Experimental study of the effect of drift angle on a ship-like foil with varying aspect ratio and bottom edge shape

A ship-like foil geometry with different aspect ratios and bottom edge shapes are tested experimentally with several drift angles (0-10°), and two Froude numbers (0.1 and 0.2). The geometry is a modified version of the foil Eppler E836 that is extruded in the span direction to make it a 3D geometry. The aspect ratios are 0.1, 0.2 and 0.3. Two different bottom edge shapes are tested: a perfectly sharp bottom edge and a rounded bottom edge. Lift, drag and yaw moment is measured. The result is presented both as raw data and data fitted polynomial functions. The experimental results are compared to simplified models for lifting surfaces, along with some discussion regarding the physics of a drift-induced forces. The simplified models do not fit the experimental data very well, but the comparison is used to discuss the importance of different physical effects. The result from the experiments show that both the aspect ratio and the shape of the bottom edge is very important. Froude number effects on lift and lift-induced drag are seen to be very small, for the two Froude numbers tested in this experiment, while the yaw moment and center of pressure is affected.