Progress report for FNE22-017
Project Information
This project aims to test whether 3D printed materials are able to withstand the harshness of the marine environment and the rigors of farming. Though the end goal is to enable the fabrication of prototypes/new designs, this project will test a standard piece of equipment to separate the suitability of materials from the strengths/weaknesses of new designs
Objective 1) Design/replicate oyster bags in four materials and 2 mesh sizes at Haystack Mountain School of Crafts Fabrication Lab, and at Hurricane Island Center for Science and Leadership (facilities with different fabrication capabilities)
Objective 2) Deploy bags on two field test sites- Winnegance Oyster Farm in West Bath, ME -a commercial oyster farm, and Hurricane island school- an experimental/demonstration farm that is part of a sustainability-focused non-profit and grow oysters for one season, with monthly inspection and photographs of wear, damage, and fouling organisms
Objective 3) Quantify wear through scope photography at end of season
Objective 4) Share results with farmers and educators in the region- with the hope that our materials test will aid innovative farmers as they create new varieties of aquaculture equipment.
Despite the variety of seafarms farms in the Northeast, there is a dearth of diversity in oyster farming equipment. Farms in the region vary in size from millions of oysters to tiny hobby farms, they are situated in the open ocean, enclosed salt ponds and everywhere in between, tides in the region range from 3 feet to over 20 feet. Farmers work out of enormous barges, the smallest of skiffs, or just hip waders.
Even with this wide spectrum of farms, farmers are limited to variations of just a few types of regionally available commercial equipment (slight variations of cages and bags), produced by a small handful of manufacturers. The slightly larger menu offered by international sellers usually requires ordering equipment by the shipping container, sight unseen, with unsure delivery dates (even before the current supply chain disruptions).
There is clearly a need for a means to design and test new oyster farming equipment that is adapted to local conditions- to find gear that is less physically demanding to work with, requires less labor and energy to keep clean, and promotes faster growth and/or a more desirable product for consumers.
3D Printing could allow farmers to design and test equipment that is better suited to their local environment, growing conditions, farm infrastructure, work style, and physical limitations.
The first step in this process is testing the materials that can be used by commercially available 3D printers and CNC routers. In this experiment, we have replicated a ubiquitous piece of oyster farming equipment (rigid mesh grow-out bags) to see how they hold up to the rigors of farming over the course of a season. By replicating oyster bags, we hope to decouple the effects of material viability from the potential fragility of new designs (with the intent of narrowing down materials suitable for testing of new designs in the future).
Cooperators
- - Technical Advisor (Researcher)
- (Educator and Researcher)
Research
Design/fabrication:
The rigid-mesh oyster growout bags produced in this experiment were contract-built by experienced 3D fabricators: James Rutter of the Fabrication Lab at the Haystack Mountain School of Craft, and John Van Dis, of the Hurricane Island Center for Science and Leadership. Fabrication methods attempted during initial material trials included using small-format 3d printers, plastic welding pens, a computerized laser cutter, and a large-bed CNC router.
Originally, we sought to test four types of materials- three extruded: ABS (Acrylonitrile butadiene styrene ), PLA flex (flexible variant biopolymer polylactic acid), and Nylon, and one CNC routed: UHMW sheeting (Ultra High Molecular Weight polyethylene). After bag design, initial materials tests, and printing calculations informed by these tests, it became clear that the extruded (printed) plastics would not be feasible in our timeframe and budget. Our focus was shifted to materials that could be cut with a CNC router or laser cutter. Supply chain disruptions eliminated our initial choice of sheeting-UHMW. In place of the initial materials, we chose three types of plastic sheeting; high density polyethylene (HDPE), very-high molecular weight polyethylene (VHMW), and polyethylene terephthalate glycol (PETG) for testing. These materials were picked for their safe use in food applications, durability in outdoor use, compatibility with our tools, and availability during a time of supply disruptions.
- HDPE is widely used in aquaculture applications- including the rigid-mesh oyster bags we replicated. It was chosen to test the durability of our construction techniques with a proven material.
- VHMW is similar to HDPE, but is comprised of longer hydrocarbon chains. it is denser, more rigid, and has a smoother surface that we hoped would inhibit invertebrate fouling. We chose a white variant (some fouling species preferentially adhere to darker surfaces).
- PETG was chosen for its ubiquity, easy recyclability (it is the material that soda bottles are made from), and the observed durability of discarded PETG in marine environments.
Field Trial:
In June, the first 3D printed bags were deployed at both farms. Bags at Winnegance were situated in floating oyster cages, while bags at Hurricane Island’s experimental farm were outfitted with floats (covering the two most common types of oyster farming in the northeast -floating cage farms and floating bag farms). These bags handled twice monthly from June to November- once for maintenance handling (air-drying, culling, thinning, manual-cleaning, etc.) and a second handling for inspection, measurements, and photographic documentation. Measurements will resume in April 2023 for this project's extension.
Monthly measurements were designed to categorize wear-and-tear by damage-type and by damage-location on each bag, in order to inform future prototype builders of specific weaknesses of each material.
Damage categories include:
• Chaffing/erosion (identifies friction damage)
• Cracking (identifies UV or chemical damage)
• Stretching/tearing (identifies damage from weight/strain)
• Discoloration (identifies UV or chemical damage-depending on location)
Bags in cages at Winnegance will maintain the same orientation throughout the trial (sun-facing-bags/shaded-bags) to further test the effects of light-damage.
Throughout the first season of this trial, we monitored several areas of potential areas of strain/damage on bags
• Top panel (potential sun damage)
• Bottom panel (friction in caged bags)
• Closure (repeated stress of handling- opening/closing)
• Folds (stress of initial bending/holding shape)
• Corners (stress of initial bending, contact with floating-cage wire)
• Float attachment points (weight stress- Hurricane floating bags only)
Fouling species were also be measured each month using the Braun Blanquet percent-cover method. Certain marine organisms (algae, invertebrates) show strong affinity for different substrates. Specific plastics are used (for instance) to attract shellfish spat, or to encourage kelp settlement. When testing new materials, it is important to understand which organisms are attracted to each material in order to guide appropriate future uses. It is our intent that fouling measurements would be useful to help future builders avoid excessive fouling on grow-out equipment, or to build more efficient spat-collectors.
End of project wear-damage observations will be made using scope photography- focusing on the same areas as the field measurements. If plastic has eroded, we will measure the amount it has degraded.
Production delays (due to material availability, need to switch contractors, and high demand for fabrication equipment at partner institutions) necessitated a project extension into 2023 for adequate field testing of our experimental oyster bags.
Material and tool suitability
The common small scale 3D printers originally envisioned for this project were not suitable even for small numbers of prototypes. The plastic filaments determined by project partners to be suitable for marine use required higher operating temperatures and printed much slower than more commonly used materials. After initial testing on available equipment, nylon filament was calculated to take 60 hours per bag with regular intervention required by the operator. Fabrication using this method would require far more labor than was budgeted for in our proposal and would tie up equipment and resources at partner public secondary schools. It would not be cost effective even for small numbers of prototypes. With this realization we pivoted to exclusively using CNC routing with sheet plastics at Haystack Mountain School of Craft's specialized fabrication lab (FabLab). This additional workload had to be fit in around existing programming at the facility, which set back our field trial. Our extension into the 2023 field season will allow us to collect a full dataset and has the added benefit of testing the effects of overwintering.
Field Trials:
Both farms received their first prototypes in June of 2022. Prototypes were finished in several waves, with the last bags deployed in early October. During this abbreviated field trial, a single PETG bag failed during a major storm at Hurricane Island. Full wear/damage and fouling data was recorded monthly and will be reported at the conclusion of the extended field trial in 2023.
Qualitatively, the experimental gear had some immediate benefits. The flat, drilled surfaces of CNC routed bags (versus the woven texture found on commercial gear) prevented oysters from clumping and from getting stuck in bag corners. Flat surfaces were also far easier to effectively clean with a paint-scraper compared to woven-texture commercial bags.
VHMW bags were exceptionally rigid for their thickness, making them easier to handle when holding a heavy load. The rigidity of this material could allow thinner sheets to be used, which could potentially reduce both costs and fabrication time.
Clear PETG sheeting made it easy to observe oysters in bags without having to handle them (though this benefit may diminish as bags discolor over time).
Quantitative analysis and a qualitative narrative of the experimental gear will be included in the final report after adequate field testing.
Education & Outreach Activities and Participation Summary
Participation Summary:
On May 24th, 2022 an overview of the project was presented during a webinar hosted by the Herring Gut Coastal Science Center to 35 participants. Backgrounds of attendees varied from farmers, prospective farmers, agricultural service providers, marine educators, to the general public.
A project overview and field updates were shared with 11 members of the New Meadows River Shellfish Co-op. Thee members visited the field site over the course of the season.
The Hurricane Island shared their work on this project with their attendees of their educational programming throughout 2022. Farm visits will continue in 2023
Outreach will expand in 2023 as more data is available - with project results being shared widely on social media.