Lines and plans

Course no. 2

Ship’s base plans

The ship’s hull is a long body restricted from above, below andsides by the complicated curved surfaces.

To make various shipbuilding calculations it is necessary todetermine the base plans and main measurements.

The sections of the hull by three reciprocal perpendicular plansgive the general idea of the ship contour.

Base plans (1)

There are three base plans from which we can measure ships lineardimensions.

1.The diametric plan, is the longitudinal- vertical plan of symmetry of thevessel which divides it into two sides.

Base plans (2)

The starboard side is the right side, facing the front of the ship, while theport side is the left.

The longitudinal axis of the vessel (centerline) is the intersection of thediametrical plan with the horizontal plan that passes through the centerof the gravity.

Centerline

Center of the gravity

Base plans (3)

2. Waterlines plan is the horizontal plan defined by ship’s surfacefloating on calm water.

Base plans (4)

Waterlines plan divides the ship afloat in two parts: emersion parts (abovethe water) called upper (dead) works, and the immerse part (below thewater), called the quick works.

Waterline is the hull intersection with the waterlines plan area. After eachloading or unloading of the ship, there are various lines and floatingplans, the maximum being at full load situation.

Base plans (5)

3. Amidships plan is the maximum cross section width of the hullobtained by intersection with a plan perpendicular to the baseline.

Base plans (6)

The part of the ship in the front of amidships is the bow andthe rear of a vessel is the stern.

Base line (bottom line) is straight its upper keel.

Ship’s Keel

Main types of keel

• Every vessel has a designed seagoing trim where the baseline isdrawn parallel to the designed summer load waterline.

• On a merchant ship, the designed loaded sea going trim is evenkeel (draughts forward and aft are the same and the keelcorresponds to the baseline).

• Smaller vessels are more likely to have rake in the keel (slopingfrom forward to aft) so that when floating at the designed seagoing trim, the after draught will usually be greater than theforward draught.

Terminology

• From the centerline of the ship toward either port or starboardside is outboard and from either side toward the centerline isinboard.

• However, there is a variation in the use of outboard and inboardwhen a ship is on berth (moored to a pier). The side against thepier is referred to as being inboard; the side away from the pieras outboard.

Terminology

• When you move toward the bow, you are going forward,when the vessel is moving forward, it is going ahead

• When you move toward the stern, you are going aft, whenthe ship moves in that direction it is going astern

Ship’s line plans (1)

Line plans are drawings of ships showing the three-dimensional shipdisplayed in two-dimensional cuts.

The sheer plan shows the buttock lines of a ship in the dimensions x-z.Longitudinal sections are curves obtained by the intersection of the hull

with plans parallel to the plan.diametric

Ship’s line plans (2)

The body plan shows the transverse sections of a ship in thedimensions y-z.

Cross sections are curves obtained by the intersection of the hull withthe plans parallel to the .amidships

Ship’s line plans (3)

The half-breadth plan shows the half horizontal sections (waterlineplans) in the dimensions x-y.

Horizontal sections are curves obtained by the intersection of the hullwith the plans parallel to the plan, and they are called thewaterline.

waterlines

Half-breadth Plan

Body Plan

Sheer Plan

Projection of ship’s lines

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Ship’s line plans