Yacht Design Office: the Design Process

The concept of Design Spiral is very popular among yacht designers, naval architects, and other yacht design practitioners, be it professionals or amateurs. The spiral considers that the design of a vessel is a complex process with many inputs and outputs affecting one another and that the optimum design can only be attained after an iterative process, making the design progress to the final solution at each turn of the spiral.

A much less known design process is the one defined by a discipline called Systems Engineering. Systems engineering’s target is to determine efficient and effective processes to guide the design and engineering of complex systems, or in other words, to define the processes that will bring a complex system into being most effectively and efficiently.

Systems Engineering covers the complete life cycle of a system: from requirements analysis and conception through engineering, operation, and maintenance, until (including) its end of life. Although manufacturing, operation, maintenance, and end of life must be considered and integrated during the early stages of the design, Yacht Design Offices’ activities usually expand only the first phases: requirements, concept, and engineering.

In this article, we define a Design Process for yachts and other types of vessels based on our own experience, lessons learned in different projects, and industry standards. This Design Process combines at the same time both the Systems Engineering and the Design Spiral approaches.

Considering what we have discussed above, we have divided a vessel’s design process into three different phases:

Requirements & Initial Brief.
Concept Design.
Engineering Design.

We do not consider manufacturing, operation, maintenance, and end of life as part of the design itself. However, they must be included as inputs to the vessel’s requirements during the first design phases.

At the end of each phase, an Evaluation Gate will be performed to assess whether the design targets have been achieved and decide the convenience of entering into the next phase.

1. Requirements & Initial Brief Phase

We divide the “Requirements & Initial Brief” design phase into two different steps:

1. Requirements: the Design Office collects information from the Client, the market, rules, regulations, and standards and creates the Vessel’s Requirements document.

2. Initial Brief: the Vessel’s Initial Brief based on the Vessel’s Requirements document is created. The Initial Brief contains preliminary information about dimensions, areas, weight, ratios, performance, aesthetics, equipment, systems, design category, accommodation, materials, applicable rules, regulations and standards, and 2D drawings and 3D views to establish the general layout and design.

The documentation generated during this phase should be sufficiently detailed to enable the Client to start the vessel’s Concept Design with either the Design Office that performed this phase or any other design office.

Throughout the phase, the Design Office should advise and guide the Client by providing expert assessments.

1.1 Phase inputs

Before starting the Requirements & Initial Brief design phase, an agreement between the Client and the Design Office must be reached. This agreement will define the assignment and its scope, including fees, payment terms, and the general terms and conditions of the service.

Typical data that is gathered from the Client during this design phase consists of:

Sailing experience.
Vessel’s intended profile: inshore/offshore, cruising/racing, sailing zones, sailing seasons, crew, guests.
Target activities: fishing, diving, traveling, adventure, exploration, etc.
Desired performance.
Aesthetics preferences.
Materials whished.
A list of sailing yachts in the market the Client uses as reference.
Region/country for homologation.
One-off, series building.
Timeframe.
Budget.

1.2 Phase deliverables

Deliverables are documents/reports/drawings or other types of documentation that the Design Office prepares and sends to the Client as outputs of its design effort.

We have defined the following deliverables for the Requirements & Initial Brief design phase:

Preliminary General Arrangement (GA) drawing.
Statement of Requirements (SoR).
Preliminary Body Lines Plan.
Preliminary 3D visualization to establish a preliminary overall vessel´s look and feel.
Preliminary Project Timing, including rough estimates for the main building and sea trials activities (*).

(*) The actual building and sea trials activities must be defined and agreed upon between the Client and the Builder.

The SoR should include the following:

Performance requirements.
Autonomy requirements.
Handling and maintenance requirements.
Stability, seakeeping, and maneuverability requirements.
Hull and deck requirements.
Appendages requirements.
Rig and sails requirements.
Accommodation requirements.
Gear, equipment, systems, and safety requirements.
Materials requirements.
Production requirements.
Environment requirements.
Homologation requirements.
Vessel’s design category.
List of applicable rules, regulations, and standards.

Some of the vessel’s data included in the SoR would be:

– Preliminary dimensions and areas (values and ranges):

Hull: length overall (L_OA), length of waterline (L_WL), max beam (B_MAX), Draft of the hull (T_C).
Hull and keel: total draft (T).
Keel: keel draft (T_K), type of keel.
Rig: distance from the mainsail top to the top of the boom (P), distance from the outer point of the boom to the aft face of the mast (E), Forestay height (I), Base of the foretriangle (J).
Sail area (mainsail + headsail).

– Preliminary weights (values and ranges):

Displacement.
Ballast.

– Preliminary coefficient (values and ranges):

Beam / Length ratio.
Displacement / Length ratio.
Beam / Draft ratio.
Sail area displacement ratio.

– List of equipment and systems required related to navigation, communications, safety, steering, anchoring, mooring, sails, engine room, propulsion, water, electric generation and distribution, HAVC, etc., and additional required equipment and/or systems such as dinghy, windvane, solar panels, etc.

– Preliminary definition of the interiors for each main accommodation area, including a preliminary list of furniture, appliances, materials, textures, and colors.

2. Concept Design Phase

Building upon the documentation (deliverables/outputs) generated during the Requirements & Initial Brief design phase, the Design Office creates 2D drawings, 3D models, and documents related to the hull, appendages, deck, and rig shapes and layouts, sails, sails inventory, tanks, accommodation, materials, equipment, systems, safety, engine/motor, and propeller.

During this phase, the Design Office estimates the weight, weight distribution, and position of the center of gravity (CoG). It performs calculations leading to hull, deck, keel, rudder, and rig scantling determination. It also carries out calculations about hydrostatics and stability, performance, balance, seakeeping, and maneuverability.

As is the case in all the design phases, the Design Office shall advise and guide the Client by providing expert assessments during the whole process.

The documentation generated during the Concept Design phase will be sufficiently detailed to enable competent builders (yards, etc.) to estimate the building costs. It will also serve as a starting point for the Engineering Design phase, typically with the same Design Office that performed the Concept Design phase. However, starting the Engineering Design phase with a different Design Office would also be possible.

Concept exploration, feasibility, and evaluation.

2.1 Phase inputs

The inputs to this phase are a positive outcome of the Requirements & Initial Brief Evaluation Gate (necessary to start this phase) as well as its phase deliverables:

Preliminary GA (General Arrangement).
SoR (Statement of Requirements).
Preliminary Body Lines Plan.
Preliminary 3D visualization.
Preliminary Project Timing.

2.2 Phase deliverables

With the information above, the Design Office will perform different activities leading to the preparation and delivery to the Client of the following deliverables:

3D model for naval architect calculations.
Hydrostatic curves and data.
Scantling data estimation: main dimensions, displacement (e.g., as per ISO 12215).
Scantling determination and scantling drawings.
Lightship weight calculation.
Deck and engine room equipment definition (*).
Definition and calibration of structural tanks (if any) – Sounding tables.
Cross curves of stability.
Equilibrium flotation and stability for 4 or 5 load conditions (**).
Stability and buoyancy assessment and categorization (e.g., as per ISO 12217 – 1).
Power-speed estimation (Savitsky method).
Study about the CoG location that would minimize resistance.
Final General Arrangement drawing.

(*) Although all the requirements should be included in the deliverables generated during the Design Concept phase, the Client could still come up with some change proposals until the beginning of the preparation of the “Deck and engine room equipment definition” deliverable.

(**) The Design office will assess at least the reglementary load conditions, but typically the Client can also propose some particular load conditions to be considered in the analysis.

3. Engineering Design Phase

Based on the deliverables created during the Concept Design phase, the Design office creates all the documentation necessary for a yard to build the sailing yacht.

The Design Office will create and provide building drawings, bill of materials (BOM), homologation documentation, equipment list and specifications, piping diagrams, hydraulic schematics, and electrical drawings.

It will also provide the weight, weight distribution, the position of the center of gravity (CoG), and perform calculations about hydrostatics and stability, performance, balance, seakeeping, and maneuverability.

The Desing Office will assist, advise, and guide the Client and perform expert assessments throughout the whole phase.

The Client can use the deliverables received at the End of the Engineering Design phase to enter into an agreement with a shipyard, builder, metal construction company, woodworking company, etc., regarding the building of the vessel.

3.1 Phase inputs

The starting point for this phase is a positive outcome of the Concept Design Evaluation Gate (necessary to start this phase) and the Concept Design phase deliverables.

3.2 Phase deliverables

The following are the typical deliverables of the Engineering Design phase:

Body Lines Plan for production.
Production drawings.
Electrical documentation: electrical balance, electrical diagram, cable trays.
Pipes arrangement diagram and drawings.
Lights, radars, navigation, and nautical equipment plans.
Mooring elements’ location

As an example, for a metallic hull vessel, the production drawings would include the following:

Definition of each of the structural parts.
Definition of each of the stiffeners.
Parts nesting for CNC.
Sketches for stiffeners manufacturing.
Bill of material with individual weights and information that enables traceability.
Parts nesting: cut length, plate’s gross and net material required.
2D/3D sketches for sub-assemblies manufacturing.
Sketch for the assembly of the hull sub-assemblies.
Production control sketches for sub-assemblies and complete hull.
3D models with shell plates and internal structure.
Calculation of the total weight and CoG of the structure.

4. Design organization

The design effort and its different phases will be organized as a Project.

The Design Office will typically assign the roles of Project Manager, Project Technical Manager, and Project Engineer. Depending on the project complexity, those roles could be fulfilled by a single individual or different ones.

The Project Manager will be responsible for the Project’s planning, execution, and monitoring. He will be the Client´s main contact/interlocutor and ensure the Project’s goals are achieved on time, within budget, and quality.

The Technical Project Manager will be responsible for all the technical aspects of the Project.

The Client will also assign a person to be the interlocutor to the Project Manager. This person shall provide (or cause others to provide) to the Design Office promptly the information, resources, assistance, comments, and approvals that the Design Office reasonably requires to perform the services.

The Project will require an important effort in coordination and the participation of both parties in regular Project Review meetings.

5. Manufacturing and Sea Trials

Typically, the Design Office will not be a party to any building contract. However, they could provide, if requested, services and advice related to solicitation, evaluation of bids, builder selection, building supervision, and other related activities.

Sea Trials are real-life tests performed on the finished vessel and agreed upon between the Client and the Builder. They are used as a protocol for the acceptance of the vessel. During the Sea Trials, the Client will carry out extensive and professional tests to be able to assess whether the Design Office and the Builder have delivered properly.

Sea trials are arranged by the Client together with the Builder and typically the Design Office is invited to them.

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