Page 231 - Practical Ship Design

Powering II 193

LENGTH BP (FT)

i
6 @ = @ FAOUDE - @ I.TTC.

Fig. 7.3. Difference between merchant ship @) values based on Froude and ITTC skin friction
corrections.

abstracted from Lackenby and Parker’s R.I.N.A. paper “The BSRA Methodical
Series - An Overall Presentation”.
In ITTC’57 the values of C,, for the model and CfS for the ship under design
(C,,) are calculated using the formula:
0.075
c, =
(logR, -2)2
At this point the difference between ITTC’57 and ITTC’78 must be taken into
account.
Cf(’57) = C,, - C,, and C,,(’57) = C,, + C,(’57)

Cf(’78) = C,, - C,, (1 + K) and C,,(’78) = C,, (1 + K) + Cr(’78)