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Fast Cruising Cat .....

TEKTRON 35

designed by: JOHN SHUTTLEWORTH

ONE OF THE MAIN AIMS of this new design (writes John Shuttleworth) was to produce a boat with comfortable living accommodation space with as little sacrifice as possible to sailing performance, windward ability and seakeeping qualities.

This 35ft catamaran exemplifies the new generation of performance cruising multihulls, designed and engineered with the latest thinking on structures and computer designed hull forms. The boat is nevertheless suited for skilled amateur construction. The first production version is currently under construction in Canada by Eugene Tekatch, who built the Tektron 50. The Tektron 35 has been developed from a previous 35 ft cat and the Spectrum 42, 44 and of course the Tektron 50. The 42's now have several ocean passages behind them and the features of exceptional pitch damping and bow slightly raised on a reach have been well tried and tested and have proven to be outstanding features in improving general cruising comfort at sea, along with greater safety and fine seakeeping qualities.

Apart from the great benefits that can be derived from flaring the hull above the waterline, in terms of keeping the bow up on a reach, the flare gives a massive increase in interior volume without increasing the windage of the hulls at all. For instance, above the waterline the hull flares outwards to give a maximum beam at eye level of 1.9m, the impression of space is tremendous and cannot be matched by any similar length catamaran whose topsides rise almost parallel from the waterline.

Construction and long term fatigue

By using integrated structural techniques the hull weight can be carefully controlled and the net effect is a strong, light displacement hull with a good long term fatigue life. Light weight with high strength pays in a cruising design because the weight saving can be translated into a payload capacity. The Tektron 35 will weigh 2.4 tons in racing trim with a further payload capacity of 2 tons. Construction is Airex foam sandwich with glass fibre skins and a limited amount of Kevlar in the inner skin of the hull bottom for impact resistance. Carbon fibre in the main beam ensures that the boat is stiff enough to maintain a straight forestay which is essential when the headsail sheeting angles are as low as 6 degrees.

Hull Aerodynamics and Hydrodynamics

The whole boat has been designed with very rounded form and the cockpit and crossbeam structure areas as aerodynamically clean as possible. All the deck edges have generous curves. The flare in the hull creates the interior volume needed for comfortable cruising, without increasing the frontal area at all. Forward the deck edge is significantly less rounded than amidships to make it easier to move around on the foredeck, but as the hull profile rises the radius increases to reduce the coefficient of drag as much as possible.

The hull and deck are designed on the computer using computer graphics and 3D modeling techniques. The computer is able to draw sections through the boat at any angle, i.e. in the direction the the wind strikes the boat. This is of great assistance in allowing us to see the lines of air flow as the wind would actually hit the topsides of the hull. To confirm and develop these ideas, we arranged to test a number of catamaran models in a wind tunnel in order to arrive at accurate figures for the aerodynamic drag to the hulls and to relate our computer modeling to real results.

Rig

A wing mast has been designed as standard even though this is a cruising boat. I feel that the wing is very simple to operate and allows a self-tracking jib on a very efficient clean rig. Tracking becomes a pleasure when the only thing you do is turn the wheel - no sheets to winch - no flogging lines, just turn and away you go. The windward sail plan is the high aspect ratio jib and fully battened mainsail, with a large genoa for off the wind speed and light winds. In a storm the wing can be used as a storm jib, or it can be tied down to stop the boat. Eugene Tekatch proved that this can be a very successful way of handling a cat in a storm while on the Tektron 50 in severe gales off Bermuda.

Interior

The most significant change in the interior from our previous designs of this type is that the saloon has been moved to the stern of the starboard hull with the galley amidships. This has been achieved by increasing the flare at the aft end of the boat. Of course this also makes a huge aft double berth in the port hull. The intention of the layout is that the daytime activities are carried out in the starboard hull, while sleeping accommodation is primarily in the port hull. If one has children aboard, they can be happily asleep while you are with friends in the saloon. Also there is much more opportunity to have some privacy on a long voyage.