Pontoon bridge in 638. The army of the Umayyad Caliphate built a pontoon bridge over the Bosporus in 717 during the Siege of Constantinople (717–718). The Carolingian army of Charlemagne constructed a portable pontoon bridge of anchored boats bound together and used it to cross the Danube during campaigns against the Avar Khaganate in the 790s. Charlemagne's army built two fortified pontoon bridges across the Elbe in 789 during a campaign against the Slavic Veleti. The German army of Otto the Great employed three pontoon bridges, made from pre-fabricated materials, to rapidly cross the Recknitz river at the Battle on the Raxa
Trimaran hull". The outrigger hulls are "floats". The structures between the main hull and the floats are called the "wings" and the structural portions thereof are "beams"). In cruising trimarans the wings are solid and cabin accommodation extends over them, while in racing trimarans accommodation is limited to the main hull and the wings are open sheets of netting. In comparison to outrigger canoes, trimarans typically feature a sail (or engine) and are not primarily designed to be paddled. Trimarans are typically significantly wider. In addition, trimaran floats are much more buoyant than those of outrigger canoes to support a large