Comparison of Array Types
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Hello fellow farmers,
This past season we did a comparison of three different array types: single-line, 5-line, and catenary. Based on our experience, we put together this list of pros and cons. Please feel free to contact us with any questions.
Skye Steritz (Noble Ocean Farms)
Skye@nobleoceanfarms.com
WSARE Array Comparison
@skye_steritz Thanks for this analysis, Skye. Can you elaborate a bit on line spacing on the 5 line and catenary arrays? Two years ago we used a 5-line array with 4x4 and 2x4 lumber instead of metal spacer bars. It worked fine (other aspects were somewhat problematic, but not wood spacer bars).
@rand_hagenstein Hi Rand! That's awesome that you were able to use lumber for your spreader bars on the 5-line array -- nice to have a cheaper option. In regards to the spacing, our 5-line spreader bars are 10 feet long, so those lines are spaced 2 feet apart on the 5-line array. Cliff Goudey designed and built our catenary array. It has a width of 75 feet and includes 25 long grow lines. Those grow lines are approximately 3 feet apart.
@rand_hagenstein Rand, wood is an economical material in this application once you figure a way to overcome its buoyancy. It's good in compression along the grain and resists bending as long as knots are small or away from the edges.
We use aluminum in order to have a consistent product that is not weakened by holes or material variability. The 10-foot long ones Skye spoke of support five lines, 2.5' apart. Three bridles of precise length minimize the horizontal bending loads.
@rand_hagenstein Hi Rand! That's awesome that you were able to use lumber for your spreader bars on the 5-line array -- nice to have a cheaper option. In regards to the spacing, our 5-line spreader bars are 10 feet long, so those lines are spaced 2 feet apart on the 5-line array. Cliff Goudey designed and built our catenary array. It has a width of 75 feet and includes 25 long grow lines. Those grow lines are approximately 3 feet apart.
Hi @skye_steritz,
Thanks for the information, it’s helpful for us to know your costs and setup structures. We are working in Australia with Golden Kelp (Ecklonia radiata) in high-energy offshore conditions, 1km out to sea. Due to the (extremely) rough waters in Disaster Bay (yes, the name says it all), with peak wave heights in excess of 12m (36ft), we have found the only option is single backbones with low buoyancy, seeded dropper lines, and screw anchors. We found there was too much drag and subsequent counteracting forces with interconnected systems like spreader bars and catenary. Golden kelp is quite small (max about 2m), has a low drag coefficient, and is relatively neutral buoyant. During these massive storm events we don’t lose any kelp (regardless of kelp age) with this rig design, thank goodness. The more storm events we go through, the better we feel about it.
When you have storm events, do you lose rigs or shed kelp? Would be interested to know, thanks.
Wishing all kelp farmers every success.
Your friends in Australia, Christopher, Auskelp, www.auskelp.net
Hi @christopher_ride,
Thanks for reaching out! In the past, we have had some issues on our farm due to storms and ice. Occasionally some gear has moved during storms, and some kelp has been lost. In our experience, these issues are the worst with horizontal single-line arrays and issues seem to be less common with the catenary array because it's really well-tensioned. It sounds like we are in a much calmer area though.
Keep up the great work with golden kelp! It's awesome to know we have friends kelp farming in Australia.
Skye
Hi @christopher_ride,
Thanks for reaching out! In the past, we have had some issues on our farm due to storms and ice. Occasionally some gear has moved during storms, and some kelp has been lost. In our experience, these issues are the worst with horizontal single-line arrays and issues seem to be less common with the catenary array because it's really well-tensioned. It sounds like we are in a much calmer area though.
Keep up the great work with golden kelp! It's awesome to know we have friends kelp farming in Australia.
Skye
@rand_hagenstein Rand, wood is an economical material in this application once you figure a way to overcome its buoyancy. It's good in compression along the grain and resists bending as long as knots are small or away from the edges.
We use aluminum in order to have a consistent product that is not weakened by holes or material variability. The 10-foot long ones Skye spoke of support five lines, 2.5' apart. Three bridles of precise length minimize the horizontal bending loads.