These are the 3-D printable kayak paddles from : Dennis J. Byard, Aubrey L. Woern, Robert B. Oakley, Matthew J. Fiedler, Samantha L. Snabes, and Joshua M. Pearce. Green Fab Lab Applications of Large-Area Waste Polymer-based Additive Manufacturing. Additive Manufacturing 27, (2019), pp. 515-525. https://doi.org/10.1016/j.addma.2019.03.006 The article shows how printing from waste plastic can be economic - using open source designs like this one made in Blender. Open access to the article is: [https://www.academia.edu/38728877/Fab_Lab_Applications_of_Large-Area_Waste_Polymer-based_Additive_Manufacturing](https://www.academia.edu/38728877/Fab_Lab_Applications_of_Large-Area_Waste_Polymer-based_Additive_Manufacturing) Project home :https://www.appropedia.org/Green_Fab_Lab_Applications_of_Large-Area_Waste_Polymer-based_Additive_Manufacturing/Green_Fab_Lab_Applications_of_Large-Area_Waste_Polymer-based_Additive_Manufacturing