i n t e r n a t i o n a l n e w s

small elements, each of which exhibits known and predict- able characteristics.

By using well-proven mathematical formulae, these known values can then be computed against variables such as variable stress to determine the performance of a given design under different operating conditions.

Thus far, the model, which is believed to be the first attempt to apply these concepts to the performance of

elastomeric seals, has produced results which are very close to those obtained by purely empirical test methods. Dowty is now looking at extending the work to include the evaluation of dynamic and temperature conditions.

The software used in this exercise is completely original, tailored specifically to the properties of sealing materials and the package is run in conjunction with the Prime-based CAD facility already available.

GRP boat-building without moulds

A new system for building GRP boats allows hulls to be produced without using moulds - which cost more to build than an actual hull- and is primarily intended to enable yards to produce 'one off' boats more profitably. The system is also cost-effective for production runs of up to 25 off.

Hultec hulls are built up on a frame of contour formers and H-section pultruded GRP battens. Glassfibre reinforcement, in the form of a new non-woven roving material that will not sag when applied, is then wetted out with polyester resin and laid up over the outer surface of the frame.

A remarkable degree of fairness is achieved and, therefore, subsequent reinforcement is able to be laid up on the inner surface of the hull. This minimises the amount of finishing work required on the outer skin.

Even before the inner skin is laminated, the hull is extremely rigid and strong enough to support the weight of several men. This means that there are no problems when handling semi-finished boats - in contrast to the relatively flimsy state of other types of no-mould hulls at a comparable stage of construction.

About 600 workboat and leisure craft designs are offered with the system by its creators, Farbond and Pultrex. Boatbuilders will be offered package deals consisting of pultrusion machinery, BIP Beetle polyester resin, glass fibre, tools, drawings and technical know-how.

Solid state hydrogen moni tor

Hydrogen monitoring is important, particularly in steel structures, since hydrogen is a primary product of the corrosion process. Free atomic hydrogen then permeates steel, where it can cause serious problems - blistering embrittlement and hydrogen-inducing cracking.

Existing hydrogen monitors include those containing liquid electrolyte, in the form of concentrated acid, or probes which rely on sacrificial corrosion to allow hydrogen to diffuse into the device prior to measurement.

As an alternative, Cormon has introduced a device based on a solid electrolyte, plus a working and reference electrode. The device gives an absolute measurement of hydrogen

MATERIALS & DESIGN Vol. 5 OCTOBER/NOVEMBER 1984 203