Sec. 66.25 



STEPS IN PRELIMINARY DESIGN 



491 



A 1^ lO-deg Flare 



All Wolerhne Heights and BuUock Dislancts ore in feel 



Parallel 



Deck L 



TT Line' of Floor 22 



I 1.5 ft-^ 



36.70 ft to Maximum Wolerline Beom ot Sto.ll 



A rea Section at 5ta. 10.3 _ 



Fig. 66.P Body Plan of ABC Ship with Single-Skeg Transom Stern 



adjustment is necessary to bring their areas into 

 conformity with the tentative 4-curve. As the 

 skeg area diminishes to zero at the forward end 

 of the propeller aperture, leaving only the main 

 hull abaft that point, a discontinuity in the 

 ^-curve appears there. 



Holding the waterline (level-line) slopes in the 

 upper part of the skeg termination to a value not 

 exceeding 15 deg involves a considerable amount 

 of drawing and erasing. It requires the use of 

 transverse fillets with rather small radii where the 

 upper end of the skeg ending merges into the hull. 

 However, these small fillets offer no particular 

 disadvantage provided the resulting flow is 

 generally parallel to the fore-and-aft line of 

 fillets and does not cross it. 



The body plan for the single-skeg transom 

 stern is reproduced in its final form in Fig. 66.P. 



The question of "clubbing" the lower part of 



the centerline skeg is discussed in Sec. 67.23. 

 Since the aftfoot is to be cut away on the ABC 

 design, working a club into the remainder of the 

 skeg, just above the keel, would leave it rather 

 far forward of the propeller to be effective. 



66.25 Bow and Stem Profiles. To finish 

 roughing in the centerline skeg the position and 

 shape of its termination are added to a large-scale 

 stern profile. This is done by starting at the 

 transom termination — the location of the AP — • 

 and working forward. With a single skeg and a 

 single screw, a single rudder is indicated. It 

 should have some mechanical clearance ahead 

 of the transom; 2 ft appears adequate at this stage. 



To meet the maneuvering conditions in Port 

 Bacine the rudder needs to have ample area. By 

 the first approximation of Sec. 74.6 this area is 

 say 0.02iL)H = 0.02(510)26 = 265.2 ft'. Assum- 

 ing for the moment that the rudder height is 



