Introduction

Currently, U.S. shipbuilders are not competitive in the growing worldwide market for high-speed passenger catamarans.  This project addresses the problem of developing a high-speed catamaran design for the U.S. and worldwide passenger ferry markets.  It emphasizes improving the productivity of U.S. shipyards by addressing the integration of catamaran design and manufacture through the research and development of a lightweight high performance vessel.

While there are a number of high-speed and hybrid type marine craft, this project was directed toward high-speed passenger catamarans.  Catamaran construction closely resembles the high-speed aluminum monohulls currently being built by U. S. Gulf Coast shipyards and, thus, represents minimum retooling of equipment.

Background

In preparation for the next generation of high-speed passenger marine craft, this project focused on the development and optimization of a lightweight aluminum hull panel.  A prototype hull panel, typical of that used in passenger catamarans operating at 35 - 40 knots, was designed with alternating floating and fixed transverse frames.

To determine its structural response, the panel design was analyzed using the finite element method.  A 5-foot by 15-foot aluminum test panel was built by Swiftships and tested in the UNO structural laboratory.  There was excellent agreement between the mid-area deflection indicated by the finite element analysis and the corresponding deflection of the test panel.

With shipyard input, the use of available aluminum extrusions was examined.  This study was performed as part of a structural optimization that used a parametric finite element analysis.  The results of this analysis indicated that it is possible to obtain a structure with a 10 - 15% weight reduction while satisfying the Det Norske Veritas (DNV) classification society requirements.  In this manner, a cost effective lightweight hull structure can be designed and manufactured using alternating fixed and floating transverse frames.

To identify a hull geometry with minimum structural loads, a series of seakeeping tests were performed with a 1/30-scale catamaran model.  It was shown that the heave and pitch responses could be reduced by changing the angle of the hulls in the range of 15 to 45 degrees compared to the conventional 0-degree upright orientation.  This effort followed earlier progress in the U. S. Navy's development of the Sea Shadow.

Objectives

1. Develop a conceptual design for a high-speed catamaran for an existing market niche, and develop the CATSSD database.  The shipyard staff and GCRMTC will review the high-speed ferry market to identify ferry routes and speed requirements to define the conceptual design.
2. Validate design loads by hydrodynamic model tests of an instrumented model of the catamaran.
3. Design a prototype structure that incorporates structural aluminum extrusions to obtain a cost-effective structure that integrates both design and manufacture.
4. With shipyard cooperation, construct the prototype aluminum structure incorporating extrusions, and perform experimental tests and finite element analyses of the resulting structure.

Conclusions

There is a market for an 80 - 120-foot high-speed passenger craft using a surface piercing catamaran hull running at speeds from 35 - 50 knots.

A surface piercing catamaran similar to aluminum high-speed passenger vessels would adequately satisfy this market.

Systematic hydrodynamic tests showed that vessel heave and pitch motion are reduced by 25% when the side hulls are angled from 15 to 45 degrees rather than arranged perpendicularly to the water surface.  The 45-degree hull angle results in maximum heave/pitch reduction.

The catamaran hull panel, designed following Det Norske Veritas (DNV) classification rules, showed that a floating transverse frame system could be adopted.  This was verified by experimental tests completed at the University of New Orleans (UNO).  The floating frame design represents an estimated welding reduction of 20%.

The panel test results showed excellent agreement with the finite element analysis.

Subsequent finite element analysis showed that by proper selection of the panel members and extrusions, a 15% weight savings could be achieved.

Industry Partner

Swiftships, Inc.

Recommendations for Future Efforts

A follow-on study should be conducted of the integration of the propulsion system and hull to achieve economies in fuel and structural weight.  This would include gas turbine propulsion to reduce maintenance downtime.

A series of systematic tests should be initiated comparing continuous and intermittent welds between the plate and stiffeners.  The focus of this effort would be to minimize labor costs while retaining sufficient structural integrity.
 

For more information contact:

Dr. Robert Latorre
Telephone: (504) 280-7183
E-Mail: rglna@uno.edu

Dr. Paul D. Herrington
Telephone: (504) 280-6050
E-Mail: pdhme@uno.edu

GCRMTC TECHNICAL BRIEFS are published periodically by the Gulf Coast Region Maritime Technology Center, a U.S. Navy Center of Excellence in Advanced Marine Technology based at the University of New Orleans.  GCRMTC's Mission is to "enhance international competitiveness in the U.S. shipbuilding industry through sponsored research."   For additional information, contact:  GCRMTC, University of New Orleans, New Orleans, LA 70148, Tel: (504) 280-3871, Fax: (504) 280-3898, E-mail: jtsen@uno.edu

The contents of this publication reflect the views of the MERIC staff and are based on information obtained from the literature.  The contents do not necessarily reflect the official views or the policies of MERIC or the Gulf Coast Maritime Technology Center.  This publication does not constitute a standard, specification, or regulation.  MERIC does not endorse products, equipment or manufacturers.  Trademarks or manufacturer's names appear herein only because they are considered essential to the object of this publication.