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 fight against the Stedingers. Imperial Mongol troops constructed a pontoon bridge at the Battle of Mohi in 1241 to outflank the Hungarian army. The French army of King Louis IX of France crossed the Charente river on multiple pontoon bridges during the Battle of Taillebourg on 21 July 1242. Louis IX had a pontoon bridge built across the Nile to provide unimpeded access to troops and supplies in early March 1250 during the Seventh Crusade. A Florentine army erected a pontoon bridge across the Arno river during the Siege of Pisa in 1406. The English army of John Talbot, 1st