Distance Draft Mark From Perpendiculars
The above picture show you the distance of draft mark to perpendiculars. Some of you may have finds the above arrangement. But how if you find it for the first time? How do you calculate it?
Commonly in the table for draft correction, the distance of draft mark measures to the nearest perpendiculars such as;
Distance of Aft Draft Mark to Aft Perpendicular, Distance of Mid Draft Mark to Mid Perpendicular and Distance of Forward Draft Mark to Forward Perpendicular.
But the above picture shows:
The X1 is represent the Distance of Aft Draft Mark to Aft Perpendicular. (same figure)
The X2 is represent the Distance of Mid Draft Mark to Aft Perpendicular.
The X3 is represent the Distance of Forward Draft Mark to Aft Perpendicular.
To calculate the distance for correction values for Mid and Forward Drafts, we need the LBP.
As you find the LBP on the above picture is 148.00 M, so the calculation as below:
The X1 is represent the Distance of Aft Draft Mark to Aft Perpendicular. (same figure)
The X1 = 6.10 M (X1 = dA)
The X2 is represent the Distance of Mid Draft Mark to Aft Perpendicular.
where X2 = 74.00 M.
X2 = X2 – (LBP/2)
X2 = 74.00 – 74.00
X2 = 0.00 M (X2 = dM)
The X3 is represent the Distance of Forward Draft Mark to Aft Perpendicular.
where X3 = 146.01 M.
X3 = LBP – X3
X3 = 146.01 – 148.00
X3 = 1.99 M (X3 = dF)
LCF From Aft Perpendiculars
See the below hydrostatic table, could you find the actual LCF?
In the above picture, the LCF show in Xf. where the values base on the distance of LCF itself from Aft perpendiculars.
So you could use the below formula :
What is LCF on Draft 1.60 M?
LCF 1.60 = LCF on table – (LBP/2)
LCF 1.60 = 78.46 – 74.00
LCF 1.60 = 4.46.
MTC Per Meter
How About MCT? the MTC on the above table show MTC per Meter not Per Centimeter as required for draft calculation. To obtain the actual MTC you should divide the MTC on table by 100.
What is MTC on Draft 1.70 M?
MTC 1.70 = 22556.42 / 100
MTC 1.70 = 22.55642
Drop your comment and advice to improve this post.
February 13, 2017
Hi Ibrahim..
There is no way to do, except telling ship’s reps to make forward draft of the ship immersed on the water. So, we can read the draft.
January 24, 2017
hello
thank you for this information
but i have a questation
( if the bow of vessel rise up of water line ( nigative value of forward draft) , how can we read a forward draft and calculate a mean of mean draft .
in this case can we use the hydrostatic tables of ship.
if what can we do? and thank you again.
December 8, 2016
Already corrected. Thanks.
November 28, 2016
Hello dear teacher
Thanks for learning, it’s just to correct the LCF calculation, the correct calculation would be
1.60 = 78.46 – 74.00
1.60 = 4.46 and not 2.46.
May Allah bless you.
Thank you very much
Abu Valgy
Marine Surveyor
Mozambique
October 21, 2016
Hi Budin.. You should refer to the explanation or notes available on sounding table itself. If no reference available, as common use, you could go with apparent trim to calculate.
October 8, 2016
what trim do i use in sounding table, apparent trim or corrected trim?