Page 288 - Practical Ship Design
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246 Chapter 8
+0.05 Cb-Cbf
Cba - Cb
LCB as %L forward
of amidships B.P.
LCB as %L abaft
amidships B.P.
Cb - Cba
Cbf - Cb
Fig. 8.10. Relative block coefficients of fore and aft bodies for a particular LCB position.
8.4.3 Designing lines direct from a sectional area curve
If the lines are being designed without the benefit of a basis ship, attention should
be paid to the following factors which influence the performance:
(i) the shape of the waterline forward and the angle of entrance;
(ii) the shape of the waterlines, buttock lines or diagonals aft which guide the
flow to the propeller;
(iii) the shape of the sections below water do not appear to have much influence
on still water resistance, although there is a view that “U’ sections forward
and “V” sections aft offer some slight advantage from a propulsive point of
view. “V” sections, generally have some advantage in waves and, of
course, provide a higher KM value which can be helpful on a design where
stability is critical.
8.4.4 Mathematical lines generation
In practice the methods described in this section have largely been replaced by
computerised methods based on similar theory.
