Expert advice: asymmetric dinghies

Paul Brotherton advises a madforsailing reader about making the switch from conventional boats

Sunday January 20th 2002, Author: Paul Brotherton, Location: United Kingdom
49er I'm making the switch from sailing dinghies with symmetrical spinnakers to asymmetric gennakers. What advice have you got for how to sail these types of boat?

Let's break this topic down into a number of specific components. One of the most significant changes you will find is that the new breed of asymmetric boats rely much more on apparent wind for their speed.

Apparent wind sailing
The important thing to understand with asymmetric rigs is when you are being blown along by the wind and when you are sailing under apparent wind. The crossover is quite stark, and calls for different techniques. One of the best ways to tell whether you are apparent wind sailing or being blown by the real wind is to pull the mainsail in. If there is an immediate and large effect, then you are apparent wind sailing. If not, then you are being blown by the breeze.

In something like an RS400 you are being blown along by the breeze up to about 10 or 12 knots of true wind. This means that if you are on a run, you want to aim deep downwind with the bowsprit well pulled back [the RS400 has a swinging bowsprit], as heading up will not give you enough extra speed to justify the extra distance you will sail.

This situation changes dramatically at 10 or 12 knots however, in so-called marginal planing conditions. At this point, it can pay to luff up 10 or 20 degrees towards the wind to promote planing. Once you get your boat on the plane, the extra speed you gain more than makes up for the extra distance you are sailing now. This is true on most planing dinghies, but more so with asymmetric spinnakers because the added apparent wind is so great. In fact, on lightweight planing skiffs like the 49er or RS800 you can end up sailing faster AND deeper by first aiming up for extra speed, than if you just pointed your boat downwind all the time.

Look around you in a race and you will see that there are many different angles and techniques for getting downwind at almost exactly the same speed. Some techniques are more appropriate than others at different points in a race, depending on the tactical situation you are in. It pays to experiment and try lots of different ways of sailing downwind, because there is often no single right answer. Get comfortable with sailing high and fast and low and slow because they are both important skills to have in your armoury.

Trimming the gennaker
Trimming the gennaker is very straightforward compared with a conventional spinnaker. Most boats have a bowsprit that once launched is fixed directly down the centreline of the boat. This means the only trimming sheet is the spinnaker sheet (no guy to worry about). Ease the gennaker with about six inches to a foot of curl on the luff. Generally having the gennaker pulled on any more than that causes too much lee helm on the rudder (the helmsman will normally keep you well informed of this fact!).

With a boat like the RS400 which has its 'wing-wang' controls for adjusting the side-to-side angle of the bowsprit, the general rule of thumb is to pull the pole as far to windward as possible for running deep in non-planing conditions, and to leave it set on the centreline for reaching in any conditions or for running in high-wind, fast-planing conditions. As always, there is no clear cut point when you should switch from one style of sailing to the other, so look around you so see who is going fast and how they've got their bowsprit set.

RMW Marine 18 ft Skiff

Steering downwind
The other thing to remember with asymmetric sailing is the importance of the mainsail to balance the feel in the rudder. You want to aim for a neutral feel in the tiller to reduce the braking component in the rudder. If you find yourself having to push the rudder to maintain a straight course, pull the mainsail in. If you are having to pull the rudder, then ease it out. In fact when you get used to the effect of the mainsail on the rudder you can actually start to steer the boat with the trim of the mainsail rather than moving the rudder, which always slows you down every time you use it.

Gybing
One of the commonest mistakes for people switching to asymmetric gennaker boats is for the helm to steer the boat too hard through the gybe. Because modern asymmetric boats tend to move more quickly, less rudder movement is required for the turn. Also, the boom tends to slam less from one side to the other because your apparent wind reduces the effect of the true wind coming from behind you. The boat needs less forcing around from one gybe to another compared with a conventional boat, so you need to tone down your movements accordingly. In light winds you can afford to apply some roll to the gybe in the way that you might do in a conventional dinghy. But in moderate winds or above, aim to gybe the boat as flat as possible all the way through the manoeuvre.

As for gybing the gennaker, the simplest method is this. As you enter the gybe, the crew should ease the sheet to keep the gennaker at optimum trim for as long as possible. Then, as you move to the centre of the boat as the boom begins to swing across, snap the gennaker sheet on with a quick tug of the old sheet. At this point you should let go of the old sheet and pick up the new one. Having given a sharp snap of the old sheet, you should find that the clew of the gennaker is backed against the jib. As the helm steers the boat up on to its new heading and you both move onto the new sidedeck, pull the new gennaker sheet on and you should find that the gennaker blows through and immediately sets on the new gybe.

The thing to note here is that you always have one sheet or the other under tension at all times. If you leave too much time between releasing one sheet and pulling on the new one, you are in danger of letting the gennaker twist itself into an 'hourglass'. So the key here is to immediately apply tension to the new sheet as soon as you have let go of the old one.

Keep it smooth
Sailing asymmetric dinghies is relatively simple compared with conventional ones. The key with fast boats is to keep them moving quickly as much of the time as possible. Like bicycles they are much more stable at speed.

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