May ‘22 - The KelpCrofters Transport Barge

Here at KelpCrofters, there is another recycled construction project to report.  Following the completion of the yurt, we have just managed to squeeze in another recycled feed pipe / hamster wheel project before our harvesting season begins.

The least optimised area of our harvesting operation last year was the transportation of the kelp, collected into large net bags, to shore, 2 miles from our farm.  We always have had the idea that keeping the kelp in the sea, post harvest, as much as possible maximises its freshness. As such, we had planned to haul the bags full of kelp into a semi-submerged barge to make the tow more efficient, but had run out of time to create the barge.  This proved troublesome; the net bags had lots of drag and were slow and difficult to tow.   

So in March this year we started chopping up our supply of recycled salmon farm feed pipe and hamster wheels, and spent a couple of weeks, fortunately with good weather, in the neighbouring field, turning the vague barge design idea into reality.

The barge is 13.5 metres long, 3.2 metres wide and 1.8 metres deep.  It uses around 780 linear metres of 90mm feed pipe (floor and walls) and one and a half hamster wheels (frame).  The plastic pipe is neutrally buoyant, but the larger diameter pipe of the hamster wheel comes filled with a polystyrene floatation core and this forms a strongly buoyant upper frame at the gunwale, giving the structure good stability despite resting almost completely submerged.  The transom (stern) is open, and will allow the hauling of six kelp-filled net bags into the structure, each with around 600kg of kelp, so a total haul capacity of around 3.5 tons.

It was an interesting engineering project, like grown up meccano or lego - simple but BIG!  As with the yurt, the structure is almost exclusively recycled other than the fixings.  Launch day, 21st April 2022, involved a bit of crossed fingers; we really didn’t know how she would float.  But our steadfast workboat Ailsa hauled her easily down the slope and into the sea and she gently flooded up to the gunwales as intended.  She tends to rise, particularly at the stern as she is towed, which is fine, and this might change when she is filled with bags.  Ailsa towed the barge comfortably the few miles to the farm, where the barge now waits for harvesting to begin.  Busy times continue!