Leeway explained

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Coxing at Scilly and want to helm your gig and crew on the shortest possible course?

Then you need to allow for leeway. And tide.

The Scilly final last year was a textbook example of the effect of leeway. With a strong wind blowing from right to left all the crews where effected.

What is leeway?

Leeway is a sailing term, but applies equally to gigs.

It is: ”the sideways drift of a ship to leeward of the desired course.”

If we take Scillies last year as an example, with a strong wind on the starboard side the boat will have not gone where it was being pointed, instead it will have ‘crabbed’ sideways.

In this image you can see this ‘crabbing’ illustrated, the wind is blowing the boat sideways and the rowers are pulling it forward, the resultant direction of travel (the red arrow) will have been this ‘crabbing’. The stronger the wind the more exaggerated this will be.

Screen Shot 2016-04-15 at 21.24.39 Screen Shot 2016-04-15 at 21.24.53Screen Shot 2016-04-15 at 21.25.05

The diagram on the left of this set may look exaggerated, but for Scilly last year this was not far off what some experienced coxes were doing to compensate for leeway, and as they closed on the finish they reduced the angle of compensation.

To compensate for leeway you need to steer up into the wind in order to stay on the shortest route between the start and the finish. If you’re at the bottom of the line and you have boats upwind of you this might not be an option, but at Scilly last year you will have noticed that experienced coxes at the right end of the line set off at an angle, heading up into the wind and to the right of the finish. Then as they got closer to the quay (see diagram above) they gradually reduced this angle until at the end they were steering straight at the finish line.

Screen Shot 2016-04-15 at 21.39.02

This image above shows a Caradon crew leaving the start. Being at the right end of the line they had the option to come up on the wind. This picture only just shows it but their cox is steering at least 10 degrees to starboard quay in order to compensate for this leeway.

Screen Shot 2016-04-15 at 21.46.48

This next image above shows the end of the ladies final. You can see it looks like they have rowed in from well downwind of the start line, the is because they had been pushed so far downwind in the start of the race.

Screen Shot 2016-04-15 at 21.54.22

This diagram above from the ladies final illustrates this further. You can see why in the photo above it looks like they are rowing in from the islands behind. The two red lines are GPS plots from two crews. The green line is an illustration of what was happening to some of the earlier heats that didn’t compensate at all.

Screen Shot 2016-04-15 at 21.57.22

The diagram above then shows the same plot from last year but with a gig laid over the top, showing  ‘very roughly’ what direction the gig would have to have been pointing at each stage of the race in order to stay on the ‘direct course’.

Staying ‘exactly’ on the direct course, or a straight line between the start and the finish, is impossible. But you still need to try and estimate how much you adjust your course. The better this is done by the cox, the less distance you will have to row. Some crews last year ended up rowing 10-20% further in the final (the green line) than they needed to.

The amount you adjust your course for leeway depends on three factors. One is the wind strength, two is the sea state and three is the distance of the race. The longer the race and the stronger the wind and sea state the more you have to allow.

If you want to understand more about how you allow for this in sailing, here is a good series of videos.

Now to complicate things even more, you also need to allow for tide. This year for example in the men’s vets race ,the tide will be running left to right, but it won’t be very strong. So if space allows coxes will need to head slightly to the left, towards the tide (assuming no wind) to adjust for this.

Estimating the balancing effect between tide and wind is then a real art in gig racing; sometimes they can cancel each other out and sometimes they can work together – that’s where a cox’s experience and knowledge comes in.

But don’t forget this is not an excuse for breaking the racing rules, weaving or hitting other boats.

Hopefully you have found this article useful. Good luck in Scillies.


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