Section 3 Wood

301. General

1. Requirements specified in this Chapter are applied to structural wood and plywood used in the hull structure of recreational crafts.

2. Wood and plywood used for hull structure of recreational crafts are to be approved by Society.

302. Wood

1. Timber shall be suitable for use in the intended marine environment and shall be of durability classes 1, 2 or 3, (see Table 3.3) except where otherwise specified in this section.

Table 3.3 Designation of durability of wood

2. A selection of such wood species is given in Table 3.4. Wood of lower durability classes may be

used, as listed in Table 3.4, provided the mechanical properties suitable preservations are applied.

are sufficient for scantlings, and

Table 3.4 Wood designation and durability classes (selection)

Ch 3 Material Ch 3

3. Timber for structural parts shall be free from defects that might impair the strength or durability of the craft, e.g. bluing, brittleness, rot, cracks, knots and sapwood.

4. Timber used for planking of the hull shall be cut with consideration of warping, shrinkage and swelling in the as-assembled condition. Timber intended to be used for planking of the hull should be quarter sawn (rift sawn), with an angle of the annular rings to the lower cut edge less than 45° for single-skin carvel construction, except for strip plank construction with small strip width.

5. The moisture content of the wood shall be within the limits required by the method of joining the parts (gluing, laminating, sheathing) and consideration of the dimensional stability of the structure. Timber for structural purposes where encapsulated or over-laminated shall have an average moisture content not greater than 15 %.

303. Plywood

1. Plywood intended to be used for external structural members, e.g. hull, weather deck not sheathed by fibre reinforced plastics (FRP) laminate or similar, superstructures and deckhouses, shall be ma- rine- grade plywood. Where a craft is intended to be only temporarily used in the water and the hull is protected by a wood-penetrating medium (e.g. epoxy resin) other waterproof and boilproof external-grade plywood may be used.

2. Other members inside the hull may be made of waterproof and boilproof plywood which does not fully comply with marine-grade plywood. It shall be durable.

304. Veneers for moulded construction

Veneers used in the construction of the hull, deck and superstructure shall in general be of dura- bility class 1 or 2. Exception: veneers of durability less than 2 may be used if adequately pre- served by resin penetration or FRP sheathing.

305. Wood composite structures

1. Coromstpriopsitpelasntrkuicntgurewsiathre cwovoeo-daennd,-bgeeanderoarllytonogfuem‒onudl-dgerdoocvoensetdrugcetiojoninatsndwimthadoeneoforlaymeorsreoflayveernseeorfs synthetic fibres incorporated taking a significant part of the stress. The synthetic fibres are generally used in the form of fabrics, for example glass, aramid, carbon fibres, or a combination of these.

When selecting wood and fibre fabrics for the purpose of composite construction, the resin used for

2. saturating the fibres shall be capable of achieving a good penetration into the surface of the wood

and a structurally sound bond between wood and fabric.

Where composite construction is used, account shall be taken of the different properties of the ma-

3. terials being used and the way in which applied loads will be shared.

306. Workshop conditions

1. The premises used for production and storage shall be suitable, and equipped to provide the con- ditions necessary for fault-free bonding by adhesives.

2. This shall enable the builder to monitor, and if necessary control, temperature, humidity and other environmental conditions during manufacturing so as to avoid changes during manufacture.

3. The workshop and equipment shall be maintained in a clean and efficient condition.

307. Storage and handling for material

1. Timber shall be stored in dry and well-ventilated premises where it is protected from direct sun- light and excessive moisture. It shall be stored horizontally, each plank or layer being separated from the other to achieve air circulation.

2. Adhesives shall be suitable for the intended purpose. The bond’s mechanical properties and life shall exceed that of the glued wood. Adhesives shall be stored as specified by the manufacturer of these materials in their original containers. They must not be used after their expiry date.

Ch 3 Material Ch 3

3. Fastening elements for load-bearing parts of the construction, e.g. nails, screws and bolts shall be corrosion resistant or hot-dipped galvanized.

308.

Manufacturing for wooden crafts

1. Manufacturing shall take place in an environment that takes into account the requirements and limi- tations specified by the manufacturer of the material (e.g. glue, resin or paint).

2. The moisture content of the wood shall be checked before gluing. The moisture content shall not exceed that which permits full joint strength. Areas to be glued shall be free from any con- tamination that might impair the strength of the bond.

3. Wooden craft shall be constructed in such a way that water cannot collect in areas where it cannot be drained. They shall also be constructed in such a way that natural ventilation is promoted to all areas of the craft.

4. A protective coating or surface treatment shall be applied to finished surfaces not intended to be left bare, for example teak decks. Any coating or treatment shall not adversely react with the adhe- sives, reduce the mechanical property of the joint or have a detrimental effect on the wood itself.