Last week we began launching new prototype rafts for shellfish aquaculture which we hope will lead to increasing the productivity and sustainability of the shellfish industry. Older raft designs in use are mostly constructed from wood and coated Styrofoam (like many older docks). These can degrade with age and in extreme weather conditions may be at risk up resulting in losses of crops and creation of marine debris. In 2006 unusually large storms resulted in large losses of rafts and we have been working with the shellfish industry since to develop new designs. With assistance of the Aquaculture Innovation and Market Access Program we engaged Dynamic Systems Analysis Ltd. in Victoria to help develop new designs through advanced engineering methods and virtual prototyping.
The video below is a virtual simulation of three of our new prototypes in an extreme weather environment.
This technique has allowed us to “virtually” model and test a variety of construction materials and over 30 designs before settling on the current prototypes.
Follow the link below for a photoessay on the actual prototypes getting built. We are now going to test the variations of our prototypes at the Deep Bay Field Station research farm and then later release the plans to industry.
Our design is based on “off-the shelf” rotomolded dock floats, and galvanized steel ‘T’ and ‘I’ beams with the idea that they can be bolted together on site (think IKEA 🙂 ) . here we are bolting the connecting assemblies to the floats.
Key in our design is that there are structural beams (steel) and interstitial beams (we are testing 2 sizes of standard wood and plastic wood). The idea here, is that the interstitial beams provide a “weak point” and in the case of extreme weather conditions leading to failure these will break osing only a portion of the crop but not the entire raft. Most traditional rafts use structural beams to deploy product and when they start to fail, the entire structure loses integrity leading to catastrophic failure. This design also allows for a raft to repaired over its lifetime, another challenge with older rafts.
Conducting some “impromptu testing” before launch. This version of the raft has 5 structural beams and 2×4 wood interstitial beams. Further wood and steel rafts will be 2×6 beams which we are happier with.
The very first raft getting launched with little ceremony. It was handy having all the machinery on site to help with this task. The raft goes together fast enough that they could be built at low tide and floated on a rising tide.
Site crew enjoyed watching Brian being set adrift to float out in the bay until the Chetlo could be brought around to tow the raft to the farm.
Details of the plastic wood version. We really like the look of the structural plastic 2×4’s and how they fit snugly within the I-beams. These will add greatly to the lifetime of the raft materials but also add to cost which we have been trying to minimize during design.
Our second launch, high enough to get an underside view, bouncing the rafts up and down and tugging between the machines as they were carried to the shore gave us an opportunity to do some fairly serious and unplanned structural testing. The rafts showed a high degree of flexibility which we liked and looked great.
Version 2 floating and tied off to the Chetlo after a very windy drift down the bay – note the shovel as paddle…. We are hoping that this version will have less “visual profile” on the water as well and contribute to social sustainability.
We will be testing the designs in real world situations, making modifications to the plans, getting industry feedback, developing business case and then releasing the final plans under open license to industry. Contact us if you would like to see the rafts on our farm.