Why Don't Tugs Turn Ships?

✩ABOUT THIS VIDEO✩
In this video, we investigate the effect of the pivot point when it comes to manoeuvring large ships. We explain how pivot point theory gives us a good explanation of the effects, but also show you the underlying forces at play so that you can get a deeper understanding of the principles.

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✩WITH THANKS✩
➼ Audio used under license from Epidemic Sound

✩DISCLAIMER✩
All content on this channel is provided for entertainment purposes only. Although every effort has been made to ensure the content is accurate and up to date, it remains the responsibility of the viewer to determine its accuracy and validity. The content should never be used to substitute professional advice or education.

[dogcarman]

Thank you for making it complicated in an understandable way.

[snowdrop]

Ships are a whole lot more complicated than I thought

[SteinGauslaaStrindhaug]

I think one big reason large ships appears to have so many counterintuitive handling characteristics isn't actually that their handling is really more complicated than smaller vessels and vehicles (though they might also be large enough that some proportionally weak effects are noticeable, too); I think one of the main reasons is that they are so large that everything seems to happen in "slow motion" which means you can't just react to how it feels in real time, you have to plan things several minutes ahead.

Bicycles also have really complex physics with weird gyroscopic effects and positive and negative feedback effects (there's a reason it takes quite a while to master it) but it's so small that everything happens in terms of milliseconds and seconds rather than minutes and hours like a ship; which means you can fairly easily train your preexisting brain circuitry for balancing on two legs to instinctively react and compensate for all the odd bike physics. But things that are so slow that you have to apply the steering inputs for several seconds before they even start to have an effect and for minutes before they start to be noticeable is simply too slow to be able to use your normal movement circuitry and you have to calculate and plan everything consciously rather than just reacting instinctively.

(Admittedly I haven't tried steering a big ship; but I have tried steering my brothers wooden boat with an inboard engine (no idea about feet but it's much bigger than a van but shorter than a bus, I think?), which is large enough that it's at the limit of how big it can be and still possible to steer instinctively. With bikes and most cars you can easily just hold the steering wheel and look where you want to go and your arms will make hundreds of microscopic adjustments seemingly on their own so that you appear to drive straight even on a slightly bumpy road, while with this boat I would suddenly notice I was veering slightly to port and apply rudder towards starboard and then a few seconds later notice I was starting to veer too far to starboard and so I had to more consciously apply just an imperceptible correction and then trust that it will start to have an effect in a few seconds. Otherwise I would be zig zagging all the time. But I feel it's still within the size that you can eventually start to develop a feel for it without having to think so much about it; but I doubt that is true for even larger vessels. I assume you have to more deliberately measure your current heading and the difference from your desired heading and then calculate an appropriate degrees of rudder input or engine power to apply for some amount of time (or use a lookup table of precalculated values) rather than just feeling it.

[patrickw]

then you add on tide wind and or bank effect then Murphey's law might pop up as well

[Ibby.M.I.]

This is by far one of the most underrated marine transportation knowledge channels on YouTube. Not going to lie

[usopenplayer]

Reminds me of how a surfboard works. You can feel this piviot theory when you push your foot down/sideways to initiate a turn.

[slyfoxx]

I'm certainly acquiring lots of good sailor talk with more than four letters these days!

[snowcat]

The transition at 2:09 is FANTASTIC. Even before you offer the explanation, we begin to have an intuitive understanding of why ships turn when tugs push their center. This is why I watch this channel <3

[QuantumHistorian]

Even removing the effects of water and all that, and just taking the simplest physical model of an extended rigid body, working out what component of a force causes translational acceleration and what component rotational is surprisingly counter-intuitive. The maths isn't all that complicated, but it's hard to picture something speeding up both its sliding and its spinning simultaneously. Add in multiple forces acting at different points and it very quickly leaves what my intuition can cope with.

[CptGoldbeak]

I've been wondering why the pivot point moves with the ships motion for as long as I've known about the phenomenon. No one has been able to explain it, until now! Thank you! It was a legit thrill to learn this :)

I had to pause the video the moment you said "moving into still water", and make sure I understood.

[morpheus]

This reminds me a lot of the explanation of how a motorcycle turns by leaning and counter steering.
Non drivers get confused of why you would push the side you wanna turn

[birdharris]

nice. I love it when the reason isn't something i'd correctly guessed, and you consistently deliver on that front :D

[RobSchofield]

That was superb! A clear explanation that is easy to follow and ends up almost being intuitive. Possibly one of the best explainers I've watched on YT 🤓👍

[ScotsmanDougal]

I've been watching your videos for about a year now. I never had any interest at all in the subject you talk about but now I love seeing a new video from you. Fantastically well explained videos. Cheers.

[dozrFAB]

I know nothing about sailing or boats, but I love this channel so much.

[RachaelSA]

I thought that was a ram chip in the thumbnails 😂

[DirkFedermann]

that was really good explained and also if I think about it, makes it pretty clear on how a ship with a bow thruster can move sideways - parallel - onto a dock

[andywomack]

Fluid dynamics aside, there are similarities with learning how to back a motor vehicle. especially with a trailer. Intuition can be mistaken.

[Tjita]

That illustration was cool. The bow thruster thrusts to starboard, so the stern wants to kick out to port. To counteract that, we obviously steer with the rudder.. to port...

[marrs]

What a great theory! Never been aware of this. Thank you sir!