I know nothing about storing beekeeping equipment, but I can see that your idea of four poles and a tarp to protect it all will not work. As soon as it rains, the water will collect in the tarp like a heavy lake - I know from trying to protect our boat with a tarp. The only way it would work would be to construct a lean-to, or free standing roofed structure. It need not be waterproof as you could then stretch your tarp over the top, as long as it is well held down against high winds. It can be open sided too for ventilation.