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Why are hydrofoils inherently impractical? The homepage claims superior ride and comfort in bad sea states. Although hydrofoils are limited to about 400 tons,

Why are hydrofoils inherently impractical? The homepage claims superior ride and comfort in bad sea states. Although hydrofoils are limited to about 400 tons, apparently, there have been several successful naval missile boats used by both sides in the Cold War. Wings in ground effect is another thing that’s cool.

CrazyStat 6y ago
> The homepage claims superior ride and comfort in bad sea states. For a limited definition of bad sea states--the FAQ says the limit before you might unexpectedly land is about 1m wave height, which wouldn't be a serious issue for an ordinary boat almost 8m in length [1]. That said, I do think there's a place for hydrofoils on sheltered bodies of water. There is (or was, 10 years ago) a regular hydrofoil ferry service that runs between Petrozavodsk and the island of Kizhi [2], which cuts travel time dramatically compared to a traditional ferry. [1] https://www.rms.nsw.gov.au/maritime/safety-rules/before-boating/wave-heights.html https://www.rms.nsw.gov.au/maritime/safety-rules/before-boat... [2] https://en.wikipedia.org/wiki/Kizhi_Pogost https://en.wikipedia.org/wiki/Kizhi_Pogost
- wazoox 6y ago
  Unless it changed recently, there is a regular hydrofoil line linking Vienna to Bratislava on the Danube. I rode it in 2015, it's a wonderfully kitsch piece of Soviet era kit, but does this beast fly!
  - 83457 6y ago
    I rode one 20 years ago to islands off the coast of Greece. One of the trips was rough though due to choppy seas. I recall seatbelts were required and barf bags were utilized by a few passengers.
    - julienfr112 6y ago
      Rode one between HK and Macao. Turbine driven, airplaine seat with seat belt fasten !!
    - wazoox 6y ago
      At sea, sure, but on a large river like the Danube it'extremely smooth, hardly any wave :)
      - sandworm101 6y ago
        Every hit the wake from a larger boat? That a river is generally flat doesn't mean that you won't occasionally hit a freak wave.
        miarohman 6y ago
        Regardless of type of boat, waves need to be considered and managed. Most of the time speed needs to be reduced. The same for Candela, when a wave is to high it works to operate just like a regular boat.
- aidenn0 6y ago
  Thanks for finding that. A 1m wave height limit makes it basically useless in the North Pacific.
- PaulAJ 6y ago
  Condor Ferries used to run hydrofoils between the Channel Islands, the UK and France. https://en.wikipedia.org/wiki/Condor_Ferries https://en.wikipedia.org/wiki/Condor_Ferries. However they retired their last hydrofoil in 1993. https://www.youtube.com/watch?v=wJLnJx9SzR8 https://www.youtube.com/watch?v=wJLnJx9SzR8 https://thesarnian.com/guernsey-history/condor-1-hydrofoil-final-sea-trials/ https://thesarnian.com/guernsey-history/condor-1-hydrofoil-f... I went on one once. It was disappointing. Going above decks was no longer allowed, so it was a bit like a very bumpy airplane ride with everyone sitting in their seats and nervously eyeing the sick-bags.
sandworm101 6y ago
>> Why are hydrofoils inherently impractical? Limitations on sea states. This gets dangerous when the waves very suddenly start striking the hull. The hull doesn't impact the bottom of the wave but mid-wave, slamming into it in a way a normal hull never would. Limitations on cargo capacity (too heavy and it won't 'fly') which is why large hydrofoils are normally limited to passenger services. Increased draft at low speeds (ie when not flying). Moving parts below the waterline are always a fouling hazard. When that delicate foil hits something it doesn't end well. Outboard engines are mounted in a way to survive such events by folding backwards. A lifting foil cannot do that. These all lead to a dangerous senerio. Say you are driving a hydrofoil in increasingly bad conditions. Because you are 'flying' slightly above the waves you don't notice that they are getting worse. Then one slams into the hull at full speed, or something breaks, and you can no longer 'fly'. The non-foil boat would have turned back long ago, but because you were flying above most of the waves you are now deep into a situation your craft was never meant to handle.

CrazyStat 6y ago

> The homepage claims superior ride and comfort in bad sea states. For a limited definition of bad sea states--the FAQ says the limit before you might unexpectedly land is about 1m wave height, which wouldn't be a serious issue for an ordinary boat almost 8m in length [1]. That said, I do think there's a place for hydrofoils on sheltered bodies of water. There is (or was, 10 years ago) a regular hydrofoil ferry service that runs between Petrozavodsk and the island of Kizhi [2], which cuts travel time dramatically compared to a traditional ferry. [1] https://www.rms.nsw.gov.au/maritime/safety-rules/before-boating/wave-heights.html https://www.rms.nsw.gov.au/maritime/safety-rules/before-boat... [2] https://en.wikipedia.org/wiki/Kizhi_Pogost https://en.wikipedia.org/wiki/Kizhi_Pogost

wazoox 6y ago
Unless it changed recently, there is a regular hydrofoil line linking Vienna to Bratislava on the Danube. I rode it in 2015, it's a wonderfully kitsch piece of Soviet era kit, but does this beast fly!
- 83457 6y ago
  I rode one 20 years ago to islands off the coast of Greece. One of the trips was rough though due to choppy seas. I recall seatbelts were required and barf bags were utilized by a few passengers.
  - julienfr112 6y ago
    Rode one between HK and Macao. Turbine driven, airplaine seat with seat belt fasten !!
  - wazoox 6y ago
    At sea, sure, but on a large river like the Danube it'extremely smooth, hardly any wave :)
    - sandworm101 6y ago
      Every hit the wake from a larger boat? That a river is generally flat doesn't mean that you won't occasionally hit a freak wave.
      - miarohman 6y ago
        Regardless of type of boat, waves need to be considered and managed. Most of the time speed needs to be reduced. The same for Candela, when a wave is to high it works to operate just like a regular boat.
aidenn0 6y ago
Thanks for finding that. A 1m wave height limit makes it basically useless in the North Pacific.
PaulAJ 6y ago
Condor Ferries used to run hydrofoils between the Channel Islands, the UK and France. https://en.wikipedia.org/wiki/Condor_Ferries https://en.wikipedia.org/wiki/Condor_Ferries. However they retired their last hydrofoil in 1993. https://www.youtube.com/watch?v=wJLnJx9SzR8 https://www.youtube.com/watch?v=wJLnJx9SzR8 https://thesarnian.com/guernsey-history/condor-1-hydrofoil-final-sea-trials/ https://thesarnian.com/guernsey-history/condor-1-hydrofoil-f... I went on one once. It was disappointing. Going above decks was no longer allowed, so it was a bit like a very bumpy airplane ride with everyone sitting in their seats and nervously eyeing the sick-bags.

sandworm101 6y ago

>> Why are hydrofoils inherently impractical? Limitations on sea states. This gets dangerous when the waves very suddenly start striking the hull. The hull doesn't impact the bottom of the wave but mid-wave, slamming into it in a way a normal hull never would. Limitations on cargo capacity (too heavy and it won't 'fly') which is why large hydrofoils are normally limited to passenger services. Increased draft at low speeds (ie when not flying). Moving parts below the waterline are always a fouling hazard. When that delicate foil hits something it doesn't end well. Outboard engines are mounted in a way to survive such events by folding backwards. A lifting foil cannot do that. These all lead to a dangerous senerio. Say you are driving a hydrofoil in increasingly bad conditions. Because you are 'flying' slightly above the waves you don't notice that they are getting worse. Then one slams into the hull at full speed, or something breaks, and you can no longer 'fly'. The non-foil boat would have turned back long ago, but because you were flying above most of the waves you are now deep into a situation your craft was never meant to handle.