Once the basic foundations have been laid down in the concept design phase, the next stage is to generate a more detailed set of design information. Typically, this process would include some tuning of the conceptual work, tow tank testing if appropriate, refinement of powering and weight calculations, structural engineering, production of materials estimates and preliminary system specifications.

The intention of this phase is to take the project to the stage where it can be offered to various yards in the form of ‘preliminary design / bid package’. The selected yards are then invited to bid for the build project. The ‘preliminary design / bid package’ generally includes outboard and inboard profile drawings, interior and machinery layout drawings, a detailed preliminary specification, which is usually referred to in any subsequent build contract, a detailed weight study, preliminary structural and system drawings and a 3D computer model of the hull and superstructure.

The preliminary specification for the vessel describes as many features and components of the boat as possible.  This document also includes all requirements of the yard, including the need to implement specific quality assurance procedures, weigh schedules for the vessel and warranty provisions.

The quantity and detail of the ‘preliminary design / bid package’ has a direct correlation on the accuracy of the yard’s costing. There is a balancing act between providing enough information for an accurate and fair costing and completing the package at a reasonable cost to the client before the final decision is made to proceed. The more work that is done during this phase will reduce the amount to be done during the ‘detail design’ phase. 

The design can still be completely or partially reviewed before going to the ‘detail design’ phase and there is often interaction between the designer, builder and client. This may need to be done to bring the predicted build costs within the available budget or to incorporate any additional requirements or ideas. 


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