APPENDIX G

 

VESSEL TECHNOLOGY

 

This appendix documents the vessel technologies most appropriate for use in the Bay Area Water Transit System, and indicates the technologies that are most suitable for specific routes and applications.

 

Reliability and safety and the ability to meet state and federal statutory requirements are essential in any water transit system. The 1992 Regional Ferry Plan, prepared by MTC, considered three critical requirements:

 

· Proven and Reliable Vessels: No hull design was recommended that had not been previously constructed and safely operated in the speed and load conditions applied to the considered routes.

 

· Flexible Interior Arrangements: No vessel was recommended unless the vessel manufacturer could accommodate special boarding and alighting arrangements, cargo and baggage stowage, disabled accommodations, etc.

 

· American Built: No vessel was recommended unless it could be manufactured in the United States. Most of the acceptable vessels are of foreign design and are manufactured abroad, but U.S. law (46 United States Code) requires that vessels operating between U.S. ports be built in American shipyards. Therefore, foreign manufactures must have arrangements to license their technology to an American affiliate.

 

Alternative Vessel Designs

 

Taking these guidelines into account, as well as criteria including passenger capacity and speed requirements, several technology options were reviewed including:

 

· Hydrofoils: For most purposes, hydrofoils are not be suitable for Bay Area use due to their deep draft requirements and susceptibility to disablement by submerged or floating flotsam. Debris impacts can lead to costly and time consuming drydocking.

 

· Catamarans: In the past 20 years, the catamaran design has steadily eclipsed other hull forms as the choice of most ferry operators for all but very high-speed (greater than 40 knots) service. The catamaran offers a more stable platform than the monohull, excellent maneuverability (owing to widely spaced propellers), "wide body" passenger spaces where more arrangement options are possible, low draft requirements at a given hull displacement, and reasonable economy of operation. However, compared to monohulls of similar size, capital costs are higher and wider vessel berths are required. At low speeds, operating inefficiency increases, which also increases fuel consumption and fuel costs. Waterjet propulsion catamarans were recommended in the Regional Ferry Plan for most Bay Area ferryboat services. Such vessels are now being used in the Bay Area, combining relative fuel economy with speed and passenger comfort.

 

· Conventional Monohull designs are still commonly used in the U.S., especially where speeds of over thirty knots in high sea conditions aren't required. The semi-planing monohull represents the low capital cost, low maintenance option for relatively protected waters.

 

· Surface Effect Ships can operate with low fuel usage and high speeds, but have high capital cost per seat, high weight sensitivity, high maintenance requirements and costs, susceptibility to speed loss in heavy sea conditions, and a less comfortable ride.

 

· Hovercraft: While Surface Effect Ships are propelled through the water (85 percent of the hull weight is lifted out of the water), hovercraft travel totally above water and are propelled through the air. This hull form is attractive for certain shallow areas of the Bay (since the vessel travels above the water and not through it) and is faster than other vessels (since it has little contact with, and hence little friction from, the surface water). For short distances, these vessels can also operate across land to sites off the Bay. Negative considerations include high capital and maintenance costs, somewhat bumpy rides, and, most importantly, high levels of exterior noise.

 

While the Regional Ferry Plan did not recommend hovercraft for use on any conventional route, their amphibious abilities offer an advantage for airport routes, where exterior noise is not an issue compared to aircraft noise, and hovercraft have the unique ability to move directly from water to dedicated terminal gates. Hovercraft also have the advantage that they do not require deep water channels to operate. At Oakland International Airport shallow Bay depths would require substantial dredging for conventional craft, a step not necessary with a hovercraft. Because of their ability to access shallow areas of the Bay, hovercraft may also offer special advantages during disasters. No commercial hovercraft are operating in American waters today, although many are operating in Europe

 

Speed versus Distance

 

Generally, the higher the speed, the much greater the power required. The common "rule-of-thumb" is that increases in speed are proportional to the cube of the power. It is common for fuel consumption to double as speeds approach 30 knots. This fuel consumption can easily increase costs by $100 per hour – requiring fare revenues from 20 to 40 passengers to pay for the additional fuel cost. The paradox of this fuel consumption curve is that on short routes higher speeds make little difference in overall travel time – for example, between Berkeley and San Francisco, a seven mile route, the difference between a 25 knot vessel and a 30 knot vessel would be about three minutes in travel time.

 

Light Cargo Vessels

 

The conceptual design for the Bay Area Water Transit System calls for light cargo (e.g., small package) transport service between major Bay Area airports, and from the airports to regional distribution points at San Francisco and Moffett Field. Other areas are currently using high speed ferries for small package and light cargo delivery, either sharing passenger deck space or on vessels dedicated entirely to cargo. For example, high speed catamarans specially fitted for carrying unfrozen fish operate on established routes between Norway and France, carrying fresh fish to European markets. On the Bay, slower vessels may be more economical to operate, as package delivery is seldom as time sensitive as service for commuters or airport passengers.

 

If cargo is moved by water, using dedicated vessels offers several distinct advantages:

 

· Cargo Deadweight: The capacity of dedicated vessels can be considerably higher for vessels of the same deadweight capacity. For example, a typical 350 passenger ferry will have a deadweight of 27 tonnes reserved for passengers, another tonne or more in passenger fresh water capacity, and the considerable weight of outfitting (seats, aisle ways, food service equipment, and carpeting) which can amount to several additional tonnes of weight. Life jacket stowage, structural fire protection, noise abatement measures are all attributes that can be curtailed on the cargo version.

 

· Cargo Volume: Cargo capacity is usually restricted by volume limitations more than weight. How space is utilized is therefore important, and vessels configured for package and cargo handling can be laid out flexibly, to accommodate either specific cargos or various cargo types simultaneously.

 

· Cargo Handling: A vessel configured for cargo loading will have an efficient means of onloading and offloading material and equipment, according to size and destination. For example, if jet engines, each weighting 10 tonnes, are being routinely moved from one airport to another, cradles can be positioned where they can be easily loaded and offloaded, using shore side cranes. The movement of priority mail (USPO, FedEx, DHS etc.) can be accommodated by dedicated skip boxes.

 

With these attributes in mind, several passenger vessel designs can be easily adapted to cargo service. Most designs can be finished as supply boats, passenger vessels, or small cargo carrying vessels. The cost of any vessel outfitted to handle cargo only will be 10-15% less than for the same vessel outfitted for passengers.

 

Future Technological Development

 

Developments in high speed ferries have been evolutionary and the next ten years can be predicted with reasonable confidence. Gas turbine efficiency should continue to improve, closing the gap in fuel economy between diesel and gas turbine propulsion systems. Composite materials will probably gain acceptance by the regulating authorities and the inflation-corrected cost of hull construction will stabilize and perhaps come down. Waterjet efficiency will not change appreciably but maintenance requirements should lessed as seals and other materials are improved. Speeds of fifty knots are being achieved today in larger ferries, but at a high price in fuel consumption. With current technology, the trade-off in speed against operating cost and safety for the Bay area will probably not justify speeds above 40 knots in the foreseeable future.

 

New hull forms may enter the competition in the lower Bay where shallow draft requirements preclude standard catamaran designs. Some air cushion vehicle forms that would be suitable for shallow water operation show promise of further development. Most significant among these is the Stolkraft, an Australian design of Dutch origin which has seen slow but promising development for use in small passenger ferries. Successful application of this form could eventually open up travel from the lower Bay without excessive dredging or other environmental impacts. Any new technologies of this nature should be proven successful in passenger vessels, however, before being applied to routes where safety and reliability are the principal measures of success.

 

Predictions beyond ten years are difficult. It is safe to say that the entire travel industry, including commuting and longer range travel, will be affected by economic, cultural, environmental, and scientific conditions still to be determined, as much as by engineering developments. The science of energy storage currently restricts us to vehicles and vessels powered by carbon-based fuels. Light weight, high energy batteries could in the future make electrical propulsion a reality, revolutionizing the high speed ferry industry, but no such breakthrough appears "in the pipeline" at this time.