Grade 11 – Nautical Science

October 23, 2020

Blocks and tackles

In order to lift heavier weights, a system of blocks and tackles was gradually introduced. Originally they were made out of wood, but as the loads got heavier and they had to withstand harder work they were made out of steel. It is very rare these days to find a […]
October 23, 2020

Purchases and tackles

Purchase. A purchase is a combination of blocks or pulleys rove with a rope, wire or chain. Tackle. A tackle is a purchase consisting of a rope rove and through two or more blocks, in such a way that any pull applied to the hauling part, is increased by an […]
October 23, 2020

Mechanical advantage

All of the above tackles/purchases are designed to increase the power utilised to the effect achieved. Because of friction between the ropes and sheaves, the actual (theoretical) weight lifted can be roughly calculated as being: Weight + (1/10 x weight) for each sheave. The mechanical advantage gained can be found […]
October 25, 2020

International regulations for the prevention of collision at sea (1972): Part A – General

RULE 1 – Application The abovementioned rules shall apply to all vessels upon the high seas and in all waterways connected therewith, navigable by seagoing vessels. Appropriate authorities may make special rules for harbours, roadsteads, rivers, lakes or inland waterways connected with the high seas and navigable by seagoing vessels, […]