main propulsion unit

基本解釋

Causes for damage of main parts of Z---type marine propulsion unit are introduced in this pa- per. it also gives the making of plan. design principle and repair methods.
介紹船用Z型推進裝置主要零備件的損壞原因以及在進行零備件國產(chǎn)化過程中的方案制定、設(shè)計原則和修理方法。
Once you are on the surface, the main unit for propulsion are your arms, so it is very important that your draw the right pattern underwater, and that is a hourglass pattern.
身體浮到水面后，最大的推進力量就來自手臂。因此正確的水下劃水路線非常重要，也就是沙漏狀劃水。