At the time the ship is being built, the ship is supported by supports such as keel blocks. If the ship will be launched, then the ship will be installed sliding ways that will glide over the launching ways.
The distance between the ground and the bottom of the ship must be sufficient to place the sliding ways and other launch equipment in place. Keel distance above the ground is about one and a half meters so that there is enough space to install the launching ways and launch equipment.
 |
| Ship Ready for Launching |
1. End launching
2. Side launching
In general, ships are launched by end launching, side launching are only used for certain conditions, for example on a river or canal.
For the end launching, the stern of the ship directed to the water so that the stern will be exposed to water first, this is to avoid the stern of the ship to hit the runway, and can reduce the speed of launch when the stern of the ship touches the water.
To reduce friction between sliding ways and launching ways, a lubricant consisting of a mixture of lime, soap, grease and paraffin is used.
The amount of resistance caused by this friction depends on:
1. Various kinds of lubricants
2. The average pressure of the sliding ways against the launching ways
3. Air temperature at launch
4. Launch speed
 |
| Launching Ways |
CALCULATION OF SHIP LAUNCHING
The first step in calculating a ship launching is calculated the weight and center of gravity of the ship when it is launched. Because the ship was launched in unfinished conditions, the weight of the ship when launched is smaller than the weight of the ship after completion.
For this reason, the approach formula is used:
P = C (Pb + Pm)
P = Weight of ship when launched
Pb = Ship Weight
Pm = Ship Machinery Equipment Weight
C = 0.85 for cargo ships, and 0.65 for passenger ships.
Read Another Article : Inclining Experiment
But the most appropriate calculation is the calculation of post by post, so that besides calculating the weight of the ship also calculates the longitudinal center of gravity and vertically center of gravity. The calculation of this weight is very important, because it is related to the calculation of tipping, stern lift, and trim of the ship when launching the ship.
 |
| Force at Ship Launching |
From the picture shows that
W Sin a> f. W cos a
Sin a / cos a> f
Tg a> f
So for small angles, where the value of sin a approaches zero (0) and the value of cos approaches 1, then the equation can be written a> f.
This means that to make ships move on their weight, the angle of the launch pad must be greater than the coefficient of friction of the lubricant used. If these conditions are unreachable, then to move the ship, it requires external impulse.
DANGER WHEN LAUNCHING OF THE SHIP
There are several critical conditions that need to be anticipated at the launch of the ship. The first danger is Tipping. Tipping is a condition when a hull has partially in the water and a partially of the hull has been released from the launch pad, but the moment of upward force of water is smaller than the moment of weight of the ship at launch. This can make the ship will continue to enter the water (can't float) or it can also happen the ship will break. To avoid this tipping, the steps taken are to extend the launch pad (under water), or by waiting until the tide, so that the water level can meet the requirements.
Video Ship Launching
The second danger from ship launching is dropping. Dropping is the condition when the bow of the ship hits the launch pad, after all the hulls have off the launch pad (launching ways). This happens when the ship has passed the launching ways but the water depth at the end of the runway is smaller than the height of the ship required to free floating.
To avoid this dropping, the steps taken are to extend the launch pad (under water), or by waiting until the tide, so that the water level can meet the requirements.
Video Ship Launching
No comments:
Post a Comment