Navigation briefing Using pre-race postponement wisely
on USING PRE-RACE POSTPONEMENT TIME WISELY
How many times last season did you sit around waiting for the breeze to fill in? Staying both chilled out and ready like a coiled spring if the wind should fill in is the challenge. If you have five knots of wind you can always do some light winds training.
This is one little trick you can do to improve your starting while waiting for the AP flag to be lowered – and you can even do it under engine. You just need the help of a coach boat or a friend in a RIB. Nominate any buoy as your pin end and set up quite a long start line with the Rib/coach boat as your committee vessel. Get one of your crew to jump into the RIB to video your ‘start’ on a smartphone.
Then sail normally or motor at, say, seven knots as if approaching the start line on starboard tack halfway along the line. Ask each crew to put their hand smartly in the air when they think your bow crosses the line. Then watch the video replay as a crew (ideally on a bigger screen such as an ipad or laptop).
Initially you’ll be amazed at the differing opinions of when your bow broke the start line. The first time I did this, the results from some crew members were shockingly bad, but it was fun and livened up the postponement as well as being a great learning aid.
Repeat the above, again starting in the middle of the line – the results should improve with practice. Then try it near the committee boat end, they should improve again. Finally let the crew get a glimpse of a transit (if available) looking down the line and the result should be a quantum improvement. Are particular crew members consistently early or late in their estimations? This is a great way to get value out of 20 minutes waiting for the wind to fill in.
Calibrations
Waiting for the wind can also be a good time to check instrument calibration. Zero wind means you can’t check wind angles, but it is useful for boat speed and compass calibrations.
These two readings are the basic foundation blocks for all yacht instrument calibration and getting them accurate is best done in flat water and little wind. It is surprising how many boat instrument systems are not calibrated.
Calibrating boat speed is usually found under ‘settings/calibrate/boat speed’ in the menu of your yacht instrument system. One of the best and easiest ways to measure an accurate mile is to utilise GPS and a chartplotter. On your plotter add ‘grid lines’ in the overlay menu (this shows lines of lat/long that scale according to the range on the chart you are using).
Find a mile of clear water in a line north/ south (this can also be done for half a mile). Then head north or south at a fixed rpm (eg seven knots) and press ‘start cal’ as you pass a minute of latitude, then ‘stop’ as you pass the next minute of latitude, which is of course exactly one nautical mile. For accuracy, a good tip is to zoom in on the chartplotter close to the grid line each time.
At the end of the run go about 150m on before turning, to ensure you are properly up to speed by the time you pass the grid line for the second run. At least two runs are needed to neutralise any current/tide. The whole thing should take about 20 minutes.
Most electronic compasses are calibrated with a turn of between 360° and 720° in one direction, at about three knots of boat speed. The bow must keep turning throughout for it to work – usually at 3° per second. This sounds slow but is 90° in 30 seconds. A common error can be to turn too slowly, but the compass calibration will tell you if you succeed straight away. This should take less than ten minutes.
Next, compare your electronic and conventional compasses against one another, and cross-check them with your hand bearing compass. To do this, ask the helmsman to steer a straight course to a distant object that is recognisable on the chart (eg a church spire). Compare all three readouts with the bearing of the landmark from the chart and note down discrepancies (make a table in your note book).
Then carry out the same procedure, ideally at 45° sectors, using points on the chart. This will give you good confidence in your equipment, help calibration and even allow you to draw up a basic deviation card for the liquid compass. Just make sure no one has left a mobile phone in the pocket next to the compass!
Wind angle corrections should be done prior to the first start of each day of racing and can be fitted into the time when the rig and sails are being set up. My preferred way of doing this is using wind data graphs, which makes it easy to visually pick matching data, comparing port and starboard tack. If the difference is 10° high or broader on port tack then you need to add half this figure in the calibration table to correct the misalignment.
Wind angle calibration is a necessary evil that needs attention on most days and for each five knot band of wind for upwind, reaching and downwind. But it should only take about ten minutes each day.
Finally, if the wind hasn’t yet filled in, this is a steering drill you can do using two marks quite close together, say 60m apart. Nominate a windward and a leeward mark, then practise your approach paths under engine as if there is 5, 10 and 20 knots of wind. Ideally get the exercise videoed. This time get the tactician to debrief after each circuit and then do a video debrief after you have done about four laps. Doing the same exercises in a tidal stream makes it more challenging and is a great steering exercise for the helmsman.