Double-ended ferries: The art of design

“Legally, a ferry is the continuation or prolongation of a highway over a navigable stream.” This quote is from the first Transactions of the Society of Naval Architects and Marine Engineers (SNAME), published in 1893. Given the impact of ferries upon society, it should come as no surprise that they have been a topic of interest to many naval architects for many years. The Pacific Northwest region of the United States contains a mix of islands, rivers, peninsulas and lakes. Salt water and fresh water transportation routes have been a critical part of the economic development of the region beginning with the native peoples and continuing today. Since the arrival of the first settlers in the 1850’s, power-driven ferries have been a common sight, linking the various communities through the movement of goods and people.

What is a double-ended ferry and why choose this configuration? A double-ended ferry is one where vehicles are loaded on and off both ends of the vessel and the direction of travel switches so the bow becomes the stern. The greatest argument for a double-ended ferry is when the route is short such as a river crossing. The time to maneuver the vessel so it can back in to the dock becomes a significant portion of the overall time between departures. The maneuvering time also consumes additional fuel and imposes the risk, however small, of any maneuver going awry. Another advantage is that the vessel will have the same handling characteristics every time it enters or departs a terminal. With its propulsion at each end, the double-ended ferry has excellent stopping power and superior maneuverability, especially if using an azimuthing or cycloidal propulsion system. This all contributes to safety, a critical factor for any ferry.

The origins of Elliott Bay Design Group (EBDG) go back to the late 1920’s with the establishment of W.C. Nickum & Sons. The earliest ferry projects were to modify the double-ended ferries from the San Francisco Bay area that were made superfluous by the bridge building activities there in the 1930s. Since that time EBDG has worked on a wide variety of vessel sizes and propulsion types, to suit routes ranging from short river crossings to 20 nautical mile transits of exposed water.

EBDG Ferries

The typical ferry we have designed has a V hull amidships with a narrow, flat of bottom at baseline. The side shell flares outboard with one or two knuckles between the heavy guard at the deck edge and the bottom. This configuration produces surfaces that are fully developable which facilitates construction. Typically, the waterline beam is 80% of the maximum beam. This shape provides excellent reserve buoyancy for damage stability and adds waterplane area as the vessel heels, thus improving intact stability. Where there is a draft limit, we increase the width of the flat of bottom. At the ends the waterline shape typically narrows to a fine entrance. Because the waterline beam decreases more quickly than the beam at deck, the effect is to create substantial sponsons. These are located sufficiently far above the bow wave to avoid increased wetted surface as the bow wave increases with speed. The shape of these sponsons also needs to consider wave slamming in rough weather, so a compromise is sometimes required between calm water resistance and speed in waves. The lower part of the hull at the ends is fitted with a skeg to support the shaftline (with traditional shafting on centerline) and to support the hull in dry dock. The skeg shape and volume are critical to the shape of the bow wave, hence we carefully consider the section area shape, including skegs. In more recent projects we have seen greater emphasis on reducing hull resistance, especially for ferries that operate on route lengths of greater than 2 nautical miles. Over the 40 to 50 year life of a ferry, small reductions in drag can result in significant fuel savings, and of increasing importance, lower emissions. Through the use of computational fluid dynamics we can find a balance between low resistance and ease of construction.

The double-ended ferry lends itself to a wide variety of propulsion configurations. Historically, these have ranged from steam-driven, side paddlewheels to a cable ferry powered by horses on a treadmill. In more recent times, we have seen the diesel engine become the dominant power source with a variety of means of putting the power into the water. Clearly, there is no preferred approach that works for every ferry. As designers, we look for the machinery configuration that meets the owner’s performance requirements with the best balance between reliability, maintainability, fuel efficiency and operability. This search typically takes the form of a propulsion study where we work with the owner to establish weighting criteria for the various aspects of the propulsion system. Typically, an owner will have strong opinions on what equipment and what configuration works well for his operation.

We are also seeing more clients interested in different forms of propulsion to reduce their overall energy consumption and thus reduce their environmental footprint. Owners are willing to trade off the simplicity and reliability of traditional geared diesel propulsion for reduced energy consumption through use of hybrid propulsion with electric drives, batteries for energy storage, and smart control systems. We are also seeing increased interest in alternative fuels such as liquefied natural gas, biofuels, and even hydrogen.

This year EBDG developed a physics-based simulation tool to evaluate different propulsion technologies for different sizes of ferries operating on different types of routes. This tool calculates hull resistance, weights, fuel requirements, and hull characteristics in an iterative fashion until the basic parameters of weight and buoyancy are in balance. The outputs from the tool are estimates of capital and operating costs as well as carbon emissions. We can now work with ferry operators to assess the economics of using technology to reduce environmental impacts.

So, what has 50 years taught us? First is that there always will be opportunities to improve the art of double-ended ferry design. Some recent trends include:

  • Access paths for passengers with disabilities
  • Critical scrutiny of fire risk and improved design of both passive and active fire protection measures
  • More vehicle clearances to improve speed of loading and unloading
  • Large passenger cabins with accessible restrooms
  • Seating arrangements to suit both individuals and larger groups
  • Greater security for vital spaces such as the engine room and pilothouse
  • Changing technologies and environmental issues are challenging to evaluate without a disciplined approach using solid engineering.
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Designs on Expansion


To mitigate the shipping industry’s contraction, Spanish engineering firm GHENOVA Ingeniería, Seville, Spain, has seized opportunities in the high-growth markets of Latin America. A key project enabling them to establish a strong foothold is the design of a fleet of LPG tankers for Transpetro, using AVEVA Marine.

According to Ignacio Grau, GHENOVA’s Head of Marketing and Communication, the naval sector has been GHENOVA’s core market since the company’s founding. However, several projects signed in Brazil, both for naval engineering and energy, are now expanding the company’s client base. As a Spanish company, GHENOVA has a head start.

“For us, expansion into Latin America was a natural choice,” says Julián Fontela, GHENOVA’s Manager of Business Development. “We have fewer linguistic or cultural barriers to entry than equivalent North American or other Anglophone companies.”

The depressed shipping market following the slump in 2008 especially impacted GHENOVA’s customer base in Europe and in the naval sector; the company recognized the need to pursue new opportunities in high-growth markets. “Our main office in Latin America is in Brazil, and from there we are orchestrating our expansion into the rest of Latin America,” explains Julián. “Projects executed from the Brazilian office are of strategic importance for us, because each one demonstrates both the high quality of our work and our long-term commitment to our customers in the region as a whole. This strategy really represents a key ingredient for the growth of the company.”

Adds Ignacio, “The focus on both Europe and Latin America has meant intensified activities and a resulting notable staff increment, which are cornerstones of a longer-term growth strategy: we want to reach EURO 50 million in annual revenue and significantly increase our workforce by 2018.”

LPG tanker engineering
In September 2011, a year after GHENOVA first entered Brazil, success came with the signing of a EURO 7 million contract with the STX Promar shipyard (now Vard, part of the Fincantieri group) to carry out the engineering of eight LPG tankers for Transpetro. A subsidiary of Petrobras, Transpetro is Brazil’s largest oil & gas distribution company. It stores and transports oil, ethanol, biofuels and natural gas, and has a network of more than 11,000 kilometers (7,000 miles) of pipelines.

“Our Brazil office is very strong on the marine side and the LPG project is a great reference case,” says Julián. “It clearly demonstrates our capabilities to neighboring countries who are also important oil & gas players on the global stage. We hope that this project will be a springboard for GHENOVA to foster relationships with other oil & gas producers in the region.”

The project consists of the detailed engineering and purchasing support for the prototypes of three LPG carrier designs. A design for four vessels with a pressurized capacity of 7,000 m3 has already been delivered. The first three are already in fabrication. The first vessel in the series has been christened Oscar Niemeyer and will be delivered in December 2014. A further vessel design for two LPGs with a smaller pressurized capacity of 4,000m3 is also complete; at the time of writing, both vessels are being constructed and will be delivered soon. GHENOVA is now working on a design for two semi-pressurized vessels that will each have a capacity of 12,000 m3. GHENOVA is responsible for all the detailed engineering of the structures, piping, equipment and outfitting, the electrical, instrumentation and electronics systems, and HVAC and accommodation. The Brazilian team are using AVEVA Hull, AVEVA Outfitting, and AVEVA Cable Design, collaborating with their colleagues at the Spanish headquarters with the help of AVEVA Global.

The business opportunity
This high-profile project provided an excellent opportunity for GHENOVA to establish a reputation with Petrobras. A link to Petrobras is an endorsement of GHENOVA’s capabilities and sends a strong message to other organizations in the region. Furthermore, GHENOVA has established a connection with this Brazilian oil & gas giant at a crucial time in Petrobras’s history. The offshore Santos Basin discovery means that Petrobras will invest in fleet expansion and renewal to support its future increase in E&P activities and, as a result, there will be opportunities for further projects.

Another key factor that will push forward growth in this market is the Certificado de Registro e Classificação Cadastral (CRCC) certificate, which is awarded by Petrobras to companies that meet all the requirements to become an approved services provider. The CRCC specifically certifies GHENOVA’s ability to carry out comprehensive shipbuilding and tanker-ship projects.

This document allows GHENOVA to tender and participate in bids for work from Petrobras and, combined with the LPG project, marks a significant step forward. GHENOVA describes it as its “passport” into the Brazilian market.

Selecting the right tool for the job
To make the most of this business opportunity, GHENOVA needed the best tool for the job. With previous experience with Tribon, GHENOVA had successfully adapted to AVEVA Marine several years ago and is very happy with the result; their designers and engineers were able to adjust quickly and smoothly to the new system. Their AVEVA deployment forms part of a suite of applications that enables GHENOVA to meet a wide range of client- and project-specific requirements. As a result, GHENOVA selects the design software on a case-by-case basis. “Our business is engineering, first and foremost,” says Julián. “Each of the different types of software that we use is one system within a diverse toolkit. Every client has different requirements and meeting those requirements is key. We don’t only design ships; among other things we also design thermal power plants, so our choice of software for any particular project is usually dictated by the nature of the project and the client’s requirements.”

As a result, AVEVA Marine was chosen specifically for this project because it best matched Transpetro’s needs and was consequently mandated by Vard Brazil. “This is an entirely new project for us, so it was essential to select a 3D engineering and design tool that could deliver true strategic value,” explains Francisco Cuervas, General Director of GHENOVA. “AVEVA Marine met all the requirements that the client set out, making it the ideal choice for such an important project. The integrated AVEVA Marine applications have helped us to save many hours during the design phase, allowing an efficient and accurate model to be delivered to our customer.”

Rui Miguel de Sousa, GHENOVA Brazil’s Branch Director, says, “The AVEVA solution was subjected to a rigorous tender process and its integrated hull and outfitting design capability stood out against the competition. It will enable us to efficiently create clash-free, production-oriented design. We are confident this will help us achieve reduced rework and deliver the highest quality designs. With concurrent global project execution we can also ensure that all sites and users have access to the latest approved data, right down to attribute details.”

“We will continue to use AVEVA Marine as part of an overall service offering as we continue to seek out opportunities in both our European client base, and our expanding new client base in Latin America,” says Julián.


The Shearer Group adds to its team


Mr. Brann graduated with a bachelor’s degree in naval architecture and marine engineering from Virginia Polytechnic Institute and State University in 2011. He has a wide range of knowledge of marine engineering specialties including ship stability, damage analysis, systems integration, ship survivability, and firefighting systems.

Previously, Mr. Brann has worked for the American Bureau of Shipping (ABS) in its ship engineering department analyzing stability calculations for engineering firms, shipyards, and vessel owners.

Before joining ABS, he worked at ICI Services Corporation as an associate naval architect working on systems design and integration for various marine projects.

Mr. Brann is a member of SNAME and an Engineer in Training in Virginia. He plans on sitting for the Professional Engineer examination in the spring of 2016.