page_title: Chain boat
section_title: Design
hierarchical_section_title: Chain boat / Design
caption_attribution_description: Deutsch: Schmatische Darstellung des Kettenverlaufs English: Schematic view of the operation of a chain boat
context_page_description: A chain boat, chain tug or chain-ship was a type of river craft, used in the second half of the 19th century and first half of the 20th century on many European rivers, that made use of a steel chain laid along the riverbed for its propulsion. The chain was hauled by a steam engine mounted on board and enabled the boat to tow a string of barges. In Germany, such a boat was variously referred to as a Kettenschleppschiff, Kettenschlepper, Kettendampfer or Kettenschiff and in France as a toueur.
  The chain was raised out of the water over a boom at the bow of the ship and led over the deck along the ship's axis to the chain engine amidships. The transfer of power from the steam engine to the chain was usually achieved using a drum winch. From there the chain was led over the deck to another boom at the stern and lowered once more into the river. By moving the stern boom and the two rudders, front and aft, from side to side it was possible to replace the chain in the centre of the river again, even when negotiating river bends.
context_section_description: The hull of these symmetrically-designed boats was almost level with the surface of the water at the bow and stern. This design reduced the power needed to lift the tow chain onto the bow of the boat and also reduced the draught at the bow. The greater height of the boat in the centre made it easier to accommodate the steam engine. This deck shape - low at the bow and stern, and higher in the centre - is typical of all subsequently built chain boats.
  Chain boats were favoured on shallow rivers with fast currents. This was the reason for the flat, shallow draught of their keels. Chain boats optimized for particularly shallow water had a draught of only 40 to 50 centimetres (16 to 20 in) when unladen. Even fully laden with coal, their draught was only about 70 to 75 centimetres (28 to 30 in). This shallow draught enabled river transportation even in the dry summer months when the water level of rivers could be very low.
  Shorter chain boats - with lengths from 30 to 40 metres (100 to 130 ft), and widths from 5 to 6 metres (15 to 20 ft) - were more manoeuvrable and well suited to narrow rivers with many bends, for example on the Saale. Longer craft - with lengths from 45 to 55 metres (150 to 180 ft), and widths from 7 to 10 metres (25 to 35 ft) - were more suited to relatively deep rivers such as the Elbe. The deeper a waterway was, the greater the power needed to lift the heavy chain. The bow of the ship was pulled down further. On larger boats this effect is less.
  The hull itself was made of iron or wood and could withstand light impacts with the riverbed. If, however, it was holed the hull was compartmentalized internally by several waterproof bulkheads that prevented the craft from sinking. Below deck were the steam engine, the coal bunkers and the crew accommodation.
caption: Schematic view of the chain system on a Bavarian chain boat: Boom (green), rudder (pink), guide rollers (blue), chain drive (red)
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