Speed Charts

Information useful to race officials including speed charts, 'sailing wind' angles and offset requirements for marks when working in tide, course setting charts, etc.
 

Available for download are charts (spreadsheets) for Olympic and Youth classes, IRC keel boats (IRC Speed Made Carpets) and Cowes Week White Group keel boats. 

Olympic classes and Youth classes charts are in Excel spread sheet format. The latest Speed Charts are given alongside. You are advised to check these before a major event in case there have been any changes. 

The Youth Charts include the 420, 29er, Feva, Mirror and Spitfire double-handed classes, together with the ILCA 4, 6 and 7 Rigs, Optimist, Topper and Topper 4.2 Classes. The Youth Chart include the Trapezoid course with a committee boat finish (designated as an "IX/OX" course in the Speed Charts).  For this form of course layout, data is given for either a different length of second beat or an additional offset for the leeward gate (class dependent).  Refer to the Speed Charts for more detailed information on these courses and any assumptions made.  As many of these Youth fleets sail on Inland waters in the UK, a Leg Length column in metres (converted from the value in nautical miles) has been added to aid Race Officers when running events on such waters.

Further updates will be posted as more information is obtained or feedback is received from any users.

Bob Milner developed 'Speed Carpets' for IRC rated boats and keel boats that race within White Group at Cowes Week (these include XODs, SB3s, Dragons, Darings, Flying Fifteens, Squibs, Redwings, Mermaids and Sonars). The original charts have been replicated using a Spreadsheet and pdf's produced for each graph. There is also a Time vs Distance chart to determine likely course size for the typical range of VMG's seen by these cruiser/racers. 

 



Speed Chart Links

Adjusting based on Portsmouth Yardstick

The Sheet to generate a chart based upon the PN of a boat with a similar speed uses a Sheet titled PY Adjusted Trial V3.  Changes made compared with the previous version are included in the header sheet.  This spreadsheet is referred to in both the Race Management Guide and the Guidance Note on using Speed Charts.

PY adjusted speed trail 3

Working in Tide

It is well known that the wind a boat sails in is influenced by tide and the resultant 'Sailing Wind' can be calculated accurately.  However, the amount of tide across a leg of a course may vary considerably so the judgement of the race officer is vital.  Sailing Wind produced by tide of 1 or 2 knots at right angles to the Ground Wind (or Gradient Wind) may be downloaded from this page.

Just as the Sailing Wind is influenced by tide, so is the course and speed a boat travels overground.  In order to accommodate this both the windward and leeward marks need to be offset down-tide. The amount of offset varies according to wind speed and cross tide.  Charts showing the offset in uniform tidal conditions when it runs at right angles to the gradient wind, can be downloaded from this page.

Sailing wind   Windward mark offset   Leeward mark offset

Course Setting

This is relatively straight forward for windward/leeward courses and sausage triangles.  When working in tide in a situation where the race officer has only marks enough for one windward mark and a gate at the leeward end, it is impossible to provide a perfect beat and a perfect run on the same course without moving the marks.  An acceptable compromise is to set the course on the 'Sailing Wind'. 

Trapezoid courses offer a greater challenge.  The reference system of laying a trapezoid course was developed at the Olympics in China in 2008.  Having defined the reference point, which is in the middle of the gate at mark 4, mark layers use the tables for the type of course being set (60 or 70 degree trapezoids) and lay each mark in the position shown in the table.  Classical methods should then be used to confirm that the position is correct.  Tables for this system can be downloaded from this page.

Setting Trapezoid courses - reference system

Working in tide and course setting are aspects of race management covered in the Race Management Courses.  Click here to see availability of both RYA Regional and National Courses.