AXE Bow Concept
Background
The design philosophy behind the ESC is brought even further by the introduction of the AXE Bow Concept. Here the minimization of the nonlinear hydrodynamic lift in the fore body of the ship as well as a further reduction of the nonlinear wave exciting forces is further achieved by taking the modifications more to the extreme.
The design now features:
• an extremely sharp bow with no flare in the sections at all,
• a very small waterline beam in the bow sections,
• an almost vertical sidewall in the fore ship, both above and below the waterline,
• a considerably increased sheer towards the bow and
• a downwards sloping bottom centerline forward of the midship, which increases the draft at the forward sections with the maximum at the forward perpendicular.
The amount of increment of draft forward and the increase in sheer as well as the amount of volume and its vertical distribution in the bow sections (needed to optimize the behavior in waves) is determined using an iterative procedure with the nonlinear motion calculation code FASTSHIP.
FASTSHIP is a time domain seakeeping code for fast ships developed at the section of Ship Hydromechanics. Special care has been taken to achieve the same reserve buoyancy and pitch restoring moment as with the original design although over a considerable longer trajectory. The mechanical analogue of this may be found in what is generally referred to as “a soft spring system”.
It has been shown that the application of the AXE Bow Concept may improve the operability of a fast ship in typical North Sea conditions with another 40 to 50 percent when compared with the ESC.
Participants
• Damen Shipyards Group
• Royal Schelde
• Marin
• Royal Netherlands Navy
• US Coast Guard
Publications
• Keuning, J.A. , Pinkster, J. and Walree, F. van, “Further Investigation into the Hydrodynamic Performance of the AXE Bow Concept”, Proceedings of the WEGEMT Conference on High Performance Marine Vehicles, September 2002, Ischia, Italy
• Keuning, J.A., "Grinding the bow" or "How to improve the operability of fast monohulls", International Shipbuilding Progress, Vol 53, No 4, 2006
Contact
Dr.Ir. J.A. Keuning
Tel: +31 15 2781897
Fax: +31 15 2781836
Email: J.A.Keuning@tudelft.nl
