Sub-micrometer-size devices are strong candidates for future use as probes of quantum fluids. They can be reproducibly manufactured with resonant frequencies in the range of kilohertz to gigahertz and have low power consumption and dissipation. Here, we present doubly clamped aluminum nanobeams of lengths from 15 $\mu$m up to 100$\mu$m operated in vacuum and the hydrodynamic regime of liquid $^4$He. We observe that in vacuum devices are described well using a simple harmonic motion with a constant Duffing coefficient and in helium quantitatively model their behavior with the conventional hydrodynamic model.