Location via proxy:   [ UP ]  
[Report a bug]   [Manage cookies]                
Wikipedia

Reaction ferry

A reaction ferry is a cable ferry that uses the reaction of the current of a river against a fixed tether to propel the vessel across the water. Such ferries operate faster and more effectively in rivers with strong currents.

Reaction ferry crossing the Rhine at Basel, Switzerland

Types and modes of operation

edit

Some reaction ferries operate using an overhead cable suspended from towers anchored on either bank of the river at right angles to the current flow. A "traveller" with pulleys runs along this cable and is attached to the ferry with a tether rope. This can divide into a two-part bridle which defines the angle of the ferry to the current. Sometimes two pulleys and tethers are used. Sometimes a single tether is attached to a bar that can be swung from one side of the ferry to the other. This type also uses a rudder in order to set the angle of the ferry to the current flow from zero - it is then stationary - to the best angle for maximal crossing speed. Ferries without a rudder change the relative lengths of the bridle or multiple tethers in order to steer. The lateral force of the current moves the ferry across the river.

A now rare type of reaction ferry uses a submerged cable lying on the bottom across a river or tidal water. This can be a wire rope or a chain and is pulled to the surface by the ferry or its operator. It passes through moveable pulleys or belaying points whose location sets the ferry's angle. In order to set off, manual work is required to initially pull the cable and also to manoeuvre, especially during the turning of the tide.[1]

The ferry may consist of a single hull, or two pontoons with a deck bridging them. Some ferries carry only passengers, whilst others carry road vehicles, with some examples carrying up to 12 cars.

Physical explanation

edit
 
Force diagram of a reaction ferry with a traveller

A reaction ferry operates as a sailing craft where the traveller pulleys represent the wheels of a land yacht and the moving fluid is the water current rather than the wind. In the case of a reaction ferry with an anchored tether, the analogy can also be to a kite. In both cases the ferry's hull itself represents a sail and is angled to the apparent water current in order to generate lift in the same way a sail is set at an angle to the apparent wind.

With an overhead cable stretched across a river at right angles to the current, the ferry is, in sailing terminology, sailing on a reach with the true current exactly at right angles to the direction of crossing. For the anchored-tether type ferry this is valid when the tether is parallel to the current, near the middle of crossing. In sailing, the speed is governed by the lift-to-drag ratios (L/D) of the sail and the hull including centerboard or keel and rudder.[2]

For reaction ferries, L/D ratios also apply except that one is very high, for example typically 30 for a traveller on a steel rope, as visible in aerial photographs, and the other can vary from low, e.g. 1-2 without a centerboard, to 3.5 with one.[3]

A diagram is shown which follows the standard force diagram for sailing.[3][4] It is drawn with a traveller L/D of only about 6 in order to make it clearer. The ferry L/D is drawn at 1.5. The lift L acts at right angles to the direction of the apparent current, the vector sum of the true current and the current component due to the crossing speed. The drag D acts parallel to the apparent current. The vector sum of L and D is the resultant force R. This force can only exist because the tether exerts an opposed force of the same magnitude (see Newton's laws of motion), in this simplified two-dimensional projection of what is really a three-dimensional situation. R can be resolved in a drag component directly downstream and a component in the direction of crossing, the thrust T which drives the ferry. This is balanced by the opposing drag of the traveller pulleys. The amount of lift required is set by the angle of incidence of the ferry to the apparent current (here 10°), often done with a rudder (not shown).

In the figure the crossing speed is the same as the speed of the true current. With a centerboard or keel, the hull's L/D could increase several times. This would increase the crossing speed also several times, but according to the drag equation the forces increase with the square of the speed and put a great load particularly on the overhead cable. With the anchored-tether type ferry, such high speeds would be unobtainable because its tether drags in the water or is supported by buoys that do and this drag would also increase with the square of the speed.

Worldwide usage

edit

Austria

edit

Canada

edit
 
The Lytton Ferry across the Fraser River in British Columbia, Canada, is a reaction ferry using an overhead cable and traveller, visible in the upper right corner.

At one time over 30 reaction ferries crossed the rivers of British Columbia, primarily the Fraser River and the Thompson River. Those still operating include:

In Quebec, the small Laval-sur-le-Lac–Île-Bizard Ferry operates seasonally across the Rivière des Prairies from Laval-sur-le-Lac to the Île Bizard.

Croatia

edit

Reaction ferries cross the rivers Sava and Drava.

Czech Republic

edit
 
The Aken Ferry, Germany

Germany

edit

A number of reaction ferries operate in Germany, particularly across the rivers Elbe and Weser. Between the 17th and 19th centuries, they were quite common on the Rhine. Currently operating ferries include:

 
The Westerhüsen Ferry across the Elbe in Germany is a reaction ferry using a floating cable attached to a mid-channel anchorage, to the right of the boat.

Italy

edit

The Traghetto di Leonardo [it] is a historic reaction ferry across the Adda River at Imbersago. It is reputed to have been designed by Leonardo da Vinci.[6]

 
Traghetto di Leonardo, Italy

Lithuania

edit
 
Uperis - small river ferry in Vilnius, Lithuania

Netherlands

edit

New Zealand

edit

Poland

edit

A number of reaction ferries operate:

 
Ferry in Czeszewo, Poland (Warta river)
 
Ferry in Gniew, Poland (Vistula river)

Slovakia

edit
 
Border-crossing ferry, Záhorská Ves in Slovakia and Angern an der March in Austria

Slovenia

edit

Spain

edit

Switzerland

edit

Four passenger ferries cross the Rhine in Basel.[11][12]

Three such ferries cross the Aare in Bern.

A small traditional ferry, the last on this river, crosses the Doubs.[13]

United Kingdom

edit
 
Hampton Loade Ferry, England

The Hampton Loade Ferry, which carried passengers only, crossed the River Severn at Hampton Loade in Shropshire until 2017. It was operated partly by the current and partly by punting.

United States

edit

Several reaction ferries crossed rivers in the Ozark Mountains of the central United States during the first half of the 20th century. The Akers Ferry across the Current River near Salem in Missouri remains in operation. Menor's Ferry in Jackson Hole, Wyoming, was a dual-pontoon reaction ferry built in the 1890s and operated until 1927. A replica was constructed by the National Park Service in 2009.[14][15]

See also

edit

References

edit
  1. ^ Luckmann, Detlev (1974). "Prahmfähre über die Oste, Baujahr 1911, Oberndorf" (Video 17 Min. with transcript and article). German National Library of Science and Technology (TIB) (in German). Institut for the Scientific Film (IWF) (Göttingen).
  2. ^ Bruce, Edmond & Morss, Harry Design for Fast Sailing. Amateur Yacht Research Society, 1976, pp. 92-117.
  3. ^ a b Bruce, Edmond (July 1962). "The physics of sailing craft as revealed by measurements at full size" (PDF). A.Y.R.S. Publication (40): 23–55. Retrieved 15 March 2023.
  4. ^ Marchaj, C. A. (1977). Sailing Theory and Practice. Adlard Coles Limited. p. 121.
  5. ^ "Murfähre - Thema auf meinbezirk.at". MeinBezirk.at (in German). Retrieved 2023-01-21.
  6. ^ Horowitz, Jason (2023-04-23). "Leonardo's Ferry Left High and Dry by Global Warming and Red Tape". The New York Times. ISSN 0362-4331. Retrieved 2023-04-24.
  7. ^ "UPERIS River crosser". Retrieved 4 May 2019.
  8. ^ "Prom rzeczny (52.215265,18.434951)" [River ferry (52.215265,18.434951)]. Google Maps. Google. Retrieved 2012-01-29.
  9. ^ "Prom rzeczny (50.290066,20.801754)" [River ferry (50.290066,20.801754)]. Google Maps. Google. Retrieved 2012-01-29.
  10. ^ "Prom rzeczny (52.055176,15.42901)" [River ferry (52.055176,15.42901)]. Google Maps. Google. Retrieved 2012-01-29.
  11. ^ Stiftung Basler Fähren
  12. ^ Video about Basel’s reaction ferry, by Tom Scott
  13. ^ Ferry of Tariche
  14. ^ Repanshek, Matt (August 4, 2009). "Menor's Ferry Back in Service At Grand Teton National Park". National Parks Traveler. Retrieved 29 October 2022.
  15. ^ "Menors Ferry Historic District". National Park Service. July 20, 2019. Retrieved 29 October 2022.
edit
 
Wikimedia Commons has media related to Reaction ferries.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Reaction_ferry&oldid=1246635930"