Ulin & Teak: Why Ironwood Still Builds the Best Phinisi Hulls

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Ask a Bulukumba shipwright what makes a hull last and the answer starts with the wood. A phinisi lives outdoors in warm salt water from its first plank, so timber is not a finish choice — it is the structure. Three woods do most of the work, and knowing why each is used tells you a lot about a hull’s quality.

Ironwood (ulin): the backbone

Ulin, or Bornean ironwood, is extraordinary: so dense it sinks, so hard it blunts tools, and so resistant to rot, insects and marine borers that it can outlast everything around it. That is exactly what the keel, stem and sternpost need — the parts of the hull that must stay soundest and longest below the waterline. It is heavy and expensive, which is why it is used where it matters most rather than everywhere.

Bitti: the working structure

For frames and planking, the traditional timber is bitti (Vitex cofassus) — tough, naturally durable, and workable enough to shape, steam and bend into a carvel hull. It holds fastenings well and stands up to the constant flexing of a hull at sea. Most of what you see of a phinisi hull is bitti.

Teak: where you walk and live

Teak (jati) is the deck and joinery timber. It is dimensionally stable, weather-resistant and non-slip when laid as decking, and it makes the interior joinery that survives humidity and salt. Teak is prized enough that it is used with care, but it is what gives a phinisi its warm, lasting interior.

Scantlings and fastening

Timber is only as good as how it is sized and fastened. Scantlings — the dimensions of keel, frames and planking — are set from the vessel’s size and class. Fastening combines traditional hardwood dowels with bronze or galvanised bolts and copper where corrosion resistance matters, chosen to avoid galvanic pairing. Get the timber, scantlings and fastening right and a phinisi hull can last decades.

Matching timber to the job

The lesson of phinisi timber is specialisation: no single wood is best everywhere, so each is used where it excels. Ironwood outlasts everything below the waterline; bitti works and bends into the hull structure ; teak lives beautifully where you walk and sleep. A builder who uses the cheapest wood everywhere is saving in the wrong place.

Seasoning and moisture

Freshly cut timber moves as it dries, so seasoning matters. Timber that is too wet when built in will shrink and open seams; the right moisture content keeps a hull tight. This is one of the quiet quality factors behind a lasting hull, and one reason timber availability can affect a build timeline .