This is not a rule of the thumb. The Berge Stahl has a loaden draft of 23 (twentythree) meters! The large ocean going sailing vessel Eendracht has a draft of 5.2 meters. I also sailed on the heavy lift vessel Abis Esbjerg which also had a loaden draft of 5.2 meters.
It also means you make the passenger next to you uncomfortable in their seat. That’s why ships have to swim across the ocean unlike the rest of us who can fly.
@@HugeRademakerit is quite obvious that the commenter did not mean to say that EVERY flat bottom ship has a lower draft than any other boat there is, but rather within its category. But thanks…
I had a design project/contest in uni. Part of it was to design a bulk carrier hull form. My class mates got all wrapped up in Reynolds and Froude numbers and whatnot. We ended up winning, because we made a rectangular boat with a pointy bow and a slight taper at the stern that was the max size of the contest limits, just like a Panamax, or Suezmax or Whatevermax. Profs were salty because we didn’t try to solve the Navier-Stokes equations for all states or some BS 😂
I'm pretty sure that Suezmax isn't a thing - because the Suez canal is straight with no locks, there's no actual length restriction on the ships that can enter it. In theory as long as the stern of your ship doesn't hit Turkey as you line up, you're fine.
@@DanStaal The Suez isn't open ocean, so there's naturally going to be a certain dimension that ships can be -- not just for Suez, but essentially any chokepoint
Jokes on them for setting up poor competition rules allowing a team like yours to just copy existing designs. Predicting how a ship design works, testing it in real world, and awarding the team that got their predictions correct should have been the format.
@@No-mq5lw Sometimes the lesson that students *really* need to learn is that you shouldn't default to reinventing the wheel. Unless you're the first person to ever have a given problem, start by finding out what others did.
What I like most about this channel is the fact it feels like this is legitimately someone who works 9-5, just loves what he does and wants to share as much information about his trade as possible.
If I where in his place fame is what would drive me. There might be tens of thousands of sailors and naval logistics workers but I am the one who is most recognisable.
@@baltulielkungsgunarsmiezis9714 See my other comment: Next time please get your research checked by someone qualified to discuss stability. This video is full of so many misleading statements and half-truths that it is downright irritating. The entire conclusion of the video is dead wrong. The ONLY reason for a flat bottomed hull is to maximize cargo capacity for a given depth of water. Nothing to do with stability. Virtually no large cargo vessel in the history of the world has ever had a center of gravity below its center of buoyancy! Even for large sailing vessels, the center of gravity is typically ABOVE waterline (and thus way higher than the center of buoyancy,) not below. A ship with a center of gravity below the center of buoyancy would have a violent, dangerous motion in any kind of a sea. The whole first half of the video is wasted by talking about a vertical distance between points, when what actually determines stability is the horizontal shift in the center of buoyancy as the hull tilts. So long as the center of gravity is inboard of the center of buoyancy, the ship will not capsize. Very plainly this is more likely to be the case when the center of gravity is lower. Which brings us to the next point: weight stability vs form stability is not binary. All ships have both types of stability to varying degrees. Even a modern flat bottomed cargo ship gets all its attention paid to weight stability, because they can change while form stability remains mostly static. Neither does a classic wineglass-shaped sailing yacht hull have poor form stability. A ship with flaring sides has better form stability than the vertical sides of a modern cargo ship! Lastly, the metacenter is mostly just a rule of thumb. It correlates with stability but does not define it. It is a measure of how snappy the vessel's rolling movement will be. It is easy to design a hull that has a very great metacenter, but which will capsize as soon as the angle of heel exceeds a certain low angle.
Though flat bottom ships are possible only for powered ships; for sail powered ships you need keel or centerboard / daggerboard anyway to counteract lateral forces when sailing at an angle to the wind.
Fun fact: The Iowa-class battleships had a flat sided hull because of the Panama Canal, placing pretty heavy restrictions on the hull dimensions in draft (upto 11.51m), length (270.43m), and beam (32.97m), which was just small enough to fit in the canal, and making the sides flat to keep the beam within the size limits, without sacrificing internal space below the waterline
@@arnoldcobarrubias6593 battleships tend to have flat bottoms, yes, but what titanicgames meant is that the Iowas had flat sides too; most battleships have curved sides with nearly no completely flat sections as you go from front to back, having a teardrop shape. The Iowas had a much boxier form to maximize internal volume (and thus available displacement) while still fitting in the Panama Canal. This is because the locks themselves are rectangular, so the closer to rectangular your ship is, the more volume it can have while still fitting inside that rectangle. This comes at a cost though, as the reason everyone else used the teardrop shape is because it is better for hydrodynamics, meaning you can get higher speed on less power. The Iowas were a compromise, and they retained high speed mostly through enormous power output. Modern cargo ships get away with having flat sides because they just don't need to be fast.
@@klakkatThe teardrop shape also comes from the fact that the belt armor on a majority of battle ships is bolted on the outside instead of the interior. The Iowa's, however, have an interior belt.
@@mpk6664 Eh, only sorta-true. Most battleships also had torpedo defenses, and those systems were absolutely widest/most-effective in the middle of the ship, and not and the bow or stern. It was less thick at the ends _because_ it would ruin the hydrodynamics if they deviated too far from that tear drop shape 🙃 Like, Prince of Wales would not have sunk if that torpedo hit had happened on her torpedo belt, or if the belt had extended all the way to the propellers... But you probably know this, and I'm just nitpicking 😅
The thing I loved about old sailing ships is that the righting force used to be measured in tons to counteract the wind force. Gives you an idea of how much power was involved
These sailing ships are rolling a lot. I sailed on one in Sydney just for a few hours and barely outside the harbour area and you get seasick quite fast if it's rolling 20 ° to each side
@@simonm1447not sure what kind of boat that was but it's not really normal to roll back and forth 20°. you may definitely heel 20° or more but that would be constant and not sickening
@@KingJellyfishII It was the James Craig, an old 70 m long steel hull sail ship from 1874. It's the oldest active ship in Australia. The masts are heavy and high, so there is enough momentum in them if the ship is rolling.
This reminds me of an old video from a Polish sail training ship showcasing how much it tilts to the side when sailing at full speed: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-SevNwGZaWgA.htmlsi=GIFVGqRpHF4reWCj
These animations and illustrations have gotten so much better than when this channel started, but it's still got the same amazing explanations that brought me here.
I think it is worth pointing out that form stability will break down at high angles of heel. Think of a beach cat which has very high form stability. But if it gets too much heel in a gust, there is no way to safe it. And once capsized, it won't right that easily because the form stability is not working against rightening. This is less of an issue for a giant cargo ship but for smaller vessels like the average powerboat it can be
I love your videos. We've got a wide, flat bottom, but we're a canal barge so it makes sense. We have friends who've taken their flat bottomed canal craft across the channel, nope, that's not for us. Thanks for an easy to understand explanation and graphics, I love the details you chose to include like the smoke and no smoking. ⚓️
I've seen narrowboats tackle the Wash, the Mersey, the Ribble, essentially open water, and it all looks a hairy business if there's any chop or fast tidal run. No wonder you can hire a pilot.
"According to Statista, cargo ships were the most lost vessel type at sea in 2022, with 311 ships lost during the period 2013-2022. In 2021, 21% of shipping accidents involved solid cargo vessels." And that's part of the reason why these cargo ships capsize in bad weather far more than any other kind of ship! It's all very well wanting to load more cargo for more money, but when you're losing vast quantities of shipped cargo every year due to unstable ships in bad weather...well, I suppose they still figure it's better to make them precarious!
According to the site marinevesseltraffic, around 60% of all marine traffic consists of bulk carriers, container ships, and other types of cargo transportation. It then stands to reason that a majority of the accidents, too, consist of cargo transportation vessels, I should think?
It also helps them move into shallower waters like canals and rivers. It also ensures sure they can navigate harbors and ports, which tend to have problems with silt deposits that make them shallower than the surrounding waters.
@@karl0ssus1 single hull racing boats are much flatter and wider than in previous decades, using shapes that are good for planing, not the traditional boat shape. usually the Skiff shape, pointy upright bow, hull widening until long past the middle, then even width or minimal taper in to a wide, flat rear. some even use the Scow shape, which has very little change of width over the whole length, and the bow is flat and wide already.
Our fuel barges are wider and deeper, carry slightly more and are more maneuverable than a tanker although slightly longer (I think about 20 extra meters) I discharged 13 million gallons (the whole load) and it took 28 hours from dock to departure
What an awesome video providing an excellent explanation of the physics of these crafts It make me appreciate the simplistic yet ingenious design of the outrigger raft, but also of course the other hull shapes mentioned in the video
And then there is the only slightly related subject of British Canal narrow boats, which are also - mostly - flat bottomed. And yes, there is one of them that is named flat bottomed girl. It happens to be a wide beam narrow boat… All of 14 feet, rather than seven.
what are the big drawbacks of form stability? you mentioned calculations, but i also know that many historic ships needed to calculate how much ballast they would need for a voyage, would drag be one of the main ones? i could see the wider, flatter hull causing more drag especially while manoeuvring rapidly
Here is a much more COHERENT analyses, which incorporates other aspects not mentioned..Weight Distribution: A flat bottom helps distribute the weight of the cargo more evenly across a larger surface area. This prevents excessive pressure on any single point of the ship’s hull and helps maintain stability. Stability: A flat-bottomed design provides a stable platform, which is crucial for loading and unloading cargo. It reduces the risk of the ship tipping or becoming unstable when loading unevenly distributed cargo. Shallow Draft: Flat-bottomed ships typically have a shallower draft compared to those with deeper or more complex hull shapes. This allows them to operate in shallower waters, such as canals or ports, where deeper-drafted vessels might not be able to go. Cost-Efficiency: The flat-bottomed design is often simpler and cheaper to construct. It reduces the complexity of the ship’s hull compared to more complex shapes that might be needed for ocean-going vessels.
Huh, I figured it was mostly due to draft considerations, where the deeper keels would hit bottom in most ports (or even in shallow bodies of water like the English Channel). But this makes a ton of sense as well.
Do they arrange the heavier containers on the bottom? I didn't hear that mentioned but it seems like a good idea. The major problem I see is the logistics of trying to sort containers by weight in the yard. That may simply be infeasible.
They do, to a point and funnily the sorting in the yard isn't the issue (every container gets put where it should get put and they have computers helping to decide that kind of stuff). It's more the balancing act in terms of time too. Putting on and taking off containers takes time and you have to ask if the extra stability worth the time it takes to lift a stack for that container's journey, if it's staying on for a while, maybe, if it's going one port over? Probably not. I think he has a video on it but i can't find it ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-DyyyL7sRBSM.html mentions it. Doesn't help that shipper aren't always honest about their shipping weight.
Bit of a minefield, yes put all the heavy containers down below but then some of them have to be taken out at ports as the ship goes along, does that mean redistribution of all the other containers for balanced onward passage?
Ferry Sewol disaster comes to mind. A ferry designed on weight stability but the owners treated it like a cargo ship adding more and more to the superstructure and upper hull, strapping cargo on deck, and filling cargo above the water line in the hull, adding additional cabins up high in the superstructure, all making the ship very unstable. Brick Immorter has two great videos on the Sewol disaster.
Stability is adjusted with ballast tanks to keep the ship straight upright even with an uneven load, it may also be used with a empty ship because it be unstable without some ballast. The ballast water isn't pumped from side to side with each rolling of the ship, it's juste a adjustement setting like trim on an airplane if you will. EDIT : some ships such as cruise ships do use moving planes on the side of the hull to neutralize the roll, but they're still stable without them, it's mostly for passenger comfort. It isn't a common feature on cargo ships.
Some do yes, but that only works when the electrical generations are working. In a storm if they get knocked out then you’re in trouble and the last thing you want in the situation is loss of stability. Same thing with the ships that have movable fins. They really help with rolling but as has happened when the generators go out they retract and you can capsize. With just weight acting as ballast you always have it, as long as the cargo stays on board
Ship ballast pumps and pipelines don't have even remotely the capacity for this to be possible. Some coal and ore ports may even force a vessel out if her ballast systems can't keep up with loading speeds - otherwise they'd have to suspend loading, and idling costs incredible amount of money. Also free surfaces in tanks are highly undesireable as they decrease stability by allowing liquid's center of gravity to move from side to side. Usually you'd try to keep a tank as full as possible - if a liquid fills 100% of a space its center of gravity can't move anywhere. Cargo tanks on tanker ships often havelongitutal vertical bulkheads in adition to transversal ones to make filling tanks to full capacity easier.
Thanks for expressing why. I had thought flat bottoms on cargo ships were to enable them to move through shallower waters and ports. Didn't know or understand the stability engineering. Q: How does all this handle rough seas? I thought keels and V bottoms benefitted ships by stabilizing their ability to cut through and handle varied rough seas. My parents moved back to USA from the Netherlands on a tubby freighter design that midstream in building had been converted to a budget liner. (The Van Halen family moved on the same ship another crossing). The tubby shape rolled a lot, increasing seasickness (till stabilizer vanes were added years later).
Not only that you can put more cargo near the bottom if keel is flat, you also organize cargo that denser cargo goes lower, and each ship has now a copy of cargo loading software which calculates stability.
@@Dane2177 I expect you're right, plus some of that cargo could be highly flammable. In the UK, you cannot smoke in a work environment at all, maybe that rule is more widely spread?
If you go to your local sports store, you can see this via fishing kayaks vs. recreational kayaks. You want more stability And a flat bottom for standing up and casting.
While not apropos to this conversation, the reason sailing vessels have deeper keels is to convert the forces delivered to the sails to forward motion. With flat bottoms, sailing vessels would just go sideways, or with the wind direction.
this also makes sense if the water is replaced with something solid. the heavy keel ship is like one of those balancing clown toys, and the ship with form stability is like a solid wood block
Thatʼs actually mind-blowing for me. On the sailing course, they taught me that light dinghies use balance of form, while heavy seaworthy yachts use the balance of weight. I would never thought that the huge cargo ships are more like an oversized Optimist than a tall ship in that regard.
The keel is necessary for sailboats because it gives something for the wind to press against, making sure the wind pushes the boat forward in the direction the bow is pointing. If a sailboat didn’t have a keel it would sort of just drift aimlessly in the direction the wind is pushing it.
On a container ship you don't want too much stability. That will give you a short fast roll that snaps back. Better long slow rolls that don't put a lot of strain on your lashing rods. The ship will have a computer that generates the lashing plan based on the assumed weather and the stability. They can change the ballast to reduce lashing and save money on lashers and time on checking that lashing.
A flat bottom also creates a rectangular loading space that can be filled easily with rectangular containers. That advantage is not relevant for bulk ships but I assume it's very important for container ships.
I would argue outrigger canoes are a type of catamaran. There are plenty of "asymmetric catamaran" designs out there. I think the extreme version of this would be a trimaran, a main central hull with two outriggers instead of one.
Good video lots of information. Unfortunately, I can't grasp all the concepts in my head. Those giant flat-bottomed container ships with high center of gravity thrashing along..? I've just seen a video of a dolphin on the surface then with a twist diving down, what's going on there?
This was a big factor with the old hay-carrying scow schooners of the San Francisco Bay. Wide, flat-bottomed craft that carried so many hay bales on deck that they had to unship the wheel and move it up on top of the load! But very stable craft, indeed.
Flat bottom is also needed for drydocking these massive cargo ships, as they need blocking not just on centerline but also farther outboard to distribute the load.
Ah, now I get why a lot of cruise ships have flat bottoms, it compensates for their top-heavy characteristic. (well, they look like they are, I know the superstructure contains a lot of empty space and the engines and ballast are low down, but even so...) And why the Queen Mary 2 (the only true ocean liner at the moment) is not so flat-bottomed. Lovely to have an explanation that is just technical enough for an intelligent layman without insulting his intelligence. (or hers...)
Flat bottle vessels can use air bubble stream layer lubrication more effectively, to reduse hull drag and fuel use. Plus flat bottom ships can and do use sails. ..it just requires careful pumped ballast water v cargo load management.. Car haullers im looking at you...🧐 😂
It is also worth noting that the manufacturing cost of a flat plate is considerably lower than a plate with curvature. Considering how big these cargo ships are, you save a lot of money extending the FOB (flat of bottom) and the FOS (flat of side).
Actually these see going ships still have a very round shape for hydrodynamic purposes. This also becomes clear if you look at the draft vs tonnes of cargo graph, it isnt linear. Inland ships are way more rectangular and flat, because they navigate shallow rivers (in summer draft can be limited to 1-1.3 meters) and the rectangular shape allows them to take more cargo in the same space, because the size is limited by the locks. The draft vs load graph is almost linear for these ships. Hydrodynamics play a less crusial role for inland ships, because their speed is mostly around 10 km/h, for sea ships this can be up to 50 km/h
1:09 In submarines, the pressurized bridge protruding out of the top acts as a way to move the center of buoyancy, since it naturally tends to want to move towards an upright position. The earliest submarines already used this shape to stabilize the ships underwater.
This explains why boats with a keel lean in to a turn because the weight pushes the bottom outward but a ship leans away from a turn because the form stability requires the hull to sit lower on one side before it can provide the countering buoyancy.
You missed the biggest mart lf a slooped hull in tour animation. As a vessel tilts the center of boyency moves into the tilt. Giving a second awis for the selfrighting torque to work.
The "righting force" would be the force that turns the ship back upright. A "turning force" is called "torque". This a little bit more technical, but a lot more accurate. Your rotating arrows are exactly torque. A key property is: torque is proportional to the turning force and the length of the lever. This could habe been visualized quite clearly and contribute to understanding stability. Maybe next time.
