Materials
273
Plywood Made from softwood and hardwood veneers placed at right angles, or sometimes 45°, to one another. The veneers are strong in the direction of the grain, weak in the other. Thus structural plywoods have odd numbers of layers so that the grain to the outside faces lies in the same direction. Adhesives used are described as WBP (weather and boil proof) for external or arduous conditions. BR (boil resistant), MR (moisture resistant) and INT (interior) are progressively less resistant. Plywoods are graded according to species and country of origin and are effectively as follows: Veneer with minimal imperfections as peeled. Veneer with imperfections plugged or filled. Veneer with imperfections which have not been repaired. Thicknesses
Sheet sizes
0.8, 1.0, 1.2, 1.5 mm (aircraft specification); 2, 2.5, 3, 4, 5, 6, 6.5, 9, 12, 15, 18, 21, 24 and 27 mm 1220 1220 mm 1525 610 mm (t & g) 1220 2440 mm 1525 1525 mm 1220 3050 mm 1525 2440 mm 1220 3660 mm 1525 3050 mm 1270 1270 mm 1525 3660 mm
Source: James Latham plc