New Retractable Tunnel for Inland Shipping

press release
Thursday, October 20, 2011
retractable tunnel specially developed for inland vessels.

The Inland WaterWays division of Van der Velden Marine Systems in the Netherlands has introduced an innovative new retractable tunnel specially developed for inland vessels.


Using a unique construction, the Van der Velden® Flex Tunnel offers major benefits to ship owners and operators in terms of speed, loading capacity, manoeuvrability and reduced fuel consumption.  Moreover, an overall propulsion efficiency of 10% can be achieved.


Water levels are unpredictable and low water levels have serious consequences for inland vessels, as it limits loading capacity and operability. According to the Inland Shipping Expertise and Innovation Centre in the Netherlands, shallow drafts are estimated to have cost the Dutch industry alone some 28 million Euros a year over the past 20 years. Tunnels are commonly used on inland ships, ensuring a proper water flow into the propellers at shallow draft. The downside of tunnels is an increase in hull resistance, a lower efficiency and consequently extra fuel consumption at deeper draft. Moreover, loaded inland ships sail in deeper water conditions for about 85 percent of the time, during which a tunnel is superfluous.


  • Optimal propulsion efficiency

The starting concept behind the Van der Velden® Flex Tunnel is its ability to retract. With the tunnel embedded into the vessel hull, resistance is lowered and efficiency increased. When sailing in shallow waters the retractable tunnel is deployed to ensure sufficient water flow to the propellers and maintain their efficiency. Vessels fitted with the Van der Velden® Flex Tunnel remain operational longer than other vessels.  In addition, this tunnel comes with further optimised hull lines, increasing cargo space and loading capacity. Also smaller propellers and rudders can be installed reducing both weight and draught in equal measure.

  • Less fuel consumption

Another benefit comes from the way the Van der Velden® Flex Tunnel is mounted on the nozzle. With conventional solutions, tunnels are installed over the nozzle in order to allow for water discharges via a vent-hole between tunnel and nozzle. This arrangement increases the length of the tunnel and causes it to stick out behind the nozzle. With Van der Velden’s new retractable tunnel this is not the case; the retractable tunnel is seamlessly constructed over the nozzle, avoiding false air between the nozzle and the tunnel. Moreover, the Van der Velden® Flex Tunnel is approximately two-thirds the size of a conventional tunnel.


Van der Velden offers integrated solutions for the whole propulsion- and manoeuvring system on board. The Van der Velden® Flex Tunnel is developed to be combined and integrated with the Van der Velden® DOLPHIN XR rudders and DOLPHIN XR spoilers. This complete package ensures optimal efficiency and thus considerable fuel saving. Also, the hydraulics to operate steering gear and the Van der Velden® Flex Tunnel is included in the entire system.
Van der Velden developed the retractable tunnel in close cooperation with the renowned German research institute DST (Development centre for Ship Technology and transport systems). It further enhances Van der Velden’s reputation for providing clients with industry-leading solutions.

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