Wooden boat joinery and varnishing

Timber on boats is beautiful, but it only stays that way if the wood and the finish are right. Varnishing is not decoration, it is weatherproofing.

Choose the right timber. Use marine-grade hardwoods or treated softwoods suitable for the job. Teak, iroko, mahogany and oak are common choices, but they all move differently with moisture.

Repair and scarfing. Splice in new timber with proper scarfs or butt blocks, not just glue and filler. Use epoxy and bronze fasteners where appropriate. Keep the grain direction and scantlings consistent with the original.

Caulking and seam compound. Traditional planked boats need re-caulking. Do not overdo it — too much cotton or compound forces the planks apart. Learn the feel of a well-seamed hull.

Varnish system. Strip old failing varnish, sand carefully, apply a sealer and then build thin, even coats of high-quality marine varnish. Sand between coats and keep dust out. Eight thin coats beats three thick ones.

Maintenance. Varnish needs regular washing, light sanding and fresh top coats. A little work every season keeps a big stripping job at bay. Store covers off when possible so air can circulate.