A cord (50) comprises: an internal strand (TI) comprising internal layer (C1) of Q=1 internal wire (F1), an intermediate layer (C2) of M intermediate wires (F2) wound around the internal layer (C1) with a pitch p2, an external layer (C3) of N external wires (F3) wound around the intermediate layer (C2) with a pitch p3; and L>1 external strands (TE) comprising an internal layer (C1′), an external layer (C3′). The external layer (CE) of the cord is wound around the internal layer (CI) of the cord in a direction of winding of the cord (50). Each external layer (C3, C3′) of each internal and external strand (TI, TE) is wound in the same direction of winding that is the opposite to the direction of winding of the cord (50). The external layer (CE) of the cord (50) is desaturated, and 0.36≤(p3−p2)/p3≤0.57.

A cord (50) comprises: an internal strand (TI) comprising internal layer (C1) of Q=1 internal wire (F1), an intermediate layer (C2) of M intermediate wires (F2) wound around the internal layer (C1) with a pitch p2, an external layer (C3) of N external wires (F3) wound around the intermediate layer (C2) with a pitch p3; and L>1 external strands (TE) comprising an internal layer (C1′), an external layer (C3′). The external layer (CE) of the cord is wound around the internal layer (CI) of the cord in a direction of winding of the cord (50). Each external layer (C3, C3′) of each internal and external strand (TI, TE) is wound in the same direction of winding that is the opposite to the direction of winding of the cord (50). The external layer (CE) of the cord (50) is desaturated, and 0.36≤(p3−p2)/p3≤0.57.

A synthetic rope (20) comprises a core (22) and at least a first layer surrounding the core (22). The first layer has first layer strands (26). The core has a fluted outer surface with spaced apart helical concave grooves. Each of these grooves contacts one of the first layer strands (26). The grooves have a radius of curvature (24) that is greater than the radius of curvature (14) of a circle having a same diameter as the contacting first layer strand before twisting.

A synthetic rope (20) comprises a core (22) and at least a first layer surrounding the core (22). The first layer has first layer strands (26). The core has a fluted outer surface with spaced apart helical concave grooves. Each of these grooves contacts one of the first layer strands (26). The grooves have a radius of curvature (24) that is greater than the radius of curvature (14) of a circle having a same diameter as the contacting first layer strand before twisting.

A multi-strand cord (50) comprises an internal layer (CI) made up of K=1 internal strand (TI) having two layers (C1, C3), with the internal layer (C1) being made up of Q internal metallic threads (F1) and the external layer (C3) being made up of N external metallic threads (F3), and an external layer (CE) made up of L>1 external strands (TE) having two layers (C1′, C3′) wound around the internal layer (CI), with the internal layer (C1′) being made up of Q′ internal metallic threads (F1′) and the external layer (C3′) being made up of N′ external metallic threads (F3′). The cord (50) has an energy-to-break per unit area ES≥145 N.Math.mm.sup.−1 with ES=Σ.sub.i=1.sup.NcF.sub.mi×Σ.sub.i=1.sup.NcA.sub.ti/Nc×Cfrag/D where Σ.sub.i=1.sup.NcF.sub.mi is the sum of the forces at break, Σ.sub.i=1.sup.NcA.sub.ti is the sum of the total elongation, Cfrag is the coefficient of weakening, and D is the diameter.

A multi-strand cord (50) comprises an internal layer (CI) made up of K=1 internal strand (TI) having two layers (C1, C3), with the internal layer (C1) being made up of Q internal metallic threads (F1) and the external layer (C3) being made up of N external metallic threads (F3), and an external layer (CE) made up of L>1 external strands (TE) having two layers (C1′, C3′) wound around the internal layer (CI), with the internal layer (C1′) being made up of Q′ internal metallic threads (F1′) and the external layer (C3′) being made up of N′ external metallic threads (F3′). The cord (50) has an energy-to-break per unit area ES≥145 N.Math.mm.sup.−1 with ES=Σ.sub.i=1.sup.NcF.sub.mi×Σ.sub.i=1.sup.NcA.sub.ti/Nc×Cfrag/D where Σ.sub.i=1.sup.NcF.sub.mi is the sum of the forces at break, Σ.sub.i=1.sup.NcA.sub.ti is the sum of the total elongation, Cfrag is the coefficient of weakening, and D is the diameter.

A cord (50) comprises: an internal strand (TI) comprising an internal layer (C1), and an external layer (C3); and L>1 external strands (TE) comprising an internal layer (C1′) of Q′=1 internal wire (F1′), an intermediate layer (C2′) of M′ intermediate wires (F2′) wound around the internal layer (C1′) with a pitch p2′, and an external layer (C3′) of N′ external wires (F3′) wound around the intermediate layer (C2′) with a pitch p3′. The external layer (CE) of the cord is wound around the internal layer (CI) of the cord in a direction of winding of the cord (50). Each external layer (C3, C3′) of each internal and external strand (TI, TE) is wound in the same direction of winding that is the opposite to the direction of winding of the cord (50). The external layer (CE) of the cord (50) is desaturated, and 0.36≤(p3′−p2′)/p3′≤0.57.

A cord (50) comprises: an internal strand (TI) comprising an internal layer (C1), and an external layer (C3); and L>1 external strands (TE) comprising an internal layer (C1′) of Q′=1 internal wire (F1′), an intermediate layer (C2′) of M′ intermediate wires (F2′) wound around the internal layer (C1′) with a pitch p2′, and an external layer (C3′) of N′ external wires (F3′) wound around the intermediate layer (C2′) with a pitch p3′. The external layer (CE) of the cord is wound around the internal layer (CI) of the cord in a direction of winding of the cord (50). Each external layer (C3, C3′) of each internal and external strand (TI, TE) is wound in the same direction of winding that is the opposite to the direction of winding of the cord (50). The external layer (CE) of the cord (50) is desaturated, and 0.36≤(p3′−p2′)/p3′≤0.57.

A production method for a headline sonar cable characterized by steps of: a. providing a first strength member (14); b. coupling to strength member (14) a conductor (122); c. forming a layer of polymeric material about the combination of strength member (14) and conductor (122) while ensuring that the conductor remains slack; d. forming a flow shield around the layer of polymeric material, thus forming an elongatable internally located conductive structure; and e. braiding a strength-member jacket layer (52) of polymeric material around the elongatable internally located conductive structure while ensuring that the conductor is slack when surrounded by the jacket layer (52). For another embodiment, an optical fibre is wrapped around the exterior of the layer of polymeric material within which is enclosed a braided conductor formed about the first strength member (14). Other embodiments employ further thermo-plastic layers and further sheaths and further conductors.

A production method for a headline sonar cable characterized by steps of: a. providing a first strength member (14); b. coupling to strength member (14) a conductor (122); c. forming a layer of polymeric material about the combination of strength member (14) and conductor (122) while ensuring that the conductor remains slack; d. forming a flow shield around the layer of polymeric material, thus forming an elongatable internally located conductive structure; and e. braiding a strength-member jacket layer (52) of polymeric material around the elongatable internally located conductive structure while ensuring that the conductor is slack when surrounded by the jacket layer (52). For another embodiment, an optical fibre is wrapped around the exterior of the layer of polymeric material within which is enclosed a braided conductor formed about the first strength member (14). Other embodiments employ further thermo-plastic layers and further sheaths and further conductors.