Abstract: A turbine head comprising: a rotatable member; a plurality of laminar blades each including a surface, the blades being rotatably mounted to the rotatable member such that the blades can each rotate relative to the rotatable member from a first position to a second position, the angle between the first and second positions being less than 180 degrees; wherein each blade is rotatably mounted to the rotatable member about an axis that is near the centre of the blade such that, if a force is applied to the blade in a direction that is perpendicular to the surface, the difference in force between the force exerted on a portion of the surface on one side of the axis and the force exerted on a portion of the surface extending to the other side of the axis is sufficient to cause the blade to rotate from the first position towards the second position.