'Chine', when talking about wooden boats and ships, refers to an abrupt change in the shape of the hull about halfway between the keel and the sheer.
The 'turn of the bilge' is the area of greatest stress on the structure of a boat. In some boats, a chine is designed in to take up this stress; in others, a chine is a sign of a severe structural problem.
Some boats, such as Chesapeake Bay workboats, Chris Craft runabouts, and other boats with a flat bottom or a lot of dead rise, have a chine built into their structure. It is easy to tell where the bottom of such a boat stops, and where the sides begin -- at the chine. A piece of wood, called the 'chine log', runs fore and aft along the chine, and is let into the stem and transom. Each of the frames of such a boat are usually sawn out of straight stock and come in two pieces, one for the bottom, and one for the side. These are cut to fit into the chine log, and are often tied together with a gusset:
___
| ||
| ||
| ||
_____________________| ||
| ||
frame- | ||
| ||
chine log | ||
\ | ||
|_||
frame _.-\_||
keel \ _.-'_.-!-'
| _.-'_.-!-' \
-._ _ _.-'_.-!-' chine
-._| |_.-!-'
'-| |-'
|_|
Enlargement of chine area, with gusset:
| | |
| |__|
_| | |
/ `-._ | |
/ * `-| |
/ * /| |
/ / | |
/ t * / | |
/ e / |__|
/ s /____| |
/ s / | |
/ u / | |
/ g / log | |
/ /\ | |
/ * * / \ _.-'-.|
_.'`-._ * / _\-' _.-'
_.-' `-./_.-' _.-'
' _.-' \_.-'
frame _.-' _.-'
_.-' _.-'
_.-' \_.-'
_.-'
-'
The bottom of a round-bottomed boat is supposed to be, well, round. There aren't supposed to be any abrupt transitions in the hull shape. A chine halfway up the ship is a really bad sign: If the boat has lapstrake planking, a chine can also be a sign that the laps have broken along the line of rivets holding them together. However, it usually means that several adjacent frames (which have been bent or carved into the desired shape) have broken.
Sound Boat Damaged Boat
___ ___
| || | ||
| || | ||
| || | ||
_____________________| || _____________________| ||
| || | ||
| || | ||
| || | ||
| || | ||
; ;; ; ;;
.' .'; broken frame / /;
.' .'.' \ / //
_.' .'.' _.-.\//
_.-'_.-!-' _.-'_.-''/
-._ _ _.-'_.-!-' -._ _ _.-'_.-!-'
-._| |_.-!-' -._| |_.-!-' \
'-| |-' '-| |-' chine
|_| |_| ($$$)
In such a boat, a chine is usually discovered only after the boat has been hauled out of the water, although it may be obvious from the inside. People looking at the boat from the outside will see a severe shape change called 'hogging' where the bow and stern droop. At any rate, frames must be replaced at great cost.