If I were asked the ideal length for a two-man racing dinghy without sitting-out aids for the crew, the unhesitating answer would be 14 ft. Of course, there are some excellent two-man boats on either side of this length, but the best of the bigger ones mostly have trapezes or sliding seats to give the crew more sitting-out power. The best of the smaller boats are just a bit too short to enable the hull to plane in less than a fairly fresh breeze, though they may have just as intriguing an all-round performance and, in some cases, even greater ability in light airs and to windward.

As a result 14 ft seems to be the magic length. It is not surprising that at this length we have two of the most interesting classes in the country from the point of view of design. The first is the International 14, and the second the Merlin-Rocket. Both of these are restricted classes, in which the design of hull, rig and sail plan can be varied within certain fairly generous limits, so that there is opportunity for the development of ideas on these subjects.

Not only is 14 ft a good length of boat from the performance and handling angle, it is also a good size from the point of view of the designer. A 12 ft racing dinghy, such as a National 12 for instance, is so short for the weight it has to carry that a designer's opportunities for variation in hull shape are comparatively limited, especially as there are certain restrictions on various measurements at mid-length. There is far more scope in a 14 ft hull.

For that reason there has been rather more development in the 14 ft classes since the war, than there has been in the 12's. For example, well-sailed pre-war types of National 12's are more often found near the head of the fleet in that class than are 1948 vintage Merlins or International 14's. In all cases the older boats are at their best, comparatively speaking, in light airs and smooth water.

I suppose it would be true to say that designers are prejudiced towards producing boats that are most suitable to the conditions with which they are most familiar. If a designer sails himself at a place where he sees full-bowed hulls pounding and having all the life knocked out of them in a sharp popple, then he is likely to produce hull shapes that take more kindly to these conditions. If, on the other hand, he sails mainly where he sees round- sectioned, heavily rockered hulls spin easily from tack to tack and accelerate rapidly on the faintest of zephyrs in a narrow and sheltered river, then perhaps he will be inclined to concentrate on that type of hull. It is unlikely, however, that a designer of experience will allow himself to disregard any of the conditions under which his boats are likely to be sailed.

My own sailing is chiefly on the sea and it is sea boats that I like designing best. Perhaps, therefore, I am a little biased in thinking that to judge the merits of a hull shape from the point of view of speed alone you must sail it on open water, and in a reasonable breeze. However, I do not think it due to any bias that I believe far more advances to have been made in the sea-sailing type of dinghy in the past decade than have been made in the light-weather, inland type of boat. Corona, designed 22 years ago, is still probably the fastest International 14 for sailing in such places as the upper reaches of the Thames - though various changes in the class rules now make her type unrepeatable.




Fig 1. The original Merlin design, by Jack Holt. Note how the turn of the bilge runs upwards at each end, producing bow sections that are very straight towards the bottom, and waterlines that are hollow at the bow. Amidships, the bilge turns into topsides with tumble-home and the section is rounded to give a low wetted surface when heeled.



Lucky, designed ten years ago by Jack Holt, is just about the fastest Merlin-Rocket in light airs and narrow waters even today (1959).

There are several reasons for this. The first is that, though in the case of the Merlin-Rockets more sailing is done with these boats on inland waters, the championships and the most important races of the dinghy classes are generally held on the sea, or in open water. Moreover, most dinghy sailors who sail primarily on inland waters like to race on more open water sometimes, whereas the reverse is not so much the case. Owners and designers, therefore, tend to concentrate more on open-water types of boat.

There is another, more technical, reason. Ability in light airs is dependent on one thing above all others as far as hull shape is concerned - low wetted surface area. The shape which gives the least wetted surface for a given displacement is a sphere, and therefore light-weather boats usually have lots of curvature in the keel, round sections and, very often, round shoulders on to which the hull can be heeled when sailing in light winds and which give support to the forward end of the boat without the wetted surface that accompanies a long slim bow. These are fairly simple, basic facts, that any experienced designer knows, and they do not allow for much argument or development.

The third reason is somewhat more subtle and not really connected with the design of the hull at all. It is that the technique of sailing in confined waters in light airs is so important that helmsmanship counts for much more than hull shape. In other words, a poor light-weather boat can be made to go reasonably well by a good light-weather sailor. This is unlike a poor sea-boat, which cannot be made to go in waves, even by the best of sea sailors.

In the early days of the Merlin Class, which was started in 1946, the boats were nearly all of the original shape and rig designed by Jack Holt and published by the Yachting World, which was instrumental in getting the class under way. Though this design was good all round and a real thoroughbred, as one would expect, there was no doubt that it had the bias towards sailing on inland water. In spite of having a modest sail area of 100 sq ft, the sail plan towered 25 ft above the gunwale, and was matched below water by a very deep and narrow centreboard. Jack Holt once told me that he had never wanted this rig himself, but was persuaded to produce it by the syndicate of dinghy owners that sponsored the prototype. These early Merlins were distinctly hard work to hold up in a blow and there were occasions when squalls, which now would not worry a modern boat, bowled them over like ninepins. After a few years new rules were made to force the maximum height of sail plan down by as much as 2 ft 6 in, which undoubtedly produced a far better rig. In the 1958 Merlin-Rocket Class championships five of the first six boats carried even lower rigs than the present maximum height of 22 ft 6 in, which is a significant fact, and more and more new boats are adopting low rigs.

At the second championship meeting of the Merlin Class, in 1947, G. O'Brien Kennedy turned up with a rather more powerful type of hull and, in spite of the fact that this dinghy, Mercury, was still almost in the fitting-out stage when the ten-minute gun went for the first race, she won it easily. She was third in the next race, but broke some gear before the third race, in which her chances were best because it blew very hard. Even so, Mercury came second on points for the whole meeting.




Fig 2. The bow of the Rocket is almost the direct antithesis of the Merlin's. The sections are rounded towards the bottom and straight on the topsides. The bilge in this boat is lower amidships and much lower at the ends. There is far less rocker to the keel, particularly forward and, as a result of this, the hull shows hollow waterlines forward in spite of the fullness of the bow sections low down.



Mercury's success was a pointer to the future of the class. The next year, 1948, Jack Holt himself produced a more powerful type of hull, which, though sailed by a light helmsman and crew in the championships that year, mostly in moderate or fresh winds, came second. This boat, Dilly, was only one point behind the championship winner and my impression was that she was a much faster boat.

Nevertheless, the influence of inland sailing was still very strong, and the next year saw the introduction of the "banana boat" type of hull, of which Lucky was one of the first. The deep, heavily rockered hulls of these boats lifted their ends clear of the water and gave them a low wetted surface and the ability to spin rapidly from tlack to tack. They were an immediate success on inland waters, but did nothing startling on open water, which was perhaps only to be expected. O'Brien Kennedy came to the championships with a new boat of a powerful type that year, but capsized and was badly damaged in the first race while in second place and challenging for the lead. The championship winners were Jack Holt and Beccher Moore in Gently, one of the original Merlins, with a tall rig; she had already won the championships twice. Dilly was second, sailed by a new owner.




Fig 3. A "banana boat" type of hull, designed primarily for light weather and quick tacking in confined waters. The rocker is more evenly curved, the end being well lifted. The sections are well rounded, especially those on which the hull sails when heeled in light airs. The waterlines also show the same roundness.



The next year was a particularly interesting one in the development of the class though, metaphorically speaking, it was a stormy one. It was in this year that the Rocket Class was started, based on a design by Digby Coppock. This was a much more powerful boat than the average Merlin, with a rig 4 ft 6 in lower than the original Merlins. Intended as a less acrobatic type of dinghy, which could be used occasionally for family sailing as well as racing, the Rocket evidently filled a gap.

The most important thing that the Rockets did for the future of the class, which by the spring of the following year was to be an amalgamation of both types into the National Merlin-Rocket Class under the wing of the Royal Yachting Association, was to illustrate clearly the potential advantages of a hull and rig with considerably more power. Having sailed Rockets against Merlins with some considerable success, Wyche & Coppock built a boat, named Rocketoo, which fitted the rules of both classes, being a little finer forward than the out-and-out Rocket, but a beamier and more stable boat than was common in the Merlins, and she was given a low rig.

Rocketoo really stirred everything up by winning an important open race at Hayling Island by a long way, soon before the 1950 championships. It was her first public appearance. At the championships, when sailed by Bruce Banks, she won the first race, retired from the next when lying fourth and was fighting for third place with Gently in the final race when she capsized. Third place, which I believe she would have got had she not capsized, would have made her tie with another boat for first on champion- ship points. As it was, she was righted and crossed the finishing line in waterlogged condition, coming sixth on final points.

Gently tied with another of the original Merlins, Clare, and a more recent Jack Holt type, Tiptoes, as championship winner that year, but even with 27 stone aboard we (I crewed for Beecher Moore) found it very hard work to hold her up. It was the last year that the 25 ft height of rig was used, for the new rules came in a few months later.

The fusion of the Merlin and Rocket Classes the following spring did not immediately result in a hybrid between the two types. On the contrary, several of the best helmsmen in the next championships sailed boats that were extremes of each type. Strangely enough, because the weather was also of extremes, each type did about as well in the overall results. However, it was soon plain that the future of the class would lie somewhere between the two types.

It was fortunate for me that I had sailed in both types and could appreciate the good points of each. Having raced Merlins fairly frequently since the class started, I had a profound respect for their capabilities, but I had also been lent a Rocket for several months and knew what she could do in a moderate breeze when there was some reaching on the course. I also had experienced the chagrin of having less powerful Merlins pass me in moderate breezes to windward simply because they cut more cleanly through the water, and I knew what it was like to have the Merlin type slide past on all points of sailing directly the breeze fell light.

In designing my first Merlin-Rocket in 1951, I tried to lake some of the good points of each and put them together. However, there was one feature common to both to which I took a rooted objection - their padded shoulders. I gave the new design much finer shoulders than the others. It is not easy for the novice designer to instil sufficient faith in his wares unless he can demonstrate their ability in practical manner and it took eighteen months to sell the prototype of this design. She was disposed of quickly enough after the 1952 championships, in which Dick Vine sailed Tony Fox's boat of this shape into second place and my own Cirrus was first.

The following year the championships were at Cowes, and it was almost a clean sweep for boats of Jack Holt's design, with the heavily rockered "banana" type Diabolo, who had been third the year before, a clear cut victor. Generally speaking, there were either light airs in those championships, or the water was too rough for a planing type to show its paces properly. A new design I had produced, rather more powerful than the "Cirrus" type, behaved in a depressing manner, though she was the first of the widely flared dinghies and came into her own several years later.

It seemed to me that what had killed my designs in the choppy conditions of the Solent was lack of rocker. Hulls with more fore and aft curvature appeared to take more kindly to the waves - and of course, with less wetted surface they went better in light airs. I could not, however, bring myself to sacrifice the long, easy run that I felt was the feature that made the "Cirrus" type plane fast, so the rocker was increased farther furward, which by taking the hull deeper at that point, permitted the sections to be more sharply vee'd. This rocker was expected also to give dynamic lift to assist planing and therefore a further slice off the shoulders could be afforded. At the same time, the hull was given a lot more flare in order to increase the sitting-out power, without increasing the waterline beam. In the next championships three of the first five places went to boats of this design, and over two hundred of these Mark VI's have been built, which is a gratifying number in an established restricted class.

The next year, 1955, saw a triumphant come-back for Jack Holt's designs in the championships. During the previous two years he had been producing more powerful boats. They were wider on the transom and a little flatter and, unlike my hulls, were also plumper forward. Leslie Brian, who had previously owned the successful Diabolo, won the championships for the second time in one of these new, powerful Holt boats, and Holt was second himself. Another of the same type was fourth, and the third, fifth and sixth were older Holt types. The best that any of my designs could do was to tie for sixth place.

This was a nasty jolt, but a jolt is sometimes a good thing, for it stirs up fresh thoughts. In any case, the situation was not depressing, for the conditions did not allow any definite conclusions on design to be reached. That year I had designed a Mark VII, which was very heavily rockered, with exceptionally vee'd bow sections, leading into a run the last few feet of which was straight and ended in a flatter than usual transom. She was experimental and, knowing her to be such, I had one built for myself to see what happened. The idea was to sit the bow sections well in when going to windward or when running and in light air, but to sit the stern down for planing reaches. This worked out reasonably well in practice, but she was a hair-raising ride in anything of a breeze and exhausting to sail to windward. However, she certainly demonstrated many points in hull design most emphatically and, as an experiment was very valuable to me.

The Mark IX design, produced soon after the championships, was a direct result of the lessons taught by the VII, which had confirmed to my satisfaction that planing ability is dependent more on the shape of a hull aft than on its shape forward. The first of these boats was Crew Cut, which was second in the next championships and won them in both 1957 and 1958. This hull, like the VII, is fine forward, but there is less rocker and the rise of floor in the aft sections is less. There is considerable flare amidships to give the crew more sitting-out power, but this flare decreases towards bow and stern, at the forward end to reduce windage and at the aft end to reduce heeled wetted surface.

Though the Mark IX was acknowledged to be a fast boat, she had, probably justifiably, the reputation of not being an easy one to sail. The main point contributing to her rather uncertain temperament is the hard turn to the bilge aft. This hard bilge, in conjunction with the flat floor, tends to dig into the quarter wave if she rolls when travelling off the wind at speed, the hull is thrown violently back on to the other bilge, then back again, until the situation is corrected by agile crew work - or the whole outfit goes for a swim.

In 1957, when I designed the next new hull, therefore, the sections aft were eased on the bilge and the deckline widened. More flare was also given forward to match this. These changes have had a quite profound effect on the handling of this type of hull, known as the Mark XI (the Mark X being, generally speaking, a flared version of the "Cirrus" type). Mark XI's came second, third and fourth, after Crew Cut, in the 1958 championships, all the others in the first ten being Mark VI's, with the exception of one Mark V.

The demand for boats suited to inland sailing conditions, with little regard to their ability on the sea, is still considerable and to meet this the Mark VIII was produced in 1955. This has a more evenly curved keel line, more curvature in the floor of the sections in the forward half of the hull, and a bilge intended to provide a low wetted surface when the boat is heeled on to it. The planing properties have been retained in fairly good measure, but they are harder to hold up in a blow than the VI's and XI's and do not like a head sea. They have been successful in the conditions for which they were designed, but the next hull shape I want to produce will be a development of this type.

For the past few years Roy Rigden has been producing beautifully finished boats to his own design which, particularly when sailed by himself, have done well on the sea. planing fast and sailing cleanly to windward.

The powerful hulls of the Adur Boatyard are very potent in moderate or fresh conditions, so long as the water is reasonably smooth. They are very full in the bow, which appears to give them lift in marginal planing conditions, but perhaps causes them to slow up a little to windward in a popple.

The most successful amateur design of recent years has been Leslie Dyball's Slippery Sam. In many ways this seems to be an almost ideal boat for Leslie and his wife to sail, for they are light and Slippery Sam has a powerful yet com- pact type of hull, in which wetted surface is saved without much sacrifice to other desirable qualities.

The modern designs of Jack Holt, who was the pioneer in this class and has produced successful boats for it for over thirteen years, now show little resemblance to his original tall-rigged Merlin. They have less shoulder than they formerly had, but they still retain some; and it is, I think, this feature that makes them quick to accelerate in the puffy conditions inland under which they frequently sail, because it resists the tendency of the first force of the puff to be absorbed in pushing the bows down, before the boat has had a chance to move forward and create a bow wave on which it can support itself. The full drive of each puff seems to be used to drive the boat forward, not to press her down.

Without doubt there is a long future ahead of this active and virile class, with many more younger helmsmen coming into it from other trainer classes. The competition within the class has never before been as keen or the skill as great as it is now (1959).