2-64 



BOAT HULL DESIGN 



Longitudinal No. 1 - Engine Support 



Engine Weight: 850 lbs. 



Thrust: 1615 lbs. at 15 knots assuming EHP = 1/2 SHP 



Engine Mounting: 4 bolting pads on engine 



Engine Support: 4 steel angle clips bolted to fiberglass hat stiffeners 



STEEL ANGLE 

 CONNECTING CLIP 



r ; 



/ 



ii it In j < 



ENGINE BEARER 



-LL 



SECTION A-A 

 SIMILAR TO FIG. 3-31 



Fig. 2-31. Engine foundation 



Assume engine weight is doubled by acceleration forces - 



Factor of Safety = 6 (Chosen because of the long term nature of the 



loading and the vibration). 



Using standard methods of vector analysis, assuming the weight and thrust forces 

 equally distributed among the four connections and including the force required to resist 

 the moment introduced by the fact that the line of action of the thrust does not pass through 

 the bolts the maximum load per attachment P = 700 lbs. 



Assume only two bolts per attachment. 



Load per bolt P^ = 35>0 lbs. 



Using a bolt and spacer combination with a 1/2 in. outside diameter D, determine 

 the required thickness of woven roving, to give an acceptable bearing stress, considering 

 all the load taken by one web of the longitudinal. 



Ultimate tensile strength, F tu = 30,100 psi (Table 5-6) 



Factor = .911] (Table 3-2) 



Bearing stress at failure, F Bu = .91h x 30,100 = 27,500 psi 



Allowable bearing stress, fg a = — j~ — = U583 psi 



(2.9a) 



