Round Texel Race Proa

The Round Texel is billed as the largest cat race in the world. The course is around the dutch island of Texel in the North Sea. There were 550 entries last year, and the winner was a Tornado. It is usually a fresh breeze event, with sizable surf making launching and retrieving interesting. The max length is 27'/8.2m.

We were asked to design a boat which would have a good chance of beating the Tornados. We therefore used Tornado numbers as a benchmark.

click to enlarge

The boat is max length and 6m beam, to give equivalent righting moment to the Tornado. It has the same sail area, but in a large windsurfer type rig. The self vanging wishbone boom removes the weight and complexity of the traveller, and reduces sheet loads significantly. A major problem was getting crew weight aft while reaching. The standard approach to this is to have equal length hulls, and a large trampoline. We took a lighter, less stressed approach and used a single beam, with the ability to be canted aft. The crew sit in seats on the end of the beam, and in breezzes avove 15 apparent should not have to move inboard. The canting beam requires a canting ww hull. This is possible, but complicates things considerably and adds weight, albeit in the right place. We decided to try another option, which was a dish mounted on the end of the beam, so that the direction of travel would not matter. To enable it to support the crew weight while shunting, this dish is 1.5m/5; diameter and 150mm/6" deep. The dish is an integral part of the beam.

The 600mm/2' wide canting beam allows us to rotate it around the mast, something Rob had successfully done on W (12m/40' cat with free to pitch hulls). This reduces hull loads and weight considerably as well as making ofr very quick set up time. There is a stay from the mast to the end of the beam, to increase the stiffness of the system.

The original idea with leeway prevention and steering was to keep the loads located near the mast with a lee board and a small 360 degree capable rudder at each end of the boat, as shown in the drawing. However, an analysis of the load paths showed that the loads on the lee hull from the lines which controlled the beam were significant, particularly when the mainsheet loads were included. The lee hull therefore had to be beefed up for at least the middle 50%, so it made sense to use the new side mounted rudders, with control lines to raise and lower them.

It is envisaged that there will not be a lot of tweaking of the sails once the breeze is enough to have both crew seated in the dish. The flexible mast, mainsheet and rudders will provide the necessary control at this point. Less breeze than this, and the crew will be positioned along the beam, and able to pull strings for the luff downhaul, boom outhaul and rudders from near the mast. The beam has a foil section, which should provide significant lift at reasonable speeds.

The boat will be launched and pushed into water 300mm/1' deep where the rudders will be partially lowered, the skipper and crew climb aboard, sheet on and sail through the surf, ideally with the dish airborne. This will be a lot easier to achieve than to get a hull of a conventional boat airborne, but will still require some practise. Returning should be easy and painless. By dumping the sheet, all power can be taken off, and by trimming the other sheet, the brakes can be applied. With bows at each end, and no sails pushing against the shrouds, it will be far more controllable than a conventional boat.

Construction of the hull and the dish is foam with 400 gsm triax glass each side, vacuumed in one shot in a quarter mould. The beam is solid foam, with carbon uni each side, wrapped in double bias glass.

Sail area and righting moment are similar to the Tornado, windage and weight considerably less, perhaps as little as 120 kgs. The proa will lose a little time tacking and gybing (not a problem on long legs), and will not be tuned to the same degree as the Tornados which have had 20 years of optimisation. Should be an interesting race (or should have been..ed.).