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
Pontoon effect each pontoon can support the vessel's entire weight (plus any lateral forces that arise like wind), the center of gravity cannot move transversely beyond the center of buoyancy at the most extreme tipping angle, and the pontoon effect cannot occur. Note, however, that this is not the sole effect to be taken into consideration when assessing the likelihood of capsize. The change in hull windage as the vessel heels is also important. In the case of a trimaran designed for cruising, with solid wing decks (as opposed to racing-type designs with mesh or open wings), those with wide-beam floats able