BOA r HULL DESIGN 2-31 



Summary of Scantlings 



Shell Laminate: 1 ply cloth on outboard face of laminate, 1 ply mat, and 1 ply woven roving. 



Centerboard Trunk: Same laminate as shell. 



Centerline Stiff ener: 1/2 in. deep x 1-1/2 in. wide, parallel roving stiff ener in 

 lieu of keel forward and aft of centerboard trunk. 



Thwart and Gunwale- molded in single unit of 1 ply cloth and 2 plies mat. Gunwale to 

 be'channel shaped with 2 in. flanges and web. Thwart to be 8 in. wide with 2-1/2 in. verti- 

 cal legs with additional 2 plies of mat on each leg. 



Chain Plate: to be 1-1/8 in. wide x 3/16 in. thick stainless steel, connected to a 5 ply 

 woven roving fiberglass bracket by three 1/8 in. stainless steel bolts. 



Mast Step: to be 12 in. x 12 in. and made of mat. 



Mast Partner: to be similar to the thwart except for a local increase in way of the mast, 

 and to be molded in single unit with thwarts, gunwale and fore deck. 



Design 



Thwart: Consider supported at side, and on centerline by centerboard trunk; loaded by 

 a 200 pound man at the center of the unsupported span. Except for the bending moment 

 equation, the calculation is similar to that for the rowboat, Design Example 2-1, and is 

 not shown. 



Use an 8 in. wide, channel shaped thwart with 2-1/2 in. vertical legs. Use 1 ply of cloth 

 and 2 plies of mat on the seat, 1 ply of cloth and 4 plies of mat on the vertical legs. 



Gunwale: The gunwale of a boat of this type must be wide enough for the crew to sit on 

 and is assumed to be 4 inches wide. By comparison with the design example for the rowboat, 

 this will obviously be strong enough. The construction adopted, shown in Fig. 2-21, is 

 similar to that used for the rowboat except that the laminate is doubled under at the inboard 

 edge. This is to provide a "hiking" hand grip without a rough edge for the crew members. 

 Vertical loading due to a person stepping on the gunwale need not be checked, since the boat 

 is not stable to permit such use. 



Transom: Since the use of the 5 horsepower outboard motor is contemplated, the 

 transom may be designed the same as for the rowboat transom. The motor will be mounted 

 on a bracket attached to the aft face of the transom. 



This will result in the following: 



OBC Standard thickness = 1-3/8 in. , from Table 2-1. 



Use 1-1/4 in, plywood core; 1 ply cloth, 1 ply mat on aft face; 1 ply mat, 1 ply woven 

 roving on forward face. 



Rigging Supports: The size of the stays on a sailboat is selected to resist the loads 

 imposed by the sails to cause an overturning moment equal to the maximum heeling moment 



