I was reading about the Battle of the Nile on wikipedia and at one point it mentions Nelson "ordered the fleet to slow down at 16:00 to allow his ships to rig "springs" on their anchor cables, a system of attaching the bow anchor that increased stability and allowed his ships to swing their broadsides to face an enemy while stationary." I was wondering how this works, if anyone knows somewhere I can find a good explanation or diagram. Thanks.
A spring line is a line run from amidships to the part of the anchor chain near the waterline, or to the pier near one or both ends of the boat or ship.
Basically, if a ship is riding at a single anchor at the bow (front), the ship will swing with the wind so that she faces the wind head on. If the direction of the wind is from, or worse! TO, the enemy, only the chase guns can be brought to bear (point) at them. In this case, running a spring line to a cleat (tie-down-point) amidships (about halfway along the front to back axis) allows that spring line to be hauled in order to swing the stern around towards the anchor and show the broadside to the enemy. An enterprising captain with sufficient room to swing may put a spring line on either side and by alternating which is pulled, can present alternating broadsides.
I'll see if I can find a useful diagram.
Edit: here you go. http://www.tor.cc/articles/rode.htm
Now picture the enemy is in front of the boat in the figure, and you'll see why the ability to turn the vessel could be advantageous.