Why Do Ships Have Flat Bottoms?

In this video, we ask why the hulls of commercial ships are flat on the bottom, while yachts and older vessels are all curved. We learn the difference between form stability and weight stability and see the impact it has on hull design.

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➼ Audio used under license from Epidemic Sound

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[raideurng]

A wide, flat bottom also means you have more clearance and can use shallower waters and ports.

[nickgoodall]

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 😂

[Ryonin]

Flat bottom boats make the rockin' world go around

[LazerFocus]

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.

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.

[titanicgames]

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

[TomSedgman]

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

[jhonbus]

Flat bottom boats, you make the shipping world go round.

[griffithwes]

I love hull sciences but it’s always confused me, I love your animations and explanations and this helps a lot, thank you casual navigation!

[paulk]

Very nice animation that clearly illustrates the concepts. The use of the outrigger canoe made the later discussion of form stability much clearer.

[Rodrigo-qenq]

I miss the days when all videos was this objective, without any bullshit. Thank you.

[AD-kvkj]

"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!

[foobar]

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

[andrewpitcher]

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.

[TefiTheWaterGipsy]

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. ⚓️

[upinarms]

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.

[Gashren]

Because we don't keelhaul anymore.
[watches the video]
Oh, yeah, that makes sense, too.

[jacobpothoven]

And straight is easier/cheaper to build, holds more cargo and provides shallower draft gaining access to more ports

[Namdor]

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.

[ethribin]

This is also why racing sail boats are more akin to the outrigger canno.
Maximum stability with minimum weight.