Stability Decay
2017-Feb-26
Do Bulbous Bows Really Work?
2017-May-08
A contractor comes up to you and confidently proclaims, “I can guarantee the stability of your ship just by looking at your hull.” Do you trust this person? Of course not! In the same line, you cannot judge the stability of a ship just by riding around in the bay. The real test of stability comes from rare, extreme events. Conjure up an image of the worst storm combined with loss of power. Those are the days when you really need stability. At those times, your ship’s stability becomes a safety tool to protect you from danger. When thinking about maintenance for the future, we need to remember extreme stability.
Take an example of extreme stability requirements: the IMO severe wind and roll criteria. This is a typical stability regulation that applies to all ships on an international voyage. Some may complain that this regulation seems unreasonably harsh. After all, it calls for a situation where the ship rolls all the way from port to starboard, driven by a perfectly timed gust of wind. That gust rolls the ship all the way to 50 deg of heel. Seems unrealistic? Instead, imagine how such requirements give you good odds of survival when the worst happens.
Imagine you are caught in a bad storm. The waves are just as tall as you hull. The helm struggles to keep the ship’s bow into the waves. And then . . . the worst happens. You lose main power, the auxiliaries go out, and the emergency generator won’t start. The ship drifts and starts to take huge waves on the beam. It gets slammed and rolls 50 deg to starboard. The deck slips out from under your feet and you cling to the console. You struggle to stay upright as pencils and coffee cups fly past your head and crash against the bulkhead. You have no chance of controlling the ship; you can barely hold onto the console. The ship hovers at the end of its 50 deg roll. It hovers there a moment. You fear it may keep rolling and capsize.
And then . . . the ship levels back out. The regulations protected you from this event. We know that bad situations happen often enough, and the ship needs to protect you as best as possible. We must consider more than your daily operations. Remember this when planning for stability maintenance. The stability of your ship is more than ride comfort and paperwork. In those extreme events, it becomes a safety mechanism designed to protect you.
