Hull structure of a modern sailing junk

Professional Construction of a Jonque de Plaisance

Construction Amateur

Matahina, 12,5m

The method is well known and has been recommended since the end of last century (or the other) by HERRESHOFF. Numerous architects have made use of it with only simple modifications according to the size and purpose of the boats, modifications also made possible by the improved quality of available glues. The timber varieties used are readily available, such as ‘Iroko’, Mahogany, Oregon pine, nordic pine, teak etc.

The strength of strip-planking (glued laminated timber) is far superior when compared to that of solid timber, the lighter structures thus built mean that for the same waterline length, the hull has a much reduced displacement. The improved resin based and epoxy glues also give unequalled durability to laminated timber and plywood, with maintenance costs greatly reduced.

The masts are also strip-planked and have a hollow centre. Contrary to what may seem, they are easy to assemble, as with most building tasks, by one person alone.

Most boats will require strip planks between 12 mm and 25 mm thick, depending on the length and width of the boat, the spacing between the frames, the ability of the planking to bend around the most pronounced curves of the hull, and the most efficient use of the timber.

Soft timbers (preferably without knots) are preferred as they are less subject to expansion and can absorb more compression. The bead and cove strips have several advantages: they fit into each other well, even if the angle of the curve is tight. Therefore, there is no gaps to fill with epoxy which can be unsightly and adds weight; except of course in the region of the midship beam which requires more attention.

The bead and cove strips are machined with a convex and a concave edge, the glue is applied to the concave edge of each strip and the next strip is added. As you progress, each strip is glued and nailed to the previous one and also glued and nailed to the frames. Discard any strip that may be twisted or split.

Dimitri Le Forestier