Hydrodynamic Efficiency Improvements to the USCG 110 Ft WPB ISLAND Class Patrol Boats

Hydrodynamic improvements consisting of the design of a stern flap, spray rails, and new 6-bladed propellers, were undertaken for application to the forty nine ISLAND Class patrol boats operated by the USCG. A large, 18 ft (5.5 m) hydrodynamic hull model was constructed for use with stern flap optimization resistance tests, spray rail evaluation, and the prediction of resistance and estimated thrust needed for a new propeller design. Eight different stern flap designs were model tested as part of a systematic investigation regarding the effects of varying the chord length, span, angle and plan form area distribution. The final flap design minimized the estimated fuel usage over a range of operating conditions that included two displacements, and a varying speed-time profile from 12 to 30 knots. The stern flap was predicted to increase the full load maximum speed by 0.8 knots to 27.85 knots. At the 24 knot cruise speed a 3.7 percent reduction in delivered power was predicted. The annual fuel savings for the prescribed displacements and operational speeds was estimated to be 13,000 gallons per boat. A new 6-bladedpropeller design was undertaken with the goal of increasing fuel economy, reducing air borne noise, and improving engine reliability by providing proper engine loading. Special attention was paid to suppressing root cavitation. The relatively simple wake field permitted accurate quasi-steady panel method calculations of blade pressure distributions. Iterative panel calculations modeling the blade and the hub were used to alter blade shape to achieve satisfactory performance. Model-scale open water and cavitation tests were not conducted. The confidence in this propeller design is based on the Naval Surface Warfare Center, Carderock Division (NSWCCD) experience gained from design, model tests, and full scale trials data on the PC 1 Cyclone Class propeller, which has operating conditions similar to those of the ISLAND Class propeller. On average throughout the speed range, the new 6-bladed propeller design is predicted to be almost 8 percent more efficient than the existing fleet propeller. In addition, it will be free of thrust breakdown. With the stern flap, spray rails, and new propeller, the maximum speed is predicted to increase by 2.5 knots to 29.6 knots in the full load condition. The speed increase is due to reduced resistance, greater propeller efficiency, and increased available engine power due to a better fit between the propeller power curve and the envelope of available engine power. Observations of the flow patterns and model trim during the resistance testing indicated the need for a supplementary spray rail. Discussions with the USCG boat operators substantiated the need for additional spray suppression. An enlargement and extension of the existing spray rail was designed and it proved to be very effective in suppressing the model spray. The stern flap and spray rails have been fitted to the USCG JEFFERSON ISLAND (WPB 1340). Initial operations show that the patrol boat gets up on a plane more readily than before. The USCG is in the process of ordering retrofit kits fleet wide for installation at haul out opportunities.

• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/isbn/9780939773879
• Corporate Authors:

  Society of Naval Architects and Marine Engineers

  601 Pavonia Avenue
  Jersey City, NJ  United States  07306-2907
• Authors:
  • Karafiath, Gabor
  • Cusanelli, Dominic S
  • Jessup, Stuart D
  • Barry, Christopher D
• Publication Date: 2011

Language

• English

Media Info

• Media Type: Digital/other
• Features: Figures; Photos; References; Tables;
• Pagination: 24p
• Monograph Title: Sustainabilty in the Maritime Industry: A collection of relevant papers

Subject/Index Terms

• TRT Terms: Fuel consumption; Hydrodynamics; Patrol boats; Propellers; Speed
• Uncontrolled Terms: Spray rails; Stern flaps
• Subject Areas: Design; Marine Transportation; Vehicles and Equipment; I91: Vehicle Design and Safety;

Filing Info

• Accession Number: 01372432
• Record Type: Publication
• ISBN: 9780939773879
• Files: TRIS
• Created Date: Jun 14 2012 10:55AM