A trimaran has outer hulls (2) detachably linked by crossmembers to the middle hull (1). The crossmembers are tubular cross bars (3) that extend over all three hulls (1, 2) and are removably but firmly mounted in socket couplings (27) fixed to the hulls that completely cross the middle hull (1) and cross at least partially the outer hulls (2). The distance at least between the outer hulls (2) is set by bolts (28) that engage the cross bars (3).
