*8 NICHOLLS'S SEAMANSHIP AND NAUTICAL KNOWLEDGE
Questions.
1. Name the different fibres used m making rope and that which is
most commonly used in merchant ships
2. A new coil of wire is to be uncoiled, how would you go about it?
3. What precautions should be taken with working wire ropes to
ensure for them as long life as possible?
4. Write down an equation to express the approximate breaking
strength of wire rope.
5. What would you consider a safe working load for a 3-inch wire
cargo fall?
6. How is chain measured? Distinguish between the breaking
strength, the proof load and the safe working load of chain.
7. What do you understand by a purchase being rove to
"advantage" and to "disadvantage"?
8. What is the theoretical^power gained by using a gun tackle, a
luff tackle and a double purchase? If a load of 2 tons is suspended
from each purchase what will be the tension on the hauling part o*
each?
9. Describe a form of differential pulley purchase.
10. A weight of 30 tons is to be lifted with a three-fold purchase,
rove to advantage, with lead block at the derrick end and another
at the masthead. Required the tension on the hauling part and a
suitable size of steel flexible wire. (Use $• breaking strength as a safe by
factor.)
Am. Tension is 7J tons. Use a 4f-inch wire.
11. A weight of 25 tons is to be lifted with a two-fold purchase
rove to advantage, and a leading block at the derrick end and another
at the masthead. Required the size of wire to use.
Ans. Tension on hauling part 7J tons. Use 4f-inch wire.
12. A weight of 10 tons is to be lifted with a two-fold purchase,
rove to disadvantage, and one lead block. Required the size of wire.
Ans. Tension on hauling part 3f tons Use a 3J-inch wire.