, French and German language. ALTURA also Portuguese. Several standard scoring software can be used when using the less advanced IMS systems as ToT, ToD, PLS etc as well as for ORC Club. For Performance Curve Scoring however, ALTURA or VELUM has to be used www.orc.org

IMS The I nternational M easurement S ystem (IMS) Version 1.0