Three timbers define a properly built phinisi: ulin (Bornean ironwood) for the keel and primary structure, bitti (Vitex cofassus) for hull planking, and teak for decks, joinery and interiors. The combination is not tradition for its own sake — each species solves a specific problem of strength, rot resistance or workability that tropical seas impose on a wooden ship.
This page explains what each wood does, where it goes in the boat, and how sourcing works today. For how the timbers become a hull, see phinisi boat building.
The Three Core Species
| Timber | Species | Where it goes | Why |
|---|---|---|---|
| Ulin (ironwood) | Eusideroxylon zwageri, Borneo | Keel, stem and stern posts, primary structural members; on premium builds, hull planking too. | Extreme density (it barely floats), exceptional resistance to marine borers and rot; the backbone timber of Indonesian shipbuilding. |
| Bitti (vitex) | Vitex cofassus, Sulawesi | Hull planking, frames, knees. | Strong, borer-resistant, available in long clear lengths near the yards; the traditional Sulawesi hull wood named in academic surveys of pinisi construction. |
| Teak | Tectona grandis, Java/Sulawesi plantations | Decks, cap rails, superstructure, furniture, interior joinery. | Dimensionally stable, naturally oily, weathers silver without rotting; the finish wood every guest actually touches. |
Why the Keel Must Be Ironwood
The keel takes the grounding loads, holds the fastenings for every frame, and lives permanently wet. Ulin is one of the few timbers on earth that shrugs at all three conditions: it is so dense and silica-rich that teredo worms — the shipworm that destroys lesser hulls from inside — make little progress, and it hardens rather than softens with decades in seawater. Builders describe ironwood structures outlasting the men who built them. The trade-off is weight and labour: ulin blunts tools, resists bending, and must be shipped to Sulawesi from Kalimantan, all of which shows up in the numbers discussed in build cost.
Ironwood-and-Teak as a Quality Signature
“Ironwood hull, teak everything else” is shorthand for a serious build, and operators say it plainly in their specifications: the dive-focused Pinta (30 m, 2021) is described as an ironwood-and-teak build, as are the premium vessels documented across our fleet directory. When a listing says only “wooden phinisi,” ask which wood — mixed hardwood hulls are common at the value end and honest, but they are not the same boat.
Sourcing, Legality and Substitutes
- Ulin is slow-growing and protected: Indonesian regulation restricts harvest and export, so legitimate yards work from licensed stock, salvaged timber and long-cured beams. Provenance paperwork is part of a credible new build.
- Bitti remains the local workhorse, cut in Sulawesi; supply is closer to the yards and less contested.
- Teak comes overwhelmingly from managed plantations in Java; old-growth teak commands collector prices and appears mainly in refits of vintage hulls.
- Substitutes you will meet in specifications: bungur and merbau for framing, ipil and kandole for planking. Reputable builders name their species; vagueness is a signal.
How the Wood Ages at Sea
A tropical wooden hull is a maintenance covenant, not a finished object. Seams move with heat and humidity and are re-caulked on cycle; teak decks are washed with seawater and left unoiled; the hull is hauled or beached for antifouling and inspection on a regular schedule. Done properly, the covenant holds for decades — the routine is detailed in phinisi maintenance. Skipped, even ironwood cannot save a boat’s systems and joinery. Operators with in-house yard programmes, such as Komodo Luxury across its fleet, build this cycle into the vessel’s calendar.
Frequently Asked Questions
What wood is a phinisi made of?
Traditionally ulin (ironwood) for keel and structure, bitti (vitex) for planking, and teak for decks and interiors. Premium builds extend ironwood into the planking; value builds substitute regional hardwoods.
Why is ironwood so prized for boats?
Density and durability: ulin resists marine borers and rot to a degree almost no other commercial timber matches, and it gains hardness over years in seawater. Its drawbacks — weight, cost, restricted supply — are accepted for the keel and backbone.
Is teak used for the hull?
Rarely. Teak’s stability and weathering make it ideal for decks and joinery, but hull planking calls for the borer resistance of ulin or bitti. “Teak phinisi” in marketing usually means teak decks and interior.
Are the timbers sustainably sourced?
Increasingly, and unevenly. Ulin is regulated and often salvaged; teak is plantation-grown; bitti is locally cut. Serious yards document provenance — buyers commissioning a new build should require it.
Evaluating a build specification or survey report? We can read the timber schedule with you — WhatsApp +62 811-3823-875.