This is an extremely useful product for very many purposes, requiring a thin board with great rigidity.

Plymax is a combination of wood and steel. It consists of a plywood core faced with light galvanised sheet steel. Adhesion of the steel face to the core is obtained by means of a special waterproof cement. The steel used for the metal faces of Plymax is high-class sheet specially manufactured for use in connection with this material.

Plymax is manufactured with the steel on one side only (Type 1. ;GS.12.) or on both sides (Tvpe 2. ;GS.12.).

Plymax possesses many valuable properties amongst the chief of which are :

Stiffness

By reason of the position of the steel on both sides of the plywood, Plymax has great rigidity, the steel being comparable to the flanges of a rolled " I " section beam, whilst the wood core takes the place of the thin central web. A rolled " I " section beam is many times stiffer, weight for weight, than a solid rectangular bar, and Plymax, taking advantage of the same mechanical principle, is many times stiffer than steel plate of the same weight.

Thermal Conductivity

In that its thermal conductivity is practically the same as that of wood, Plymax has a very marked advantage over steel for partitions and similar purposes. The wood core reduces the tendency to "sweat " to a minimum. Experiment shows that Plvmax has a lower thermal conductivity than asbestos cement.

Fire Resistance

The wood core of Plymax is, of course, inflammable, but since air is excluded by the steel faces, the material is fire-resisting. When exposed to a sufficiently high temperature the wood will char, but there can be no flame without air.

Resistance To Decay

Provided the exposed edges of sheets are effectively protected to prevent access of moisture to the wood, Plymax is rot-proof. The steel itself is protected by a coating of zinc.

Freedom From Noise Due To Vibration

Since Plymax is largely composed of wood, there is an entire absence of the very objectionable " drumming " which is so often experienced with sheet metal. Plymax is more sound-proof than wood of the same thickness.

Behaviour Under Changes Of Temperature

Plymax is not appreciably affected by temperature changes ranging from Zero to 100° Centigrade. If the heat is of a moist nature, special care should be exercised in the protection of the edges. Plymax can be stove-enamelled without any difficulty, provided that the stoving temperature is within the above limits.

Hygienic Properties

-By virtue of its galvanised steel faces Plymax is hygienic and is thus suitable for lavatory and bathroom partitions. Being vermin-proof, it is most useful for the construction of store rooms.

Types

-Plymax is supplied-

With galvanised steel on both sides (Type 2.GS.12.).

With galvanised steel on one side only (Type 1.GS.12.).

Where Plymax is used structurally and not merely as a covering material, the former type (2.GS.12.) should be used, since this type gives maximum rigidity for a minimum weight.

Sheets with steel on one side only (Type 1.GS.12.) are naturally not as rigid as Type 2.GS.12., but have many uses and can often be employed with great advantage when economy in weight is a prime factor. This type (1.GS.12.) should be used only as a covering material in conjunction with a frame of wood or steel, because when such sheets are delivered it is unlikely that they will be dead flat. The reason is that the wood core is protected by the steel sheet from atmospheric conditions on one side, whilst, on the other, the exposed wood is free to absorb moisture and swell, or dry out and shrink. When the sheets are attached to a frame, any curvature is overcome without any difficulty and the surface will become flat. In effect, Type 1.GS.12. is in a naturally unbalanced state as far as atmospheric conditions are concerned.

As a frame is almost invariably used in vehicle construction and saving in weight is of great importance, Plymax with steel on one side only (Type 1.GS.12.) is extensively used for panels, and the slight initial curvature of sheets is by no means a disadvantage. In the thickness ordinarilv used for van panelling, Type 1.GS.12. is about one-third lighter than Tvpe 2.GS.12.