Question 43 QMED04 - Boiler Technician-Watertender

The Correct Answer is A **Explanation for Option A (unbalanced rudders):** The unbalanced rudder is the simplest, most common, and most cost-effective type of rudder construction. In this design, the turning axis (rudder stock) is positioned near the leading edge, but the entire rudder area is aft of the stock. Because lifeboats are typically smaller vessels operating at low speeds or intermittently, and are designed for utility and ease of construction/repair rather than high-performance maneuvering, the inherent simplicity and mechanical advantage (the pressure on the leading edge assists the turning effort) of the unbalanced rudder makes it the standard choice for most lifeboats and smaller craft. **Explanation for Incorrect Options:** * **B) balanced rudders:** A balanced rudder has a portion (typically 20% to 40% of the area) forward of the turning axis. This significantly reduces the torque required to turn the rudder, making it easier to steer, especially on larger, high-speed vessels. While easier to turn, they are more complex to design and install and are generally not necessary for the small, low-speed application of a standard lifeboat, making them an overly complex and expensive choice. * **C) contra-guide rudders:** The contra-guide rudder (or reaction rudder) is a specialized design that has a curved shape intended to correct the rotational slipstream coming off the propeller, generating lift and improving propulsion efficiency. Lifeboats are often fitted with fixed-pitch propellers (or sometimes jet drives/oars), but the added complexity and cost of a contra-guide rudder are not justified for emergency craft where simplicity and reliability are paramount. * **D) straight rudders:** "Straight rudder" is a general descriptive term but does not specifically denote a standard type of hydrodynamic design as unbalanced, balanced, or contra-guide does. All standard rudders (unbalanced, balanced, semi-balanced) have a "straight" stock and blade, but hydrodynamically, the unbalanced design is the specific type universally employed on most standard lifeboats.