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Reducing Headsail Area to Improve Your IRC

1st February 2023
Salona 45 – Tom Roche with his XD Carbon Main and Headsail in perfect balance upwind
Salona 45 – Tom Roche with his XD Carbon Main and Headsail in perfect balance upwind

When it comes to reducing the area of your headsail (HSA) as a way to improve your IRC rating, Barry Hayes from UK Sailmakers Ireland has the low down. you’ll learn how complicated while also straightforward the process can be and different approaches to achieve the same objective. Here’s what Barry shared:

I know everyone wants the lowest rating possible for their boat and I often get asked if shortening headsail luff a little can I bring down my rating. Basically, the answer is yes; almost any reduction in sail area, if done in the right places, will lower your rating. However, there is a fine line between the net gain of a lower rating vs losing power. This can be tricky business; let me explain why.

Most owners want to optimise their boat’s rating to suit the conditions they most regularly sail. Consider this example: a boat is fully powered up at nine knots and at its optimum healing angle, given the conditions and the amount of crew they have. If the owner still feels the boat has too much power despite being already maxed out on the backstay, by reducing the righting moment in the sails, and eliminating that unnecessary power may make the boat perform better and hopefully result in a lower rating. If this is the case, then reducing the headsail area is a viable option, but be careful this reduction in ( HSA )won’t change where the lead is set on the boat when sailing

IRC Genoa – XD Silver sails fully powered upIRC Genoa – XD Silver sails fully powered up

There are three main ways to reduce your HSA on IRC: 1) reducing the luff length, 2) reducing the LP, and. 3) hollowing the leech. Each has its pros and cons.

1) Making the luff shorter. This has a significant effect on reducing your rating but actually may increase your HSA. That may sound counter-intuitive, but if the luff is shorter, all the girth measurement points move further down the sail, so you may lose real headsail area, but it will increase your IRC HSA. In this example below, you can see how reducing the luff length will move the girths down the sail and the sail, but it will be larger in area when measured in IRC.

reduced leech

2) Reducing the LP. This will bring your rating down, but it will also greatly affect the shape of the sail as you are cutting/changing the leading-edge camber. This rarely works well as it totally changes the sail’s shape and aerodynamic design.

reduced LP

3) Hollowing the leech of the sail. This will reduce the area in terms of IRC measurements. While this process will take actual area out of the sail, usually it’s only a small amount, normally about a square meter or so, depending on the size of the sail. For most boats, that is all you need for IRC, and it won’t affect the sail shape. It’s also normally the cheapest options as well, given the amount of work needed in the other two options.

hollow leech

Oyster 575 Lisanne – Fully powered up. With her XD Endure sailsOyster 575 Lisanne – Fully powered up. With her XD Endure sails

Here is an example of a genoa being recut :

Historically, when your sail is new, it will shrink a little, but today this effect is greatly reduced with new sail technology. The amount of shrinkage is tiny, but it is worth getting your sail re-measured for IRC a year after first use.

An even better option than the three I reviewed is to get a new headsail designed to the specific HSA you desire. I’m not saying that so much as a sailmaker, but a new sail that is designed and built to a desired size will deliver better performance than an older sail that has been recut. And, given you may need to sail with less crew with the reduced HSA, you can see the effect of this on Formula 28 ANIMAL IRL 6563. We worked with ANIMAL’s owner and reduced his HSA and increase his SPA, He reduced unneeded power he had upwind, and optimised his rating downwind.

IRC Genoa UpwindIRC Genoa upwind

In contrast, if you need more power because your headsail area is too small and you don’t want a new headsail, try sailing with less crew as a means to balance the boat to the optimum power and weight ratio for the conditions at which you have your rating set.

Let me close by answering your email question before you ask it; the effect of the recut on your headsail changes I’ve discussed here will be the same on non-overlapping headsails as well before you even send the e mail. ;0)

If you’re thinking about optimising your boat for the coming season, give us a call, and we can help you get the best out of your rating.

Yachts racing upwind at KinsaleYachts racing upwind at Kinsale in County Cork


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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


County Cork

P43 EY26

Republic of Ireland

Tel: +353 21 4831505

Fax: +353 21 4831700

Email: [email protected]

Barry Hayes

About The Author

Barry Hayes

Email The Author

Barry Hayes, Director of UK Sails Ireland, managed the main UK Production facility for UK Sails in Hong Kong until last October and has been a sail designer with UK sails for over 15 years.

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