4 ms·
The article mentions the Bulbous Bow but it doesn't really explain it. A ship going through water has hull drag which shows up as a bow wave. This drag is a (d
by CalChris 3y ago
The article mentions the Bulbous Bow but it doesn't really explain it.
A ship going through water has hull drag which shows up as a bow wave. This drag is a (decreasing!) function of hull length (sqrt(LWL)). Longer boats have less drag. What the bulbous bow does is it creates a counter bow wave which further reduces this drag. However this magic only works at a specific speed tuned for this hull.
On the San Francisco Bay, for example, a container ship will leave the container port (Port of Oakland) at a slow restricted speed (5 knots) inside the Bay. But once she exits the Bay and the shipping channel and hits the open ocean, she will increase her speed to maybe 25 knots to hit that tuned speed with less hull drag and efficiently cruise across the Pacific.
However, the shipping industry noticed that no one wanted to pay for that speed. Enter Slow Steaming. Boats could be retuned for a slower but more fuel efficient speed, maybe 20 knots. The industry literally took existing ships into dry dock and re-nosed them. This meant transits took longer but also used less bunker fuel, the cheapest and worst fuel which is only allowed to be used offshore. This both saved money and reduced pollution.
https://en.wikipedia.org/wiki/Bulbous_bow https://en.wikipedia.org/wiki/Bulbous_bow
https://en.wikipedia.org/wiki/Slow_steaming https://en.wikipedia.org/wiki/Slow_steaming
- pests 3y agoIt's not an article about ships and their parts. Its an article about how ships communicate things to each other - thus the focus on markings, writings, etc.
- chrisatthestudy 3y agoNevertheless it's an interesting addition, and I appreciate it.
- pests 3y agoYes me too, I was cranky this morning. Nice addition.
- gumby 3y agoFWIW I didn't interpret that first sentence of the comment as criticism of the article.
- pests 3y agoOops, I may have too strongly. I agree it's still interesting.
- helloooooooo 3y agoBunker fuel isn’t used anymore.
- SoftTalker 3y agoWhat is done with it? It was my understanding that bunker fuel was basically the remains of crude oil after refining. Has refining improved to where there is no significant remainder in the process?
- bluGill 3y agoBunker is more like unrefined crude. It isn't completely unrefined as they will take out the really valuable parts, but they do minimal refining.
- amiga386 3y agohttps://www.iea.org/reports/oil-2021 https://www.iea.org/reports/oil-2021 > In 2020, due to the Covid crisis and a decline in international trade, bunker demand is estimated to have fallen by 4.3%. As the new IMO rules were introduced, we estimate that higher sulphur fuel oil (HSFO) consumption more than halved, to 1.1 mb/d as ship operators switched to marine gasoil and very low sulphur fuel oil (VLSFO) to comply. In the same document, it estimates global demand for residual fuel oil is about 6 million barrels per day (compared to around 100 million barrels per day for all oil products). That's a lot of consumption for something that "isn't used any more"
- 15457345234 3y ago25kts for a container ship was really flying even before the days of slow steaming, that's passenger speed.
- CalChris 3y agoFast container ships, they still exist with speeds of even 29 knots. But they're for shippers who pay for that speed. https://www.freightwaves.com/news/maersk-container-ships-biggest-and-fastest https://www.freightwaves.com/news/maersk-container-ships-big...
- Cthulhu_ 3y agoWould actuators on the bow help, or is that too fragile and error prone given the abuse it gets?
- CalChris 3y agoThe bulbous bow can already get 15%. There are bow thrusters on cruise ships but they're used for maneuvering. https://www.sciencedirect.com/topics/engineering/bulbous-bow https://www.sciencedirect.com/topics/engineering/bulbous-bow
- amiga386 3y agoIf people are interested in ships, their parts, how they work, and so on, there's a fabulous Youtube channel called Casual Navigation [0] which has simple and informative videos on lots of topics, including bulbous bows [1] and slow steaming [2] [0] https://www.youtube.com/@CasualNavigation/videos https://www.youtube.com/@CasualNavigation/videos [1] https://www.youtube.com/watch?v=6FrCusDG41U https://www.youtube.com/watch?v=6FrCusDG41U [2] https://www.youtube.com/watch?v=VjpGidILzb0 https://www.youtube.com/watch?v=VjpGidILzb0
- fatbird 3y agoIsn't "slow steaming" just what passenger airplanes do with cruising speed? There's an optimal point on the speed/fuel consumption curve that minimizes fuel use, and this is what ships are doing, isn't it? Or is there some other consideration for ships that makes the slow steam speed optimal beside fuel consumption?