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Racing Flying Sails

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The colored lines show the relative sizes of the three different reaching sail options available due to recent changes in racing rules.

Until recently, there were only two types of reaching sails. Headsails and spinnakers. A headsail was defined by the rules as having its mid-girth measurement <75% of the foot length. A spinnaker was defined as a sail whose mid-girth measurement was ≥75% of the foot length. In 2018, the sail design landscape radically changed when the ORR handicap rule created a class of sails called “Large Roach Headsails” or “Tweeners,” sails that have mid-girths between 50-75% of foot length. Recently, the ORC and IRC rating rules followed suit to rate these sails that they refer to as Flying Headsails, however, the IRC rule is slightly different in that a Flying headsail is a sail with a mid-girth between 62.5% -75% of foot length.

For yachts with overlapping genoas, the reaching performance gap between a genoa and a flat spinnaker is pretty narrow. But over the years, yacht design changed from masthead rigs with overlapping genoas to fractional rigs with smaller genoas and then finally to fractional rigs with non-overlapping jibs. The changes were driven by more efficient yacht design plus advantages under the rating rules. While yachts with non-overlapping jibs have rated favorably on windward-leeward racecourses, when these boats went distance racing, they sorely missed having an overlapping genoa for tight reaching.

Now there are several options for filling that reaching performance gap on boats with non-overlapping jibs. The three options are the flying jib (a jib topsail flown in front of the headstay), the newly defined flying headsail, and the code zero. The main difference between a flying jib and a flying headsail is the flying jib is non-overlapping and is no bigger than the boat’s largest-rated headsail. The flying headsail is slightly larger, jib/genoa whose mid girth fits within the required rules. The new sail measures somewhere between a code zero and a headsail. Currently, all major rating rules, including IRC, ORC, ORR, and PHRF, allow and rate these sails, with a slightly different interpretation.

The polar diagram to the right shows the Large Roach Headsail (purple line) fills a gap on some boats between jib and spinnaker at close-reaching angles. In this sample, the LRH provides the fastest solution between 65 and 90 degrees true wind angle. Click on the image to see it at full size.

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Computer image comparing the relative sizes of a flying jib, flying headsail and code zero.
2018 ORR LRH Polar Diagram
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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 cruiser racers the power needed working upwind in light air which the code zero 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.
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The flying headsail is flatter than a code zero – more-or-less the shape of a headsail. The sail has a positive roach. The clew is below the boom level. It’s normally sheeted behind the keel; in most cases, the best spot to sheet it is forward of the genoa winch. It must be tacked forward of the forestay. We recommend a top-down furling system as you need to furl the roach away and get a tight furl. Allowing it to be left on the bowsprit furled making changing from flying sail to standard headsail very easy and quick.

The measurement rule for the flying sail is complex. This adds new measurements to the IRC and ORC measurement rules. Below you can see the different measurements needed to calculate the area of the sail. You need to measure it both as a headsail to determine area and as a spinnaker to determine the mid-girth ratio. Under IRC and ORC, flying headsails must be set forward of the forestay, and their mid-girth needs to be 62.5% and 74.9% of the foot length. Under ORR, these sails just need to have a mid-girth >50% and <75% of the foot length.

Your local UK Sailmakers loft will determine what mid-girth flying headsail will work for your boat. Your Sailmaker can suggest the proper sized sail based on what races you’ll be doing, what sails are in the boat’s current inventory, the boat’s stability, and what the expected rating change should be. In general, the smaller the flying headsail’s mid-girth, the flatter it can be designed. 

IRC RULE FOR CALCULATING AREA (HSA & FSA):

·       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)

Flying Headsails are mainly used between 50 and 125 degrees TWA, which are reaching angles. Moreover, they truly stand out on planing boats with reaching struts or whisker poles that allow the sails to be sheeted away from the mainsail. Reaching struts or whisker poles open the slot between the main and the flying headsail. As the boat speed increases, this sail just gets faster and faster as your TWA comes forward.

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Above are three views of the flying jib set outside a J3 on the XP44 WOW.

For most production racing boats, this sail is a considerable rating hit and would not give you bang for your buck. For lightweight planing boats like C&C 30s, Fast 40s, Open 40s and TP52s, the flying headsail used with a reaching strut, is an excellent option because these boats can get their AWA forward quickly and build speed with this sail.

For most boats, the flying jib is still the best option as it’s the same size as your headsail and can be flown off the bowsprit. Under IRC, the flying jib is still “free” rating-wise and can give you an extra knot or more when close reaching. The flying jib is still the way to go for most boats being flat, easy to furl and you can leave it on the bowsprit. Click here for more about flying jibs.

In conclusion, if you’re racing a production racer/cruiser, stick with the flying jib and code zero. But if you’re a fast or foiling yacht, or perhaps doing a long offshore race including a lot of reaching, the flying headsail is probably worth the money!

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