第四篇

Passage 04

The axial thrust of the propeller is the force working in a fore and aft direction. 

This force causes the ship to move ahead through the water or to go astern. 

Because of her shape，a ship will move ahead through the water more easily than going astern.

The transverse thrust is the sideways force of the propeller as it rotates. 

The transverse effect of the propeller blades at the top near the surface of the water is not strong enough to counteract the opposite effect of the lower blades. 

For right-handed propellers this cants the ship's stern to starboard and her bow to port，when the ship is going ahead. 

The effect is small and can be corrected by the rudder. 

When the engines are put astern，the effect is the opposite and the stern cants to port. 

This effect is stronger and cannot easily be corrected. Vessels with left-handed propellers behave in the opposite way.

螺旋桨轴向推力是工作在首尾方向的力。这种力量使船在水中前进或后退。因为她的线形，船舶在水中向前移动比向后更容易。 

横向推力是当其旋转的螺旋桨横向力。螺旋桨叶片，在靠近水面上的横向效应不够强去抵消较低的叶片相反的效果。对于右旋螺旋桨这个转向是船尾向右船首向左，当船向前进时。这个影响很小，可以由舵纠正。当主机倒车是，效果是相反的船尾向左转向，这种效果是更强大而不可轻易予以纠正。左旋螺旋桨船舶表现相反的方式。