“S” Boat Design Centennial

By: David Hubbard

Updated: 2019-05-13

2015-07-17 Clara J Rail InOne hundred years ago, the most famous boat designer of all time, Nathanial Greene Herreshoff, aka “Captain Nat”, aka “The Wizard of Bristol”, was 71 years old, and quite possibly at the height of his powers as a sailboat designer. If you own a sailboat, or have ever seen a modern sailboat, you should give him a nod for what he was about to do, that is to design the “S Boat”. Of which about 94 were built by Herreshoff between 1919 and 1941, and a few under license by Lawley. Today, almost 70 still exist, and over 30 are actively raced in Narragansett Bay, the western Long Island Sound, and Quissett Massachusetts. And of course, a 100 year old design that popular deserves a celebration!

Nat was well into preparing the next America’s Cup yacht, “Resolute”, for the 1920 Cup Regatta. A few years prior, he had been instrumental in creating the “Universal Rule”, a formula for handicapping sailboats. Prior to this, the rules in use did not account for the displacement of the boats, which was leading to huge sail areas, but light boats, and things were getting dangerous. So, his new rule accounted for displacement, as well as things like sail area, and waterline length.

The formula puts out a number, and each range of numbers was assigned a letter. The largest range was given “J”, and the venerable America’s Cup yachts of the time were the big 120’ “J Boats”.

The smallest was assigned the letter “S”, but until 1919, none had been designed.

The new rule heavily weighted waterline length (a longer boat would get more of a handicap), but only with the boat upright. Thus, the Universal Rule boats were all designed with beautiful overhangs in the bow and stern. This was not really for good looks, but because as the boat heeled over, it also got longer in the water. And since boat speed for a displacement hull is limited by waterline length (known as ‘hull speed’), this allowed the boats to use this ‘unrated’ length to go faster. Hull speed is caused by the hull making it’s own wave, and as the stern dips into the wake, the boat is now trying to go up hill and requires a lot more energy to do so. This is from the speed of a wave through water, which in knots is limited to 1.34 times the square root of the wavelength in feet from crest to crest.

The story goes that in 1919, a group from Seawanhaka Yacht Club in Oyster Bay, Long Island, approached Nat and asked for a high-performance day-sailer, suitable for racing on Long Island Sound. Although it seems that the first shipments went to other clubs.

And thus, the “S Boat” was born. Now strictly speaking, Universal Rule boats are “Formula Boats”, meaning there is some flexibility in the design. You can trade off sail area for length for example. But in fact, the S boats were all identical, so they are also a “One Design” in fact.

But the S boats were not just another Herreshoff design! For starters, Nat was known for designing boats specifically for the area they would be sailed, accounting for wind, waves, depth, etc. And he was known to not let his customers design the boats. He just got the general requirements from them and did his own thing! So, these were the first production line of boats to have what we now accept as a standard, the “Bermudan” or “Marconi” rig with the triangular main sail we know today. Prior to that most boats were gaff rigged. Those had a 4-sided main sail supported by an upper ‘gaff boom’. In fact, it is said that the America’s Cup folks were evaluating this new design for “Resolute”, and probably sailed an S boat, but may have decided it was too risky a change, so stayed with the gaff rig. But after the 1920 cup race, all future America’s Cups were sailed with the new rig.

The S boats have a 20.h’ waterline length (LWL), but the overhangs extend the overall length (LOA) to 27.5’, allowing them to stretch out to 24’ or so in the water when heeled over. They have what is known as a ‘hollow bow’, a new design at the time to help handle waves. They weigh in at 6,750 lbs of displacement, with a big 3,350 lb piece of lead as the entire bottom of the keel. The keel is also fairly short, allowing the boats to turn on a dime, faster than many modern boats! Another feature is the signature curved mast. The top of the 42’ mast curves backwards. The theory I’ve heard is that in heavy conditions, as the boat heels, the top of the main dumps air, and brings the ‘center of effort’ down and forward, and that combined with the low weight and 50% ballast, stiffens the boat as they get their rail in, and balances the boat. And with the rail in, they fly! Most racers don’t even reef, and when properly trimmed up, owners say they can be sailed with just 2 fingers on the tiller, even in a good breeze!

Another unique feature was that the spreaders, which hold the stays away from the mast, are on a ring which can rotate when the main presses against them downwind. This removes torque on the Sitka Spruce hollow mast, allowing more horsepower safely.

They also are easy to sail. They have a very small, self-tacking jib, which has its own boom that swings inside the bow. Unlike modern boats which get a lot of their power from the jib, the S boat jib is more for trim. It just needs one sheet, has its own traveler on the foredeck, and when tacking upwind you don’t need to touch it! You can just drive!

They also had an adjustable forestay, which allowed for flexibility in shaping the huge 340 square foot main sail, which gives the boats a 19-1 sail area to displacement ratio. This is very high even by today’s standards, and they can overtake modern boats downwind. This huge main for a boat this size resulted in the boom overhanging the stern, and thus no backstay. So they have “Running Backstays”, which are stays on tracks on each side, and lines that run through “cheek blocks” on the deck to pull them forward and backwards. Back on the upwind side to support the mast, and forward to get them out of the way of the boom when off the wind. Although when close hauled they can both be left back. This is the only tricky part of jibing! You must switch these or risk breaking your mast! This is a feature shared with the famous “12 Meter” yachts of the America’s Cup.

With these features, the S also can out point (sail closer to the wind), most modern boats, expect those designed specifically for racing.

They are also beautiful boats, with Eastern white Cedar over tapered oak frames. The owners could choose from Oak, Teak, or Mahogany for the wood trim, including the signature Herreshoff ‘Molded Sheerstrake’ (The topmost plank meeting the deck), which is left varnished, never painted, and is striking.

They have a small cuddy cabin, and the design showed an option for a bigger cabin for light cruising, although it seems maybe only one of these were built.

In the summer of 2019, we will celebrate the centennial of the design with regattas in Larchmont, NY, Newport, RI and the Herreshoff Museum in Bristol, RI. There will likely be close to 30 boats on the line to race! Making this one of the largest races of classic one-design boats ever, not to mention a 100-year-old design! There are still 3 fleets of “S” Boats who race actively as a one-design. One in the western Long Island Sound, one in Narragansett Bay around Newport Rhode Island, and one in Quissett Massachusetts. And several race in mixed fleets on a handicap basis (PHRF around 210 depending on area). We have located over 67 of the original 100+ boats!

There are always a few of these boats available for sale. Some in excellent shape, such as those restored by IYRS, the International Yacht Restoration School in Newport RI. (which restored mine, ‘Clara J’) and other classic wooden boat shops, such as Bristol Boat, Baltic Boatworks, East Passage Boatrights, and Wooden Boatworks. And there are always a few in need of a new caretaker! (We don’t really own our boats… most of us see ourselves as caretakers of a piece of history).

So, come on out during 2019 to watch (or even crew) some of the classic races we have planned!

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