Ireland's sailing, boating & maritime magazine

The IRC New Flying Headsail: What's the Buzz?

14th January 2021
A UK Sailmakers Flying Headsail A UK Sailmakers Flying Headsail Credit: UK Sails

Barry Hayes of UK Sailmakers Ireland (in conjunction with Jenny Howells of the RORC Rating Office) explains the main difference between a flying Jib and an IRC flying headsail 

The main difference between a flying Jib and an IRC flying headsail is the flying Jib is non-overlapping and measures in as a headsail (Headsail Area HSA). The flying headsail (flying sail area FSA) is a small, flat and overlapping code zero which is a new sail type in IRC. 

The flying headsail is a code zero development and has very little to do with a headsail as it's measured as a spinnaker/genoa. As big boats and double handed boats developed their offshore sails over the past few years, particularly now that there are more foiling boats, a hybrid sail was developed with the code zero as the starting point. The new sail measures somewhere between a code zero and a genoa. This sail didn't fit in any rating rule and was rated as a headsail if under 75% mid girth so was heavily penalised. IRC now has moved to include it in their measurement rule. So boats can use the sail offshore and have it rated.

Flying headsail

You can see from the above photo the size of the sail in basic area.

The flying headsail is flatter than a code zero, more or less the shape of an overlapping genoa 1. The sail has a positive roach and the luff also projects forward a little off the straight line, but the clew is below the boom level. When you're reaching, you can ease the boom down without it running into the flying headsail sheet. It's normally sheeted behind the keel, but not on the stern of the boat. Normally, the best spot is next to the genoa winch. It must be tacked forward of the forestay and it's always a top-down furling sail as you need to furl the roach away and get a tight furl. It's also normally left on the bowsprit furled up so it need a clew strop and Velcro clew patch to keep it furled.

The measurement rule for the sail is complex. This adds a lot of new measurements to the IRC rule. Below you can see the different measurements needed to calculate the area of the sail. You need to measure it both as a genoa to determine area and as a spinnaker to determine the mid girth ratio, under the rule so the measurements are clear to IRC and they will know how the sail is set. Notably, the sail is set forward of the forestay, it's overlapping the rig, and has between 62.5 and 74.9% mid girth.

Flying Headsails
Headsails and Flying Headsails

21.7.1 Headsail area (HSA & FSA) shall be calculated from:

  • HSA = 0.0625*HLU*(4*HLP + 6*HHW + 3*HTW + 2*HUW + 0.09)
  • FSA = 0.0625*FLU*(4*FLP + 6*FHW + 3*FTW + 2*FUW + 0.09)

The sail is mainly used between 65 and 125 degrees AWA, so it doesn't go upwind or downwind. It is mainly used for reaching. Moreover, it's excellent on foiling boats with reaching struts or whisker poles who can sheet the sail outboard away from the mainsail. This really opens the slot between the main and the flying headsail. As the boat speed increases, this sail just gets faster and faster as your AWA comes forward. Like a blast reaching genoa in old money.

For most IRC racing boats, this sail is a considerable rating hit and would not give you bang for your buck. The points increase would not be worth it. If you're foiling, sail in a lot of apparent wind or have reaching struts, however, then this sail is worth it as it overlaps the rig and is only slightly smaller than your code zero. So, for boats like Fast 40s and Open 40s, it's an excellent option because they can get their AWA forward quickly and build on that with this sail.

For most IRC boats the flying jib (non-overlapping) is still the best option as it's the same size as your headsail and can be flown off the bowsprit. It's still "free" on IRC and can give you an extra knot plus upwind or reaching. The flying jib is still the way to go for most IRC boats being flat, easy to furl and you can leave it on the bowsprit.

In this photo, you can see the shape difference in the three sails: flying jib, flying headsail, and code zero. You also can see how flat the flying headsail is compared to the code zero. This flat sail would not give most IRC cruiser racers the power needed working upwind in light air which the code zero totally does. Also, the same applies to the flying Jib. It's a lot flatter and doesn't overpower the boat upwind over 10 kts., allowing you to sail at high angles.

Flying headsail Shape shotFlying headsail Shape shot

In conclusion, if you're racing ISORA or in the bay, stick with your IRC flying Jib and code zero. But if you're a fast or foiling boat, or perhaps doing a long offshore race including a lot of reaching, the flying headsail is probably worth the money!

IRC rules 2021 and related advice is here

UK Sails Summer

About the Loft

UK Sailmakers Ireland brings modern professional sailmaking to Irish Sailing.​ Formerly known as McWilliam Sailmakers; the company was started 50 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

Contact Information:

UK Sailmakers Ireland

Kilnagary Business Park


County Cork

P43 YR22

Republic of Ireland

Tel: +353 21 4831505

Production: +353 (86) 198 0199


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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