What Boat Is Faster?

October 16, 2026

My kid has been racing his ILCA against the local college team's FJs lately. Different boats, different crews, different sail plans, on the same course. At some point we wondered which boat is actually faster. And it turned out to be a pretty cool rabbit hole.

The system used to compare different race boats is called the Portsmouth Yardstick, and it turns out sailors have been settling this exact argument since the 1940s.

It's a handicap system for racing different boats against each other. It's kinda important for yacht clubs that run race days with a variety of classes. Every class gets a number, and the lower the number, the faster the boat. US Sailing describes the number as the time a boat needs to sail a common but unspecified distance. A boat rated 80 sails that distance in 80 minutes, and a boat rated 90 needs 90.

To score a race, you take each boat's elapsed time, multiply by 100, and divide by its number. That gives a corrected time, and the lowest corrected time wins. A boat rated 97.9 that finishes in 60 minutes gets a corrected time of 61.3 minutes. A faster boat has to finish sooner than that to beat it.

The numbers aren't a designer's estimate. For a class with plenty of race history, they come straight from statistics. US Sailing's committee collects results from clubs around the country and adjusts each class's number based on how it actually finishes against reference boats. (For a brand-new boat with no results yet, the committee can start from a formula based on its dimensions, but real race data takes over once it exists.) The anchor for the whole system is the Thistle, rated 83.0 since 1961. The idea started in England in 1947, at a club that needed a way to score different dinghies against each other. The US system grew out of the British one, though the two are separate now and use different scales (US numbers sit around 100, UK numbers around 1000). A UK number isn't just a US number times ten, so you can't convert between them.

So which is faster, an ILCA, a C420, a Flying Junior or a Sunfish?

US Sailing's published tables list the ILCA 6 (under its old name, Laser Radial) at 96.7, the 420 at 97.6, the FJ at 97.9 and the Sunfish at 99.6. The table's 420 entry covers both the club and international versions, so it doesn't separate the C420 from the i420. Lower is faster, so the ILCA comes out ahead, the C420 and FJ are next to each other, and the Sunfish is last. Those numbers come from an older table, though. US Sailing's 2021 update revised the ILCA to 95.7, the 420 to 97.2 and the Sunfish to 99.2. The order didn't change. Curiously, the FJ isn't in that update at all.

The gaps are smaller than they sound. Using the older numbers, which are the only ones that include all four boats, a 45-minute race puts the ILCA about 25 seconds ahead of the C420, 33 seconds ahead of the FJ and 80 seconds ahead of the Sunfish. The C420 and the FJ are only 8 seconds apart, which is a tie for any practical purpose. In a fleet where the middle of the pack is separated by minutes, all of that is close to a tie.

I also wondered whether the answer changes with the wind. The older table breaks each boat's number out into wind-strength columns, from light to heavy, so it's possible to check:

Portsmouth numbers by wind strength; lower is faster. Source: US Sailing, North American Portsmouth Yardstick Table of Pre-Calculated Classes (2017)

The ILCA is the fastest in every row where it has a number. The rest of the order changes with the wind. In the lightest air the FJ is the best of the other three, a couple of points ahead of the C420 and the Sunfish. As the breeze builds the C420 improves the most, closing to within 1.4 points of the ILCA, and it passes both the FJ and the Sunfish. The FJ improves the least. In the heaviest row the C420 is well ahead of the FJ and Sunfish, which are tied at 95.8, but the ILCA has no number there, so there's nothing to compare. (The FJ's number is in parentheses, which US Sailing's handbook says marks a number based on only 5 to 15 data points.)

The tables tell you who's faster, but not why. I couldn't find anything that explains the differences between these four boats, so treat what follows as theories from a non-credentialed Mom and her kid.

My kid's first guess was the sail angles going upwind, and he's probably on the right track. A boat can't sail straight at the wind, so it has to tack (zigzag). How close to the wind it can point decides how much each tack gains toward the next mark. A sail works like a wing. How well a boat points depends on how much forward and sideways force the sail makes compared to how much it drags. Tall, narrow sails tend to be better at that, and so does a jib that sets up a slot of air next to the main. How well the centerboard and rudder resist sliding sideways is probably a factor too. As a rough illustration, at the same boat speed a boat pointing 45 degrees off the wind makes about 10% more progress upwind than one pointing 50 degrees. But pointing higher usually costs speed, so the fastest setup is a balance of the two.

Weight and sail area probably matter too. The ILCA 6 is a light boat, about 130 lb (59 kg) with a single 62 sq ft (5.76 m²) sail. The C420 weighs about 176 lb (80 kg) with 80 sq ft (7.45 m²) of main and 30 sq ft (2.8 m²) of jib. The Sunfish is about 120 lb (54 kg) with a single 75 sq ft (7.0 m²) sail, and the FJ carries about 104 sq ft (9.7 m²) of main and jib. In a breeze, boat speed is limited by how flat the crew can keep the boat. Two sailors hiking out can hold a bigger rig flat than one, and that may be why the C420 gains so much in the heavy columns, though that's my guess, not something the table says.

Downwind, the spinnaker is the big difference. The C420 flies one, the FJ has an optional one, and the ILCA and Sunfish don't. A spinnaker nearly doubles the sail area when the wind is behind you.

One more thing the number can't tell you is who's in the boat. A Portsmouth number describes an average boat with an average crew in the conditions people usually race in. A college sailor with years of FJ time will swamp a 33-second handicap difference. If your kid is winning or losing against the college boats, the number isn't the reason.

Where the yardstick earns its keep is practice and club racing, where you want a result that means something even though nobody owns the same boat. If your coach runs mixed-fleet races, or your club has a Wednesday-night series, you might see these numbers on the results sheet.

Handicap or not, nothing does more for my high schooler's confidence than smoking a college FJ across the finish line.