If I tell you that left or right-handed ships are a real thing, you might not believe me
But actually they are! Of course, we're not talking about left or right-handed in the conventional sense
What we're actually referring to is the direction in which the propeller turns
Looking at the ship from astern
You'll know that propeller would be spinning to power the ship ahead. From this angle if it's spinning clockwise,
We say that the ship is right-handed and if it's anti-clockwise
Then she's left-handed. An easy way to remember it is to think about which way the top of the propeller is moving
If it's moving to starboard or to the right, the ship is right-handed. Obviously with a controllable pitch propeller
It will always be spinning in the same direction. No matter if the ship is going ahead or astern
so it's easy to see whether she's right or
Left-handed based purely on propeller rotation. With a fixed pitch propeller, when you go astern
You need to make the propeller spin in the opposite direction. Now although you change the direction
You've not changed whether it's right or left-handed
You still reference only their head rotation when talking about right-handed or left-handed ships
Even though you make the propeller spin anti-clockwise to go astern, she is still Right-handed
So why do we even care if your ship is right or left-handed?
Actually, it has a huge impact on how the ship will handle. It even has an impact on smaller boats,
So like your normal yachts and things like that, even for those it's important to know if she's right or left-handed
Unlike cars ships don't have any brakes.If you stop the propeller spinning, she's gonna continue running ahead
purely under her own momentum
Of course, she will gradually slow down due to the resistance of the water
But that's not much good if you're approaching a berth and trying to stop in a certain position
To stop you, actually run the engine astern. This is where right or left handedness of a vessel starts to have a real effect
A right-handed fixed-pitch propeller will make a ship take a dive off to starboard when you run the engine astern
Of course if you're expecting it
You can use that to help you get the ship to go where you want it to go
Maybe you want to kick the stern towards a berth as you're approaching or something like that. But why does this actually happen?
Well, looking at the site profile of a ship you can see she's designed to run ahead
The propeller is pushing water straight astern applying a little bit of spin to it as it goes
When that same propeller runs astern, water is thrown towards the hull still with its small amount of spin
The interaction with the hull is what causes the effect
Imagine the pressure areas around each of the propeller blades
The water ahead is experiencing higher pressure and the water behind lower pressure. The blade is throwing the water off
so that higher pressure is rotating around in the same direction as the
propeller itself. As it is thrown towards the hull, the higher pressure hits the hull first
Inducing a force moving the stern sideways. Likewise the low pressure is sucking water away from the hull on the other side
Exaggerating the effect looking from above if there's a force applied to the stern clearly the ship is going to start to turn
Under the influence of that force as long as you're expecting it you can work with it to make your life easier when docking
So far, we've looked at the effect of a right-handed fixed pitch propeller, but the same applies to controllable pitch propellers
just happens in the opposite direction a
Right-handed controllable pitch propeller will tend to turn the ship to port when running astern
This is because the propeller always spins in the same direction
Regardless of whether it's producing a head or a stern force
Check out my video on how a controllable pitch propeller works if you want to see more
But how do we apply all this in real life?
Let's take this ship as an example. I'll say she's got a fixed pitch propeller
She's right-handed and we want to do a three-point turn here in this river
This is exactly the same as turning around in a tight marina if you're in a small yacht
The nautical phrase for a three-point turn is turning short round
Right hand fix pitch means she's going to want to turn to starboard when you're running astern
So as we approach we're going to run the engine astern to take off the last the forward motion
She's going to naturally start a slight turn to starboard at this point once you have us stopped
You can put your eider hard over and give a good kick ahead on the engine
Depending on the rudder she might start to pick up speed quite quickly
But she should also be turning to starboard at the same time
All you do is you run astern again taking off that little bit of headway
And she should continue to turn in the direction that you want
The same applies when you're approaching a berth same vessel approaching a key
can come in at a slight angle as she gets close the engines can go into a stern to stop her the right handedness of
The propeller warps the stern in towards the key almost making it look like the ship has docked herself
The act of walking the stern one way or the other has meant the effect is called propeller walk
You may hear a lot of boaters referring to propeller walk when their boat handling on larger ships
We tend to call it transverse thrust instead. It's just a slightly more technical way of describing the same effect
So next time you're on a boat and somebody tells you that she's left-handed. You'll know that they're actually being serious
And that brings us to the end of today's video. Hopefully you found this topic interesting for more like this every other Friday
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