Geometric Definitions of Ships
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Geometric Definitions of Ships

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What does the term 'Fore Perpendiculars (FP)' refer to?

  • The aft edge of the rudder post at the waterline.
  • The point where the summer load line meets the baseline.
  • The vertical line through the centerline of the ship.
  • A line drawn perpendicular to the waterline at the forward edge of the stem. (correct)

    • Which definition correctly describes 'Midships'?

  • The point midway between the forward and aft perpendiculars. (correct)
  • The section of the ship at the waterline.
  • The point where the beam is the widest.
  • The central vertical plane dividing the ship into two halves.

    • What is the feature of 'Baseline (BL)' in ship geometry?

  • The maximum width of the ship measured at the waterline.
  • The line where the main deck meets the hull.
  • A reference line at the upper surface of the keel. (correct)
  • The highest point of the ship's structure.

    • What does 'Centreplane (CL)' signify in ship geometry?

    <p>The longitudinal reference plane dividing the ship between port and starboard.</p> Signup and view all the answers

    What characteristic is measured by 'Deck Camber'?

    <p>The rise or crown of a deck athwartship.</p> Signup and view all the answers

    Which option best defines 'Loaded Waterline'?

    <p>The waterline when the ship is at full load.</p> Signup and view all the answers

    How is 'Sheer Line' defined in ship geometry?

    <p>The curvature of the deck in a longitudinal direction.</p> Signup and view all the answers

    What does the Length Overall (LOA) measure in a ship?

    <p>Distance from extreme points of the ship forward and aft</p> Signup and view all the answers

    What does the term 'Midship Section' refer to?

    <p>The cross-section at midships perpendicular to the centreline.</p> Signup and view all the answers

    Which area is specifically defined as the bulbous bow section area at the fore perpendicular?

    <p>Bulbous bow section area (ABT)</p> Signup and view all the answers

    What characterizes the Parallel Body (LP) of a ship?

    <p>The area where the hull form remains unchanged</p> Signup and view all the answers

    How is the molded draft measured?

    <p>From the molded base line to the waterline</p> Signup and view all the answers

    What is the significance of the Length of Waterline (LWL)?

    <p>It indicates the horizontal distance at which the ship floats</p> Signup and view all the answers

    What does the term 'deadrise' refer to in ship design?

    <p>The angle of the bottom of the hull to the flat of the keel</p> Signup and view all the answers

    What does 'Breadth of Waterline (BWL)' measure?

    <p>The distance from port to starboard edges at the waterline</p> Signup and view all the answers

    Which of the following describes Draught (T) in ship terminology?

    <p>The vertical distance from the waterline to the base line</p> Signup and view all the answers

    What is the area of the midship cross-section when calculated as $A_M = 10 \times 1 + \frac{10 \times 0.5}{2}$?

    <p>12.5 m²</p> Signup and view all the answers

    What is the block coefficient ($C_B$) calculated for a displacement volume of 1250 m³ with the given values?

    <p>0.833</p> Signup and view all the answers

    For the provided barge dimensions, what is the vertical prismatic coefficient ($C_{VP}$)?

    <p>0.5</p> Signup and view all the answers

    What is the value of the waterplane area coefficient ($C_{WL}$) as calculated for the described barge?

    <p>1</p> Signup and view all the answers

    What is the prismatic coefficient ($C_P$) for the described barge with a midship section coefficient of $C_M = 0.5$?

    <p>1</p> Signup and view all the answers

    Calculate the midship section coefficient ($C_M$) for dimensions where $A_M = 5 \times 3$ and $B_{WL} \times T = 5 \times 2$.

    <p>0.5</p> Signup and view all the answers

    If the waterplane area coefficient ($C_{WL}$) equals 1 and length is given by $L_{WL}$, what is the implication for the design?

    <p>The hull shape is optimal.</p> Signup and view all the answers

    Determine the area coefficient ($C_M$) for a midship section if $A_M$ is twice $A_{WL}$ based on standard formulations.

    <p>0.5</p> Signup and view all the answers

    What is the formula used to calculate the block coefficient (CB)?

    <p>$CB = \frac{\Delta}{L_{WL}B_{WL}T\rho}$</p> Signup and view all the answers

    What is the midship section coefficient (CM) if the prizmatic coefficient (CP) is 0.75?

    <p>0.972</p> Signup and view all the answers

    If the loaded waterplane area (AWP) is 3500 m² and the waterline length (LWL) is 200 m, what is the waterplane area coefficient (CWP)?

    <p>0.795</p> Signup and view all the answers

    What is the vertical prizmatic coefficient (CVP) if the block coefficient is 0.729 and the waterplane area coefficient is 1.0?

    <p>0.729</p> Signup and view all the answers

    Given the sea water density of 1.025 t/m³, how does it affect the calculation of block coefficient (CB)?

    <p>Decreases CB value</p> Signup and view all the answers

    What is the significance of the coefficient CB being less than 1?

    <p>Indicates a more efficient hull form</p> Signup and view all the answers

    What do you understand by the term 'prizmatic coefficient (CP)' in ship design?

    <p>Measures volume efficiency of a ship’s hull</p> Signup and view all the answers

    If a ship has a waterline breadth (BWL) of 22 m and a draught (T) of 7 m, how would changing the BWL to 25 m affect the block coefficient (CB)?

    <p>CB would increase</p> Signup and view all the answers

    What is the definition of freeboard in naval architecture?

    <p>The vertical distance from the summer load waterline to the top of the freeboard deck.</p> Signup and view all the answers

    What does the term 'flare' refer to in ship design?

    <p>The outward curvature of the side shell at the forward end above the waterline.</p> Signup and view all the answers

    What is meant by 'rise of floor' in the context of ship hull design?

    <p>The height of the bottom shell plating above the baseline.</p> Signup and view all the answers

    Which term describes the inward curvature of the midship side shell?

    <p>Tumblehome</p> Signup and view all the answers

    What does 'bilge radius' refer to in ship construction?

    <p>The radius of the plating joining the side shell to the bottom shell.</p> Signup and view all the answers

    In ship terminology, what is 'rake'?

    <p>The angle of the stem in relation to the vertical.</p> Signup and view all the answers

    What is the purpose of the horizontal section in a ship's design?

    <p>To illustrate how the ship's shape changes across different waterlines.</p> Signup and view all the answers

    What does the term 'body plan' refer to in naval architecture?

    <p>A drawing illustrating the cross-sections of the hull.</p> Signup and view all the answers

    What is the significance of the Waterplane Area Coefficient (CWP)?

    <p>It determines the area of the ship in a waterplane condition.</p> Signup and view all the answers

    In hull design, what does the term 'flat of keel' define?

    <p>The width of the horizontal portion of the bottom shell.</p> Signup and view all the answers

    What role does the offset table play in ship design?

    <p>It serves as a reference for creating accurate hull shapes.</p> Signup and view all the answers

    Which design aspect does the term 'transverse section' refer to?

    <p>A cut through the ship at right angles to its length.</p> Signup and view all the answers

    What does the Midship Section Coefficient (CM) indicate in ship design?

    <p>The efficiency of the hull shape against water resistance.</p> Signup and view all the answers

    What is the primary purpose of a lines plan in naval architecture?

    <p>To display different views of the ship's hull shape.</p> Signup and view all the answers

    Study Notes

    Geometric Definitions

    • LOA (Length Overall): The total length of the ship from the extreme point at the bow to the extreme point at the stern.
    • LWL (Length of Waterline): The length of the ship measured along the designed waterline.
    • LBP (Length Between Perpendiculars): The distance between the fore and aft perpendiculars, which are lines perpendicular to the waterline at specific positions.
    • D (Depth): The vertical distance from the baseline to the upper continuous deck.
    • T (Draught): The vertical distance from the baseline to the waterline at the forward and after perpendiculars.
    • f (Freeboard): The vertical distance from the summer load waterline to the top of the freeboard deck plating.
    • B (Beam): The width of the ship, usually measured at amidships (middle of the ship’s length).
    • BL (Baseline): A reference line along the ship’s keel for measuring vertical dimensions.
    • FP (Fore Perpendicular): A line perpendicular to the waterline at the point where the forward edge of the stem intersects the summer load line.
    • AP (Aft Perpendicular): A line perpendicular to the waterline at the aft end of the ship.
    • CP (Centreplane): A longitudinal reference plane which divides the ship into port and starboard sides.
    • Midships: The point midway between the fore and aft perpendiculars.
    • Parallel Body (LP): The portion of the underwater hull form that remains unchanged along the length of the ship.
    • Bulbous Bow: An area at the bow of the ship designed to reduce resistance in the water.
    • Section Lines: Lines used in drawings to represent the hull form and help define key dimensions.
    • Sheer Line: The curvature of the deck in a longitudinal direction, measured between the deck height at midships and a point along the deck.
    • Deck Camber: The rise or crown of a deck, athwartship, also called round of beam.
    • Deadrise: The angle of the bottom of the hull from horizontal.
    • Bilge Radius: The radius of the plating joining the side shell to the bottom of the ship.
    • Tumblehome: An inward curvature of the midship side shell in the region of the upper deck.
    • Rise of Floor: The height of the bottom shell plating above the baseline.

    Main Dimensions

    • Length Overall (LOA): The total length of the ship.
    • Length Between Perpendiculars (LBP): The distance between the fore and aft perpendiculars.
    • Length of Waterline (LWL): The length of the ship measured along the waterline.
    • Length Overall Submerged (LOS): The horizontal distance between the most forward and aft points of the ship submerged below the designed waterline.
    • Parallel Body Length (LP): The length of the ship along which the underwater hull shape remains unchanged.
    • Draught (T): The vertical distance from the baseline to the waterline.
    • Moulded Breadth (BM): The distance measured from the inside edges of the ship's plating on the port and starboard sides.
    • Breadth of Waterline (BWL): The breadth of the ship measured at the waterline.
    • Depth (D): The vertical distance from the baseline to the upper continuous deck.
    • Freeboard (f): The vertical distance from the summer load waterline to the top of the freeboard deck plating.
    • Flare: The outward curvature of the side shell at the forward end above the waterline.
    • Rake: The angle of a line from the vertical, used to describe the shape of the stem or other features.
    • Flat of Keel: The width of the horizontal portion of the bottom shell.

    Hull Form

    • Transverse Section: A cross-section of the ship viewed from the bow or stern, showing the shape of the hull at a particular point along its length.
    • Stations: Positions along the ship’s length where transverse sections and waterlines are defined for the hull form.
    • Body Plan: A drawing that shows the shape of the ship’s hull using multiple transverse sections.
    • Horizontal Section (Waterline): A drawing showing the shape of the ship’s hull as cut by a horizontal plane at a specific height above the baseline.
    • Waterlines: The shape of the ship at different heights above the baseline.
    • Plan View: A drawing that shows the shape of the ship as seen from above.
    • Vertical Sections (Buttocks): Drawings that represent the shape of the ship’s hull as cut by vertical planes perpendicular to the centreline of the ship.
    • Profile View: A drawing that shows the shape of the ship’s side, viewed from the side.
    • Lines Plan: A set of drawings that includes the body plan, waterlines, buttocks, and profile view.
    • Offset Table: A tabular representation of the hull form that shows the location of points on the hull along with their dimensions, aiding in construction.

    Form Coefficients

    • Midship Section Coefficient (CM): A dimensionless value that represents the ratio of the area of the midship section (AM) to the area of a rectangle formed by the breadth (B), draft (T), and waterline length (LWL) at midships.
    • Waterplane Area Coefficient (CWP): A dimensionless value that represents the ratio of the waterplane area (AWP) to the area of a rectangle formed by the waterline length (LWL) and waterline breadth (BWL).
    • Block Coefficient (CB): A dimensionless value that represents the ratio of the ship’s displacement volume () to the volume of a rectangular box enclosed by the ship's length (LWL), breadth (BWL), and draft (T).
    • Prismatic Coefficient (CP): A dimensionless value that represents the ratio of the ship’s displacement volume () to the volume of a prism with the same base area as the midship section (AM) and the same length as the ship (LWL).
    • Vertical Prismatic Coefficient (CVP): A dimensionless value that represents the ratio of the ship’s displacement volume () to the volume of a prism with the same base area as the waterplane (AWP) and the same vertical height as the draft (T).

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