eli5: Why is a ship’s steering at the back and not at the front like cars?
In: 5
I think it is because the turning-torque thingy is in the back instead of the front (eg. A car’s front wheels).
A ships steering is much more efficient if it is behind the propeller, since the water current is much higher behind the propeller. Since the prop is in the back, so is the steering.
Cars have their steering in the front because the steered end is the end that swings out when you steer, so you want good visibility of that end, and car drivers are sitting in the front
There’s some tradition and exceptions to the rule which I can elaborate on later.
But the simplest answer is because in a car, the steering mechanism is at the front, while in a boat the steering mechanism is at the back. Mechanically, keeping the driver close to the steering mechanism has benefits (smaller mechanism, lower weight, less of a problem to extend steering to wherever they are sitting). And for the driver, being as close as possible to the point of turn makes spatially understanding driving s lot easier.
In a car, the front wheels turn to turn the whole car.
In a boat, the rudder (which is what does the turning) sits in the back of the boat at the bottom. You could design a way to transfer the power of the steering wheel from the front of the boat to the back, but this is a larger engineering challenge and could mean cutting back on usable space inside the boat. The easier solution is to put it in the back.
There are lots of reasons, primarily by having the rudder behind the rudder behind the propeller it’s more effective, it also means the hull can be designed to optimise the flow over the rudder, this isn’t possible at the front. Being at the rear make it lees vulnerable to collision which is a fair consideration (especially if it’s me sailing)
For cars it’s different because the friction is far higher, steering at the rear means there’s a far greater imbalance of forces which causes all sorts of issues and would make for a horrible ride.
It’s not particularly eli5 but have a read of https://www.marineinsight.com/naval-architecture/rudder-ship-turning/?amp for boats
https://www.oponeo.co.uk/blog/steering-systems-understanding-the-forces-of-front-wheel-turning for cars
E:forgot about cars – added
Aside from the comments you have on the rudder placement, think about driving a car in reverse. The vehicle is highly responsive. Imagine that level of response but driving forward – it’s far too responsive to drive at high speed with only rear wheel steer.
Rear wheel steer is used on certain cars and heavy duty vehicles, but tends to be to stabilise the vehicle at higher speeds, and reduce turning circle at lower speeds.
Because cars have wheels on the ground that prevent the car from sliding sideways or suddenly turning 180 out of control. Boats don’t have this, so if your steering mechanism is at the front, and the “pushing” power is in the middle (like with sails) or at the rear (propeller), the moment you try to steer, the boat will flip around.
[The boat would behave like this](https://www.youtube.com/watch?v=w7bF0FEhdcM); note how the car’s tires are actually slipping, and the car is technically “out of control” and sliding sideways like a boat would in water.
Rudders have been in the back of boats since long before propellers. Water provides much more resistance to motion than the air a car travels through. To minimize that resistance, the bow needs to be narrow, slicing the water. This means it needs to be small.
The aft end of the boat can be much wider. Sails push the boat from the middle, so moving the steering to the far aft end gives the rudder a larger lever to rotate the boat around the pivot point that’s cutting into the water. Any drag from the rudder helps the boat track straight in rough seas, if your rudder was in the front it would tend to spin you broadside to rough seas, which fills the boat with water and everybody dies, so they don’t do that.
Airplanes and ships move in a fluid, air and water respectively.
To move in a fluid, you need a large nose and a very thin tail. That’s how you can have the least resistance in the fluid.
Because the tail is so narrow, the fluid moves more parallel to the ship/plane. It’s a lot more effective to steer using the a rudder on the tail for that reason. The nose has much more turbulence and the fluid is displaced laterally. Ok you can make a pointy nose but you lose efficiency. Then for a plane, I guess the pilot would not be happy to have a rudder between him and the runway he wants to spot.
For a ship, the nose is connected to the keel and is very strong, as it is expected to slam on sandbanks and rocks, sooner or later. A rudder in the nose would be quite vulnerable.
For cars, they steer with wheels, not fluid, so it works totally different. Rear steering vehicles are too unstable.
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