IRC Rating Optimization
Aktualisiert: 15. Dez. 2020
The idea behind a rating rule is enabling yachts to race against each other by attributing a rating based on corrected time. A racer will aim to have the lowest possible handicap and the fastest boat. IRC, ORC, PHRF and ORR are the major rating rules which take a variety of measurements and characteristics of each boat to develop a single number or set of numbers, across various conditions and angles, allowing race committees to equalize performance on the race course.
How to optimze a boat for IRC?
IRC is a measurement system which is co-managed by the RORC in Great Britain and UNCL in France. A common conception about IRC is that it is not transparent. The calculation method is secret in order to prevent designers from exploiting potential loopholes in the rules, but this doesn´t work. To get indications, you can to compare different boats. You can buy the IRC certificates of the good performers and compare those certificates to your own. Collect all all the information in a spreadsheet, the differences can show where performance-gaps could be found. Designers, who do this kind of work more often, have a better database on which they can find the gaps. If you consider that one trial certificate is around 120€, it could become a costly procedure.
It is a fact that the IRC rule has trends. What is also clear is that the rule has moved more towards performance over the past few years, which I like. But a lot of the ambitious sailors spend a lot of time time and money changing boats every couple of years and constantly running trial certificates to beat the system.
To that reasons I am working together with a specialized rating optimization company, which has access to more than 2500 certificates.
Singe, double or crewed sailing
Crew has a big impact on the trim of our boat. With less weight in the rail, you will look for less pressure. The range of the large downwind sails will become much smaller, you could not push so hard and sail changes become slower.
Size of the boat.
For boats that are longer the emphasis is more en more on performance. The smaller the boats get, the more important the rating is.
A lot of modified IOR quarter and half tonners have added keel extensions. If weight was only added in the Bilge, it appears that every 1% of weight added equates to about 1 point of rating approximate reduction. The bow down trim is another important factor on IRC boats. On modern boats extra weight placed forward will not add a lot of length at the bow, but will lift the stern a lot more and results in the rated length coming out shorter, which indicates a smaller, slower boat.
Some ideas which could work on your boat:
- shorter mast
- longer keel
- adding weight in the boat
- small rudder
- steel fin (instead of carbon)
- steel bulb (instead of lead)
- no bulb, thicker keel Weight Yachts are often much heavier after 2 years than when they came out of their moulds - the difference can be up to 100kg with a 40" yacht. Additional accessories - which can´t be removed - like extra batteries are examples of items which you can add to the rated weight. If you have a series production boat, IRC accepts the weight numbers of the yard, but sometime the are big differences between the same boat type. It´s worth looking at this. There are some critical voices which say that this offers some freedom for interpretation or manipulation.
Measure your sails a least one time in a season. All sails shrink.
Be aware of the length of the luff is not measured, but the marks at mast and boom: At the top of the mast (P measurement) on the End of the Boom (E measurement). Some girths will have default (width) sizes which do not involve a penalty.
Overlapping jibs seems to get penalised quite heavy. It appears that not full length luff (LL) is treated well by IRC, but pushing the girths to the maximum which fits in the foretriangle is increasing speed without penalties.
Symmetric or asymmetric spinnakers
Are better, because in windward/leeward racing you are running square downwind. On heavy non planing boats the advantage is bigger, as you will going deeper. In heavy wind the advantage is bigger.
- Once above 12 knots, they are very efficient running with pole pulled back, with an asymmetric you will go the same speed 10 degrees or more higher
- Tactically, they offer an experienced crew greater options downwind.
- Very little time lost while gybing.
- Expensive on rating – on 10m boat converting to a same sized spinnakers costs about 7 points
- Not as efficient when reaching due to shape
- More difficult to hoist and gybe
Asymmetric spinnakers are more efficient on long distance or coastal racing, because there is a lot of reaching. On light planing boats the advantage is bigger, as you will always be going higher angles.
- larger asymmetric spinnakers for the same rating
- more efficient when reaching than symmetric
- Easier hoisting, less equipment
- more difficult to trim on deep courses
- Code zero models (very flat asymmetrics for close reaching) is a must for offshore boats
- Needs a bowsprit
- They don’t run as deep as symmetric spinnakers
- fast gybing is difficult, needs a lot of training
- they can wrap around the forestay when gybing
What about boats having both sail setups?
To do this efficiently, it needs a small sprit or prodder, that does not extend out further than the pole does.
Code 0 are perfect for offshore sailing, even short handed, because they are versatile and easy to handle. If its too windy to hoist the kite, choose the code 0, when you broach, you just furl the sail up. With a mid-girth bigger than 75% it fits in the IRC rule.
The shape of the Flying Jib is fuller than a jib, but with a hollow leech to meet the IRC rule of less the 50% of the LP. You can use it from 45 to 100 degrees true wind. The overlap is a lot less as a code 0, so you can sheet the flying jib much higher.
The most important rule: make a plan!
Plan which race you want to sail and try to wind in the season. Check, which conditions you can expect at that spot. Have a look at the type of races; short-course with up and down, round the cans, costal racing, long distance offshore racing. You have to make sure that your boat goes as fast as possible in the conditions you choose and get no penalty for speed in conditions which you not expect.
Collect and store all data you can get: So you can evaluate after the season. Plan the adjustments for the new season.
But with all this consideration:
Speed is still your friend in any rating game. You don't want to sail a slow boat, you want just to win races. It's terrible to slow down a ship and not knowing whether it will be of any use next season because they have closed the gap.
However, understanding where advantages can be made to improve the rating is also critically important. For our new 30" racing machine we try to find the parameters, which can be adjusted again without the need of buying a new boat.
More Information: AEOLOS YACHTS www.aeolosyachts.com