Course Setting

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Trapezoid Course
The trapezoid is a recognised method for accommodating two fleets on the same course area at the same time.  Mark layers have for many years laid the course by the daisy chain method, where each mark is laid in turn to a range and bearing form the previous mark.  When resources are more available as is often the case at large events, the marks can be all laid at the same time using the Reference Point system.  The charts required for this are: 

Trapezoid Charts - 60 degree internal angle

Trapezoid Charts - 70 degree internal angle

Fixed-Width Trapezoid Courses
For some classes it is desirable to have a fixed-width trapezoid course.  This is useful for the RS:X Class when the boards sail so deep in planing conditions that the width of the course beyond a certain distance becomes meaningless.  The problem with this is that the both the angle and distance between Mark 4 (the reference point) and Mark 2 increase as the length of the beat increases.  So separate charts are required for this angle and distance.  

In the charts here, designed for RS:X, the length of the reach between Mark 1 and Mark 2 is fixed at 0.5nm and the angle of the trapezoid is 70 degrees:
Fixed-Width Chart - 70 degrees
Angle and distance of Mark 4 from Mark 2 - 70 degrees
Angle and distance of Mark 2 from Mark 4 - 70 degrees 

A fixed width trapezoid may be useful in spinnaker classes with an internal angle of 60 degrees:
Fixed-Width chart - 60 degrees
Angle and distance of Mark 4 from Mark 2 - 60 degrees
Angle and distance of Mark 2 from Mark 4 - 60 degrees

Trapezoid Courses and the RS:X
On a normal trapezoid course it is ISAF policy to set Mark 3 0.05nm (approximately 100m) to windward of the start line.  When planing, boards may come from Mark 3 to cross the start line.  In order to prevent this Mark 4 should be set further to windward.  A spreadsheet has been developed by SolentXtra to calculate the optimum distance for this (essentially Mark 3 should be in line and across the wind from the start line).  Click here to view the app.  This can even be viewed off line on a mobile device.

The RS:X slalom requires a skill that is not found in other areas of conventional race management.  The techniques for laying this are described together with the necessary charts required to complete the process accurately.

RS:X Slalom Course Mark Laying Procedures

RS:X Slalom Course Reference Point Charts

Sailing Wind
When racing in tide the wind seen at the committee boat is not the 'Sailing Wind' but the 'Ground Wind'.  The sailing wind can be calculated and then used as the first guess when setting the start line.

Sailing Wind Chart

Tidal Offsets
When racing in tide, in addition to the sailing wind being influenced by that tide, both the windward mark and the leeward marks also need to be set downtide to allow for the effect of the current on a boat's course over ground.

As a rule of thumb the windward mark, when the wind is 10kts or greater, needs to be placed 15o downtide from the ground wind.  In winds of less than 8kts, 20o or more downtide offset is required.

Windward Mark Offset Chart

Leeward Mark Offset Chart

© SolentXtra 2012