Jewel of Muscat

A comfortable wind speed would be 15-27 knots (about Beaufort Force 5 to 6). The best wind direction is from the ‘quarter’, that is from behind, but slightly from one side or the other, not directly behind. In sailing terminology that is called a ‘broad reach’.

The maximum efficient speed of a boat is called the ‘hull speed’. The Jewel's hull speed is about 8 knots, according to the tank tests we did on a model. Beyond 8 knots, it takes a great deal of power (wind speed and sail area) to push the boat faster.

We got to 6.8 knots during the squall when it rained hard during our test runs (the top end of Beaufort 5). The hull speed is limited by the laws of physics, and is mainly related to the waterline length of the boat, although hull shape also has influence. The general rule is hull speed (in knots) = 1.34 X √LWL (when LWL calculated in feet). According to that formula, Jewel should have a hull speed of nearly 10 knots, but it is probably the wide beam of the vessel that reduces the hull's speed in practice. The ‘1.34’ constant is an ideal, and in reality is usually closer to 1.1 or 1.2 in displacement boats (as in the case of Jewel).