An evaluation of the tilt angle variation observed recently when unrubbed polyvinylic alcohol is deposited on obliquely evaporated SiO layers is presented. The method of calculation supposes that the variation of the tilt angle is due to the modification of the initial topography of SiO during the coverage process with the polymeric film. The Laplace equation was obtained by minimizing the elastic energy of the system in the uniconstant approximation and was analytically solved. The found variation of the tilt angle is in good agreement with the experimentally observed one.