Stability

Video Length: 5 minutes and 20 seconds

Transcript

Narrator:

From fishing vessels to water taxis, tugboats to police craft, small non-pleasure vessels are a common sight on Canada’s waters.

But accidents can happen at any time – and to anyone. As the operator of a small non-pleasure vessel, it’s your responsibility to make sure your vessel operates safely and is properly equipped for emergencies.

Interview 1:

“When I am talking with other fishermen, invariably stability comes up. We’re in the coffee shop and somebody mentions what they’re going to do to change something on their boat and what invariably comes up is ‘how will that affect stability?’

Narrator:

When a vessel loses stability, there’s a chance it could capsize – a very dangerous situation for anybody on board.

Capsizing can be avoided by knowing how your vessel reacts to wind and waves – and by making sure it’s loaded properly.

Stability refers to a vessel’s ability to right itself after tipping sideways. Normally, the downward force of gravity is equal to the upward force of buoyancy… …So when the vessel leans, the two forces work together to bring it upright.

But on a vessel that’s been loaded improperly, the centre of gravity shifts… …Reducing stability and making it easier to capsize

Interview 2:

“Well I think the regards to stability varies with the type of boat it is. Some boats, when you start loading them, you might start loading from the very front part of the fish hole, some in the middle part, some on the stern. But, I always tell the boys, I mean, you just have a feel for the conditions at the time.”

Interview 3:

“The roof of the cabin is a great place to store things. ‘Let’s throw it up there let’s throw it up there!’ Next thing you know, the boat’s doing this and you’re still at the dock. These are things that people have to really look at before they leave and I’ve seen a lot of cases where people just won’t do it.”

Narrator:

Your cargo affects stability in many ways.

For instance, overloading your vessel can decrease its freeboard – the distance between the water and the deck. If the edge of your deck goes underwater, the stability of your vessel will quickly be reduced

Interview 4:

“I was told that freeboard is your friend. So we have about two and a half feet of freeboard even when we’re loaded and that allows buoyancy to move outboard and that gives us our righting lever. And so, the more freeboard you have, a lot of times, the stiffer the vessel it is and that means that the roll is quicker.”

Narrator:

There’s also what’s called the “free surface effect”. As the contents of a partly filled liquid cargo tank shift with the movement of the vessel, so too does the vessel’s centre of gravity – making it less stable.

Interview 5:

“Free surface effect is very very important. A lot of these vessels are equipped with scupper plugs and the decks are very close to the water. So when they load them up with these big loads of lobster pots, the guys have to put their scupper plugs in to prevent ingress of water.”

Interview 6:

“We hired a marine engineer who gave us some very, very good recommendations. For example, when we bought the boat, there wasn’t enough capacity to discharge water. Now we have scuppers, holes in the side, so that if we’re ever at sea and take a big wave, we’ll be safer.”

Narrator:

You can improve stability by dividing your holds into smaller sections to decrease the amount of space cargo has to move around.

Before lifting or towing anything, make sure your vessel’s been tested to ensure it can do so without losing stability.

And when you’re on the water, always look out for signs of instability. These include changes to the way your vessel handles, having less freeboard than expected, or increased activity from the bilge pumps.

Interview 7:

“We’ll be walking down the dock and look at boats and just, really notice how much freeboard they have, are they listing? and weight that is up high. That could be a boom, or lights, or gear and it just seems to be that nowadays it’s part of our conversation.”

Interview 8:

“On board my ship it’s my business, it’s my vessel, and it’s my responsibility to ensure that I make it back to the port, and my crew.”

Narrator:

For more information about how you can help Canada’s waters remain a safe place to do business, visit the Transport Canada Marine Safety website.

Date modified: