4-2 



MATERIALS AND MOLDING METHODS 



Usually, fiberglass filaments . 00020 to . 00100 inches in diameter, with most plastic rein- 

 forcement filaments averaging 0. 00040 inches, are manufactured in parallel bundles known 

 as strands. The strands usually consist of 2 04 fine glass filaments drawn together without 

 twisting. The basic strands of glass filaments are used to make all of the different types of 

 fiberglass reinforcements (1, 5). The types used in boat construction are roving, chopped 

 strand mat, cut strands, cloth and woven roving. Table 4-1 presents current uses of the 

 various types of reinforcements in boat hull construction. 



Rovings 



Rovings consist of straight bundles of con- 

 tinuous strands resembling a loose untwisted rope, 

 Fig. 4-1. Rovings are one of the most economical 

 forms of fiberglass reinforcements for boat con- 

 struction. 



Rovings are used as unidirectional reinforce- 

 ment, woven into heavy coarse fabrics, chopped 

 into short lengths for use in preforms and mats; or 

 sprayed directly on the mold. 



Unidirectional Roving: Consists of heavy un- 

 crimped parallel bundles or rovings in the warp 

 and a smaller number of thinner bundles in the fill 

 which may be slightly crimped, Fig. 4-2. Non- 

 woven individual strands or rovings can also be 

 laid parallel on the mold in alternate plies, at the 

 same or predetermined angles, to obtain maximum 

 efficiency in one or more directions. 



Fig. 4-1. Fiberglass Roving 

 of Continuous Filament Strands 



Woven Roving: Consists of flattened bundles or rovings of fiberglass filaments 1/8 " to 

 1/4" wide, woven into a plain square pattern, Fig. 4-3. A number of different weave pat- 

 terns are available ranging in weight from 14 to 27 ounces per square yard. Woven roving 

 is not a cloth in the sense that the filaments are spun or twisted. The straight bundles of 

 filaments are woven as strands. In general, the reinforcement in the warp direction is 

 slightly greater than in the fill direction. 



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Fig. 4-2. Woven Roving 

 Unidirectional Weave 



Fig. 4-3. Woven Roving 

 Plain Weave 



