2-2 6 BOAT HULL DESIGN 



DESIGN EXAMPLES 



The design loadings and methods explained and illustrated in this Chapter can be used 

 for guidance by the designer in determining the scantlings of major structural components 

 and other important details for fiberglass boats. A study of Chapter 3, 'Design Details'' is 

 strongly recommended before beginning a fiberglass boat design, since this material, like 

 wood and other laminated materials, requires proper structural arrangement of panels and 

 framing members. 



Examples of typical structural calculations are given for five different boat types as 

 follows: rowboat, open sailboat, high speed runabout, cruising sailboat, and power cruiser. 

 The calculations are based on the design loads and factors of safety summarized in Table 

 2-2. The physical properties values used for the various types of fiberglass reinforcement 

 are the low average values given in Tables 5-6 to 5-14. These values have been selected 

 for consistency in the design examples and are suggested when test data are not available. 

 When it is desired to use higher values to save weight, cost and building time, it is neces- 

 sary that tests be made of the actual production laminate to justify these higher values. 



Since the purpose of this manual is to guide the designer in the selection and application 

 of fiberglass laminates, the calculations are based on simplifying assumptions, both for the 

 loads applied and the methods of analysis. These simplifications are also justified to some 

 extent by the uncertainty regarding actual service loads which may occur, particularly for 

 the boats of the sizes discussed. 



The methods of calculation used in these design examples are standard methods of 

 analysis which are readily available in many standard texts, and are therefore not referenced. 

 Those calculations which are different from the standard methods because of the character- 

 istics of the material, such as section modulus calculations, are similar to the methods de- 

 veloped and explained in Chapter 6. 



Because the design examples are intended to illustrate structural calculations, details 

 are not indicated except where necessary to provide structural arrangement for analysis. 

 Selection of a particular detail or method of construction for analysis does not imply that 

 the detail chosen is the only one which may be used. 



In all the design examples, unless otherwise noted, reinforcement weights are: 



Cloth - 10 ounces per square yard 



Woven Roving - 25-27 ounces per square yard 



Mat - 2 ounces per square ft. 



DESIGN EXAMPLE 2-1. ROWBOAT 



This rowboat is a common type suitable as a tender for a large yacht, or for fishing 

 and general pleasure and is usually used in protected waters. If used as a work boat or a 

 utility tender for a large commercial fishing vessel the scantlings should be suitably in- 

 creased. This design allows for the use of a 5 horsepower outboard motor. 



Principal Dimensions - See Fig. 2-19 for details. 



Length Over -all: 13 ft. - in. 



Beam: 4 ft. - 6 in. maximum 



