Flipflopi is an East African organisation with a mission to end single use plastic, driving this agenda using circular economy principles applied to the design and build of fully recycled plastic sailing dhows from their boatyard in Lamu Kenya. Flipflopi has achieved measurable global impact by showcasing the world’s first ocean going recycled sailing boat, Ndogo, a 9 metre long, lateen rigged dhow which has sailed the East African coastline and across Lake Victoria. Flipflopi is now aiming to build a much larger ocean-going dhow, named Kubwa, which presents further technical challenges from a marine design perspective. To meet these challenges. Flipflopi are utilising a combination of generational heritage boatbuilding expertise in Lamu; specific design experience from building and sailing Ndogo; technological progress driven by other recycled plastic projects; and more formalised naval architecture and engineering design approaches. This paper introduces the context within which Flipflopi is centred, the links to circular economy design principles and the specific design challenges from working with recycled plastic as a boatbuilding material.