please be advised that there is a mistake about solving out the question ,when you use Dock allowance formula, you are finding the draft change , when the vessel sails to salt water from dock water and it is 8 cm so 8+7 =15 cm below the summer load line when you are salt water , from that point , you need to use TPC for salt water not dock water , because you consider the vessel is in the salt water.
I believe that is the regulation ( load line convention) that distance between T and S or S and W marks should be 1/48th of summer draft. I still need to figure it out how this number ( fraction) is arrived. Presently beyond the scope of teaching this topic. However will revert as soon as get some info.
1/48 x summer draught = mtrs difference then subtract it by summer draught to get winter draught as the differnce between summer to tropical is 0.48 mtr and summer to winter is 0.48 mtr and winter to wna is 50 mm
tropical to summer 1/48*SD, meaning if you load maximum cargo in tropical, when you arrived to Summer zone, your draft will be 9.6meters (as given in the sample in the video), meaning to say your Tropical Draft previously is 20cm more than 9.6m, or 9.8meters....BOTTOMLINE, if you are coming from a Tropical Zone and going to Summer zone, do not load more than 1/48th of your summer draft,, or simply just load at the upper edge of your Tropical Zone so that when you arrived in Summer Zone you will still be in your upper edge of Summer Load line (assuming the load port and discharge port is seawater density)
