4-16 



MATERIALS AND MOLDING METHODS 



Lightweight Plastic S phe res Embedd ed in Resin or Syntactic Foams 



Lightweight gas filled phenolic spheres embedded in either polyester or epoxy resin 

 forms a denser troweled in place type of core material, Fig. 4-15, presently being used in 

 certain areas of some boat hulls (26). 



Polystyrene beads expanded to approximately 1/8" diameter spheres and embedded in 

 epoxy resin are a new type of troweled in place core material that is presently being in- 

 vestigated (25). 



The advantage of these troweled in place core materials is apparent due to the sim- 

 plicity of application, particularly in small restricted areas. 



Fig. 



4-15. Syntactic foam 

 being troweled in place (Courtesy Union 

 Carbide Corporation) 



MOLDING METHODS 



Nearly every type of molding method developed for reinforced plastics has been used to 

 make fiberglass boats (1). Many methods are in current use and all have distinct advantages 

 and disadvantages. The selection of a proper molding method for a particular boat construc- 

 tion is dependent primarily on the size of the boat, production rate, total number to be pro- 

 duced, and cost of both molding equipment and molded boat hull. The familiarity of the 

 molder with a given process and the availability of related tooling and equipment may well 

 be the most important considerations. The molding process most widely used in boat hull 

 construction is the contact method (6). This discussion indicates available methods and is 

 not intended to specify any specific molding process for any particular boat. 



