1-8 INTRODUCTION 



reinforcement, his new data will then be comparable with the older data and any other new 

 data accumulated by the same standard process regardless of where it originates. In prac- 

 tice the engineer or fabricator should use the data presented for initial selection of a 

 material combination and molding process. He can then calibrate each material combination 

 and molding process to obtain refined design data. 



The test program was an extensive one which is described in Chapter 5. Aside from the 

 obvious physical characteristics which are tabulated, there are other significant factors which 

 are indicated in appropriate parts of this manual. The designer or manufacturer will be able 

 to draw other conclusions from having the broad body of comparable data to analyze. One of 

 the most obvious but most important aspects of the data is the indication of the spread in per- 

 formance values which occurs with material made by different manufacturers all attempting 

 to reproduce identical specimens. This spread may be the result of many factors besides 

 the experience of the man making the laminate. Any designer or manufacturer contemplating 

 a new product must realize that he may inadvertently produce items of varying quality while 

 following what appears to be good practice. 



In order to assist in the use of the data presented, it has been found desirable to divide 

 some of the data into high and low ranges. If the manufacturer can satisfy himself by sample 

 testing that he can reproduce materials of the higher quality, then it will be safe to use the 

 higher values for that material combination and process. It will be noted that in the test pro- 

 gram, manufacturers were not consistently high or low quality producers. Each fabricator 

 produced both high and low quality laminates depending on the reinforcements used. There 

 was no material which appeared to be easy to produce and no material or process which 

 seemed to be uniformly difficult. The producers making the test laminates were all selected 

 as highly qualified and dependable fabricators. Therefore a manufacturer may expect to 

 find that he is a low quality producer for some material or combination. 



It will be apparent that a marine design manual deals with structural loads and forms 

 similar to those that apply to many other construction fields. While there has been no 

 attempt to consider artistic effects and surface problems, these considerations can be super- 

 imposed upon the basic structural factors discussed and illustrated in this manual. One re- 

 striction of this document is that the reinforcements and processes for which detailed data 

 are available are those of most interest to the marine industry. Some of the higher per- 

 formance material combinations and forming processes are not included simply because the 

 magnitude of the job of accumulating and analyzing the data precluded more than this first 

 basic approach for a major field of interest. It should be noted that the procedure for making 

 samples, testing and analyzing data will be suitable for any selected material. The data in- 

 cluded here will serve as a comparison to indicate trends and the illustrations would be ap- 

 plicable if new data were fed in as acquired and as appropriate. 



It may be expected that one of the most interesting and significant advances will be in the 

 direction of larger structures for boat applications. For this reason the illustrations in this 

 manual have included an array of sizes to suggest the factors which influence different design 

 selections. With judgment these factors may be extrapolated to larger sizes than those in- 

 cluded herein. 



As more dependable data is obtained and as quality control develops either through more 

 precise forming processes or inspection techniques it will be possible to design much more 

 closely to the potential performance of these materials. Safety factors are discussed in this 

 manual for specific applications. Some areas of structural loading are imperfectly under- 

 stood at the present time. If fatigue, for instance, is a critical condition of loading, the 



