Hull Timber & Ironwood — Ulin, Bitti, Teak and the Craft of Fastening

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A phinisi is only as good as its timber and its fastening. The hull lives outdoors from its first plank, worked hard in warm salt water, so the woods are chosen for what each does best — ironwood where durability matters most, bitti for the working structure, teak where you walk and live. This page is the material story behind every hull we build at the Bulukumba yards .

The three timbers

Timber	Where it goes	Why
Ironwood (ulin)	Keel, stem, sternpost, backbone	Extreme density; resists rot, insects and marine borers
Bitti (Vitex cofassus)	Frames and planking	Tough, workable, holds fastenings, naturally durable
Teak (jati)	Decking and joinery	Stable, weather-resistant, non-slip when laid

Timber is specified and sourced legally before keel-laying — species, dimensions and moisture all matter to the finished hull.

Scantlings — sizing the structure

Scantlings are the dimensions of the structural members: keel, frames, planking thickness, floors and keelson. They are set from the vessel’s size and class category, calculated on the design and then cut from sawn timber. Under-scantling a hull saves weight and money but costs longevity and class; we size to standard, not to the minimum.

Carvel planking

A phinisi is carvel-planked: the planks meet edge-to-edge to form a smooth hull, rather than overlapping like clinker. In the Bugis shell-first method the planks are shaped, steamed and bent to the hull form and edge-fastened to one another before the frames go in. Fairness — a true, sweet curve with no flats or hollows — is judged by eye and long battens.

Fastening a hull to last

Traditional pinisi were fastened largely with hardwood dowels, called paso’, driven through the planking. Modern builds combine that craft with bronze or hot-dip galvanised bolts and drifts where the loads demand it, and copper or bronze where corrosion resistance matters. Good fastening — the right metal, the right bedding, no galvanic pairing — is much of what makes a hull last.

Caulking and protection

Seams are caulked with cotton or fibre and payed with a marine sealant to keep the hull watertight as the timber works. Below the waterline the hull is protected against marine borers and fouling. Maintenance — hauling out, cleaning and recoating on schedule — is what turns a sound new hull into a hull that lasts decades; see refit and restoration .

Sourcing timber responsibly

Good hardwood is finite, and sourcing it responsibly matters both ethically and for the vessel’s papers. Timber is specified by species and dimension and sourced through legal channels before keel-laying. Building to class also means the structure and its materials are documented, which protects the owner and encourages responsible supply.

How timber fails, and how to prevent it

A timber hull’s enemies are rot, marine borers and neglected fastenings. Rot needs moisture and poor ventilation; borers attack unprotected timber below the waterline; galvanic action eats mismatched metals. Each is prevented by design — durable species like ironwood where it counts, protective coatings, correct fastening, and ventilation — and managed by maintenance. See refit and restoration for when repair is needed.

The copper-nail tradition

Copper and bronze earn their place because they resist corrosion in salt water and pair safely with other bronze fittings. Traditional builders combined hardwood dowels with metal fastenings where loads demanded; the discipline is choosing metals that will not set up galvanic corrosion against each other. Good fastening is invisible when right and catastrophic when wrong.

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