Class 2 (2nd Engineer) MEKG 📅 Jan 2023

Exam Question

(a) Describe a transverse bow thrust unit using a controllable pitch propeller. Mention should be made of how it is supported and how the strength of thrust and reverse thrust is achieved.

(b) State with reasons, a suitable prime mover for the controllable pitch propeller

(c) State whether the thrust unit delivers a relatively low-pressure head with high volume output or high-pressure head with low volume output.

Reference Answer

### (a) Transverse Bow Thrust Unit (Controllable Pitch Propeller)
A transverse bow thrust unit is a propulsion device installed in the bow of a ship, running athwartships, to provide lateral thrust. This greatly enhances the vessel's manoeuvrability at low speeds, particularly during docking, undocking, and navigating in confined waters. The controllable pitch propeller (CPP) variant allows for precise and rapid control of thrust magnitude and direction without changing the prime mover's speed or direction of rotation.
**Construction and Operation:**
* **Tunnel:** The core of the unit is a cylindrical tunnel running transversely through the vessel's forepeak, well below the waterline. The tunnel ends are faired into the hull to ensure smooth water flow and minimize drag. Protective grids are fitted at both ends to prevent the ingress of foreign objects.

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