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The Lead in Sailmaking: What Is It & Why Is It So Important?

14th January 2020
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Hubo with deck awash in the Fastnet Race Hubo with deck awash in the Fastnet Race

Determining just how much lead is required depends on what type of yacht you have. Here, Barry Hayes from UK Sailmakers Ireland explains what lead is and why it is so important to sailmaking.

In sailmaking terms, the ‘Lead’ is the distance between the sail plan’s Centre of Effort (usually the working sail area which is the main and fore triangle “CE”) and the Centre of Lateral Plane of the hull/foils (CLP). Both the CE and CLP are approximate positions for the centres of pressure for the sail area and the hull underbody, respectively, and are used by yacht designers at the drafting stages to ensure that the keel and rig positions are well balanced. CE is always forward of CLP by a small amount when in equilibrium mode. This is because when the yacht heels, the CLP usually moves forward due to the new heeled hull form until it lies almost under the CE. The result: helm balance.

There is an amount of Lead (pronounced “leed” as opposed to “led”) that is acceptable, but if the design falls outside this area, the boat will have either too much weather helm (‘Lead’ is too short) or too much lee helm (‘Lead’ is too long). Too much weather helm results in drag (and in some cases helm exhaustion) and too much lee helm can result in dangerous situations such as crash gybes or worse, particularly if self-steering or helm issues come into play.

Lead Gfx sailmaking

Determining just how much Lead is required depends on what type of yacht you have. There is a rule of thumb that compares the Lead to the static waterline length. You divide the Lead by the waterline length and the result is ‘Percent of Lead.’ Depending on the methods you are using to work out CLP, the allowable percentage can vary from 4% up to 17% after incorporating a number of factors. Hull shape is a key factor affecting Lead. A wide hull with hard bilges will require more Lead in static mode to compensate for the additional helm generated by the heeled hull shape. A narrow hull needs less Lead. Similarly, a tall rig creates more weather helm than a shorter one so the POL needs adjusting accordingly.

A yacht designer would adjust the lead by either moving the keel fore or aft or moving the CE of the sail plan fore/aft. they would get it perfect on paper (or CAD) so that, when launched, they will know that the boat will be well balanced with no vices from the outset. Interestingly, the reason they look at moving keel first is that this would require a very small change to affect Lead as opposed to moving the rig and resulting sail plan which would require bigger changes to have the same affect. When building a new boat from scratch. Its always best to get extra holes in the keel box so the lead can be easily adjusted.

Mermaid Beneteau 50First 50 Mermaid - well-balanced lead with non-overlapping headsails

If you have a pre-owned yacht that is not well balanced and want to make changes, then the Lead can be corrected simply by adjusting the sail plan, mast rake, sail configuration or set up. Of course, you can also incur the expense of moving the keel, but this is a major refit and should only be looked at once you have looked through all other options above the waterline.

Windsurfers are a good example of how Lead works above the waterline. If you want weather helm, or to go to weather, you tilt mast aft till it is in that upwind groove and going well. When you want to fall off, you tilt the mast forward, thus moving the CE forward until you find yourself going downwind, and again within that sweet groove. Too much tilt aft she tacks; too much forward she gybes. It’s a matter of finding that balance between the direction you are going in relation to the wind.

Waarschip36 Hubo upwindWaarschip 36 Hubo upwind - well-balanced lead

Of course, in most yachts with rudders, the direction the boat will travel is done through steering. If the balance is off, the rudder ends up fighting it and the result is increased drag affecting performance and the loading up of everything attached to the steering such as autopilot and sheaves. How can you change Lead while sailing? You can start by adjusting the shape of the mainsail with halyard or outhaul tension or mast bend. A reef in the main also moves the CE forward thus reducing weather helm. Putting a smaller headsail on will also move CE forward thus reducing helm. Though a reduced main makes a bigger change than does a reduced headsail. It’s all about finding that balance between the two.

If you need your boat assessed or looked at. To get the balance right for you. Then get as much information as possible about the problem and give us a call at UK Sailmakers Ireland. We are happy to help your performance.

uksails topper

About the Loft

UK Sailmakers Ireland brings modern professional sailmaking to Irish Sailing.​ Formerly known as McWilliam Sailmakers; the company was started 47 years ago to bring the latest technology to Irish sailors - we continue this mission today.

Under new leadership in 2018; our loft is dedicated to fulfilling the needs of all Irish sailors. ​As sailmakers, we do not just design sails for boats. We design and build sails for your boat. Our extensive and versatile product line allows us to produce sails to suit your requirements and expectations.   

​As a core loft within the UK Sailmakers Group, we are uniquely placed to draw from a worldwide pool of knowledge and experience - these ties have been recently strengthened with the return of Barry Hayes and Claire Morgan from Hong Kong. ​Barry held a key role in our primary production facility on Hong Kong Island for the past fifteen years. With their return comes a renewed focus on technology R&D on Irish waters.  

​With a wide variety of sailing conditions and an impressive pool of talent, the Irish cruiser racing fleet is the ideal testbed for new technologies.​ 

​As with all things in sailing; the secrets will be closely guarded - but for the first time in decades Irish sailors will be at the forefront of sail technology development.​

Although much has changed; some constants remain. The same great sail and customer service we have provided in the past will continue, as does our commitment and passion for growing the sport of sailing all over the country. 

Barry Hayes [email protected]

Contact Information:

UK Sailmakers Ireland

Hoddersfield Mill

Crosshaven

County Cork

P43 EY26

Republic of Ireland

Tel: +353 21 4831505

Fax: +353 21 4831700

Email: [email protected]

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