Trimaran sailplan. They contribute to drag when heavily immersed, and their level of immersion indicates when to reef. Two types of trimaran exist: the regular trimaran and the open trimaran, which features a trampoline between the hulls instead of plating. Trimarans have a number of advantages over comparable monohulls (conventional, single-hulled sailboats). Given two boats of the same length, the trimaran has a shallower draft, a wider beam, less wetted area, and is able to fly more sail area. In addition, because of the righting moment provided by the wide beam, trimarans do not need the weighted keel that is required
Pontoon bridge Earl of Shrewsbury crossed the Oise river across a pontoon bridge of portable leather vessels in 1441. Ottoman engineers built a pontoon bridge across the Golden Horn during the Siege of Constantinople (1453), using over a thousand barrels. The bridge was strong enough to support carts. The Ottoman Army constructed a pontoon bridge during the Siege of Rhodes (1480). Venetian pioneers built a floating bridge across the Adige at the Battle of Calliano (1487). The Spanish Army constructed a pontoon bridge at the Battle of Garigliano (1503). The Spanish Army of Flanders under Alexander Farnese, Duke of Parma built an