IRC time versus distance handicap correction

Time handicap correction
Lets consider two sailing boats A and B. We assume that they both sail at the same speed of 6 knots.
Under IRC A rates better (0.900) then B (1.100). The race course is 10nm, the results will look like this:
A elapsed time is 10 / 6 * 3600 = 6000 seconds * 0.900 = 5400 seconds corrected
B elapsed time is 10/6 * 3600 = 6000 seconds * 1.100 = 6600 seconds corrected
A wins over B as expected.

Distance handicap correction (Flexboy)
A and B sail now a Flex race. A is set to sail 0.900 * 10 Nm = 9 Nm, B is set to sail 1.100 * 10 Nm = 11 nm.
A elapsed time is 9 Nm / 6 Knots * 3600 = 5400 seconds.
B elapsed time is 11 Nm / 6 Knots * 3600 = 6600 seconds.
Again A wins and we herewith prove that distance correction is equivalent to time correction using TCC in both case as correction factor.

Flexboy has the advantage of having all the boats sailing at the same time on the race course and makes the racing more interesting as all finish together at the same time. Flexboy has the disadvantage of a less accurate mark rounding. Experience shows that the differences between boats is 20 to 50 meters navigational error arround Flexboy.
The position of all the marks on the Flex course must also be as precise as possible, the accuracy of the geographical position of the marks must be in the same order as the precision of time calculation meaning a precision of at least 1 in 3600 or half a meter over one nautical mile. 

Marc Brugger
ADCA Racing Secretary
Abu Dhabi, 17 February 2014

Race 07, 15 February 2014

Race 07 was a flex race with course EPMg - FD2 - Flexnorth then back.  Winds at start where very light from NW making for a beat up to FD2 then a reach to full North to Flexnorth.  After rounding Flexnorth a tight spinnaker run brought the fleet back to FD2 and then bearing away to EPMg.  Idefix had great speed up to Flexnorth but then on the run  back at to work very hard to keep Mistress at bay.  Experience shows that the best way to round a flex mark is to make two 90 degree turns rather then one 180.

Here is a plot if Idefix V:

Seven boats started and here are the results :

Race 07    Yachts at start: 7
001  01:36:42  005802 * 1.000 =  005802    IdefixV
002  01:40:08  006008 * 1.000 =  006008    Mistress
003  01:55:23  006923 * 1.000 =  006923    Unwind
004  02:06:38  007598 * 1.000 =  007598    FLOOSIE
005  02:22:35  008555 * 1.000 =  008555    Saeeda
006  03:00:23  010823 * 1.000 =  010823    KOSAVA
007  03:10:22  011422 * 1.000 =  011422    BarometerSoup

Race 06, 25 January 2014

Race 06 was quite a long race with the following course: EPMg - FD2 - gate - ADDelta and then back.  gate (FLEX deltaW) was set at mid course in order to able a short course for the less then 0.900 at their discretion.  Winds were light from the west enabling a reaching start then reach up to FD2 and gate, after gate the wind slowly shifted to north and made for a beat up to ADDelta in very light conditions.  The return after ADDelta was running with spinnaker which made for a great sail as the wind increased from the North.

Here are the results with 6  boats at the start, Mistress sailed very well and won:

Race 06    Yachts at start: 6
001  05:31:17  019877 * 0.958 =  019042    Mistress
002  05:00:41  018041 * 1.079 =  019466    IdefixV
003  05:32:08  019928 * 1.021 =  020346    Unwind
004  06:14:53  022493 * 0.968 =  021773    FLOOSIE
005  09:32:24  034344 * 0.821 =  028196    KOSAVA
006  10:11:20  036680 * 0.863 =  031654    BarometerSoup