The article considers the problem of changing vessel stability characteristics due to the optimization of the hull design and the increase in mass due to the choice of polylactide as a hull material for manufacturing by additive technologies. The stability characteristics of a small vessel hull of the "Nerl" kayak type was calculated in two approximations: in the first - for a standard prototype vessel made of fiberglass weighing 35 kg, in the second - for a project under development for additive manufacturing using polylactide weighing 70 kg. Stability was calculated according to the requirements of the Russian River Register using the FreeShip+ and Hydromax software. It was found that not all stability characteristics of the prototype vessel (maximum restoring moment arm) meet the requirements of this register, while for the projected vessel of additive manufacturing all requirements are met. The results of the study may be useful to shipbuilding enterprises planning to organize manufacturing products by 3D printing.