Species selection is a structural decision, not a preference. On this coast a hull is typically built from several timbers, each chosen for where it sits: dense and rot-resistant for the backbone and areas that stay wet, more workable stock for planking and joinery. Repairs that ignore the original logic create the next generation of problems.
What the yard is actually choosing between
| Property | Why it matters | Where it dominates the choice |
|---|---|---|
| Natural durability | Resistance to decay and marine organisms without relying on coatings. | Keel, stem, sternpost, garboard, anywhere permanently wet. |
| Density and hardness | Strength and fastening grip — but also weight and difficulty of working. | Structural members, bearers, high-load areas. |
| Dimensional stability | How much the timber moves with moisture change. | Planking and anything that must hold a seam. |
| Workability | How readily it can be shaped, bent and fastened without splitting. | Planking, deck, joinery, curved members. |
| Availability in section | Whether long, deep or grown-curve stock can actually be obtained. | Everything — the constraint that quietly overrides the others. |
The backbone
Keel, stem, sternpost and deadwood are the members that must last longest and are hardest to replace. They are conventionally cut from the densest, most naturally durable stock available, accepting the penalties: weight, cost, and timber so hard that every fastening hole must be drilled and every cut takes time. Ironwood-class timbers earn their place here precisely because this is where durability is worth paying for.
The corollary matters for repair. When a backbone member does eventually need attention, the work is slow and the stock is difficult to source in the required section. This is why pre-purchase inspection pays disproportionate attention to stem, transom and keel joints: a soft plank is a job, and a soft stem is a decision about whether to keep the vessel.
Planking
Planking stock is a compromise between durability, stability and workability. It has to bend to the hull’s shape without splitting, hold a fastening reliably, keep a fair edge for the seam, and resist decay in a hull that will spend its life wet. Very hard timbers resist decay well but are difficult to work and unforgiving when a plank has to be sprung into place; softer, more workable species plank more easily but need more coating discipline and better drainage to last.
Seasoning matters as much as species
Well-seasoned stock of a modest species outperforms green timber of a prestigious one. Green planking fitted tight will shrink and open the seams; green frames will move and slacken every fastening in them. Timber acceptance at the yard checks seasoning as carefully as species.
Frames, floors and beams
Frames need strength, fastening grip and, where they are grown or laminated to a curve, the right grain direction. Floors — the members that tie frames across the keel — live in the bilge and take the worst of any standing fresh water, so durability weighs more heavily there than anywhere except the backbone. Deck beams need stiffness without excessive weight high up in the vessel.
Why mixed hulls need careful repair
Because a traditional hull is deliberately built from several species, the single most common repair error is treating “wood” as one material. A plank of a different species from its neighbours will move differently through the seasons, so its seams open when the others close. It may also hold fastenings differently, which changes the load path locally. Where the original species genuinely cannot be obtained, the substitution should be chosen for compatible movement and durability, and it should be recorded in the vessel’s history so the next person knows.
Fastenings and species interact
Dense timbers grip mechanical fastenings extremely well but split if fastenings are driven without pilot holes. Softer species tolerate driving but rely more on fastening area for their hold. Some timbers are chemically aggressive to certain metals in the presence of salt water, accelerating corrosion around the fastening and softening the surrounding wood. This interaction is the subject of the article on fastenings and joint failure, and it is why fastening material is specified alongside timber species rather than chosen separately.
Sourcing, legality and lead time
Large-section boat-grade timber is not a commodity sitting in a warehouse. Long planks, deep keel stock and grown curves take time to find, and increasingly they take documentation as well. Any programme that depends on specific species in specific sections must treat timber procurement as a long-lead item identified at scope stage — a discipline built into yard project management here, because a hull open and waiting on timber is the most expensive form of idle.
What owners should record
Every vessel should carry a written record of what it is built from and what has since been replaced, species by species and area by area. Astonishingly few do. Where the record exists, repairs are faster, quotations are more accurate, and surveys start from knowledge rather than guesswork.