2-42 BOAT HULL DESIGN 



Maximum shear, f — (2. 23) 



s Ib 



For longitudinal number 3 between the bulkhead and the transverse island: 



V 



= Pp x s x L = 9.7x7.5x51 = 1852 lbs (2.24) 



2 2 



Stif fener Properties : 



Size: 3 in. deep x 1-1/2 in. wide x 5 plies of 

 woven roving, from Fig. 6-37 



Thickness of 5 plies of woven roving = 0.185 in. (Table 5-2) 



T =3.6 in.k This value is based on woven roving equivalence 



and all material inboard of the neutral axis is woven roving. 

 Therefore no modulus connections are necessary. 



Sm - M* in ' 3 



Distance to neutral axis y = ~ - ^JT = 2, ° 6 in * (2.25) 



Q = Moment of area inboard of neutral axis about neutral axis 



= 1.5 x 0.185 x (2.05 - £ii£2 ) + 2 x 2.06 x 0.185 x il^ = 1.33 in. 



b = 2 x 0.185 = .370 in. 



Maximum shear, f = ] 8 ^ 2 x hM = 1852 psi 

 ' s 3.6 x .370 



Ultimate Parallel Shear Stress for Woven Roving, F su = 7500 psi (Table 5-14) 



Factor of Safety = 1.5 



TTT 



Allowable Parallel Shear Stress, f = 1^2. = 5000 psi Satisfactory 



Finally the stiff ener must be checked to ensure that the allowable deflection is not ex- 

 ceeded. A typical calculation is shown; the remaining stiffeners have been checked and 

 found satisfactory. 



Deflection d = Pp „ x s x L Shear deflection not considered (2.20a) 



' 38U EI 



For longitudinal number 3 between the bulkhead and the transverse island: 



d = 9.7 x 7.5 (51)^ . 0>173 in< 



38h x 2.06 x 10 6 x 3.6 



Allowable deflection, d = ^ = 0.51 in. Satisfactory 



