Introduction to Naval Terminology and Maneuvering

Posted on Aug 6, 2024 in Technology

1. Naval Technology

1.1. Dimensions

Maximum Length: Length of the boat, measured parallel to the design waterline between two planes perpendicular to the centerline, one forward and one aft, excluding non-structural elements of the hull.

Beam: Width of the boat, measured at the widest point of the hull, including fixed structures.

Depth: Can have three possible meanings:

1. Maximum vertical dimension measured from the top of the keel to the main deck.
2. Each of the pillars supporting the roofs.
3. Mast used to handle loads.

Freeboard: Vertical distance between the waterline at maximum load and the watertight deck above.

Draft: Depth of the submerged hull, excluding rudder, keel, propellers, and other similar appendages. There are several types of draft:

• Draft Aft: Distance between the bottom of the keel and the waterline at the stern.
• Draft Forward: Distance between the bottom of the keel and the waterline at the bow.
• Draft Amidships: Distance between the bottom of the keel and the waterline at the middle of the boat’s length.
• Mean Draft: Average of the draft at the bow and stern.
• Hogged: When the mean draft is less than the draft amidships, indicating a U-shaped hull.
• Sagged: When the mean draft is greater than the draft amidships, indicating an inverted U-shaped hull.

Trim: The difference between the drafts forward and aft.

• Trim by the Head: The draft forward is greater than the draft aft.
• Trim by the Stern: The draft forward is less than the draft aft.
• Even Keel: The drafts forward and aft are the same.

Weight: Weight of the boat, measured in metric tons.

Maximum Displacement: Maximum weight the boat can safely displace in the water.

Tonnage: Expresses the interior volume of the vessel. Measured in Gross Tonnage (GT) or Gross Register Tonnage (GRT). One Gross Ton equals 2.83 cubic meters or 100 cubic feet.

Net Tonnage: The volume of the ship’s commercially usable spaces.

1.2. Names of the Hull

Bow: The front of the boat that cuts through the water.

Stern: The back of the boat.

Port: The left side of the boat when facing forward.

Starboard: The right side of the boat when facing forward.

Sides: The outer surfaces of the hull. Often confused with the Topsides.

Topsides: Each of the halves divided by the fore-and-aft line (centerline).

Stem: The curved, most forward part of the bow.

Sternpost: The aftermost structural member of a boat, extending upward from the keel at the stern.

Frames: Ribs of the hull that start from the keel and define the shape of the sides.

Beams: Pieces that cross the vessel from port to starboard, supporting the decks.

Gunwale: The upper edge of the side of a boat, where the hull meets the deck.

Sheer: The upward curvature of the deck from midships towards the bow and stern.

Bulkheads: Partitions or walls within a vessel.

Centerline: The longitudinal axis (fore-and-aft) of the boat.

Waterline: The line where the surface of the water meets the hull of a floating vessel.

Underwater Hull: The part of the hull below the waterline.

Deck: Each of the floors of the boat.

Bottom: The lowest floor of the boat.

Bilge: The lowest internal part of the hull, where water and other fluids collect. Bilge pumps are used to remove this water.

1.3. Structure

Hull: The main body of a vessel, excluding moving parts such as masts, superstructure, machinery, rigging, etc.

Keel: The backbone of a boat, running along the centerline from bow to stern. It provides stability and supports the hull structure.

Stem: The forwardmost part of the keel, often reinforced to form a cutwater.

Sternpost: The aftermost part of the keel, supporting the rudder.

Frames: Ribs of the hull that start from the keel and define the shape of the sides.

Beams: Pieces that cross the vessel from port to starboard, supporting the decks.

Gunwale: The upper edge of the side of a boat, where the hull meets the deck.

Sheer: The upward curvature of the deck from midships towards the bow and stern.

Bulkheads: Partitions or walls within a vessel.

1.4. Concept of Watertightness

Watertightness: The quality that prevents water from entering the vessel, ensuring buoyancy. Maintaining watertightness is crucial to prevent flooding.

Cockpit: An open chamber, typically located aft on pleasure boats, where the helm or wheel is usually situated.

Scuppers: Holes or openings in the deck or cockpit that allow water to drain overboard.

Drains: Conduits that carry water away from various parts of the boat, serving the same purpose as scuppers.

Seacocks and Through-Hull Fittings: Valves installed below the waterline that control the flow of water for cooling systems, toilets, kitchens, and other services.

Engine Exhaust: A tube that carries exhaust gases from the engine overboard.

Stuffing Box: A packing gland that seals around a rotating shaft, such as a propeller shaft, to prevent water ingress.

Rudder Port: The hole in the hull where the rudder stock passes through.

Portholes: Circular openings in the sides of the boat or bulkheads that provide light and ventilation.

Hatches: Rectangular openings in decks that allow access between different compartments of the boat.

Cover: A closure that protects an opening in the boat.

Skylights: Covers fitted with glass to provide light and ventilation to interior spaces.

Ventilation Cowls: Steel or fiberglass pipes installed vertically on deck, capped with a hemispherical or oval top, used for ventilation.

Bilge Pumps: Machines designed to remove water that collects in the bilge.

1.5. Accessories

Handrails: Pieces that serve as handles for moving around the boat.

Stanchions: Vertical posts that support handrails, typically found along the sides of the boat.

Cleats: T-shaped fittings secured to the boat, used for tying off ropes. They can be oriented vertically or horizontally.

Bollards: Strong, vertical posts mounted on deck, used for securing mooring lines, especially during docking and anchoring.

Anchor: A heavy, hook-shaped device used to secure a boat to the seabed. It is attached to the boat by a chain or rope.

Windlass: A horizontal-axis machine used to raise and lower the anchor chain (also known as a winch).

• Gypsy: A grooved drum on a windlass that engages the links of the anchor chain.
• Clutch: A mechanism that engages and disengages the gypsy from the windlass motor.
• Brake: A mechanism that holds the windlass drum stationary.
• Chain Stopper: A device that secures the anchor chain when not in use.
• Capstan: A vertical drum on a windlass used for hauling lines (also known as a cabiron).

Winch: A vertical-axis machine used to haul lines.

Hawsepipe: An opening in the hull through which the anchor chain passes.

Chain Locker: A compartment that stores the anchor chain.

Rudder: A submerged device used to steer a boat. It consists of a blade that pivots on a vertical axis (rudder stock).

• Balanced Rudder: A rudder with a portion of the blade area forward of the rudder stock, reducing the effort required to turn it.
• Unbalanced Rudder: A rudder with the entire blade area aft of the rudder stock.
• Rudder Blade: The flat surface of the rudder that creates the turning force.
• Rudder Stock: The vertical shaft on which the rudder blade pivots.
• Tiller or Wheel: Mechanisms used to control the angle of the rudder blade.

Propellers: Devices that propel a boat through the water. They consist of blades that rotate on a shaft.

• Pitch: The theoretical distance a propeller would advance in a solid medium with one full revolution.
• Slip: The difference between the theoretical pitch and the actual distance traveled by the propeller in water.
• Diameter: The distance across the circle described by the tips of the propeller blades.
• Right-Handed Propeller: A propeller that rotates clockwise when viewed from astern.
• Left-Handed Propeller: A propeller that rotates counterclockwise when viewed from astern.

Cavitation: The formation of vapor bubbles in water due to low pressure, often occurring near the tips of propeller blades when rotating at high speeds.

1.6. Lines

Lines: Ropes or cables used on board a vessel.

Line Construction:

Lines are typically constructed by twisting multiple fibers together to form yarns. Multiple yarns are then twisted to form strands, and multiple strands are twisted to form the final rope.

Bitter End: The inboard end of a rope or cable.

Bight: A curve or loop formed in a rope.

Standing Part: The longer, inactive section of a rope, as opposed to the working end.

Eye: A permanent loop formed in the end of a rope.

Stopper: A short length of rope used to temporarily hold another rope under tension.

Mooring Line: A line used to secure a boat to a pier, buoy, or another vessel.

Synthetic Fiber Rope:

• Polyester (Dacron, Tergal): Strong, flexible, low stretch, resistant to UV and abrasion. Used for running rigging.
• Nylon: Very strong and elastic. Used for anchor lines, mooring lines, and tow ropes.
• Polypropylene: Floats, resistant to abrasion, inexpensive. Used for lifebuoy lines.
• Kevlar: Extremely strong and low stretch, but expensive. Used for halyards and sheets on racing sailboats.

1.7. Terminology

Heel: The leaning motion of a boat to one side.

Righting: The action of returning a heeled boat to an upright position.

Rolling: The side-to-side (starboard-port) motion of a boat.

Pitching: The fore-and-aft motion of a boat.

Pounding: The violent impact of a boat’s hull against waves, typically occurring during pitching.

Windward: The direction from which the wind is blowing.

Leeward: The direction towards which the wind is blowing.

Haul: To pull on a rope.

Tension: To apply force to a rope, cable, or chain.

Ease: To slacken a rope that is under tension.

Cast Off: To release a rope completely.

2. Maneuvering

2.1. Mooring Lines

Mooring Lines: Ropes or cables used to secure a boat to a dock, pier, or another vessel.

Bow Line: A line leading forward from the bow, used to prevent the boat from moving forward.

Stern Line: A line leading aft from the stern, used to prevent the boat from moving backward.

Spring Line: A line running diagonally from the bow to the stern or vice versa, used to prevent the boat from moving forward or backward.

Breast Line: A line leading perpendicular to the centerline, used to prevent the boat from moving sideways.

Effects of Mooring Lines:

Using Wind and Current:

Line Handling:

• Coil: To arrange a rope in circular turns.
• Belay: To secure a rope to a cleat, bitt, or other fitting.
• Make Fast: To secure a rope firmly in place using knots or hitches.
• Dip the Eye: To pass the eye of a rope over a bollard or other fitting.

Knots:

• Figure Eight: A knot used to form a stopper at the end of a rope.
• Round Turn and Two Half Hitches: A secure knot used for tying a rope to a cleat or bitt.
• Reef Knot: A knot used to join two ropes of equal diameter.
• Bowline: A knot used to form a fixed loop at the end of a rope.
• Clove Hitch: A knot used to temporarily secure a rope to a post or rail.
• Sheepshank: A knot used to shorten a rope without cutting it.

2.2. Steering

Tiller: A lever used to control the angle of the rudder blade. When using a tiller, the blade moves in the opposite direction to the tiller.

Wheel: A circular device used to control the angle of the rudder blade. When using a wheel, the blade moves in the same direction as the wheel.

Steering Cables: Cables or rods that connect the wheel or tiller to the rudder.

Steering Effect: The tendency of a boat to turn in the direction the rudder is turned.

Speed of Steering: The minimum speed at which the rudder becomes effective in turning the boat.

Way: The forward motion of a boat through the water.

Propeller Walk: The tendency of a single-screw propeller to push the stern of the boat sideways, especially in reverse.

• Right-Handed Propeller Walk: The stern tends to move to port in reverse.
• Left-Handed Propeller Walk: The stern tends to move to starboard in reverse.

Turning in Place:

To turn a boat in a confined space, use a combination of rudder and engine power. With a single-screw propeller, use short bursts of forward and reverse power, along with rudder movements, to pivot the boat.

Turning with Two Propellers:

With twin propellers, turn the boat by operating the propellers in opposite directions.

2.3. Factors Affecting Maneuvering

Wind: Wind can significantly affect a boat’s handling, especially if the boat has a large sail area or superstructure. Wind can cause leeway (sideways drift) and affect the boat’s heading.

Current: Water currents can also influence a boat’s movement, causing it to drift off course.

Waves: Waves can make maneuvering more difficult, especially in rough conditions.

Keeping a Clear Downwind: When maneuvering in close quarters, it’s essential to keep a clear area downwind to avoid collisions in case of loss of control.

True Wind: The actual direction and speed of the wind, unaffected by the boat’s motion.

Apparent Wind: The wind experienced on a moving boat, which is a combination of the true wind and the wind created by the boat’s motion.

2.4. Docking Maneuvers

Mediterranean Mooring: A technique where the boat is moored stern-to (or sometimes bow-to) the dock, with anchors set from the bow.

• Maneuver: Approach the dock slowly, considering wind and current. Secure the stern lines first, then the bow lines.
• Lines: Typically use two stern lines, a bow line, and a spring line.

Rafting Up: Mooring alongside another boat that is already secured to the dock.

• Maneuver: Approach the other boat slowly and carefully, ensuring fenders are in place. Secure lines to the other boat and adjust as needed.
• Lines: Typically use breast lines, spring lines, and bow and stern lines.

Coming Alongside a Quay or Jetty:

• Headwind: Approach the dock at a shallow angle (20 degrees), securing the bow line first, followed by the stern line.
• Tailwind: Approach the dock slowly, using the engine to control speed. Secure the forward spring line first, then the stern line, and finally the bow line.
• Wind from the Sea: Approach the dock at a steeper angle (60-70 degrees), allowing the wind to assist. Secure the bow line and forward spring line first, then the stern line.
• Wind from the Dock: Approach the dock at a moderate angle (40-50 degrees), using the wind to help position the boat. Secure the bow line first, then the stern line.

Mooring to a Buoy:

• Maneuver: Approach the buoy from downwind, keeping the buoy slightly off to one side. Secure the mooring line to a bow cleat or bollard.
• Lines: Use a single mooring line attached to the buoy’s chain or ring.

2.5. Anchoring

Definition: Securing a boat to the seabed using an anchor and rode (chain or rope).

Choosing an Anchorage:

• Bottom Type: Good holding ground includes sand, mud, and clay. Poor holding ground includes rock, shale, and grass.
• Location: Choose an anchorage that provides shelter from wind and waves, has adequate depth, and offers a clear path for departure.

Sounding: Measuring the depth of water to determine the amount of anchor rode needed. Use a lead line or depth sounder.

Length of Rode: Use a rode length of at least 3-4 times the depth of water. In strong winds or currents, use a longer rode (5-6 times the depth).

Swing Circle: The area in which a boat will swing around its anchor due to wind or current.

Dragging Anchor: When the anchor fails to hold firmly in the bottom and the boat drifts. To prevent dragging, use a heavier anchor, longer rode, or change the anchorage.

Monitoring the Anchor: Regularly check the position of the boat to ensure the anchor is holding. Use visual bearings or electronic navigation aids.

Anchor Buoy: A buoy attached to the anchor line to mark the anchor’s position and assist in retrieval.

Anchoring Maneuver:

• Single Anchor: Approach the desired position from downwind, motor past the spot, and then stop the boat. Slowly pay out the anchor rode as the boat drifts backward. Once sufficient rode is paid out, stop the boat and allow the anchor to set.
• Two Anchors: Used in strong winds or currents to increase holding power. Common techniques include:
  • Tandem Anchors: Set two anchors in line with each other, one ahead of the other.
  • Bahamian Moor: Set two anchors at a 45-degree angle to each other.
  • Fore and Aft Anchors: Set one anchor from the bow and one from the stern.

Weighing Anchor: The process of raising the anchor and retrieving the rode.