Improving the Performance of the Dredge Tender Ivanoff

  • Clients:
    Port of Portland, JT Marine
  • Completion Date:
    November 2017
  • Project Type:
    Vessel Design & Modification, Tugs & Workboats
  • Service Categories:
    Naval Architecture
    Marine Engineering
  • Vessel Overview:
    Dredge tender for the cutter suction dredge Oregon
  • Challenge:
    Modify the vessel’s stern hull and propulsion system to improve steering and bollard pull performance.

Understanding an Underperforming Vessel.

The dredge tender W.E. Ivanoff was built to maneuver the Port of Portland’s dredge Oregon and its pipelines as it performs maintenance dredging along the navigation channels of the Columbia and Willamette Rivers. The Ivanoff lacked the required propulsion and steerage, both ahead and astern, to meet the Port’s operational needs. Despite having more power, the Ivanoff was routinely outperformed by the Port’s other dredge tender, the Clackamas.

In 2015, the Port of Portland commissioned Glosten to investigate design improvements to the Ivanoff. Glosten determined that the Ivanoff’s performance issues were related to the stern hull shape, rudder configuration, and propeller size. After discussions with the Port, it was decided that the best solution would be to completely redesign the vessel’s stern and propulsion system.

Computational Fluid Dynamics (CFD) analyses provided baseline comparisons of the original Ivanoff hull and the hull of the Clackamas. These analyses provided quantifiable metrics that showed the Clackamas hull was superior to the original Ivanoff hull, matching the real-world results from a head-to-head push test. Glosten then designed and modeled a new Ivanoff stern using CFD to add to the comparison. This final analysis showed a significant improvement over the original design as well as over both the Port’s other dredge tenders, Clackamas and W.L. Williams. The new stern shape also allowed additional improvement gains through increased propeller diameter and pitch, an associated decrease in gear reduction ratio, and much larger rudders, facilitating the Port of Portland’s desired performance improvements.

After Stern Removal

After stern removal


The Ivanoff began her transformation in early 2016. The selected shipyard, JT Marine, hired Glosten’s production engineering team to provide detail design for the retrofit. After leaving the yard, a bollard pull test confirmed that the newly modified Ivanoff exceeds the bollard pull of its old design by 29% and exceeds that of the Clackamas by 34%, closely matching the improvement predicted by the model.