Asymmetrics Analysed

Course racing used to be viewed as 90% plus won on upwind, 9% on reaching, and 1% on the downwind. TImes change. Whilst this blog is focussed on fast boat racing, the principles apply equally to every boat being raced out there, so we hope this is a blog for all to gain from.

Not too long ago in a lot of classes crews could be seen visibly relaxing as the kite went up, and the procession began. Happily now in all racing we understand how to make gains and use the downwind to our advantage. Even more so in boats with asymmetric kites, where a small increase in pressure can lead to a few knots additional speed AND an angle advantage of around 30-50 degrees compared to those boats not sailing in pressure. Because the losses and gains in asymmetric kite boats are so much more significant than conventional kites, we have split the blogs so that this asymmetric blog follows the symmetric one of two weeks ago.

In order to understand the effects of pressure on angle, we have to refer to that old favourite of apparent wind. Whilst apparent wind has a big effect on every boat, with an asymmetric kite it has a massive and often race winning effect. The reason for this is that every knot of boat speed you can gain has a positive effect of the air flowing over the sail. Once wind speed is exceeded, the boat sails entirely on her apparent wind. If you stall the boat for any reason, we go more into a conventional sailing mode and have to reestablish airflow, which allows those still sailing on full on apparent wind to gain massively on us. The reasons for stalling can be a rogue wave, a slip or error, or hitting a wind hole. Obviously there are others, but these are the main things to work on.

As with every other form of complex racing technique,rationalising the skills involved and simplifying them are what pays dividends. The asymmetric downwind technique can therefore be thought of in these task forms:

1. Keep the luff just on the point of curling and make sure the luff tell tales are flying
2. Sheet accurately over waves and out of gybes
3. Keep the boat totally flat, fore and aft and side to side
4. Keep the mainsail perfectly trimmed so as not to block airflow or cause oversheeting turbulence.
5. Keep your eyes open for pressure ahead of you (assume you’re going greater than wind speed).
6. Keep your eyes on what the other boats are doing and which is the pressure side of the course.
7. Stay totally smooth in every action, and ANTICIPATE change, don’t wait for it.

There now comes a split of labour. Who does what in the boat? Assuming there’s a two person crew, we can assume that the majority of the downhill sleigh ride the crew will be occupied in keeping that big sail perfectly trimmed – everything else is secondary to that chore. This includes sheeting to waves and out of gybes, where good communication on the turn and intent of the helm is critical to success. Obviously the crew must also balance the boat and be pretty smart out on the wire whilst being perfect with the sheets – not much to ask for, is it?

This leaves the driver to a large extent responsible for trimming the mainsail and boat. The mainsail is relatively easy, light sheet load and airflow is visible through telltales, especially the leech ones. It is however a task that can really be negative to speed if the helm gets it wrong. The interesting thing now is the boat trim. The boat must be flat, maybe loading occasionally a small amount when the helm wants to reach pressure or is slightly fat on the layline. So the combined crew weight to a large extent dictates the angles that a boat will be steered, because in simple terms the boat needs to be flat, and the main weapon once both crew are out on the wire is the tiller. This is a baseline, and the crew must then sheet the kite to the wind angle. The differences in technique between a light crew and a heavy one are therefore quite profound and noticeable, a lighter crew going deeper and usually not as quickly as a heavier crew putting more leverage on the boat.

This profound difference caused by relatively small differences in crew weight should not be ignored, either from a technique development viewpoint or when choosing your crew. It is not so unusual for a 49er/FX to gain five or ten places in one downwind, or indeed to lose them. Weight and style play a significant part in your ability to do this.

So we see that the helm keeps the boat flat simply by steering the boat to be flat when both are wiring. That’s a slight oversimplification as the leverage on the mast can be altered by sail trim, however, that’s the basis of good speed downwind. The next thing to consider is boat trim, fore and aft, which tends to be a joint responsibility, with bow splash being totally visible to the crew without taking their eyes off the critical curl and flow. What tends to happen with the fast guys downwind is that the driver will anchor into the rear straps as soon as its above maybe 12-15 knots, and the crew will trim the boat by moving along the gunwale. This is a really easy technique once mastered, and can have a large effect on the angles a helm can steer the boat at, and certainly is critical to keeping the apparent wind going.

Observation downwind on a fast boat is THE key element to success. If you have the best technique in the world and miss the vital puff of wind, you’re toast. Critical elements of observations are these:

Is the pressure moving fast or slow? If gusts are moving fast across the water you have to look behind you for pressure which will hit you. If it’s moving slow, look in front of the boat because you’ll catch it up. The difference in this is massive, and needs analysing at the prestart.

How big are the gust patches, and what angle are they moving at? To stay in a gust will bring massive rewards, so you should always consider gybing to stay with a big one. Bear in mind that if you gybe too early, or take a big gust down into a corner, you have to be certain that gusts are happening often enough to dig yourself out of that corner!

Where are the other boats looking for pressure? If there is a pressure side then you have to go with them and make the most of what you get. If you go to the low pressure side you are officially “at the casino”, and will probably lose a lot. Weighing up risk is a huge part of the skills of becoming good at downwind tactics.

FInally we come to simple courage. Every fast boat going downwind is at some time on converging courses with another fast boat, equally determined to get to the mark first. The rules should enable a reasonable understanding of how much courage or force of personality is needed on these occasions. However, in practise they don’t, and the number of protests sailors are involved in generally before finding where rules meet common sense is usually high, or the sailors are not confident enough to be hungry. Knowing the rules is a massive part of being fast downwind so you know where and when you can take an assertive position against nearby boats.

In lighter winds the dynamics DO change, but the priorities remain simple. The skills of optimising VMG really count for a lot, so movement in response to any acceleration of wind speed becomes a major success factor. The touchy/feely part of downwind sailing with an asymmetric kite needs a lot of practise, and yes, the gains and losses are often bigger!

At Toplevel sailing we always encourage our athletes to push the boundaries. Sailing an asymmetric kite boat downwind enables this to happen at full chat. It’s fun, its safe (as long as the boundaries are in place), and its profitable. If you have any questions about this blog, please don’t hesitate to contact us, either on Facebook or by email.