Page 219 - statbility for masters and mates

Bilging and permeability 207
NewKB 1 Newdraft d2 22
New BM

NewKB New KM As before, KG
2:89m B2=12d2
24 24 12 5:77
8:32m 2:89m
11:21 m 11:20 m
Ans. New GM 0:01 m
This is ve but dangerously low in value!!
Permeability k
Permeability is the amount of water that can enter a compartment or tank after it has been bilged. When an empty compartment is bilged, the whole of the bouyancy provided by that compartment is lost. Typical values for permeability m are as follows:
Empty compartment
Engine room
Grain ®lled cargo hold
Coal ®lled compartment
Filled water ballast tank (when ship is in salt water)
m 100%
m 80% to 85% m 60% to 65% m 36% approx m 0%
Consequently, the higher the value of the permeability for a bilged compartment, the greater will be a ship's loss of bouyancy when the ship is bilged.
The permeability of a compartment can be found from the formula:
m Permeability Broken Stowage 100 per cent Stowage Factor
The broken stowage to be used in this formula is the broken stowage per tonne of stow.
When a bilged compartment contains cargo, the formula for ®nding the increase in draft must be amended to allow for the permeability. If `m' represents the permeability, expressed as a fraction, then the volume of lost buoyancy will be `mn' and the area of the intact waterplane will be `A mn' square metres. The formula then reads:
x mn A ma
Example 3
A box-shaped vessel is 64 metres long and is ¯oating on an even keel at 3