The International Offshore Rule - Part 2: Measuring Depth

In this article we look at the rated depth (D) and the draft correction (DC) aspects of the IOR formula for measured rating (MR). 

Light air bow down trim aboard Jiminy Cricket (photo Farr YD)

The D value represented the rated depth of the yachts hull. This was based on mid and forward depth stations (MD and FD respectively), which were located at points at half and quarter the length of LOA from the bow, and then measured from specified widths from the centreline. These points were eventually expressed through visible 'flats' between these measurement points as designers sought to shed unnecessary hull volume and unmeasured displacement from a yacht's hull. Additional depth measurement points were added to the rule as early as April 1971 in order to discourage the emergence of these flat sections in the garboard area of the hull in particular. The effect of this change was limited, however, and flat sections between the depth measurement points were considered to be fast under the rule (relative to rating), and persisted throughout its life.

Noticeable flats between measurement points displayed here on the 1976 Farr Two Tonner Uin-na-Mara

Because all depth measurements were in the centre and the forward part of the yacht, boats typically featured a bow-down static trim when properly optimised, sometimes assisted by a more for'ard location for the yachts engine than might otherwise be ideal. The mathematics involved in determining D looked like this:

The B x D component of the MR formula thus provided an estimate of the boats volume through an approximation of the cross-sectional area of the hull. A larger value for one or both factors would result in a reduction in rating, all else being equal.

Bow down trim is evident here on the Davidson One Tonner Pendragon, circa 1988

The centreboard on Resolute Salmon

The DC component allowed for differences from 'base' draft (DB) and rated draft (RD) values, calculated as a function of rated length, with deviations on either side of the base value becoming a positive or negative factor for the resulting rating. The rule did not initially measure centreboards in their fully lowered position, and this conferred a negative, and therefore advantageous, DC value to the MR formula. This was not so much a loophole as a recognition of centreboard craft popular on the east coast of the US due to the shallow nature of the cruising grounds prevalent in that area. However, US designer Britton Chance recognised a potential advantage under the IOR if the centreboard was designed solely as a useful lifting foil, in combination with internal ballast. The result was Resolute Salmon, a big heavy One Tonner that was ideally suited to the conditions off Marseilles, France, to win the One Ton Cup in 1976. 

Comparative rating statistics between some of the top boats at the 1976 One Ton Cup

The issue of centreboards became a hot topic at the next meeting of the International Technical Committee at their annual meeting after the 1976 series, but it was left for another year while the Committee focussed on what was seen as the bigger issue of broad sterns that were evident on some of the new light displacement yachts that had come on the scene. With the centreboard option still open, the 'Ton' Cup events for 1977 were set to be dominated by a new generation of offshore centreboarders.

Another advantage of a centreboarder was the ability to launch at low tide!

The advantages of the centreboard lay not just in the DC measurement benefit. With ballast mostly internal, the new vanguard of centreboard yachts took advantage of lightweight construction techniques that provided for a high ballast ratio - with that ballast held in the bilges their pitching moment in waves was much reduced. Use of a centreboard also allowed a designer to incorporate a little more displacement into the keel area of the hull because the centreboard displaced less than a keel which provided a depth measurement increase. The boats were measured with the centreboard up and this also allowed the boat to sink a little more and thus further reduce rating.

With her centreboard retracted Gunboat Rangiriri is prepared for launching (mid-1977)

However, the use of centreboards, in combination with light displacement and light construction, led to a great deal of controversy through the 1977-78 Southern Hemisphere season, and new stability tests (via a new 'Screening Value' promoted by the Cruising Yacht Club of Australia) were devised in attempt to outlaw such yachts from competing from events such as the Sydney to Hobart.

The Farr One Ton centreboarder Hecate undergoes a pull down test before the 1977 One Ton Cup to assess the effect of the new CYCA Screening Value formula

The ITC belatedly acted in its November 1977 meeting to change the rules relating to centreboards, and to introduce a moderated form of the Screening Value test, but it still remained an option to use them, but unless it was pinned in place the appendage would carry a penalty. Their short reign practically ended in the 1978 Northern Hemisphere season, and it was notable that in the 1978 Half Ton Cup, and even though Waverider won, there was no real difference between centreboarders and keelers. Indeed, a full scale experiment between two otherwise identical Holland Half Tonners showed that the keeler was faster. 

An unusual sight in offshore sailing, the crew of Silver Shamrock III install the centreboard before racing in the 1977 Half Ton Cup in Sydney

A centreboard made its most prominent re-apperance at the 1985 SORC on the Ted Irwin design Razzle Dazzle, a heavy masthead yacht with an elliptical centreboard shape that attracted a 0.3ft rating penalty. In comparison to earlier approaches, the board weighed some 5,000lbs and required hydraulics to lift it. Razzle Dazzle's modest effort in the series did not lead to any further development of the concept.

Waverider, with her centreboard pinned in place, taking the gun in the first race of the 1978 Half Ton Cup

The next article will look at the measurement of rigs, which was an area that yielded some of the more radical looking rule cheaters of all. 

 
A scanned copy of the IOR rule (Mk III 1985) can be viewed here.

Part of the text used for this article is adapted from the book A Lighter Ton - The Champion NZ Yachts of the 1970s, 2012

Smir-Noff-Agen (Farr One Tonner)

Smir-Noff-Agen was a centreboard One Tonner designed by Bruce Farr (Design #63, 27.5ft IOR) for a syndicate headed by Don Lidgard for the 1977 One Ton Cup, held in Auckland, New Zealand. Smir-Noff-Agen joined three other Farr centreboarders The Red Lion, Mr Jumpa and Jenny H.  All these yachts were to a similar design but various small differences were apparent on the rating sheets, with Smir-Noff-Agen sporting a larger mainsail and smaller jibs to reflect the crew's background in skiffs and dinghy sailing, and a simple deck layout to minimise variables in sail-setting, especially at night. 

These new generation One Tonners  were considered experimental at the time, combining light displacement and high ballast ratios with the use of a deep and efficient centreboard and a more flexible and complex rig than Farr's earlier fixed keel One Tonners. The yachts were a significant development of Farr's earlier keelboats from 1975/76 and after the rulemakers failed to close the centreboard loophole exposed to great effect by the Britton Chance design Resolute Salmon a year earlier, a centreboard was chosen rather than a keel, although the fins on the Farr yachts weighed about 750lbs, despite the fact that this was discouraged by the IOR. 

Smir-Noff-Agen heads downwind under spinnaker, shooter and reefed main - NZ One Ton Cup trials 1977

Smir-Noff-Agen faced an early challenge over sponsorship advertising, and changes were made to the yacht's signwriting before the New Zealand One Ton Cup trials began, but the name survived. Challenges to the stability of the new centreboarders were also met in the case of Smir-Noff-Agen by undergoing a pull-down test, with the centreboard half-retracted, which she easily passed.  

Smir-Noff-Agen undergoing a pull-down test in Westhaven, September 1977 (above and below)

Lidgard and his crew went on to contest the trials to determine the New Zealand six-boat team for the One Ton Cup. She started solidly with a second in the first and second races, but lost her rig in the middle distance race. The mast was repaired in time for the fourth race which she won, and followed this with a second in the long ocean race to qualify for the team in third place overall.  

The crew are in for a long night after a failed spreader caused Smir-Noff-Agen's rig to come down in the middle distance offshore race (photo DB Yachting Annual)

Smir-Noff-Agen also entered the Southern Cross Cup trials, to select the New Zealand three-boat team that would compete for the Southern Cross Cup to be held in Sydney at the end of the year. In a mixed boat fleet Smir-Noff-Agen had a close tussle with other centreboarders that dominated the results and joined the Half Tonner Swuzzlebubble and Jenny-H for the trip across the Tasman. 

Smir-Noff-Agen during the One Ton Cup trials, with The Red Lion about to try to cross on port (photo DB Yachting Annual 1978)

The Southern Cross Cup trials showed Smir-Noff-Agen to be a touch quicker than her sisterships, and her new status as favourite of the Farr yachts looked well founded after she won the first race of the One Ton Cup. She couldn't follow this up in the second race where she finished fifth and then sixth in the middle-distance race, and a loss of rig tension was the suspected culprit. With a tightened rig she looked good early in the fourth race, but had to retire when a forestay fitting was discovered to have parted, and talk of sabotage ensued.

Smir-Noff-Agen during the 1977 One Ton Cup (photo Maritime Museum)

Smir-Noff-Agen crosses behind The Red Lion during the 1977 One Ton Cup (photo Farr Yacht Design)

Smir-Noff-Agen sailed an impressive race in the final long ocean race to claim the White Horse Trophy, and finished in third place overall. Her win in the long offshore was despite a near calamitous broach in the gale-afflicted race - Lidgard had called for a spinnaker in 50 knots on the leg between Channel Island and Flat Rock - the boat recovered from the resulting wipeout, but this event was nevertheless used as evidence of the safety deficiencies of the yachts by those at the time who were not in favour of the new light displacement trend that offshore racing was taking. 

Smir-Noff-Agen during the 1977 One Ton Cup (photo Maritime Museum)

Smir-Noff-Agen sailing to windward, with Smackwater Jack to leeward (photo Farr Yacht Design)

Smir-Noff-Agen made her own way across the Tasman for the Southern Cross Cup (after a controversal process to obtain the necessary Category 1 safety certificate). In Sydney and in a fleet of mixed company, with teams made up of anything from Half Tonners to Maxis, the New Zealand team was dominant.

Smir-Noff-Agen competing in the 1977 Southern Cross Cup series

The New Zealand team went into the Sydney Hobart race finale with a massive 130 point advantage over the second placed New South Wales team. Atrocious conditions in the Sydney Hobart meant, however, that this points buffer became the New Zealand teams' buffer as Smir-Noff-Agen retired with damage to the rib frames for'ard after falling off a large wave, and then Swuzzlebubble also withdrew after Ian Gibbs and his crew decided that the conditions were too extreme for a small Half Tonner. Jenny H continued on, though not without their own problems with another failure in a for'ard frame. Haslar and his crew nursed the boat through the worst of the storm and managed to finish in fifth place, and securing the Southern Cross Cup for New Zealand and finishing as the top yacht overall.

Scallywag II before the start of the 1982 Sydney to Hobart race

Smir-Noff-Agen was later sold in Australia and became Vanguard. She was later re-named Scallywag II (this was confusingly close to the new name of Jenny H which had been re-named Scalawag by her new US owners). Her most notable result in later years was winning the 1982 Sydney-Hobart race. Later she became Best by Farr, and she was recently laid up in Mermaid Beach (Queensland Gold Coast). 

Scallywag II on her way to winning the 1982 Sydney to Hobart race

Photos of Smir-Noff-Agen under construction and on her launching day can be seen here.

Smir-Noff-Agen was shipped to Dubai in 2016 and is undergoing a full restoration. More here.

Jiminy Cricket and 45 South II (Farr One Tonners)

This post follows on from an earlier article on the Farr 1104 with two custom race versions of the famous 36 foot design - Jiminy Cricket which was built for Stu Brentnall, and 45 South II, built for Graeme Woodroffe and a follow up to his successful Quarter Tonner 45 South.

Jiminy Cricket under construction at Alexander Boats

Jiminy Cricket was built by Alexander Boats and launched in time for the 1975 Dunhill Cup series - an international regatta that followed the Southern Cross Cup and the Hobart to Auckland race and which, it was hoped, would become a new fixture on the international ocean racing scene. Against an international line up Jiminy Cricket reinforced the impressive credentials of the Farr One Tonner (Design 51) that had been displayed by Prospect of Ponsonby in Australia, and won the regatta with some ease.

Jiminy Cricket racing in the Hauraki Gulf in the 1976 One Ton Cup trials (photo Farr Yacht Design)

Jiminy Cricket in light airs on Auckland Harbour

45 South II (originally launched as The Number) was built in fibreglass and was slightly lighter than her sistership. She achieved the same sail area as other versions built in Europe by placement of the engine being located further for'ard, just behind the mast. 45 South II featured a special deck and cockpit layout, with an open stern and an unusual raised deck area behind the companionway. 

The Number during the 1976 One Ton Cup trials (photo Maritime Museum)

45 South II (as The Number) during the gale lashed long offshore race in the 1976 One Ton Cup trials

By the time of the 1976 New Zealand One Ton Nationals (doubling as trials for the One Ton Cup) the Farr 1104s were prolific and filled the top four places. 45 South II with her lighter displacement and larger sail area was by far the best light air performer in the fleet, and won the three inshore races and the series overall, while Jiminy Cricket finished a close second by winning the two offshore races. So impressive were the performances of the two boats that a decision was made to send both yachts to the 1976 One Ton Cup, to be held in Marseilles, France.

Following her selection, rapid changes were made to the trim of Jiminy Cricket, including shifting the engine forward and installing a taller rig, although her rated sail area remained less than that of 45 South II.

As with 45 South at the Quarter Ton Cup the year before, the New Zealand yachts were something of an anomaly amongst the 43 yachts that arrived in Marseilles, being lighter, shorter and with smaller sail plans than most of their competitors. The first race, held in a good breeze, suited the two Farr boats perfectly, with 45 South II taking the gun and Jiminy Cricket finishing second.

Close up view of the stern sections and cockpit layout of 45 South II in Marseilles

45 South II tacks around the windward mark in the first race after a port tack approach, Jiminy Cricket comes in on starboard to the far left

45 South II (left) to leeward and ahead of Jiminy Cricket 

Lighter winds for following races put a stop to the Kiwi onslaught, however, and the abandonment of the second race, when the New Zealand duo finished with solid results, proved to be a disaster. Jiminy Cricket sailed poorly to finish well down the fleet to effectively scuttle any chances she had to win the regatta. By this stage the US yacht Resolute Salmon, a big heavy centreboarder designed by Britton Chance, had gone on to win the second race (both the abandoned version and the re-sail) and the third, the middle distance offshore race, to look unassailable.  

45 South II on a tight reach during the 1976 One Ton Cup

45 South II in light airs during the 1976 One Ton Cup, with the German yacht Sabina to windward (photo Jonathan Eastland)

45 South II and Jiminy Cricket finished together in the third race (eighth and ninth), and then took out first and second in the fourth. Jiminy Cricket then showed what might have been, by winning the long offshore race finale through a combination of great speed when the wind picked up, and excellent navigation.  

Jiminy Cricket sails downwind during the 1976 One Ton Cup (photo Facebook)

45 South II broad reaching with spinnaker and staysail set, 1976 One Ton Cup

Jiminy Cricket in fresh conditions during the 1976 One Ton Cup

45 South II (Farr Yacht Design)

In the end, 45 South II finished fourth overall, just ahead of Jiminy Cricket in fifth, and Resolute Salmon, although 20th in the last race, won the Cup to lead a clean sweep of the podium places by the US, with Ted Turner's Peterson design Pied Piper second and the Scott Kaufman design America Jane III third. Two other Farr One Tonners, Solent Saracen from Britain and Puma IV from Sweden, were less successful than their Kiwi counterparts, finishing 17th and 27th overall, both having their best result in the fourth race (finishing sixth and seventh).

It is not known what happened to Jiminy Cricket as she did not return to New Zealand. 45 South II did not return either, but I have recently heard from her current German owner who bought 45 South II in 1998 and maintains her in excellent condition. He has recently fitted her with a carbon mast, this provided a weight saving of about 23kg, with further savings through replacement of the nitronic rod stays with carbon.

Above and below - 45 South II sailing in Germany (the pink stripe is now blue)

The 1104 design further evolved with Country Boy which was commissioned by Clyde Colson and went on to win the New Zealand One Ton Nationals in early 1977. The speed of the Farr One Tonners in a breeze was further underscored however with an emphatic win by Piccolo (Australia) and second placing by Rockie (New Zealand) in the storm tossed 1976 Sydney-Hobart race. 

Country Boy, winner of the 1977 New Zealand One Ton Nationals

Country Boy in close company with Magic Pudding (ex-B195) during the 1978 Clipper Cup (photo Phil Uhl/Facebook)

While the design was outclassed later that year by the new centreboarders in the One Ton Cup series, the US yacht Sweet Okole won her class in the 1977 SORC. The design was particularly hard hit by changes to the IOR aimed at light displacement and wide sterns, but Sweet Okole was able to overcome her increased rating in mostly downwind conditions to win the 1981 Transpac race.

Sweet Okole sweeps to victory during the 1981 Transpac

Newspaper Taxi (Whiting Half Tonner)

Newspaper Taxi was designed by Paul Whiting in 1976 with an eye towards a challenge for the Half Ton Cup, to be sailed out of Sydney in December 1977. Newspaper Taxi was a development of Whiting's earlier Half Tonner Candu II, and was designed to take account of  the November 1976 changes to the IOR, the first in a tranche of rule amendments that sought to check the emerging trends in the New Zealand-style of yacht of light displacement and wider sterns. 

Newspaper Taxi on launching day - Westhaven, Auckland

 The broad aft sections of Newspaper Taxi were therefore designed to mitigate the new penalties in this area, and were offset in part by a shortening of the yachts' length between girths, and the forward depth measurement was pushed to the limit. A shortening of measured length allowed for an increase in sail area, yielding a better all-round yacht than Candu II.

The most obvious difference from Candu II was that Newspaper Taxi was a centreboarder. The advantages of this concept had been demonstrated by Resolute Salmon in the 1976 One Ton Cup, and Fun had provided more evidence of this at the Quarter Ton Cup as well.  The centreboard weighed only 92kg, and the boat otherwise relied on internal ballast and crew weight for stability. 

The engine was also designed for rating advantage - the 12hp diesel was positioned for'ard of the mast and slightly to port so that the shaft could clear the centrecase.

While Whiting chased everything possible regarding hull shape and appendages, Murray Ross pursued rig developments and new handling techniques and gear, with the same careful attention to detail that Ross had employed so successfully on the Quarter Tonner Magic Bus.

Showing her windward form in light airs, Half Ton Championship, Auckland 1977 (J Malitte)

The Whiting/Ross led team aboard Newspaper Taxi went on to produce a near flawless performance in the South Pacific Half Ton Championships held in April 1977 and hosted by the Royal Akarana Yacht Club. The series featured a wide cross-section of Half Ton designs, with 20 boats entered, the product of ten different designers, and only three boats had competed in the previous year's contest. 

A clear lead at the wing mark in the NZ 1977 series (J Green)

Newspaper Taxi asserted a demonstrable speed advantage in all conditions, combined with immaculate boat handling. She won four of the five races, losing first place in a close tussle with the custom Farr 920 Cotton Blossom which jumped on a rare tactical error by Ross in the fourth race.

While Newspaper Taxi had been designed and built with the 1977 Half Ton Cup in mind (Sydney), the Whiting/Ross team elected to contest the One Ton Cup to be held in Auckland in November 1977. Newspaper Taxi was sold to an Australian yachtsman and finished in 10th place in the Half Ton Cup, behind near sistership Magic Dragon, with placings of 10/11/8/8/DNF.

Newspaper Taxi undergoing a self-righting test ahead of the 1977 Half Ton Cup in Sydney (photo Facebook)

At the Half Ton Cup - Sydney, Australia (December 1977)

Unfortunately, Newspaper Taxi later sank during the 1995 edition of the Three Peaks Race (Launceton, Tasmania, to Hobart), after losing her rudder off Cape Tourville on the outside of Freycinet Peninsula. According to the owner at that time (see comments below), the rudder stock snapped at the weld point above the hull line and tore the stern tube out. The crew took to a liferaft and were later rescued by the tanker Island Gas which had been diverted to the scene, and Newspaper Taxi now lies at a depth of 60m.