Shortness parameters of families of regular planar graphs with two or three types of face

This paper is concerned with non-Hamiltonian planar graphs. It is shown that the class of 3-connected cubic planar graphs whose faces are all pentagons or 10-gons contains non-Hamiltonian members and that the shortness coefficient of this class of graphs is less than unity. For several classes of 3-connected regular planar graphs, of valency 4 or 5, it is shown that the shortness exponent is less than unity.