Page 304 - Practical Ship Design

262 Chapter 8

This again reduces shipbuilding costs and improves cargo stowage particularly
on container ships and car ferries.

8.8.3 Knuckles
The “fair” lines of the shell are sometimes interrupted by a knuckle line or lines.
These can be introduced for a number of reasons:
(i) to enable a high angle of flare to be used in the lower part of the sections
without this carrying on become too extreme in the upper part;
(ii) to avoid the end of a forecastle deck projecting in a way that might cause
contact with dockside cranes or similar;
(iii) to improve seakeeping (although there is disagreement over this) by the
detachment of waves from the shell;
(iv) to reduce shipbuilding cost by increasing the number of plates that do not
need to be rolled in two directions.
For economy in fabrication, knuckles are generally best positioned a short
distance above a deck.