Ships once used Tugs to Maneuver around in Small Spaces but Today they use Tunnel Thrusters
As technology progressed the more things we needed to make other things. Small factories grew into large manufacturing plants. Which consumed vast quantities of material to produce vast quantities of goods. Requiring ever larger means of transportation. And we have built some behemoths of transportation.
Water transport has been the preferred method for heavy transport. Which is why most early cities were on rivers. As time passed our cities got bigger. Our industry got bigger. And our ships got bigger. Huge bulk freighters bring iron ore, coal, limestone, etc., from northern ports across the Great Lakes to docks on small rivers and harbors further south. On the open lakes these ships can put the pedal to the metal. Roaring across these lakes at breakneck speeds of 15 mph. If you’ve ever seen a Great Lakes freighter at full throttle you probably noticed something. They push a lot of water out of their way. Something they can’t do in those small rivers and harbors. As their wake would push the river over its banks. So they slow down to a non-wake speed of something slower than a person walking.
Lakes are huge bodies of deep water. But these Great Lakes freighters, or lakers, often enter narrow and shallow rivers. Some rivers even too shallow. So they dredge a channel in them. So these lakers don’t bottom out. Some lakers have to travel upriver to offload. Then turn around. Which isn’t easy in a shallow river when your ship is 700-1,000 feet long. They once used tugs to push these ships around. But today they use tunnel thrusters. An impeller inside a tunnel through the ship at the bow and stern perpendicular to the beam and below the water line. Which can turn a ship without the forward motion a rudder requires. Allowing it to move as if a tug is pushing it. Only without a tug.
Interesting thing about Trains is that they don’t have a Steering Wheel
With the introduction of the railroad cities moved away from rivers and coastlines. But the railroads only became a part of the heavy transport system. Cities grew up along the railroads. Where farmers in a region brought their harvests to grain elevators. Trains took their harvests from these elevators to ports on rivers and coastlines. Where they could offload to ships or barges. And it would take a large ship or a barge. Because one long train can carry a lot of harvest.
Interesting thing about trains is that they don’t have a steering wheel. For there is only two directions they can go. Forward. And backward. If you’ve traveled passenger rail to the end of the line you may have experienced a train turning around. The train will reduce speed to a crawl as they switch over to a perpendicular-running track. For trains do not travel well on curves. Because the wheels are connected to a solid axel. So in a turn the outer wheel needs to travel faster to keep up with the inner wheel. But can’t. Causing the wheels to slip instead. Causing wear and tear on the train wheels. And track. Which is why curved track does not last as long as straight track. The train travels a while on this perpendicular track at a crawl until the rear end passes another switch. It then stops. And goes backward. Switching back to the track it was originally on. Only now backing up instead of traveling forward. The train then backs into the passenger terminal. Ready to leave from this end of the line going forward. To the other end of the line.
Freight trains are a lot longer than passenger trains. Some can be a mile long. Or longer. And rarely turn around like a freight train. Rail cars are added to each other creating a consist in a rail yard. A switcher (small locomotive) moves back and forth picking up cars and attaching them to the consist. In the reverse order which they will be disconnected and left in rail yards along the way. Once they build the consist they bring in the go-power. Typically a lashup of 2-3 locomotives (or more if they’re the older DC models). The lead locomotive will typically face forward. Putting the engineer at the very front of the train. In the old days they had roundhouses to switch the direction of these locomotives. Today they turn them around when they need to like the passenger train turning around. Which is much easier as they only have to turn around one locomotive in the lashup.
Planes may Fly close to 500 mph in the Air but on the Ground they move about as Fast as Someone can Walk
Airplanes are big. In flight they’re as graceful as a bird in flight. But it’s a different story on the ground. Planes are big and heavy. They have a huge wingspan. And the pilots sit so far forward that they can’t see how close their wingtips are to other things. Such as other airplanes. When they leave a gate they usually have a tug push them back and get them facing forward. At which time they start their engines. As it would be dangerous to start them while at the gate where there are a lot of people and equipment servicing the plane. They don’t want to suck anything—a person or a piece of equipment—into the jet engines. And they don’t want to blow anything away moving behind the engines as the jet blast from a jet can blow a bus away. And has. In flight they use their ailerons to turn. The flaps on the tips of each wing that roll a plane left or right. Causing the plane to turn. The rudder is used for trimming a plane. Or, in the case of an engine failure, to correct for asymmetric thrust that wants to twist the airplane like a weathercock. On the ground they use a little steering wheel (i.e., a tiller) outboard of the pilot (to the left of the left seat and to the right of the right seat) to turn the nose gear wheel.
Pilots can’t see a lot out of the cockpit window while on the ground. Which is why they rely on ground crews to give them direction. And to walk alongside the wings during the pushback. To make sure the wings don’t hit anything. And that no one hits the plane. Once the tug disconnects and the plane is under its own power the flight crew takes directions from ground controllers. Whose job is to safely move planes around the airport while they’re on the ground. Planes may fly close to 500 mph in the air but on the ground they move about as fast as someone can walk. For planes are very heavy. If they get moving too fast they’re not going to be able to stop on a dime. Which would be a problem if they’re in a line of planes moving along a taxiway to the runway.
When we use big things to move people or freight they work great where they are operating in their element. A ship speeding across an open lake. A train barreling along straight track. Or a plane jetting across the open skies. But when we rein these big things in they are out of their element. Ships in narrow, shallow rivers. Trains on sharply curved track. And planes on the ground. Where more accidents happen than when they are in their element. Ships that run into bridges. Trains that derail. And planes that hit things with their wings. Because it’s not easy moving big things in small places.
Tags: airplanes, airport, barge, freight train, freighters, Great Lakes, harbors, heavy transport, lakers, locomotive, passenger train, planes, ports, railroad, rivers, ships, track, train, tug, tunnel thrusters, wing
Typical River Transport has a Flat Bottom and a Shallow Draft with Little Freeboard
What do most of the oldest and greatest cities in the world have in common? Madrid. Lisbon. Paris. London. Amsterdam. Belgrade. Vienna. Rome. Cairo. Kiev. Moscow. Baghdad. New Delhi. Shanghai. Ho Chi Minh City. Bangkok. Hong Kong. São Paul. Buenos Aires. Santiago. Quebec City. Montreal. Detroit. Boston. New York. Philadelphia. Pittsburgh. What do these cities have in common? Rivers. Coastal water. Or safe harbors on the oceans.
Why is this? Is it because their founders liked a good view? That’s why people today pay a premium to live on the water’s edge. But back then it was more necessity than view. These were times before railroads. Even before roads connected these new cities. Back then there was only one way to transport things. On the water. And rivers were the early highways that connected the cities. Which is why we built our cities on these rivers. To transport the food or raw materials a city produced. And to transport to these cities the things they needed to survive and grow. And some of the earliest river transports were flat-bottomed boats. Like the scow. Punt. Sampan. And the barge.
Rivers are calm compared to the oceans. Which allows a different boat design. River transport doesn’t have to be sturdy to withstand rolling waves and high winds. Which allows the design to focus on the main purpose of a boat. Hauling freight. Typical river transport has a flat bottom. A shallow draft with little freeboard (i.e., sitting very low in the water with the top deck very close to the surface of the water). And a square bow. This allows these boats to operate in shallow waters. Allowing them to run up right onto a river landing or beach. Where they can be easily loaded with their cargoes. Or unloaded. And their flat, rectangular shapes maximize the cargo they can carry. Propulsion is simple. A man can push a small boat along with a pole. Animal power can pull larger barges. Or, later, motors were able to power them. Or a tugboat could pull or push them.
The Chinese Junk had a Flat Bottom with no Keel allowing them to Carry a Lot of Cargo
These flat-bottomed boats are great for hauling freight. But they are not very seaworthy. Because the ocean’s waves will toss around any boat with a shallow draft and little freeboard. Breaking it up and sending it and its cargo to the bottom of the ocean. Which has confined these to the calm of rivers, bays and coastal waterways. Cargoes that have to travel further than these allow are loaded onto an ocean-going vessel with a deeper draft. And a higher freeboard. With a keel. That can withstand the leeward force of the wind. So instead of being pushed sideways (or simply rolling over) the keel allows those sideway winds to fill a sail and propel a ship forward. By sticking deeper into the water. So as the wind tries to push the boat sideways the large amount of water in contact with the keel pushes back against that leeward force. Allowing it to sail across the wind.
But there is a tradeoff. The curved sections of the hull that form the keel reduces the amount of cargo a ship can carry in its hull. Also, these ocean-going vessels have a lot of sail. And a lot of rigging to hold it in place. Standing rigging. While the sails required running rigging. To raise and lower sails depending on the wind conditions. Which takes up space that can’t be used for cargo. And requires a lot of sailors. In fact, much of the upper deck is full of rigging and sailors instead of cargo. But this was the tradeoff to sail into the rougher waters of the ocean. You had to sacrifice revenue-earning cargo. But there was one ship design that brought together the benefits of the flat-bottomed river scow and the ocean-going fully rigged sailing ship. The Chinese junk.
The Chinese junk dates as far back as the 3rd century BC. And began crossing oceans as early as the second century AD. Long before the Europeans ventured out in their Age of Discovery. The junk has a flat bottom with no keel. But a high freeboard. Which lets it carry a lot of cargo. And operate in shallower waters than a fully rigged sailing ship. But it could also sail in the rougher seas of the ocean. When it did it lowered a daggerboard. A centerboard that can lower from a watertight trunk within the hull into the water to act like a keel. To resist those leeward forces. Often installed forward in the hull so as not to take up valuable cargo space in the center of the ship. Because they mount this forward the leeward forces could cause the back end of the ship to torque around the daggerboard. To counteract this force they use an oversized rudder on the stern. To balance the resistance to those leeward forces. Because the rudder was so large and had to deflect a lot of water it was difficult to turn. Taking a team of men to operate it. To help turn such a large rudder they developed ‘powered’ steering. With a balanced rudder. The axis the rudder turned on was just behind the leading edge of the rudder. So when they turned the rudder the water hitting the part in front of the turning axis helped turn the rudder in the direction the crew was trying to turn it. So the large rudder area past the turning axis could deflect the large volume of water necessary to turn the ship.
The Chinese gave us Papermaking, Printing, the Compass and Gunpowder but the Europeans Conquered the World
So the junk could travel in the shallow waters of harbors and rivers. And the deep water of the ocean. It was the first ship to compartmentalize the hull. Making it very seaworthy. Especially if it struck bottom and punched a hole in the hull. Because of the compartments the flooding was contained to the one compartment. Allowing the ship to remain afloat. A design all ships use today. The junk also used a different sailing rig. The junk rig. It’s low tech. Was inexpensive. And required smaller crews.
A three-mast junk has three masts. And three sails. One sail per mast. And the masts are free standing. They don’t need any standing rigging to hold them in place. Because they don’t carry heavy loads of running rigging and sailors. The sail is stretched between a yard and a boom. The yard is at the top. The boom is along the bottom. Between the yard and the boom battens give the sail strength and attach it to the mast. Think of a batten as that stick in the bottom of a window shade. Grabbing this batten allows you to apply an even force on that window shade when pulling it down. If this stick wasn’t there and you pulled down on the window shade the uneven forces across the shade would tear it. Same principle on a junk rig. Which allows them to use less expensive sail material. To raise this sail up the mast you pulled up the yard via a block and tackle at the top of the mast. From the deck. With fewer crew members. The sail is attached to the mast near one edge. It’s pivoted to catch and redirect wind to the stern. Propelling the ship forward. And the battens will bend in strong enough winds to curve the sail. Creating lift on the other side of the sail to pull the ship forward.
The Chinese gave us papermaking, printing, the compass and gunpowder. But it was the Europeans that used these inventions to conquer the world. For the Chinese had no interest in civilizations outside of China. For when you had the best, they thought, what was the point? So the Europeans came to them. Even took Hong Kong from them. When it was the Chinese that could have had the technologically advanced civilization. An army fielding muskets and cannon. And a navy of junk warships that could have gone anywhere the Europeans could have gone. And farther. Into the shallow waters and up the rivers where the European warships could not go. They could have sailed up the Thames to London. Up the Seine to Paris. Even into Amsterdam. Home of the Dutch East India Company. That took such a great interest in all those Asian goods in the first place. That brought the British to China to compete against the Dutch. Leading to the Opium Wars. And the loss of Hong Kong. Imagine how different the world would be had China embraced their technology. Like they are today. Perhaps we will soon see the answer to that great ‘what if’ question.
Tags: balanced rudder, barge, batten, boat, boom, bow, cargoes, China, Chinese, Chinese junk, compartment, daggerboard, deck, draft, flat-bottomed boat, freeboard, Hong Kong, hull, junk, junk rig, keel, leeward, mast, ocean, rigging, river, rudder, running rigging, sail, sailors, scow, seaworthy, shallow draft, ship, standing rigging, stern, warships, water, waves, wind, winds, yard