I try to compare relative pressure and global pressure. The pressure of water on the cone give the weight of the water. I put a part of helicoid in water, this helicoid can only turn. I chose the slopes and thickness of the helicoid like there is no torque on it, p2>p1 but s1>s2, I think it's possible to have C1=C2 or p1*s1*r1=p2*s2*r2. If there is no torque on the helicoid I can turn it without need energy. Like this I have suppress part of surface of the cone, so a part of its weight. Sure like I put part of helicoid in water I had weight, the weight is give like a local differential pressure, it don't depend of the position (d in drawing). The surface canceled, in the contrary, depend of the position at bottom we suppress more weight than at top. So if it's possible to cancel the torque on the helicoid, how the weight added in the cone is equal at the weight suppress to the cone ? I think this is the same study with other pressure created by electrostatic or magnet.