Far from reducing a designer to ‘jack of all trade’ status, the ability to embrace both disciplines of sail and power can be the making of a yacht designer, says Stimson Yachts’ Christian Stimson.

Against a backdrop of ever increasing specialisation, where designers are encouraged to hone their skills to meet increasingly specific design criteria, the marine world is bucking the trend. Yacht designers are being called upon to broaden their proficiencies, to embrace both sail and power disciplines, heralding the return of the ‘old school’ of designers, epitomised by the likes of the great GL Watson, who could design equally successfully in either camp. Far from being a ‘jack of all trades’, Watson’s ability to transfer innovation, knowledge and experience gained in one area to another proved vital in creating boat designs with more rounded performance profiles and better sea-keeping characteristics.

At Stimson Yachts we believe the key areas of ‘concept transfer’ are firstly that performance sailboats are now so light and powerful that they are exhibiting speed/length relationships more akin to powerboats; and secondly that the design of powerboats can draw on the racing sailboat designer’s aim of extracting as much speed from as little power as possible and maintaining that performance in a full spectrum of weather and sea states. This is particularly notable at a time when powerboat builders, due to rising oil prices and environmental concerns, are looking for more fuel-efficient solutions rather than simply installing bigger engines.

Historically, the production powerboat market has been driven to sell fairly formulated accommodation solutions, with products differentiating themselves only on a price/quality and price/speed basis. Formulated accommodation drives the hull form to be broader, fuller, and with greater volume. Attempts to ‘shoe-horn’ the 10-gallon interior into 10-pint hull, along with current production build techniques and an ever increasing list of ‘extras’ result in high displacement/length ratio (read ‘heavy’) and low beam/length ratio (read ‘fat’) hulls. These shapes require more horsepower to pip the competition in the speed stakes, often compromising the hull form further (in the form of flatter Vs, wider beam and broader chines) to make the maximum speed (often the measure of a boat’s value). However, this is a speed only attainable in flat water, and any sea often results in such severe slamming and an uncomfortable ride, that throttling back is the only outcome that leaves the cutlery draw shut and the skipper’s fillings in place — but with the unpleasant side effect of a bows-up, wallowing motion.

At Stimson Yachts we are taking a different approach. For us it’s back to basics, combining smart design with well thought-out material specification to fulfil requirements, yet still addressing the economic issues in a production environment. Our current 50ft powerboat, designed in conjunction with JQ Barnett in Seattle, Washington, features a sea-kind, modified-V hull form, which has overcome the drag penalty of the sea-kindly-shaped hull through the adoption of lightweight construction techniques. This has improved the power-to-weight ratio to the extent that the speed/power relationship is very close to that of the ‘optimum’ deep-V form, yet is attainable in far more severe sea states. We have specified foam cored, E-glass and epoxy laminates and have incorporated load-bearing furniture and partitions in the accommodation to help save weight.

Racing sailboats, on the other hand, have always been weight aware, and with the advent of canting keels, the shorthanded performance cruiser can now attain significantly higher speeds than the traditional ‘blue water’ cruiser. As an example, we have a design in progress for a 60ft, canting-keel deck-saloon cruiser. The carbonfibre mast sets a huge sail plan, yet by drawing from current developments in sail handling and deck layout — particularly from the Vendée Globe Open 60 fleet — it is one that two people can manage easily. As a result of a slender hull, light displacement, high stability and big rig, the yacht is sailing upwind at near ‘hull speed’, and is fully planing in 12kt of wind.

Given that these boats now sail at very low heel angles (due to the high stability afforded by the canting keel), the design of the bow sections to minimise slamming requires a departure from the ‘traditional’ shapes for a lower speed, heeled yacht form, and is more akin to a V’d powerboat form. The hull laminate spec is pretty much that of a VOR 60 utilising Kevlar and epoxy laminates for impact and slamming resistance. Aft, the planing speeds attained have resulted in the adoption of chines for both drag reduction and dynamic stability at high speed. The sizing of rudders and selection of foil sections is becoming critical as the forces generated vary exponentially with speed — so a small rudder is required for low drag.

With projects such as these running concurrently we’ve been able to draw on the lessons learned and solutions arising — and improve the final product as a result.

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