The synthesis and calculation of beampatterns for cylindrical arrays can be greatly simplified by factoring the problem into a line array of identical hoops under very mild restrictions on array geometry. For example, elements may be directive and hoops may be nonuniformly spaced. This result has particular significance for large arrays of many elements. The design approach consists of using one of several techniques to design a good hoop beampattern combined with a standard technique for designing a good line array beampattern. The technique is illustrated by application to an array of more than 2000 directional elements where other design techniques are impractical and straightforward computation of beampatterns is several orders of magnitude more time consuming. [Work supported by ONR.]