of the tubes 11 to 16 can be polished to a high gloss as well the individual tubes 11 to 16 are rotatably supported they may be supported for example by rollers not shown supported in ball bearings and coated with rubber said rollers running in a deepening formed in the tubes furthermore provision is made for driving means not shown in detail which put the individual tubes 11 to 16 into rotation the driving means are accommodated in the hull 2 and can drive the individual tubes 11 to 16 for example via teflon toothed gears not shown in detail which gears mate with bent teflon toothed racks the latter being mounted on the tubes along their circumference preferably electric motors are selected as driving means the driving means drive the individual tubes 11 to 16 independently of one another and are controlled in this connection by controlling devices not shown in detail in a way such that two adjacent tubes contrarotate in each case relative to one another and that the angle of rotation speed of the tubes 11 to 16 decreases with the increase in diameter thus the innermost tube 11 has the highest number of revolutions whereas the outermost tube 16 is driven with the lowest number of revolutions furthermore provision is made for oil stripping drains resting on both sides against the wall of each tube for reasons of clarity only the inner and outer oil stripping drains associated with the outermost tube 16 are shown denoted by the reference numerals 18 and 19 with the exemplified embodiment.