Pt 1.19 – From Kings to Bouncing Cats: the British development classes

Gypsy, the first National 12. Pic from the class site.

While boats like the Thistle and Firefly show us what happens when the design of the classic British racing dinghy remains frozen in time, boats like the Merlin Rocket, National 12 and National 18 show us what happens when shapes are free to change. These classes give us a unique insight to the ways dinghies have developed over three quarters of a century, because while their shapes and technology have developed, the rules they fit into have remained largely unchanged. They give us a picture of development that is not obscured by major rule changes (as in 14s) or by radical design developments (as in Moths and Skiffs).

The National 12 was launched in 1936 as a reaction to the rapid obsolescence and rising costs involved in England’s only existing national dinghy class, the International 14. The labour and expertise required to create boats like Thunder and Lightning meant that they would always be what the fans called “aristocratic”, and others called expensive, so the National 12 was introduced as “a training ground and a feeder to the already established fourteens.”[1]

In most other countries this category would have been filled by a hard-chine boat, but the British opted for a round-bilge clinker hull; clinker because it was “generally far easier to the average boatbuilder, and therefore considerably cheaper”; round bilge, because to the British racing fraternity a curvey hull stamped a craft as a “real” racing boat, rather than a hard-chined box for “messing about in boats”. The hard chine, Uffa once wrote, was “desirable for high planing speeds, as it throws the water out and makes a sharp edge for the water to leave, and is the reason why all high speed motor-boats are designed with chines. It is, however, the wrong thing for the lower speeds of sailing craft, as it increases the wetted surface and this corner, or the lee bilge, being continually pushed in and out of the water sets up a great amount of resistance. The professional and the amateur built boats can be spotted a mile off, because the first is a smooth, round craft as sweet as an apple to look at, while the other looks like a box.” The preference for round bilge racing boats remained strong in British racing for decades.

The National 12 carried a small but (by the standards of the day) tall and efficient-looking rig without a spinnaker, and cost about a third of an International 14. The class had everything going for it – but no one bought one. The problem, curiously, was Uffa. He totally dominated the I-14s, so he stayed away from the “Nationals” on purpose to allow other designers a chance. In fact, his refusal to become involved almost killed the class from birth. Ian Proctor, one of the top British designers of the ‘50s and ‘60s, later wrote that “many people felt unwilling to take the chance of building a boat to their own, or perhaps some other builder’s design, if there was any possibility of the maestro perhaps designing and building to the rules a little later on – and outclassing all those boats in existence at one fell swoop. It is an easy attitude to understand.” The class did not move ahead until Yachting World magazine and Uffa created the “Uffa-King” design (and yes, I’d wondered about that name for years and according to this link, my suspicions were right!).

Uffa-King sailplan and lines.


There is much to be learned from the tale of the Uffa-King. Although Uffa was famous for creating the planing dinghy (or so it was said) he cautioned that “this 12-footer, because she was shorter, and still carrying two people, and still carrying two people, would be so heavy, that the occasions on which she could plane would be few and far between”. [2]  In that sentence, Uffa highlighted three problems for dinghy designers – one is that crew weight is a huge influence on design. The second is that short boats sailed by more than one adult will always be comparatively heavy; even if the hull is ultra light, the designer still has to try to package enough volume to float about 130kg of crew weight into a waterline of 4m or less. The third is that length is such a critical factor in dinghies that a concept that works brilliantly at one size, such as the Avenger-style planing hull, may be much less effective in a boat just two feet shorter. In bigger boats like yachts, the effects of scale are not so dramatic, and it’s possible to scale boats up and down quite effectively.

Because Uffa believed the 12 was unlikely to plane very often he designed a “knifing, rather than a planing, type of dinghy” with very deeply Veed sections. Uffa and Yachting World magazine sold the plans for little more than the cost of printing – another symbol of the future, because Yachting World was to go on to play a major role in promoting dinghies. One hundred sets of plans were sold in the first week, and within three and a half years the National 12 was the most popular class in Britain.[3]

The Uffa-King’s speed upwind in all winds and downwind in non-planing conditions was so great that the design remained competitive for many years, as Uffa had intended when he created such a radical shape. It was also quite unstable, and so the class created a “rise of floor” restriction to “prevent vessels being narrower on the waterline” and stop even more unstable boats from being designed. It was another indication of the future – the restricted classes were determined to create rules that ensured that the boats remained suitable for a wide range of sailors, not just the experts.

Even the Uffa King’s eventual obsolescence provided a lesson. As Proctor put it “as helmsmanship in the class developed, it was soon discovered that not only could these little boats be made to plane when it blew really hard, but they would also get up and plane when there was no more than a moderate blow. Planing ability therefore became a more important point.” [4]


Above – the Uffa-Ace, the first National 18 design. The class has adopted an unusual approach to development and new ‘glass boats must be made from the Phil Morrison design below. The difference between the shapes capture seven decades of development.


Just two years after the National 12 was launched, the National 18 was created along generally similar lines as an economical “dual-purpose boat suitable for ordinary day sailing, and at the same time fast enough to interest those concerned with racing.” Once again, Yachting World promoted an Uffa design, the Uffa-Ace (above) For some reason the National 18 never took off like the smaller development classes. Many sailors stayed faithful to the local one designs of similar size and style, and the National 18 has only ever had a few fleets. The UK is therefore one of the few major sailing countries where there has never been a major national class of big multi-crewed dinghies.

The last of the national development classes was the Merlin Rocket, an amalgamation of two similar classes. Both were light 14 footers with the inevitable clinker hull and small rigs (around 10m/108ft2) that were aimed at providing high performance for older sailors, women and family crews, without the “grunt” of the I-14s or the athleticism of the N-12s.

Kate, prototype for the Merlin. The very narrow cockpit kept water out in a capsize. Although other designers and builders claimed that boats without decks were lighter, the Merlin class found that the 1/8″ ply decks “serve to stiffen up the hull which is converted into a very rigid box structure” in the words of Ian Proctor. “The complete boat, therefore, can be made lighter than could possibly be the case for an open boat, and the rules in fact permit a hull weight as low as 190lb., identical with that of the smaller “National 12″.”  He also noted that the decking also allowed freeboard to be reduced by about 2″ compared to a National 12, which must also have helped to reduce weight. Pat Blake photo from the class site.

The first Merlin was designed in 1945 by Jack Holt for a syndicate who specified a light, low-freeboard, exciting boat mainly for river sailing, with a rig small enough for female crews. Right from the start the syndicate was interested in a boat that was challenging to sail. After the first boat (Kate) was launched the syndicate asked for a boat with more Vee, less stability and a sky-scraping 7.6m (25ft) mast “to make the boat more lively, and require rather more “sitting out” in the average strength of wind. Those indefinable elements of “liveliness” and sensitivity are just as important to fans of the Merlin and National 12 today.

Kate’s lines plan show the slender and deeply Veed shape of the early Merlins. Proctor wrote that the originators of the class wanted the “rise of floor” (which in those days basically meant the angle of the Vee around the centre of the boat) to be about midway between that of the International Fourteen and the National 12, to reduce wetted surface and make the boat more sensitive.

The impetus for the Rocket came from N12 sailors from the sea and estuary clubs of north-east England. They were in search of a larger, roomier and steadier version of the 12 that still had a thoroughbred’s feel. In 1949 boatbuilders Wyche and Coppock took one of their clinker Int 14 hulls and gave it decks and a smaller, lower rig. The International 14 heritage meant that the Rocket’s hull was flat, firm bilged and stable compared to a Merlin or a National 12.

To modern sailors it is odd to see that the “river boat”, the Merlin, had a tiny cockpit and wide sidedecks, while the open-water Rocketeers preferred a more open deck layout. From our perspective it seems back to front, but the reason lay in the lack of bailers and lightweight buoyancy. As Rocket pioneer Robin Steavenson explained, in the Merlin “the fully-decked hull required by the rules limits the size of the cockpit and makes emptying a swamped boat very difficult…in smooth water this arrangement is excellent and allows a rapid recovery to the upright position, as only splash water enters the cockpit. But in a swell or amongst small breakers nothing will keep the water out if the boat is once knocked down. When the hull is full, bailing in the restricted space is a most difficult operation, and although pumps are allowed, those which are capable of competing with a bailer are usually heavy and cumbersome – and expensive.”  In areas where boats were sailed off beaches that were open to the sea, wrote Steavenson, the need to have boats that had less decking and therefore could be more easily be bailed out was even greater; “it is quite impossible to beach a waterlogged boat on any but the quietest of days without the risk of serious damage.” And so (in a logical move that seems strange to those of us who grew up with self bailers) the Rocket had less decking, to make it more seaworthy.

Lines of an early Rocket. This flatter, firm-bilged hull looks more modern than the shape of the contemporary Merlins.

Both the Merlin and the Rocket were instant successes. Their comparatively light weight and efficient design made them almost as fast as the International 14s, but they were easier to sail and were suitable to a wider range of crews. The rules of the two classes were similar enough to allow a Rocket to fit into the Merlin class, and much to the surprise of the Merlin sailors, the first hybrid proved as fast as the tippier, tall-rigged Merlin. Not all were converts; as Steavenson noted, “there were many owners in the Merlin class who tried sailing Rockets and who said that, although they appreciated their fine performance, they did not enjoy sailing them quite so much.” However, the similarity between the classes and the desire to avoid conflict between them encouraged the two classes to merge in 1951 to create the National Merlin Rocket class, with over 330 boats.

The early Merlin Rocket.

The development path

It takes a book to properly chart the complex history of a class like the Merlin or National 12, but a brief look at the way the boats have changed can show us the direction of racing dinghy hull development. True to the “restricted development” ethos, the basic rules and concept of the N12 and MR have remained essentially the same over the decades. Loopholes in the class rules are plugged to maintain a balance between progress and obsolescence. As veteran N12 champ Robin Steavenson put it, “nothing has been allowed to develop which would rapidly outdate existing boats.” Although the Merlin Rockets have adopted minor changes such as larger spinnakers and the N12 has reduced its weight, dropped the clinker skin and introduced self-draining double-bottom boats, in general terms the aim is refinement within the same concepts rather than radical change as in classes like Moths or International 14s.

These days, when a new development or restricted-class boat is a rarity, it’s hard to remember how intensive the design race was in the 20th century. In the dinghy heyday of the 1970s, MR and N12 championships would regularly attract well over 100 boats. In the Merlin Rocket class alone, over one hundred different designs were created, and the National 12 was not too far behind with over 70. The decades of intense refinement and experimentation attracted amateur and professional designers alike, and as we’ll see much later, some of them were to become among the biggest names in the dinghy design world.

The nature of UK sailing grounds are a strong influence on both classes. These classes race seriously on restricted waters like narrow rivers and flooded quarries, as well as on estuaries, bays and the open sea. Designs are chosen and tailored for their owner’s preferred conditions as well as for crew weight and sailing style. Manoeuvrability, the ability to sail all angles (including tight reaches or square runs) and handle both rough and flat water, and light air pace count at least as much as pure top speed. “The appeal of National 12’s is their ability to perform in a wide range of wind conditions and on rivers and open water” says N12 designer / sailor David Greening. “Finesse, not grunt” is how some MR sailors put it, with the air of people who feel that the skiff types are less versatile and refined.

The detailed evolution of Merlin and National hull shapes are a story for another time (and better told by people who know the classes properly!) but as usual in dinghy design, the long-term trend is a tale of Fs – a consistent move towards hulls that are flatter, finer forward, fatter aft, flared and faster. Materials technology has always been a critical driver of these changes. The early Nationals, with their 190lb/86.2kg bare hulls, 45-50lb (20-22.7kg) centreboards, copper buoyancy tanks (4-5lb/1.8-2.3kg) and floorboards to protect the delicate ribs normally weighed over 118kg/260lb.  Rule changes and wooden centreboards reduced the all-up weight by 100lb/45kg or so.  When lighter sailplans and self bailers came along, bows no longer had to be full enough to lift a heavy rig over the waves and to stop spray coming aboard. Ian Proctor was a pioneer in alloy masts that allowed more powerful and predictable sails to be set. As spars, sailcloth and fittings improved rigs became more powerful, and in turn planing became more common and more important.

The boats of the late ’50s show the way the trends were moving. As noted above, as techniques improved it was found that the National 12s could plane more and more often, and hull shapes changed to put the accent on planing performance. As Uffa noted, “the tendency therefore has been to widen the topsides, transom and the run which enables them to pick up their skirts and scuttle along before the wind. The wider topsides give them a little extra sitting out power, but must never be allowed to get down into the water where the extra beam would slow them.” A late ’50s N12 design from his board (below) shows these changes.

This National 12 plan from Uffa’s 1959 book Sailing Boats appears to be of Smuggler, one of only two Nationals he ever drew. The bow section has changed little since the Uffa King, but the stern is significantly flatter and dramatically wider. The Smuggler was said to show “radical new thinking” and have “the widest transom ever seen in this class” – a tribute to Uffa’s ability to remain current.

As Uffa’s star faded, that of Ian Proctor grew brighter. Proctor’s early Merlin-Rockets, he wrote, were an attempt to combine the way the Merlin’s river-style shape could slice upwind and in light winds, and the way the more powerful Rocket could reach in moderate air. They were comparatively fine in the bow and unusual because they lacked the “shoulders” – volume in the topsides around the mast – that was common at the time. Over the years, Proctor moved towards finer bows, wider overall beam and less bow rocker. Because his designs are narrow by modern standards, they are now considered only as “river boats”, but their low wetted surface and manoeuvrability still make them surprisingly competitive in light winds and narrow waters.

An early Proctor Merlin Rocket, from the book “British and International Racing Yacht Classes”, published in 1954. It has a flavour redolent of the Uffa Fox boats of the ’30s.

The trend to greater emphasis on planing continued with the introduction of dacron sailcloth in the ’60s. Suddenly, sailmakers could build more controllable shapes, with larger roaches. The Merlin and National 12 both developed big roaches on their mainsails. The National 12’s actual sail area started to climb from the original nominal 8.4 m2 (90ft2) towards the current area of around 11m2 (118ft2). The Merlin followed the same route. According to the Portsmouth Yardstick of the time, the National and Merlin both increase their speed by 5% when dacron came in- about twice that of other classes.

From the outside, one of the most significant boats of the time seems to be March Hare, the brilliant creation of amateur designer Mike Jackson. Technically, March Hare (which we’ll hear more of later on) is notable for being perhaps the first round-bilge conventional dinghy (as distinct from scows) to completely abandon the Vee-shaped sections that Uffa had introduced, in favour of U-shaped sections with a flat area along the keel line. Today it’s often called a “planing flat” but those who design clinker hulls use the term “flat garboards”.  The arrival of the “planing flat” and U sections marked the end of the era when the Vee-shaped hull that Avenger had introduced was a standard feature in racing dinghies. The U-shape allowed for narrower waterline beam, less wetted surface, and more planing area, and today it is a standard shape for a racing dinghy.

A sketch by Ian Proctor in a Yachting World article in November 1954 gives a clue to the way designers of the time thought about flare. Proctor wrote that a boat with concave flare “is easily capsized once it has been allowed to heel more than usual in a heavy puff, simply because the wind gets under the resistant expanse of flared topside and pushes…and the gunwale is taken closer to the water by the flare”. He noted that convex flare “is better but suffers slightly in the same way”. Observers from the early days of the wide National 12s noted that they had to be sailed very upright to keep the leeward gunwale from scooping water in heavy chop, but the greater power of the wide boats more than made up for it.

Another major shift was towards ever-increasing topsides flare. In earlier times, designers kept boats comparatively narrow. They were were concerned about reducing weight and windage, and that wider boats would scoop up water when they heeled. As late as 1966 the Proctor Mark IX, just 1.52m (5ft) wide, could still win a national Merlin Rocket title.

Perhaps because of improvements in gear like self bailers and transom flaps and more powerful rigs, in the late ’60s a new breed of designers increased flare and gunwale beam year upon year, creating more leverage for the crew and allowing them to drive the boats harder.  Designers like Martin Jones increased the gunwale beam of Nationals and Merlins by up to 76mm (3in) per year while still keeping the wetted surface to the minimum. A boat like Xpectant, generally considered the first truly wide Merlin, was 1.9 m (6ft3in), across the gunwales but only 1.1m (3ft8in) on the waterline. The leverage the crew could exert made such boats enormously powerful upwind and reaching, and they made the old narrow boat obsolete in strong winds.

Both classes banned hollow flare and eventually placed limits on overall beam, but not before the Merlin had swelled out to a massive 2.2m (7ft3in) and the National to 6’6″ – over half as wide as they were long. The righting moment increased in proportion, making the righting moment of later Merlins about 25% greater than earlier boats, and giving the crew about as much leverage as a conventional trapeze dinghy like a 470.


Baggy Trousers, a hig hly successful 1981 vintage National 12 by Rod Peebles, shows the dishy, flared shape the class developed. Unlike the Merlin, the National 12 dropped the old rules requiring hulls to be clinker planked, and Baggy was one of the first ‘smooth skinned’ boats. One of the features of the National 12 is that a wide variety of different designs, of widely different ages, can still perform well in certain conditions and the Baggy Trousers is still known as a very powerful boat and an excellent high-wind performer. In contrast, the Baggy’s predecessor, Pipedream, was known as a light-wind flyer.  Peebles believes that they were both actually good all-rounders that became known as specialist designs for reasons that were not related to the design. There’ll be more information on National 12 development later. Copyright Rob Peebles; reproduced with permission.


Today the Merlin fleet is dominated by variations on the Canterbury Tales design by Ian Holt with Jon Turner. They are supremely sophisticated boats that are so highly refined that they can out-perform many boats that should, by many theories, be faster. The modern Merlin, for example, is only one or two percent slower than the longer, trapeze-powered Fireball. It’s a tribute to the refinement of these boats that a two-person hiking boat that still has a 98 kg hull (although one loaded with 10kg or more of corrector weights) hull to be able to sail at such speeds.


Keith Callaghan was one of the most successful Merlin designers of the 1970s, an era when dozens of new boats were launched each year. The lines of his 1977 design Hazard (above) show the flat bottom sections and huge flare that remains a characteristic of the Merlin and National 12. The very heavy rocker aft was a Callaghan trademark that has been dropped in his latest design (bottom) “to take advantage of the power developed by the sophisticated modern rigs”.  With permission from Keith Callaghan; more from him about Merlin design later.


The National 12 has followed a different route. It’s one of the few development classes that still has a wide variety of different designs at the front of the fleet; a menagerie of little thoroughbreds. On the many British racecourses where tacks, tide-cheating and turns are frequent, good and unbiased observers say that the N12 can keep up with longer and generally faster boats like Tasars. In very light and tight racing it can even beat lightweight skiff-types like Cherubs. “On handicap they do best on beat and running courses, and in wind up to when trapeze boats start planing” says Greening.

Dave Greening’s Annie Apple shows the flared shape of the modern 12. The current boat have sophisticated features like an automatic “dangly” jib pole that can be flown to leeward to improve jib shape on broad reaches, and T-foil rudders to reduce nosediving. Pics from the class association site.
Dead Cat Bounce, currently the most successful design in the National 12s, was designed by Jo Richards, Olympic medallist and one of the most versatile of sailors and designers. The pic below, of a wooden version under construction by boatbuilder Simon Hipkin, shows the huge flare of the modern N12.  The Dead Cat Bounce design features a T-foil rudder which provides lift and allows the planing flat down the centreline to be much narrower than in earlier boats. The bottom pic is of a production version by Pinnell and Bax, showing the rudder angle adjustment system. Pic above from the class site; centre pic from Simon Hipkin, with permission; bottom pic from the Pinnell and Bax site.



Both classes have suggested handicaps for older boats that suggest that the MR and N12 go about 10% faster since the days of Kate, Rocketoo and Gypsy when compared to one-designs and earlier development class boats.  Not surprisingly, comparison with the Firefly seems to confirm that figure.  In their early days, the National 12s were almost the same speed as the strict one-design Firefly; now they are now rated as 9% faster than the Firefly (which has also been slightly updated) and the very latest N12s would be even quicker.  That, of course, is the way MR and N12 sailors like it; they get the security and big fleets that go with boats that hold their value, along with the technical interest of development classes.

The modern Merlin; carbon and corrector weights everywhere, a sophisticated rig that rakes and depowers with the pull of a single string, and huge flare for hiking power. For many years, the class has almost been a one-design based around variations of the Canterbury Tales design of Ian Holt and Jon Turner. Pic above from the HD Sails site, pic below from the Pinnell and Bax site.


Where the MR and N12 are unusual is that many of the older boats remain competitive in certain conditions. The more rounded sections, narrower sterns, greater rocker and smaller beam of the old boats add up to shapes with lower wetted surface and less loss of pace when tacking or heeling to gusts and lulls. On confined tidal waters, rivers and small lakes where fast tacking and low-speed characteristics count high, the old boats can be extremely competitive. Most sailors agree that some of the old boats are equal to the newest designs on inland waters; some believe that some boat decades old are actually faster in light winds on places like the River Thames.

So looking at boats like the Merlin and National 12 shows us that if rules stay largely the same, sixty or seventy years of intense development in design and technology can increase a class’ performance by about 10% – enough to transform a boat from a malleable family boat into a sensitive and demanding racing machine that can beat trapeze-powered lightweights much of the time.  On the other side, the continuing competitiveness of older designs in light winds and confined waterways shows that the classic-style hull is still hard to beat in its conditions, as well as (according to some) being easier to sail in some ways. That sounds like a win/win situation.

[1] ‘The National Twelve-Foot Class’ by Ian Proctor in “British and International Racing Yacht Classes”, H E Whitaker (ed) 1954, p 167

[2] “this 12-footer, because she was shorter, and still carrying two people”:- ‘R.Y.A. 12 Foot Dinghy’, in  “Sailing Boats”, Uffa Fox, 1959, p23. Much of the other information about the Uffa King comes from this piece.

[3] “and within three and a half years the National 12 was the most popular class in Britain”:-  The National Twelve-Foot Class’ by Ian Proctor in “British and International Racing Yacht Classes”, H E Whitaker (ed) 1954, p 166

[4] The National Twelve-Foot Class’ by Ian Proctor in “British and International Racing Yacht Classes”, H E Whitaker (ed) 1954, p 175

5 “Sailing Boats” p 27


Author: cthom249

A former sailing journalist and magazine editor, I was lucky enough to grow up in Sydney, one of the world's sailing hotspots and to win national and state championships in classes like J/24s, Windsurfer One Designs, offshore racers, Laser Radial open, Windsurfer OD Masters, Raceboard Masters and Laser Radial Masters, to get into the placings in a few other classes, and do a few Sydney to Hobarts.

One thought on “Pt 1.19 – From Kings to Bouncing Cats: the British development classes”

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