The stress and deformation state of various shapes of bended shells caused by different forces was researched, and their critical areas located. Curved plywood seat shells of different shapes were made in the same model. According to the requirements of European standard methods the following tests were made: the test of static load, durability test, test with material failure, test with material withdrawal, and the test of shear and bending strength of plywood. The results show that the shells have a high safety factor, and are in the range of European standard requirements. By additional result adjustments it was possible to compare shells, and see differences in quality among them. Taking the results into account we could make the production of the shells more efficient, using less material: from the aspect of constructor and designer the shells could have shape that stands out and still is in the range of standard requirements.