This paper presents the results of experimental modal analysis of a system of two very slender cantilever beams connected by a rigid hub. The effect of gravity is examined together with the influence of an attached cable. Natural frequencies and mode shapes are determined for a number of configurations. The practical application of these types of systems is as the structural support frame for solar sails, in which the current set of results represents an intermediate step in going from the behavior of an isolated solar sail boom towards the four boom configuration favored by many current designs. Copyright © 2008 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.