Sheer strake is a term used in ship construction to describe the uppermost strake of the side shell plating. A strake is a section of plate placed in fore and aft direction on the hull of the ship. The shear strake is usually of higher thickness and strength than other strakes, because it can resist a lot of physical damages during the life of the ship. For example, it can withstand the impact of waves, wind, ice, or other objects that may hit the ship’s side.
The sheer strake also plays an important role in resisting the longitudinal stress that can cause the ship to break up due to hogging and sagging conditions. The longitudinal stress is resisted by all continuous longitudinal members that are placed far from the neutral axis of the cross-section area, such as the double bottom, the main strength deck, and the side shell. The shear strake is one of these members, as it is located at the upper edge of the side shell.
The shear strake has some specific requirements according to the class rules that regulate the ship construction.
Sheer Strake requirements
– The width of the shear strake should be not less than a certain value depending on the length of the ship. For example, for a ship with a length of 100 m, the width of the shear strake should be not less than 1.2 m.
– The fillet weld at the connection of the welded shear strake and deck plate should be either full penetration or deep penetration (back-gouging) weld.
– The upper edge of the welded shear strake should be rounded smooth and free of notches.
– Where guard rails are provided, the upper edge of shear strake should be kept as low as possible.
– The distance between two adjacent butts in the same strake of shell or deck plating should be greater than two frame spaces.
– If the shear strake is rounded, its radius should be not less than 17 times the net thickness of the shear strake.
– Longitudinal seam welds of rounded shear strake should be located outside the bent area at a distance not less than 5 times the maximum net thicknesses of the shear strake.
– Fixtures such as bulwarks, eye plates should not be directly welded on the upper edge of shear strake, except in fore and aft parts.
The shear strake is an important plate of ship that contributes to its strength, stability, and safety.