Contour stern flap

Details Contour stern flap Contour stern flap

2002-08-14

2004-10-19

Morano, S. Joseph (Department: 3617)

Ships

Hull or hull adjunct employing fluid dynamic forces to...

C114S343000

Reexamination Certificate

active

06805067

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to the hydrodynamics of marine vessels, more particularly to adjuncts, appendages and auxiliary devices for affecting same.
A stem flap is an extension of the hull bottom surface which extends aft of the transom. It is a relatively small appendage (typically constructed so as to include internal metal bracing beams and external metal plate material) which is fitted to the ship's transom. Critical stern flap geometry parameters include: (i) chord length, (ii) span across the transom; and, (ii) an angle denoted as “trailing edge down” (TED), referenced to the local buttock slope (run) at the transom. The main purpose of a stern flap device is to reduce the shaft power required to propel a ship through the water, thereby reducing the engine's fuel consumption and increasing the ship's top speed and range.
The application of stern flaps to large displacement vessels is a fairly recent innovation. The U.S. Navy has been investigating the use of stern flaps on many different hull types. Stern flaps have now been proven by the U.S. Navy to reduce the requisite amount of propulsive power during navigation, with several concomitant advantages. Stern flaps: foster reductions in operating and life-cycle costs through fuel savings; increase both ship speed and range; decrease the amount of pollutants released by ships into the atmosphere; and, reduce propeller loading, cavitation, vibration and noise tendencies.
Incorporated herein by reference is the following United States patent which is pertinent to stern flaps: Karafiath et al. U.S. Pat. No. 6,038,995 issued 21 Mar. 2000, entitled “Combined Wedge-Flap for Improved Ship Powering.” The following papers, each of which is incorporated herein by reference, are also pertinent to stern flaps: Karafiath, G., D. S. Cusanelli, and C. W. Lin, “Stem Wedges and Stern Flaps for Improved Powering—U.S. Navy Experience,” 1999 SNAME Annual Meeting (paper), Baltimore, Md. (September 1999); Cusanelli, D. S., “Stern Flaps—A Chronicle of Success at Sea (1989-2002),” SNAME Innovations in Marine Transportation, Pacific Grove, Calif. (May 2002); Cave, W. L., and D. S. Cusanelli, “Effect of Stem Flaps on Powering Performance of the FFG-7 Class,” SNAME Chesapeake Sect Paper, (October 1989); Cusanelli, D. S., and W. L. Cave, “Effect of Stern Flaps on Powering Performance of the FFG-7 Class,”
Marine Technology
, Vol. 30, No. 1, pp 39-50, (January 1993); Cusanelli, D. S., and K. M. Forgach, “Stem Flaps for Enhanced Powering Performance,” Proceedings of 24th ATTC, College Station, Tex. (November 1995); Cusanelli, D. S., “Stern Flap Powering Performance on the PC 1 Class Patrol Coastal, Full Scale Trials and Model Experiments,” PATROL '96 Conference Proceedings, New Orleans, La., (December 1996); Cusanelli, D. S.; “Integrated Wedge-Flap, an Energy Saving Device,” 21st UJNR Marine Facilities Panel Meeting, Tokyo, Japan (May 1997); Cusanelli, D. S., and G. Karafiath, “Integrated Wedge-Flap for Enhanced Powering Performance,” FAST '97, Fourth International Conference on Fast Sea Transportation, Sydney, Australia, (July 1997); Cusanelli, D. S., “Stem Flap Installations on Three US Navy Ships,” ASNE 1998 Symposium—21st Century Combatant Technology, Biloxi, Miss. (January 1998); Cusanelli, D. S. and L. Hundley, “Stern Flap Powering Performance on a SPRUANCE Class Destroyer, Full Scale Trials and Model Experiments,” Research to Reality in Ship Systems Engineering Symposium, Tysons Corner, Va. (September 1998); Cusanelli, D. S. and L. Hundley, “Stem Flap Powering Performance on a SPRUANCE Class Destroyer, Full Scale Trials and Model Experiments,”
Naval Engineers Journal
, Vol. 111, No. 2 (March 1999), Cusanelli, D. S., S. D. Jessup and S. Gowing, “Exploring Hydrodynamic Enhancements to the USS Arleigh Burke (DDG 51),” FAST'99, Fifth International Conference on Fast Sea Transportation, Seattle, Wash. (August 1999); Cusanelli, D. S., and G. Karafiath, “Energy Savings and Environmental Benefits of Stern Flaps on Navy Ships,” ASNE Symposium: Marine Environmental Stewardship for the 21st Century, Arlington, Va. (October 1999); Cusanelli, D. S., and G. Karafiath, “Stem Flaps on Navy Ships, Fuel Savings and Environmental Benefits,” IMT'99, Innovations in Marine Technology, New Orleans, La. (December 1999); Cusanelli, D. S., “Stern Flaps and Bow Bulbs for Existing Vessels—Reducing Shipboard Fuel Consumption and Emissions,” United Nations Environmental Programme (UNEP 2001), Brussels, Belgium (February 2001); Cusanelli, D. S., and G. Karafiath, “Stern Flaps”,
Professional Boat Builder Magazine
, pages 81-87, (April/May 2001); Karafiath, G, D. S. Cusanelli, S. D. Jessup and C. D. Barry, “Hydrodynamic Efficiency Improvements to the USCG 110 Ft. WPB Island Class Patrol Boats,” 2001 SNAME Annual Meeting Paper, Orlando, Fla. (October 2001).
The standard (traditional or conventional) stern flap is designed with parallel, linear (straight) leading and trailing edges for orientation of these linear edges perpendicular to the ship centerline. The present inventor was tasked to apply existing stern flap technology to U.S. Coast Guard ships such as the HAMILTON Class or FAMOUS Class, wherein the hull design includes a highly curved transom. The inventor found that the standard stern flap had its limitations and would be disadvantageous for the task at hand. A configuration involving a standard stem flap and a curved transom would present various practical problems and would not be propitious.
To elaborate, installation of a standard stern flap on a highly curved transom would necessitate recession of the leading edge of the standard stern flap, at its centerline, under the transom. Full-scale installation and implementation would be difficult, particularly with regard to the arrangement and attachment of the partially recessed appendage to the curved transom. Moreover, such application of a standard stern flap with respect to a curved transom would inherently fail to fully utilize the entire stern flap chord length. In principle, a stern flap itself produces drag, and the stem flap's interactions with the hull, wave systems and propulsor produce the net decrease in required power. Generally, chord length is one of the parameters to be optimized; increase in effective ship length enhances reduction in ship wave resistance, and increase in stern flap total surface area increases the associated drag (resistance). The partial recess of the installed standard flap would directly limit the increased effective ship length associated with the stern flap installation. Furthermore, the partial recess of the flap would not make full use of the flap surface area.
SUMMARY OF THE INVENTION
In view of the foregoing, it is an object of the present invention to provide a stern flap which is superior to a standard stem flap for applications wherein a stem flap is being coupled with a marine vessel having a curved transom. The term “curved transom,” as used herein, refers to a transom which is curved laterally, athwart, crosswise or transversely—i.e., a transom at least a portion of which describes a curve, across the transom, wherein the curve lies in an imaginary geometric plane which cuts across the transom so as to be at an angle with respect to (that is, so as not to be coincident with) the imaginary geometric plane generally described by the transom itself. Typically, a “curved transom” is a transom that “bulges” so as to be approximately symmetrically curved in a bilateral direction.
The present invention features a stern flap which is contoured to fit a curved transom. The inventor, a naval architect employed by the U.S. Navy, conceived his invention based on his realization that the application of stern flap technology to the highly curved transom of the U.S. Coast Guard ships of interest (such as the HAMILTON Class or FAMOUS Class) would necessitate a new flap plan form design shape. The inventor initially investigated his contour stem flap concept by conducting model-scale tests on this hullform whic

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