A cubic foot of fresh water weighs, 1,000 ounces, a cubic foot of seawater 1,026 ounces. The increased depth above the centre of the freeboard disc to which a vessel is allowed to be loaded in fresh water, weighing 1,000 ounces per cubic foot, is indicated by a line market F.
The allowance to the draft for loading in fresh water being known, the allowance, when loading in partly salt water can be easily ascertained from the following table:
Allowance to the draft in sea-water
| Density |
Draft (inInches) |
| |
|
|
|
|
|
|
|
|
|
|
| 1.000 |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
| 1.002 |
0.92 |
1.85 |
2.8 |
3.7 |
4.6 |
5.6 |
6.4 |
7.4 |
8.3 |
9.2 |
| 1.004 |
0.85 |
1.70 |
2.55 |
3.4 |
4.2 |
5.1 |
5.9 |
6.8 |
7.6 |
8.4 |
| 1.006 |
0.79 |
1.54 |
2.3 |
3.1 |
3.8 |
4.6 |
5.4 |
6.2 |
6.9 |
7.7 |
| 1.008 |
0.7 |
1.38 |
2.1 |
2.8 |
3.45 |
4.1 |
4.8 |
5.5 |
6.3 |
6.9 |
| 1.010 |
0.62 |
1.20 |
1.9 |
2.5 |
3.08 |
3.7 |
4.3 |
4.9 |
5.6 |
6.1 |
| 1.012 |
0.54 |
1.06 |
1.6 |
2.2 |
2.7 |
3.2 |
3.8 |
4.3 |
4.9 |
5.3 |
| 1.014 |
0.45 |
0.95 |
1.38 |
1.9 |
2.3 |
2.8 |
3.2 |
3.7 |
4.2 |
4.6 |
| 1.016 |
0.38 |
0.8 |
1.15 |
1.5 |
1.9 |
2.3 |
2.7 |
3.1 |
3.5 |
3.9 |
| 1.018 |
0.3 |
0.6 |
0.9 |
1.2 |
1.54 |
1.8 |
2.2 |
2.4 |
2.8 |
3.1 |
| 1.020 |
0.23 |
0.4 |
0.7 |
0.9 |
1.15 |
1.4 |
1.6 |
1.8 |
2.1 |
2.3 |
| 1.022 |
0.15 |
0.3 |
0.5 |
0.6 |
0.8 |
0.9 |
1.15 |
1.2 |
1.4 |
1.5 |
| 1.024 |
0.07 |
0.15 |
0.2 |
0.3 |
0.4 |
0.46 |
0.54 |
0.6 |
0.7 |
0.8 |
Example: A vessel is allowed to load 5 inches deeper in fresh water than in sea-water. What will she be allowed in water of which the density is 1.016?
| Fresh water density is |
1.000 |
Loading water density is |
1.016 |
| Sea-water density is |
1.026 |
Sea-water density is |
1.026 |
|
.026 |
|
.010 |
Allowance in loading water density is then 5 inches x 10/26 = 50/26 = 1.9 inches, this being the extent to which she may be loaded over the sea-water mark.