Design and construction of a low-impact amphibious vehicle for efficient and sustainable oyster farming

Design and construction of a low-impact amphibious vehicle for efficient and sustainable oyster farming

Summary

Many oyster farms in the United States, as well as in many other countries, are located in inter-tidal zone, near shore areas that are covered at high tide and exposed at low tide. While offering benefits, such areas also provide many challenges for the oyster farmer. Dynamic topographies of alternating sand bars and sloughs, tide-dependent work windows, and environmentally sensitive habitats create challenges when developing environmentally sound, optimal and efficient farm operations. Focusing their efforts during the low tide, many oyster farmers who operate intertidal farms have at best 2 hours on either side of a low tide to carry out daily husbandry and harvest tasks. This limited period heightens the need for equipment and practices that maximize efficiencies while minimizing environmental impacts. A critical problem is the lack of a low impact versatile vehicle that allow oyster growers to efficiently transport oysters and gear to and from, and within the farm, and provide a platform for production activities, such as harvesting and sorting stocks. The purpose of this project was to design, build, and evaluate an Amphibious Farm Vehicle (AFV) customized for working an intertidal oyster farm.  Central to the design was the desire for the vehicle to be low impact—quiet and environmentally friendly. The manually operated platform, which rolls on land and floats in water, contains a pump station, gear storage bins, and two removable sorting tables.  

Objectives/Performance Targets

1. To design and build a specialized amphibious farm vehicle to improve farm operation efficiency and minimize environmental impacts.
2. To optimize vehicle design through an iterative process of trial and modification.
3. To demonstrate the amphibious farm vehicle to local and regional shellfish growers through various outreach initiatives.

Accomplishments/Milestones

Milestones and Accomplishments

1. Design and Development. The project team consisting of oyster farmer (Gustavo Calvo, Sweet Amalia Oyster Farm), architect (David Bosco, Bosco Architects), and steel fabricator (Dan Dutra, Dutra Fabrication) met in early May 2015 to develop plans for the prototype AFV. Factors such as function, efficiency, material compatibility, and life cycle costs were carefully considered. The team selected the core components for the vehicle, which included a 10-foot Jon Boat (Model 1032, G3 Boats, Lebanon Mo.) and 19.3” x 9” polyurethane low-pressure balloon wheel/axle kits (Wheel Axle Kit 49UC, Wheeleez, Inc, Benicia, CA). The pre-manufactured, readily available Jon Boat was selected due to its shape/size, affordability, weight, and material, which resists the marine environment. The volume of the vessel allowed ample space for programed/transient storage. For the wheel assembly, the team selected four fixed axel wheels that could be anchored to the Jon Boat. The commercially available low-pressure polyurethane wheels are designed for the harsh marine environment and are proven to transport large loads across sand and irregular beach terrain. The vehicle design also included a work surface, shading, pump-station cradle, storage bins. The work surfaces were designed to accommodate multiple workers/tasks. Marine grade aluminum was chosen as the construction material for its resistance to the harsh environment as well as its ability to be easily machined and adapted.

2. Fabrication. Fabrication began in mid-May with the construction of a temporary structural frame connected to the vessel. The frame was developed to accommodate the wheel mounts in a manner to allow adjustment of spacing between axles enabling determination of the optimal distance, in respect to weight distribution and the ability to load on a standard pick up truck. Vessel components were constructed and mocked up out of a combination of light gauge steel and plywood. Their final construction was of marine grade aluminum. Design goal was to have the vehicle best address the oyster farmer’s day-to-day operations with the ability to accommodate additional projected tasks. Some task are less frequent but just as critical in the overall scheme of the farm’s production and maintenance, such as the task of power-washing the mud packed oyster bags or the transportation of the (10’) ten foot long steel support racks. Construction was guided by field-testing. Images of the construction process are available in Figures 1-4.

3. Field-testing. Field tests were conducted on June 5 and 14, 2015. Vehicle maneuverability was evaluated with an eye to optimize wheel span, wheel mounting height, and the handle/steering component. The work surface configuration was also evaluated to inform storage layout/availability. The vehicle on and off loaded efficiently into a standard pick up truck bed, easily rolling on and off using store bought aluminum ramps. The vehicle rolled well on sand surfaces, across mud bottom, and floated adequately at depth of less than 2’. The vessel was easily pulled while floating with a lead line affixed to the bow. A temporary bi-level push bar was mounted to the stern to identify best height for pushing. The field test indicated that both bar heights were useful allowing adaptable leverage for pushing on dunes and in water. An optimal table height and position was identified to ensure that several workers could comfortably work around the table at the same time. Finally the pump cradle was evaluated at multiple heights to ensure that the height did not exceed the distance from which the pump could draw water and to ensure stability on the craft. Overall the vehicle was found to function very well. Weaknesses were identified to be a limited ability to turn, which was anticipated and some difficulty in pushing across mud and up dune inclines. Though somewhat challenging, the vehicle was still maneuvered by a single individual.

4. Prototype Modification. Modification and redesign occurred as a result to the field/task testing. This process involved physically altering some of the key components to accommodate structural integrity and additional functions/flexibility. An interlocking table design was developed so that two table surfaces would be on the vessel, one could be removed and set up on standard plastic saw horses while the second could remain attached on the vessel platform. The stationary table was mounted on a frame structure that was latched to the vehicle with rubber clip mounts, enabling complete frame removal for transit of large loads (ie. racks and large numbers of oysters/grow out bags). Optimal positions for the wheel axles were determined, the temporary mounting frame was removed, and axle brackets were mounted directly to the Jon Boat. Once the key components were identified, storage cubbies were equipped to maximize space with in the vessel. Hose mounts were welded to the pump-carrying frame to add capacity and ease transport of the pump and accessories on and off the vessel. Final fabrication was completed and the vehicle was delivered to the farm on July 23, 2015 (Figure 5).

5. Outreach. The vehicle was demonstrated to several visiting oyster farmers on an ongoing basis. A formal outreach presentation and demonstration was conducted on December 21, 2015. The presentation was held at the Rutgers Cape Shore Laboratory as part of the University’s Shellfish Growers’ Forum program. Additional web and print materials are in development.

• Figure 2
• Figure 4
• Figure 3
• Figure 1

Impacts and Contributions/Outcomes

An amphibious farm vehicle was designed and constructed for working intertidal shellfish farms. The vehicle has been utilized on the Sweet Amalia Oyster Farm located in the lower Delaware Bay, NJ. The vehicle has proven to increase production efficiencies on the farm, enhancing the accomplishment of all farm tasks including transit of materials and gear, providing work platforms for sorting oysters, and on-farm power washing. An important benefit of the vehicle is that it enables ingress and egress to the farm on falling and rising tides, extending the actual work period during the tidal cycle.

The vehicle has been demonstrated to local shellfish farmers, scientist and extension professionals.

• Figure 5

Collaborators: