Why Are Big Ships Faster Than Small Ships?

-------------------ABOUT THIS VIDEO-------------------
In this video, we ask the question: Why Are Big Ships Faster?
Most people think that it is because bigger ships have bigger engines, but that is only part of the story.

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[FrontNine]

As a Naval Architect, I really wish I had access to these videos when I started my degree. Such a practical demonstration of the theoretical concepts.

[davidsellon]

Thanks for the explanation. I've often wondered the same. Years ago, I was on a 42' private vessel crossing the Panama Canal. The Canal obviously has too much traffic to let a puny motoryacht take up an entire lock, so the Harbormaster put us in with a cargo vessel -- large, but sufficiently short to accomodate us both -- for each leg of the trip. On the way up, the big ship entered first, and we behind her. When we reached the lake elevation and that ship fired up her engines, her prop wash was so intense that the only thing keeping us from getting bashed into the sides of the lock were the six lines the Canal staff gave us (delivered by the famous "monkey fist") that held us tightly in the center. Still, all open beverages were immediately spilled. When she got underway and we followed, I was amazed at how quickly she put distance between the two vessels. In no time at all, we lost sight of her. Of course she made it across Gatun Lake in a fraction of the time it took us. The Canal staff knew this would happen, so they had previously scheduled us for a departure with a different vessel. This time, her length wasn't an issue, as they put us in ahead of her, and her bow literally covered the space we occupied. You don't truly get a sense of the scale of these beasts until you have looked straight up from the deck of your boat and seen nothing but metal above your head.

[subnormality]

I live 800 miles from an ocean, and yet I find your videos fascinating, including this one. Cheers!

[cyberfutur]

wow, I think this is the first time in my life, where someone used the term "wave length" and is actually talking about waves. (I am an audio engineer with a fable for physics, and I know, that those other waves are waves, too... but you know what I mean)

And also, that was an utterly interesting video, thanks, I learned a lot^^

[hawkeyeted]

I spent 23 years on aircraft carriers. Being retired, I now work around a lot of Airforce dudes. None of them believe me when I tell them carriers are the fastest ships in the fleet.

[steelbaron]

4:40
"But of course that isn't the hull story."
Proceeds to give talk about the Hull design.
Nice.

[mastasolo]

Those jet engines on the ship are 100% what I would do If Kerbal had sea fairing vessels.

[scose]

Really appreciate that this video is pure information. no sponsorship, no Patreon pitch, no asking to subscribe

[toddkes]

I was thinking it was due to a ship 2* as long, wide, and tall having 4* the surface area (for drag), yet having an engine 8* as powerful. Didn't think about the wave interference. Good video

[bartbliek]

I used to sail small boats as a teenager, and despite not knowing how any of this worked I remember intuitively feeling the phenomenon of hump speed and planing. Especially the boat 'falling' off the top of a wave, going from planing to hump speed, as a gust of wind dies off. Super facinating to learn how this actually works!

[theVoyage]

I've seen a boat running at "hump speed" before, a motor yacht. even to my untrained eye, it looked horribly inefficient, like the boat was trying to climb a hill.

[borysnijinski]

I heard a story about a US navy carrier group deciding to have a drag race for amusement. As expected the smaller ships got the jump at the start, but it was not long before the carrier caught up and passed every other boat…much longer hull length.

[ThomasSteffien]

it maybe of interest: the bulbous bow works only at a limited range of speeds, because its wave has to interfere as designed with the normal bow-wave. Cargo ship hulls (including the bow-shape) are designed for a resonable range of cruising speed, to be fuel efficient. Intrestingly you can guess a ships speed by looking at its generated wave lenght at the hull. you only need to know how long the ship is, judge the length of the wave and use the formula depicted in the video to calculate the speed of the ship (through the water) ...

[capt.eissaeissa]

As a retired Captain now involved in ship construction I find this presentation fantastic. Thanks for sharing, keep up the good work.

[KaptainFuzzy]

Informative, no nonsense, and very well structured for my layman mind to understand. You run a phenomenal channel and are a great teacher. Thank you!

[Bruce-]

I sailed on VLCCs in the '70s and their top speed was 15 knots. During the oil crisis we never sailed faster than 8 knots.

[jaquigreenlees]

You could easily expand this video with the hull shape aspect alone, ldl hulls are faster and lower fuel costs.
a good example, an 85' loa motor yacht with a draft of 4 feet designed for displacement cruising. Top speed is 18 knots, cruising speed is 15 knots. 15 knots speed gives her 1, 500 nm range on 1000 US gallons of diesel, 18 knots gets you 500 nm from the same quantity of fuel.

These same factors are in play with the big cargo ships, yet most people can relate to being told if they slow down by 5 miles an hour they will travel 1000 miles further in their pleasure boat over it's cheaper to ship a 6 week trip than a 1 month trip for your overseas delivery..

*ldl = low displacement length.

[awsalminen]

Wow. Great video. I’m completely land locked but totally in love with the ocean. Just amazing information. Mind is blown right now

[thomashammel]

Very happy about your new pace of publication, especially seeing that the quality of the videos didn't go down a notch! Good work!

[PakBallandSami]

"If you want to build a ship, don't drum up people to collect wood and don't assign them tasks and work, but rather teach them to long for the endless immensity of the sea"
--Antoine de Saint-Exupery