Ship Design, Shipbuilding Cost Models, and Trials

1. Cost Models in Ship Design and Shipbuilding

A. Overview of Cost Models

Cost models in shipbuilding are used to estimate, budget, and optimize expenses across the design, construction, and operational phases. These models help shipyards and owners predict costs, allocate resources, and ensure profitability. Common cost models include:

2. Cost Estimating Relationship (CER)

A. Definition

A Cost Estimating Relationship (CER) is a mathematical or statistical model that relates ship characteristics (e.g., displacement, length, power) to cost. CERs are derived from historical data and regression analysis.

B. Types of CERs

C. Advantages of CERs

• Quick estimates: Useful for early-stage design when detailed data is unavailable.
• Scalability: Can be applied to different ship sizes within a class (e.g., bulk carriers, tankers).
• Data-driven: Based on historical trends, reducing subjective bias.

D. Limitations of CERs

• Accuracy depends on data quality: Poor historical data leads to unreliable estimates.
• Assumes linearity: May not capture non-linear cost drivers (e.g., complex machinery).
• Less accurate for innovative designs: Works best for conventional ships with existing data.

E. Example CER for Shipbuilding

For a bulk carrier, a CER might look like:

Cost (USD) = 12,000,000 + 18,000 × (DWT) + 30,000 × (Engine Power in kW)

Where:

• DWT = Deadweight Tonnage
• Engine Power = Main engine power in kW

3. Hull Block Construction Method (HBCM)

A. Definition

The Hull Block Construction Method (HBCM) is a modular shipbuilding approach where the hull is constructed in pre-fabricated blocks (sections) that are later assembled in the dry dock or on the slipway. This method is widely used in modern shipyards (e.g., Hyundai, Samsung Heavy Industries).

B. Cost Savings in HBCM

C. HBCM Process

1. Block Design: Hull is divided into 3D-modeled blocks (e.g., bow, midship, stern).
2. Pre-Fabrication: Blocks are cut, welded, and outfitted in workshops.
3. Transport: Blocks are moved to the dry dock using cranes or transporters.
4. Assembly: Blocks are welded together to form the hull.
5. Outfitting: Piping, electrical, and machinery are installed.

4. Advantages of Pre-Fabrication

A. Cost and Time Savings

B. Examples of Pre-Fabrication

• Hull Blocks: Pre-welded sections of the hull.
• Pipe Spools: Pre-fabricated piping systems.
• Electrical Panels: Pre-assembled and tested electrical distribution boards.
• Accommodation Modules: Pre-built living quarters (e.g., cabins, galleys).

5. Estimating Finished Steel Weight of a Ship

A. Methods for Estimating Steel Weight

B. Parametric Formula for Steel Weight

A simple parametric formula for estimating steel weight (for a bulk carrier):

Steel Weight (tons) = C × (L × B × D)^(2/3)

Where:

• L = Length Overall (m)
• B = Breadth (m)
• D = Depth (m)
• C = Constant (varies by ship type, e.g., 0.015–0.025 for bulk carriers)

C. Lightweight Analysis

1. Hull Girder Weight:
   • Bottom, side, deck plating + longitudinals, transverses, webs, and stiffeners.
2. Superstructure Weight:
   • Accommodation, bridge, funnel (if applicable).
3. Outfitting Weight:
   • Piping, electrical systems, machinery supports (if included in steel weight).

6. Basic Ship Design vs. New Ship Design

A. Basic Ship Design (Shipyard’s Standard Design)

• Definition: A proven, standardized design that the shipyard has built before (e.g., a Newcastlemax bulk carrier or a Suezmax tanker).
• Characteristics:
  • Pre-existing drawings, calculations, and specifications.
  • Optimized for construction efficiency (e.g., pre-fabricated blocks, standardized materials).
  • Lower design costs (no R&D required).
  • Faster delivery (familiar to the shipyard).

B. New Ship Design (Custom Design)

• Definition: A bespoke design tailored to the owner’s specific requirements (e.g., a specialized LNG carrier or a polar icebreaker).
• Characteristics:
  • Unique hull form, machinery, and outfitting.
  • Higher design costs (R&D, model testing, class approval).
  • Longer delivery time (new tooling, training, and processes).
  • Higher risk (unproven performance, potential cost overruns).

C. Narrowing the Differences

To bridge the gap between a basic design and a new design, the following steps are taken:

7. Slog-Slog Method

A. Definition

The “Slog-Slog” method (also called the “Log-Log” method) is a graphical cost estimation technique used in shipbuilding to compare costs across different ship sizes or designs. It involves plotting cost vs. ship parameter (e.g., DWT, LOA) on a logarithmic scale for both axes.

B. When is it Used?

• Early-stage cost estimation (when detailed data is unavailable).
• Comparing costs of different ship sizes (e.g., scaling a 50,000 DWT bulk carrier to 80,000 DWT).
• Benchmarking against industry standards.

C. How It Works

1. Plot historical data (cost vs. ship parameter) on a log-log graph.
2. Draw a best-fit line (represents the cost trend).
3. Use the line to estimate costs for new ship sizes.

D. Example

If the cost of a 50,000 DWT bulk carrier is $30M, and the cost of a 100,000 DWT bulk carrier is $50M, the Slog-Slog method can estimate the cost of a 75,000 DWT bulk carrier by interpolating on the log-log plot.

8. Estimating Labour and Material Costs in Shipbuilding

A. Labour Cost Estimation

Formula for Labour Cost

Labour Cost = Σ (Man-Hours × Hourly Rate × Productivity Factor)

B. Material Cost Estimation

Formula for Material Cost

Material Cost = (Steel Weight × Cost per Ton) + (Other Materials Cost) × (1 + Wastage Factor)

C. Productivity Factors

Productivity factors adjust labour and material cost estimates to account for real-world conditions. Common factors include:

9. Ship Trials

A. Overview of Ship Trials

Ship trials are conducted to verify the performance, safety, and compliance of a newly built or refitted ship. They are typically divided into:

1. Harbour Acceptance Trials (HAT): Basic checks in port (e.g., engine startup, navigation equipment).
2. Sea Acceptance Trials (SAT): Performance tests at sea (e.g., speed, maneuvering, fuel consumption).
3. Final Acceptance Trials: Comprehensive tests before delivery to the owner.

B. Measured Mile Trial

A. Purpose

• Measure the ship’s speed and power performance under controlled conditions.
• Verify contractual speed and fuel consumption guarantees.

B. Procedure

1. Selection of Measured Mile: A calibrated, straight track (typically 1–2 nautical miles long) with known current and tide conditions.
2. Test Conditions:
   • Calm weather (Beaufort Scale ≤ 3, wave height ≤ 1.25 m).
   • Stable loading (ballast or cargo as per contract).
   • Engine at MCR (Maximum Continuous Rating) or specified power.
3. Measurements:
   • Speed over ground (SOG) (using GPS or Doppler log).
   • Speed through water (STW) (using a paddle wheel log or electromagnetic log).
   • Engine parameters (RPM, fuel consumption, exhaust temperature).
   • Propeller shaft power (using a torsion meter).

C. Data Analysis

• Speed-Power Curve: Plots ship speed vs. engine power to verify contractual performance.
• Fuel Consumption Analysis: Compares actual fuel consumption vs. guaranteed values at different speeds.
• Hull Efficiency: Assesses hull cleanliness and fouling impact on performance.

C. Fuel Consumption Trial

A. Inputs to be Measured and Recorded

B. Outputs to be Measured and Recorded

D. Ship Maneuvering Trials

A. Turning Circle Trial

• Purpose: Measure the ship’s turning ability and tactical diameter.
• Procedure:
  1. Ship approaches the turning point at steady speed (e.g., 80% of service speed).
  2. Hard starboard/port rudder (typically 35°) is applied.
  3. Turning circle is recorded using GPS or radar tracking.
• Key Metrics:
  • Tactical Diameter: Distance between the initial and final course lines (should be ≤ 5 × LOA for most ships).
  • Advance: Distance traveled along the original course before the ship turns 90°.
  • Transfer: Distance traveled perpendicular to the original course when the ship turns 90°.
  • Time to Turn 90°: Should be ≤ 2–3 minutes for most commercial ships.

B. Crash Stop Trial

• Purpose: Measure the ship’s stopping ability in an emergency.
• Procedure:
  1. Ship is brought to full ahead speed (e.g., 80–100% MCR).
  2. Full astern power is applied, and engine is reversed (if applicable).
  3. Stopping distance and time are recorded.
• Key Metrics:
  • Stopping Distance: Distance traveled from full ahead to full stop (should be ≤ 15 × LOA for most ships).
  • Stopping Time: Time taken to come to a complete stop (typically 10–20 minutes for large ships).
  • Head Reach: Distance traveled ahead of the initial position before stopping.

C. Fuel Consumption at MCR

• Purpose: Verify fuel efficiency at Maximum Continuous Rating (MCR).
• Procedure:
  1. Ship is brought to MCR power (100% engine load).
  2. Fuel consumption is measured over a steady-state period (e.g., 1–2 hours).
  3. Exhaust emissions are analyzed for compliance.
• Key Metrics:
  • Specific Fuel Consumption (SFC): kg of fuel per kWh (should match contractual guarantees).
  • Brake Specific Fuel Consumption (BSFC): g/kWh (typically 170–210 g/kWh for modern diesel engines).
  • Emissions: CO₂, NOx, SOx (must comply with IMO Tier III, EEXI, CII).

10. Short Notes with Diagrams

A. Lines Plan

A. Definition

The Lines Plan is a 2D representation of a ship’s hull form, showing the shape and dimensions of the hull in three views:

1. Body Plan (Cross-sectional views).
2. Sheer Plan (Side view).
3. Half-Breadth Plan (Top view).

B. Components of a Lines Plan

+-------------------+-------------------+-------------------+
|     Body Plan     |    Sheer Plan     | Half-Breadth Plan |
+-------------------+-------------------+-------------------+
| - Forward (FP)    | - Deck lines      | - Waterlines      |
| - Midship (MS)    | - Sheer lines     | - Buttock lines   |
| - Aft (AP)        | - Keel line       | - Diagonal lines  |
| - Vertical sections | - Stem profile    | - Station lines   |
+-------------------+-------------------+-------------------+

C. Diagram (Text Representation)

Sheer Plan (Side View):
  ___________ Deck Line
 /           \
|             | Sheer Line
|_____________| Keel Line

Body Plan (Cross-Section):
   _______
  /       \
 /         \
|           | Midship Section
 \         /
  \_______/

Half-Breadth Plan (Top View):
   ___________
  /           \
 /             \
|               |
 \             /
  \___________/

D. Significance

• Hull Fairing: Ensures smooth curves for hydrodynamic efficiency.
• Structural Design: Basis for scantling calculations and strength analysis.
• Regulatory Compliance: Used for stability calculations (e.g., GZ curve, intact/damage stability).
• Construction Reference: Guides hull fabrication and block assembly.

B. Design Spiral

A. Definition

The Design Spiral is an iterative process used in ship design to refine and optimize the ship’s characteristics. It involves multiple cycles of analysis, evaluation, and modification.

B. Stages of the Design Spiral

1. Initial Design → 2. Weight Estimate → 3. Stability Check → 4. Powering Estimate →
5. Resistance Calculation → 6. Propulsion Selection → 7. Cost Estimate →
8. Feasibility Review → [If not satisfactory, return to Step 1]

C. Diagram (Text Representation)

       +------------------+
       | Initial Design   |
       +--------+---------+
                |
                v
       +--------+---------+
       |  Weight Estimate  |
       +--------+---------+
                |
                v
       +--------+---------+
       | Stability Check  |
       +--------+---------+
                |
                v
       +--------+---------+
       | Powering Estimate|
       +--------+---------+
                |
                v
       +--------+---------+
       |Resistance Calc.  |
       +--------+---------+
                |
                v
       +--------+---------+
       |Propulsion Select.|
       +--------+---------+
                |
                v
       +--------+---------+
       |   Cost Estimate  |
       +--------+---------+
                |
                v
       +--------+---------+
       |Feasibility Review|
       +------------------+
                |
                +---> [If OK: Final Design]
                |
                +---> [If Not OK: Revise Initial Design]

D. Significance

• Iterative Refinement: Allows designers to adjust parameters (e.g., dimensions, power) based on performance feedback.
• Balancing Trade-Offs: Optimizes speed, fuel efficiency, cargo capacity, and cost.
• Feasibility Assurance: Ensures the design meets technical, regulatory, and economic requirements.

C. Iterations in Ship Design

A. Definition

Iterations are repetitive cycles of design refinement, where each cycle improves the ship’s performance, cost, or compliance with requirements.

B. Types of Iterations

C. Diagram (Text Representation)

Initial Design → [Iteration 1: Adjust L, B, D] → Check Performance →
[Iteration 2: Optimize Scantlings] → Check Strength →
[Iteration 3: Refine Hull Form] → Check Resistance →
[Iteration 4: Balance CAPEX/OPEX] → Final Design

D. Significance

• Convergence to Optimal Design: Each iteration narrows down the best possible design.
• Risk Mitigation: Identifies and resolves issues early (e.g., stability, strength).
• Cost Optimization: Ensures the design is economically viable.

D. Contract Design

A. Definition

The Contract Design is the finalized ship design agreed upon between the shipyard and the owner, forming the basis of the construction contract. It includes:

• General Arrangement Plan (GA).
• Lines Plan.
• Structural Drawings.
• Machinery and Outfitting Specifications.
• Performance Guarantees (e.g., speed, fuel consumption, cargo capacity).

B. Key Features

• Technical Specifications: Detailed dimensions, materials, and systems.
• Regulatory Compliance: Meets SOLAS, MARPOL, class society rules (e.g., ABS, DNV, LR).
• Commercial Terms: Price, delivery schedule, payment milestones.
• Performance Clauses: Speed, fuel efficiency, maneuvering guarantees.

C. Diagram (Text Representation)

Contract Design Components:
+-------------------------------------+
| 1. General Arrangement Plan (GA)     |
| 2. Lines Plan                        |
| 3. Structural Drawings               |
| 4. Machinery Specifications          |
| 5. Outfitting Specifications         |
| 6. Performance Guarantees             |
| 7. Regulatory Certificates            |
+-------------------------------------+

D. Significance

• Legal Binding: Forms the basis of the construction contract.
• Construction Reference: Guides shipyard production and quality control.
• Owner’s Requirements: Ensures the ship meets the owner’s operational needs.

E. Preliminary Design

A. Definition

The Preliminary Design is an intermediate stage between conceptual design and contract design. It refines the basic ship characteristics and provides a detailed feasibility assessment.

B. Key Activities

1. Hull Form Optimization: Refine lines plan for hydrodynamic efficiency.
2. Weight and Stability Analysis: Estimate lightweight, deadweight, and stability (GZ curve).
3. Powering and Propulsion: Select engine type, power, and propeller design.
4. Structural Design: Define scantlings, materials, and construction methods.
5. Cost Estimation: Develop a detailed cost breakdown (materials, labor, overheads).
6. Regulatory Compliance Check: Ensure design meets SOLAS, MARPOL, class rules.

C. Diagram (Text Representation)

Preliminary Design Process:
+-------------------+     +---------------------+     +-------------------+
|   Conceptual      |---->|  Preliminary Design |---->|  Contract Design   |
|   Design          |     |                     |     |                   |
+-------------------+     +---------------------+     +-------------------+
       |
       v
+-------------------+
| - Hull Form       |
| - Weight Estimate |
| - Stability Check |
| - Powering        |
| - Structural      |
| - Cost Estimate   |
+-------------------+

D. Significance

• Feasibility Confirmation: Validates technical and economic viability.
• Owner Feedback: Allows the owner to review and modify the design before finalizing the contract.
• Shipyard Planning: Helps the shipyard prepare for construction (e.g., material procurement, block planning).

11. Discussion Questions

1. How does the Hull Block Construction Method (HBCM) compare to traditional shipbuilding in terms of cost and time savings?
2. What are the key challenges in estimating labour costs for a new ship design with unfamiliar features?
3. How can productivity factors (e.g., learning curve, tooling) be quantified and incorporated into cost estimates?
4. What lessons from the Emma Maersk fire can be applied to improve fire safety in modern ship designs?
5. How does the Slog-Slog method help in scaling costs for ships of different sizes?
6. What are the critical differences between a preliminary design and a contract design?
7. How do ship trials ensure that a vessel meets its contractual performance guarantees?
8. What innovations in shipbuilding (e.g., automation, AI) are likely to reduce costs in the future?