Do you want to know what the IOR is? The people who gave birth to him tell you about it


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“Jacobite” – Swan 48 “Jacobite” – 1971

Walking around any port, IOR you will find many, many of them. Boats with slender bows, elongated closed sterns, maximum beams concentrated in the center, large genoa and small mainsails. In short, unmistakable and often beautiful boats that we have talked about often, and many are part of our

Classic Boat.

But perhaps not everyone knows what the IOR (International Offshore Rule ) is, a racing rule that knew how to involve great designers, great sailors, great boats and great creativity. We asked Nicola Sironi, regulations guru
Deputy Chief Measurer ORC
(Offshore Racing Congress) as well as a sailor and a planner born right with the birth of the IOR – to tell us about How the IOR was born, how it evolved, how it waned.

Here is the story of the
Golden Age of sailing
, the history of boats from 1970 to 1994.

IOR? The people who gave birth to him tell you about it

The IOR was born together with theORC, and was presented in 1970 at the meeting of theIYRU (world sailing body), headed for the first time by Italian Beppe Croce as president. It was soon adopted worldwide, opening the door to an unprecedented expansion of “offshore” boating. Until then, offshore handicap racing was done under the rules of the London-based RORC (Royal Ocean Racing Club), which in Italy had been extended below the 22′ rating limit, creating a Class “C”-a conspicuous number of series boats (even small ones) from the nascent fiberglass production.

By the RORC, thanks to Mary Blewitt, new secretary of the London club, and a group of lineage sailors, in 1957 theAdmiral’s Cup, a national team regatta with 3 boats each, which was enthusiastically joined by crews from all over the world, first by the Americans, who had founded the development of offshore sailing that was taking place in parallel on the other side of the Atlantic, using the regulations promulgated by the Cruising Club of America (CCA).

Alpa 12.70 – Sparkman & Stephens

Thanks to the work of the shipowners, who gradually joined in by enthusiastically participating in these international events-among whom at the time was Edward Heath, then prime minister of England who participated in the Admiral’s Cup with his Morning Cloud – there was a clamor for the creation of a new regulation, and after more than a decade of meetings and correspondence Olin Stephens, together with Paul Spens (an Englishman who headed the naval tank in New Jersey) and other experts, created a rather complex formula, which required a computer to work given the large number of operations required (PCs did not yet exist at the time, but the programmable calculators of the time were sufficient for calculation). In parallel, RORC members were studying a way to form an entity independent of the IYRU but aggregated with it, and the ORC was born.

“Police Car” (42′ by Ed Dubois) at the 1979 Admiral’s Cup.

The operation of the IOR

The British lawyers who formed it (ORC) put in place a process to achieve continuity over time, establishing a structure and an annual cycle of issuing certificates, with a “levy” for each issued certificate capable of financing its structure, consisting of a “Council” and numerous standing committees, primarily the ITC, the Technical Committee charged with making necessary changes to the Rules from year to year, which, since 1985, when the IMS was added alongside the IOR, I have had the honor-and the burden-of chairing at that time. Alongside the ITC, other committees were also in operation, and from year to year they deliberated changes to the regulations and tonnage formulas, with new pages to be replaced or strips of paper to be applied to the books. The updated program listing was being distributed to Rating Offices around the world, including Italians.

After an initial phase in which the certificates were managed by the FIV, the management passed to a new association, the AICI, at the initiative of a number of prominent shipowners of the time, including Max Boris, Spadolini, and Marina Spaccarelli Bulgari, headed by Pippo Po, assisted by Riccardo Provini. Once they learned how to punch the cards and take them to a CED that could print the certificates, worldwide IOR certificates multiplied from a few dozen to thousands of boats racing around the world.

The formula was convincing: very open-minded compared to the traditional “metric” classes promulgated back in 1907 and endured until after the war, when races were held in protected waters near the coast, and boats were unsuitable for the open sea.

“Ydra,” a project by Dick Carter for Marina Spaccarelli Bulgari. He won the One Ton Cup with Straulino at the helm, 1973.

In the two founding countries of the IOR, the United States of America and Great Britain, the system thrived immediately, but also in Italy and other European nations-and also in Australia, New Zealand and South America-the IOR boomed, and again Mary, having left (temporarily) England and married Commander Gianni Pera, became a leading player in offshore sailing. With La Meloria, a second-class RORC designed by Nicholson he participated in the 1969Admiral’s Cup, along with Serena Zaffagni’s Mabelle and Beppe Diano’s Levantades. Mary returned to England chairing the IYRU Racing Rules Committee, then the ORC Special Regulations Committee, and thenAdmiral’s Cup Juries and numerous Ton Cups before passing away in 2000.

Regattas, “races” and IOR rating

The One Ton Cup, moved from the 6m SI (International Tonnage) to the 22′ RORC in 1966 (by decision of Jean Peytel, of the Yacht Club de France, owner of the prestigious cup), was followed shortly thereafter by the Half and from the Quarter Tonners, pushed by the French, adopting the RORC system even for boats rated below 22′. This intensive design and construction development was instrumental in exposing some shortcomings in the regulations. In an early edition of the One Ton Cup, crews stood on the trapeze, which was promptly banned. Another problem that emerged was the excessive influence on the rating of building materials. The example that caused a scandal was the 1967 Listang, a Quarter Ton built of steel to gain on the rating, which at the finish of the long race had won, but was all warped.

This convinced to avoid the definition of “scantling,” but “special regulations” were introduced for safety equipment. The IOR basic hull measurement system is an evolution of the RORC system, determining a tonnage length calculated from lengths and “chains” in cross sections fore and aft, and “toe-in” to estimate displacement. The multiple measurements were taken ashore, in the chain sections at the ends and in the toe and BWL (Maximum Beam) sections, with water level to measure the heights of the 30 or so points to be measured, and plumb lines to project the points to the ground, and measure lengths and widths, which the program was able to correct for based on the free edges taken in the water to determine the waterline plane in buoyancy trim and then calculate tonnage length and rating.

Since the salinity of the water was not initially considered, the most competitive sought fresh water to make tonnage, which gave an advantage and was corrected later by measuring salinity at the time of “flotation.”

Ziggurat 916, Half Tonner IOR

Also included in the in-water test was stability, which was carried out by rigging a spinnaker on one side of the boat, perpendicular to the plane of symmetry, hanging an incremental weight on it and measuring the resulting angle, using a pendulum hung from the backstay, and then a horizontal pressure gauge. Basically a transparent little tube where you can read the level and a reservoir on the opposite side. Invented by Eng. Emilio Vatteroni of Carrara, who had christened it a “vinometer,” since it used red wine as the liquid, which was then drunk at the end of the operation. The new tool was built by many tinkerers of the time, and its length represented a kind of “signature” of each tinker.

  • Do you have an IOR boat and want to sell it? Or, are you looking for one? Remember our Flea Market!

For sails and rigging they started from the American model of the CCA, which led to masthead rigging and large-covered genoa. In fact, the formula stipulated a minimum jib area of 150% of J. The spinnaker also considered a minimum area, below which there was no rebate.

The IOR formula is well described in Finot’s book “Elements de vitesse des carènes” translated into Italian, and the product of the formula is a “rating” represented as tonnage length. However, this length in order to be applied in racing must be transformed into a fee, which is a fee in seconds/mile if the “time on distance” method is adopted or a multiplicative coefficient of real time if the “time on time” method is adopted. The former was being adopted in the Mediterranean under the CIM formula. (Comité International de la Mediterranée), and in the U.S., while in England and Australia the latter was preferred.

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Protagonists, racing and innovation

The highest level regattas developed in the IOR era were the
“Ton Cups”
, each defined by a rating limit. The first was the One Ton Cup, which originated back in the days of the RORC at the lower limit of 22′, which in the IOR were changed to 27.5′ and then, from 1984, to 30.5′. Next came the Half Ton at 21.7′, the Quarter Ton at 18′ and subsequently the 3⁄4 Ton at 24.5′, the Mini Ton at 16′ and then also the Two Ton – which had various limitations-and finally the 50′, which was very successful for a few years in the early 1990s.

These fleets consisted of both prototypes, first made of wood and then with the emerging “exotic fibers,” and production boats, more or less transformed and optimized for racing. The design and construction of so many new boats, which until then had been almost a monopoly of a few designers and shipyards, spread around the world to a multitude of new recruits, and many of the boats were designed and built in-house. Craft yards sprang up everywhere, while large construction sites consolidated industrial production.

By the mid-1970s some designers had found ways to make much longer and lighter boats for the same rating, far removed from the initial “type” of the IOR. As early as the IOR Giulio Cesare Carcano with the Villanella pioneered a new typology, which was also applied by Bruce Farr and several French designers. The ITC intervened shortly thereafter, studying a coefficient called DLF (Displacement Length Factor), which severely penalized this new type. These changes caused much dissatisfaction, and Bruce Farr, leader of light displacement, abandoned the IOR for a decade, returning only in 1987, convinced by King Harald of Norway to design them a One Tonner that won the One Ton Cup in Kiel in 1987.

Other French designers abandoned the system, but it continued on its way, gradually making changes to the formula and regulations. Meanwhile, technology evolved from the first production boats made with “chopped strand” sprayed on the mold along with resin to increasingly elaborate and “exotic” fabrics and sandwich constructions that outclassed traditional materials. Carbon has always been forbidden, even in trees. When Williwaw reinforced his aluminum shaft with carbon strips, at the suggestion of Lowell North, the ITC promptly intervened, introducing an “Exotic Material Factor” of 2 percent.

Lunic 3 – 1997

In 79 on a British boat, “bumps,” that is, local alterations made with putty at measuring points, first appeared. The ITC intervened by limiting the radius of curvature at the measurement points. Criticism of the system prompted a group of U.S. shipowners to fund a project, the “Pratt Project,” commissioned from MIT in Boston, to study with an analytical tool a new regulation that would be able to avoid the “pitfalls” that had emerged with the IOR.

This gave rise to the establishment of the MHS regulation, which was adopted by the ORC in 1985 under the name IMS, renamed ORC in 2008. Since 1995, the ORC has ceased distribution of the updated program and regulations, and has continued its work with the IMS, and further evolutions and derivations.

Since then, the IOR has continued its activities in some nations into the new century, notably in Mexico and Russia, as well as being reinterpreted in various forms of simplified formulas, including that of the CIM, for which an extensive revision was proposed at the turn of the century, introducing the concepts of toe and width to the IOR buoyancy by Olin Stephens and Doug Peterson, who for various reasons spent considerable time at Argentario reformulating the CIM.

Admiral’s Cup 1995


The “rebirth”

It is a great pleasure, as well as an honor, to find myself involved in the rebirth of the IOR system, which I experienced as a sailor while still a teenager in its early days, managed in its declining phase, and is now being reborn under the auspices of the


and the Italian



Boats born with IOR have spent the years in various ways. Some have withstood the passage of generations, and have remained in the same family, some have been bought by new owners, and others-unfortunately not the majority-have been lost. In 40 years or so there has been a need for repairs, or replacements of masts, keels, rudders not to mention sails, which inevitably require periodic replacement.

The CIM has decided to apply – on an experimental basis for 2023 – its regulations applied for Epoch and Classics to a third Division called Classic IOR. To be eligible you must show proof of having had an IOR certificate, be in good repair, and for series boats demonstrate some palmares or achievements. The new class will be admitted to 17 regattas in Italy, 12 in France and 10 in Spain and will have facilities to obtain an ORC or IRC certificate to participate in other regattas.

QUIKPOINT AZZURRO, S&S 34 during a recent Syndey-Hobart

Edited by Nicola Sironi, Deputy Chief Measurer ORC (Offshore Racing Congress)



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