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Performance Genoa Trimming

Roger Cerrato of Banks Sails UK and Chris Williams of Banks Sails USA take you to the front of the pack with their tips on trimming your sails for optimum race performance.

Introduction

So you have been invited to sail on the fastest boat at the club and want some tips on trimming the genoa super fast. If you have ever wondered how to get the very best performance from your genoa, this article will show you the trimming techniques you need to take you to the front of the fleet.

A good genoa trimmer needs to tune the headsails taking into account five main variables. These are the boat type, trimming adjustments, the windspeed verses the sail's range, tactical situation, and the weather condition at hand.

We will find out more about each of these (and more) over the next few pages. Remember that the size of adjustments suggested in the article with reference to genoa lead position etc. are based on a boat of around 40 feet and should be modified to suit the size of boat you sail.

Boat type

Every boat is different and therefore they all require slight differences in sail trim techniques. The first factor to establish is what type of boat you are sailing: is it an average, moderate or high-performance yacht?

A high-performance sailboat will sail with a much tighter slot than a heavier cruiser/racer. This is because a boat such as an ILC 46 has a much more easily driven hull than, say, a Jeanneau Sunfast 40. The more refined designs do not need as much power to keep them at speed and will therefore sail with different settings. The high performance racing boat will need tighter headstay tension to enable the genoa to trim closer to the mainsail. Secondly the genoa lead will need to be slightly farther aft than for a cruiser. This allows you to trim the headsail up against the lower shrouds and lets the middle of the sail fly closer to the mainsail before the top spreader hits the sail. When sailing most high-performance racers in over 7-8 knots of true wind speed, you should be able to trim the genoa tightly against the top spreader.

Cruisers should sail with the genoa leads farther forward, less headstay tension and less sheet tension. This allows for more air to flow through the slot and creates a more powerful relationship between the mainsail and the genoa.

When sailing a moderate performance yacht such as an IMX 38, you can carefully sail with the genoa tight against the spreaders but must be ready to ease the sail if the speed shows any signs of dropping. After you ease the sail and the speed builds, you can trim it in again slowly. Usually you only need to ease the sail a few inches.

Headstay and halyard tensions

To get the most accurate performance from your headsails you must make all adjustments in the proper order.

First you need to sheet in the headsail to its maximum trim for the conditions. After trimming in the genoa you must set the proper headstay tension. If the headstay is too loose or tight you will not be able to adjust the halyard tension or the leads correctly. Headstay tension is controlled by the backstay on masthead rigs, the runners on modern fractional rigs, and the shroud and backstay tension on fractional rigs with sweptback spreaders.

Remember: if it is choppy or if the breeze is light you will have to sail with a much looser sheet, headstay and halyard.

The headstay tension controls both the draft position and the depth of the sail. A loose headstay will make the sail deeper and more draft forward, therefore your halyard tension must be looser or your draft will be too far forward. Conversely, if you are sailing with a tight headstay, say in flat water at the top of the sail's range, you will want a tight halyard. The tight headstay will flatten the sail and move the draft aft slightly but a tight halyard will move the draft near its designed position.

After you are comfortable with the headstay and halyard adjustments, you must attend to your lead positions.

Genoa lead positions

The best way to adjust your lead position is to bear off slightly and watch for the leeward tell tales to break. This is because the airflow on the lee side of the genoa is much more volatile than the weather side. When your helmsman bears off he or she will cause the flow to detach quickly on the lee side of the sail. If the leads are correct then the tell-tails will drop at the same time. If the top tell tale drops first then your lead needs to move aft, whereas if the bottom tell tale stalls first then your lead needs to move forward. This is the opposite of the traditional heading-up method but is much more accurate.

It sometimes helps to have the bowman watch the top tell tale and call as it breaks. This will help you get a much more accurate setting.

These adjustments are all very delicate and should be made gradually as the wind increases or dies.

Genoa's wind range

As the wind changes, so must the way you trim your sails. At the bottom of a genoa's wind range you must sail with the backstay a little looser than usual for a given windspeed. Sailing with the looser headstay will require you to also ease halyard tension to keep the draft from moving too far forward. If your leads are easily adjustable you may need to move them forward slightly to help make the sail more powerful for sailing with a loose sheet. As the windspeed increases you must first add headstay tension, and when you tighten your headstay you must also tighten your halyard.

Once at the top of the Heavy No.1's wind range the boat may start to heel over too much, causing leeway which will not help you be first to the windward mark! Pull the backstay (or runner) on harder and add more halyard tension and sheet. Move the genoa cars aft, flattening the bottom of the sail while allowing the top to twist off.

Trimming the No. 3

When sailing with the No.3 your primary adjustment will be the backstay (or runner). Most of the time you will be on the rail and therefore not in a position to adjust sheet tension easily or quickly. And on most boats the No.3's cars are not easily adjusted.

If you need power, ease the backstay (or runner) and the halyard. If the boat is still under powered you will need to switch back to the Heavy or the No.2 if you have one. It is always better to sail a boat overpowered rather than under powered. When at the top of the No.3's range you can ease the cars back and tighten both the backstay (or runner) and the halyard. A neutral trimming setting will have all of the battens pointing parallel to the centerline of the boat. Once overpowered it becomes the mainsail trimmer's responsibility to keep the boat on its feet as much as he or she can by dropping the traveller and depowering the main as much as possible. If it gets too windy, switch to the No.4!

Tactical situations

Now we will discuss some special circumstances and conditions that a genoa trimmer needs to be aware of for better trim. These are: starting, tacking, working up the beat, sailing with wind shear, waves, and different air densities. Any time you are starting, trying to hold a lane, or even tacking a boat, there are tactical problems that must be addressed.

In a racing situation you will need to switch back and forth between many different modes of sailing. When switching modes, you are said to be "changing gears." If you are fortunate enough to be starting with a large hole to leeward, the trimmer must keep the boat powered up by having a loose headstay, halyard, sheet, and the leads forward 2-3 inches. If at the start there is a boat just to leeward you will have to sail in pinch mode until the tactician can find a lane with clear air. When racing in pinch mode the genoa leads need to be 1-2 inches aft of their neutral position; the halyard loose; the sheet hard; and the backstay (or runner) tight. Do not tighten either the backstay (or runner) or the sheet too much in lumpy or very light conditions or the boat will stop. While you are holding the lane, it is very important to talk to the helmsman and keep him from sailing down into the leeward boat's bad air. Remember that the other boat will usually be trying to pinch you off so she will be clear to tack at will.

The open course

After clearing the starting line and establishing a lane you will need to trim the genoa for speed. Time on the boat and good instrumentation will help you determine how to set up your genoa for best VMG. Good communication with the helmsman is again critical as he will be able to "feel" when the boat is in the groove.

Laylines require a much different setting than the normal upwind modes. When on the layline on the first beat, there is always that large clump of boats reaching the mark around the same time. Here you need to trim with the same settings that are used during a start with a boat to leeward. If, on the other hand, your tactician has over-stood the weather mark, put the leads forward, ease the sheet and loosen the backstay (or runner). This will help you to roll any boats to leeward.

Mark roundings

There are certain techniques that need to be applied while tacking and rounding marks. At every mark rounding in today's windward-leeward courses you will have your genoa up and will need to help the helmsman round the mark. When rounding the weather mark, keep the sheet tight while the boat is beginning the initial bear-off to the leeward mark, provided the boat is not overpowered! After the boat bears off 20-30 degrees, quickly ease the sheet out by a few feet. This helps the helmsman bear away and lets the spinnaker get around the lifelines easier.

It is really important to get the genoa down to let the kite fill. It can be worth dropping the genoa halyard for the pitman so he can concentrate on getting the spinnaker up and flying and adjust the pole height. When at the leeward mark, do not trim the genoa in too tight. Having the main trimmed in before the genoa will help the boat to turn towards the wind, minimise rudder drag and help keep your boat speed up.

Tacking

When tacking the most common mistake made is releasing the genoa too quickly. The trimmer must let the sail backwind and then quickly get the sheet off the winch. By backing the sail it will blow across the mast and shrouds easily, making the grinder a very happy person. If you have easily adjustable leads it can be worth pulling them forward a few inches before the tack. This will allow for the sail to be eased for power out of the tack without spilling wind from the head of the sail. While the genoa comes in try to ease the cars aft slowly.

Wind shear

Every time you are sailing there is wind shear. It is very important to know the differences between the two types of wind shear.

The first kind of wind shear is differential velocity shear. While sitting still, there will be no difference in direction between the upper breeze and the lower breeze. While you are sailing at an angle through the breeze, the wind that is moving faster at the top of your rig will create a lift near the masthead. You must compensate for this by moving the leads aft 2-3 inches. The larger the boat you are sailing the more noticeable this shear will become. It is also important to know this shear will not vary from tack to tack. The second shear is twisted shear. This shear is caused by the wind coming from two slightly different directions from the boom height to the masthead. Twisted shear is easy to recognise because apparent wind angles will vary from tack to tack.

Here you will sail with one lead further forward than the other to keep your sail breaking evenly. The tack that has the car slightly farther aft will always be a little faster than the other tack. The closer you sail to the poles (North or South) the more often you will sail in sheared wind.

Air density

Often the breeze will vary in density. Air density differences are caused by colder air temperatures, fog, mist or very humid conditions. When sailing in these dense conditions the wind will lose its attached flow quicker and will not regain it as rapidly. Here you need to sail with much cleaner lanes and a slightly larger slot between the mainsail and the genoa.

Waves

The final consideration while trimming the genoa is waves. Often large waves will not affect your settings greatly, but you need to play the sheet while going up and down the waves. As the boat starts working its way up the wave, give the sheet a little ease. Once over the swell, trim in tight and let the boat ride down the backside of the wave. Obviously this is not practical in a 30 footer were it will be more important to get your weight out!

If there are short choppy waves you will need to move the leads forward 2-4 inches and ease the backstay (or runner) and sheet tension. Waves will usually be into the waves or more broadside on one tack than the other tack. When this occurs you need the leads further forward with the backstay (or runner)and sheets eased more on the tack sailing into the waves. This tack will be slower than the tack with the waves broadside.

A final word...

All of the adjustments we have reviewed are very fine and there is no substitute for experience. Good trimming requires constant concentration and the best way to prolong your attention span is to get as much sleep as possible the night before a race!

This article was originally written by Chris Williams, sail designer with Banks Sails USA; and has been modified by Roger Cerrato at Banks Sails in the UK. © Banks Sails 2000.

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