Hull Speed Chart
Displacement hull speed is an
important indicator of how fast a displacement-type boat will go. It is
the speed at which a boat begins to climb it's own bow wave, essentially going
uphill. It is calculated by the
formula: velocity in knots=1.35 x √waterline length. I got tired of
looking around for my calculator, so I made up this handy chart. Since I
usually think in terms of statute mph, I included that too. I also
included kilometers per hour. (Note that this hull speed formula does not apply
to needle-like hulls such as racing shells).
|
Waterline length in feet |
Hull speed knots |
Hull speed mph |
Hull
speed
kmph |
|
Waterline length in feet |
Hull speed knots |
Hull speed mph |
Hull
speed
kmph |
| 8 |
3.8 |
4.4 |
7.0 |
|
20 |
6.0 |
6.9 |
11.1 |
| 9 |
4.0 |
4.7 |
7.4 |
|
21 |
6.2 |
7.1 |
11.5 |
| 10 |
4.3 |
4.9 |
8.0 |
|
22 |
6.3 |
7.3 |
11.7 |
| 11 |
4.5 |
5.2 |
8.3 |
|
23 |
6.5 |
7.5 |
12.0 |
| 12 |
4.7 |
5.4 |
8.7 |
|
24 |
6.6 |
7.6 |
12.2 |
| 13 |
4.9 |
5.6 |
9.1 |
|
25 |
6.7 |
7.8 |
12.4 |
| 14 |
5.0 |
5.8 |
9.3 |
|
26 |
6.9 |
7.9 |
12.8 |
| 15 |
5.2 |
6.0 |
9.6 |
|
27 |
7.0 |
8.1 |
13.0 |
| 16 |
5.4 |
6.2 |
10.0 |
|
28 |
7.1 |
8.2 |
13.2 |
| 17 |
5.6 |
6.4 |
10.3 |
|
29 |
7.3 |
8.4 |
13.5 |
| 18 |
5.7 |
6.6 |
10.5 |
|
30 |
7.4 |
8.5 |
13.7 |
| 19 |
5.9 |
6.8 |
10.9 |
|
31 |
7.5 |
8.6 |
13.9 |
Example: The
Odyssey 180 rowboat has an overall length of
18'-2" and a waterline length of 17'-7". On the chart 17'-7" is about
half way between 17 and 18 feet, so hull speed is 6.5 mph.
Back to rigs and row
boats
|
