Helmsman Gerry Driscoll is joined aboard Intrepid by French Cup challenger Baron Marcel Bich. As well as introducing the separate keel (plus trim tab) and rudder to the 12 Metre class when she first went afloat in 1967, Olin Stephen’s Intrepid featured many other innovations including a lower boom to maximise endplate effect
Nothing new under the sun (definitely)
Dave Hollom was designing championship-winning model yachts and glider foils for many years before he created his slender International 14 design Departure in 2013 – which is still the 14 to beat six years later. He suggests that his unusual back story plays a crucial part in the success of his current full-scale designs
Once upon a time, a long time ago in an era now long gone, a designer of model sailing craft had an idea to make boats sail faster. He reasoned that, in classes that only restricted physical overall length rather than waterline length, by designing a boat with overhangs that exceeded that length, but having a waterline length at or a little less than the maximum allowable overall length, and then cutting the over- hangs off to comply with that maximum physical length, he would produce a boat with the lines of a much larger boat and thus with greater form stability and a higher potential speed. The cut-off bow was rounded off and the resulting shape looked much like the front of a duck and so the designer, HB Tucker, named the type ‘Ducks’ but they became universally known as ‘Tucker Ducks’. He designed boats to the two, at the time, restricted or box rules that measured
overall length: the International Marble- head class (50in LOA), and the 36in Restricted class. To my knowledge there were two Marblehead designs, Jemima Duck and Emma Duck, and the 36in design was, I believe, Donald Duck. They were successful too, the 36in boats win- ning the British Nationals in 1948 (Donald Duck) and 1950 and 1952 (Quacky 2). There were also other successful designs
by other designers that adopted this design philosophy. My own first design, Blue Disa, was lucky enough to win the 36in Nationals in 1957 and Alex Austin’s Exasperachun won in 1977. A development of Alex’s design for radio sailing, Taxachun, went on to win the Radio Nationals nine times. I believe the Tucker-designed Marble-
head ducks also won a number of national championships but I have been unable to itemise these successes. However, there were plenty of other winners of both com- petitions with more conventional bows so in no way could it be described as a design breakthrough, just a design path that worked and sometimes produced a winner. Recent developments in some offshore
classes, notably the Mini Transat racers, have followed a similar design path, though around 60 years later, and are described, inaccurately I would suggest, as scows. But what’s in a name? As Shakespeare
said, ‘A rose by any other name would smell as sweet.’ A scow to me is a wide and shallow flat-bottomed boat having a short waterline, when upright, and a long over- all length. It also features almost parallel sides in plan view and works best with the
crew supplying the righting moment and having twin bilge boards. This combination allows the boat to be
sailed heeled on one bilge where, because much of the displacement contained in its wide upright shape has been lost, it sinks lower in the water to maintain equilibrium and thus uses all, or nearly all, of its length. It then becomes a long, narrow boat with minimal wetted area, low wave drag and, because the centre of buoyancy has moved a long way sideways and the crew have moved a long way in the oppo- site direction, the righting moment is large. This is a recipe for speed and the low drag of the long, thin, low-wetted area shape, in some cases, overcomes the inefficiency of sailing with a heeled rig. But the proof of the pudding is in the
eating. In head-on racing in the Moth class before they foiled there were two distinct types: the scow, much as I have described it, and the skiff, a slim craft with a conven- tional bow. Initially the scows won in a breeze and the skiffs when it was lighter, but in the end the skiffs, particularly the Magnums designed by Mervyn Cook, dominated in all weathers. There are two main reasons that make a
true scow less effective with a ballast keel. Firstly, in light airs it will sail too upright to make it efficient. The wide beam means both a high wetted area and a high wave drag when upright. To get the advantages of a scow it must be sailed heeled on one bilge and a ballast keel prevents this in all but a brisk breeze. Secondly, when heeled the centreline of the hull jacks out of the
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