Naval Architecture & Design — Phinisi Lines, Stability and Displacement

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Before a keel is laid, a phinisi is a set of drawings and numbers. Naval architecture is what turns a brief — “a 35-metre dive liveaboard for ten cabins” — into an engineered hull with a known displacement, stability and tonnage that will carry that load safely and pass class. This page covers the design work specific to the phinisi form.

The lines plan and hull form

The lines plan defines the hull’s three-dimensional shape. A phinisi is a displacement hull — it pushes through the water rather than planing over it — with a full body for load-carrying and a form the Bira shipwrights can build shell-first by eye. We reconcile the traditional form with the modern requirements of stability, tankage and the interior arrangement .

Principal dimensions

Dimension	What it is	Why it matters
LOA	Length overall	Sets scale, cost, berth and cruising feel
Beam	Moulded breadth	Drives stability, interior volume and comfort
Draft	Depth below waterline (loaded)	Governs where the vessel can go and anchor
Displacement	Weight of water displaced	The vessel’s true weight; sets structure and power
Gross tonnage	Enclosed volume measure	Drives class, crewing, fees and registration

Displacement, stability and load

Displacement is the vessel’s real weight — hull, systems, fuel, water, stores and people. Stability calculations show the vessel will stay upright and recover through the range of loading it will meet, from full tanks and guests to near-empty. These calculations feed straight into class compliance and the inclining test at completion.

Gross tonnage and how it shapes the vessel

Gross tonnage measures enclosed volume, not weight, and it quietly governs a great deal: the class category, how many crew the vessel must carry, port and park fees, and how it is registered. We estimate GT at the design stage so an owner understands the operating implications before committing — a small change in superstructure can move the vessel across a threshold.

Where our design ends and the national desk begins

We do the phinisi-specific naval architecture for the vessels we build. For a full, standalone national yacht-design commission, our sister desk offers a full naval-architecture and yacht design service. For the numbers that set your budget, see build cost and timeline .

Reconciling tradition with calculation

The interesting challenge in phinisi design is honouring a hull form developed by eye over generations while proving it with modern calculation. We take the traditional shell-first form and verify its tonnage , stability and structure against class requirements — keeping the character while meeting the numbers.

Weight, trim and the loaded boat

A vessel’s behaviour changes with what it carries. Fuel, water, stores, tenders and guests all move the trim and the centre of gravity, so the design accounts for the full range of loading, from departure with full tanks to the end of a long charter. Getting weight distribution right is what makes a boat feel sea-kindly rather than tender or stiff.

Designing for the itinerary

A boat for sheltered Bali day-cruising and a boat for open passages to Raja Ampat are different designs even at the same length — different range, tankage, freeboard and stability margins. We design to the itinerary the owner actually intends, which is why the brief starts with intended use, not just a length.

Construction, new-build and refit contracts are issued by PT Komodo Galangan Nusantara. Part of Juara Holding Group.