Capturing droplets from a stream with a fibrous material is a well-known process, from coalescence filters to fog harvesting. The collection efficiency strongly depends on the drop distribution on the fibers, thus on their wetting properties.

Empirical data reveals a broad variety of hull shapes among the different ship categories. We present a minimal theoretical approach to address the problem of ship hull optimisation. We show that optimal hull aspect ratios result -at given load and propulsive power -from a subtle balance between wave drag, pressure drag and skin friction. Slender hulls are more favourable in terms of wave drag and pressure drag, while bulky hulls have a smaller wetted surface for a given immersed volume, by that reducing skin friction. We confront our theoretical results to real data and discuss discrepancies in the light of hull designer constraints, such as stability or manoeuvrability.have a much smaller immersed volume [4]. Here we wonder how all these shapes compare to the optimal aspect ratios in terms of drag.