Exam Question
(a) Describe a method for the attachment of bilge keels. (5)
(b) State THREE reasons for not extending bilge keels the entire length of the vessel. (6)
(c) Explain TWO principles of roll damping that bilge keels exploit. (5)
Class 2 (2nd Engineer)
SC&S
📅 Jun 2025
Reference Answer
(a) Method of Bilge keel attachment to the hull:
Bilge keels are fitted port and starboard at the turn of the bilge. They do not extend outside the lines of the side and bottom shell. The bilge keels are attached directly in line with an internal stiffening member such as a girder or longitudinal. The bilge keel comprises a flat bar doubler welded directly to the shell, and an offset bulb plate (OBP) with 'scallops' cut in it is welded to the flat bar doubler. The ends of the bilge keels are tapered (minimum 3 in 1) and will end in line with transverse internal stiffening, such as a frame. Using a hull doubler protects the hull in case of damage to the keel, as the crack would not extend into the hull.
(b) Bilge keels are not fitted for the full length of the vessel because:
The 'lever' to the ship's axis of rotation is reduced at the ends;
Bilge keels are fitted port and starboard at the turn of the bilge. They do not extend outside the lines of the side and bottom shell. The bilge keels are attached directly in line with an internal stiffening member such as a girder or longitudinal. The bilge keel comprises a flat bar doubler welded directly to the shell, and an offset bulb plate (OBP) with 'scallops' cut in it is welded to the flat bar doubler. The ends of the bilge keels are tapered (minimum 3 in 1) and will end in line with transverse internal stiffening, such as a frame. Using a hull doubler protects the hull in case of damage to the keel, as the crack would not extend into the hull.
(b) Bilge keels are not fitted for the full length of the vessel because:
The 'lever' to the ship's axis of rotation is reduced at the ends;
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