It is very important to know the current ship’s draft before navigation.
Here are the formulas for getting a ship’s draft:
Formula for getting Mean Draft:
MD = FD + AD / 2
Where:
MD for Mean Draft
FD for Fore Draft
AD for Aft Draft
/ 2 the result is to be divided by 2
x 2 to multiply by 2
Port meaning left ship’s side
Starboard meaning right ship’s side
Formula for getting Fore Draft:
FD = MD x 2 – AD
Formula for getting Aft Draft:
AD = MD x 2 – FD
Here is the Example Problem:
Fore Port = 12 feet
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Fore Starboard = 14 feet
Aft Port = 16 feet
Aft Starboard = 18 feet
Find the ship’s Mean Draft, and here is the Solution:
Forward Port Draft 12’
+ Forward Starboard Draft 14’
is equals to 26’
/ 2 is equals to 13’
Aft Port Draft 16’
+ Aft Starboard Draft 18’
is equals to 34’
/ 2 is equals to 17’
MD = FD + AD / 2
MD = 13’ + 17’ / 2
MD = 30’ / 2
MD = 15’
Therefore, Mean Draft is equals to 15’
Another Example Problem:
Fore Port = 8.20 meters
Fore Starboard = 8.22 meters
Aft Port = 8.70 meters
Aft Starboard = 8.76 meters
Find the ship’s Mean Draft, and here is the Solution:
Fore Port Draft 8.20 meters
+ Fore Starboard Draft 8.22 meters
is equals to 16.42 meters
/ 2 is equals to 8.21 meters
Aft Port Draft 8.70 meters
+ Aft Starboard Draft 8.76 meters
is
equals to 17.46 meters
/ 2 is equals to 8.73 meters
MD = FD + AD / 2
MD = 8.21 meters + 8.73 meters / 2
MD = 16.94 meters / 2
MD = 8.47 meters
Therefore, Mean Draft is equals to 8.47 meters
Another Example Problem regarding AD:
FD is 3.5 meters, and MD is 4.05 meters.
Find the AD
AD = MD x 2 – FD
AD = 4.05 meters x 2 – 3.5 meters
AD = 8.10 – 3.5 meters
AD = 4.60 meters
Therefore, Aft Draft is equals to 4.60 meters
Another Example Problem regarding FD:
AD is 24 feet, and MD is 22 feet.
Find the FD
FD = MD x 2 – AD
FD = 22 feet x 2 – 24 feet
FD = 44 feet – 24 feet
FD = 20 feet
Therefore, Fore Draft is equals to 20 feet.