The Water Line

Page updated: 18 November 2005

Go to TopIntroduction

Look at a selection of photographs of SeaHawks at their moorings. It seems that when it came to winter maintenance, some owners had lost track of exactly how their boat sits in the water. Once painted badly, it will often be simpler to continue painting to that line than get to it right. This page is a "first attempt" at providing the necessary measurements when painting the waterline or applying anti-fouling.

The boat pictured on this page provides a good example of a mis-placed water line. A line of matt black anti-fouling paint can be made out in both pictures but can be seen to be redundant, as at no point does it come within an inch of the true water line!

Go to TopMeasuring from the Bow

The picture below shows a SeaHawk immediately after being lifted from its summer berth. The true water line can be clearly seen from the line of fouling. As it comes forward, the painted water line can be seen to have been allowed to follow the line of the planking for too long, becoming too deep before it returns to a more appropriate level as it finally reaches the bows. However, as the fouling was about to be hosed away no indication of the true water line would be left by the time it came to re-apply paint or anti-fouling. Some measurements needed to be taken.

The waterline from the starboard bow

At the bow, and following its curve, it was found that the distance from the lowest artificial "plank" to the water line was 16". Then, moving from the bow towards the stern, along the line of the lowest "plank", points 12" apart were marked. From each of these points the shortest distance to the waterline was measured. Once level with the aft end of the bilge fins, the curve of the hull was such that the water line was fast moving under the boat and it became difficult to determine a line to take. Accordingly, a different approach was used for measuring the position of the water line aft of this point.

Go to Top Measuring from the Stern

Under the transom, on the centre line of the hull there is a distinct "crease line" running forward. Starting at the transom, working along this line, points every 3" were marked out. The first few of these points were redundant as the closest the water line came to the transom was 13". However, thereafter the width of fouling was measured. There came a point where these measurements were close to overlapping with the measuring technique working from the bows. No attempt has been made to reconcile these, but they appear to form a reasonable template from which to work!

The waterline under the stern

Go to TopKey Measurements

Distance from lowest plank
to waterline:

Distance from plank to water line
at the following distances from the bow:
1 ft - 12" 8 ft - 3.75"
2 ft - 11.25" 9 ft - 3.5"
3 ft - 10.25" 10 ft - 3.25"
4 ft - 9" 11 ft - 3.5"
5 ft - 7.5" 12 ft - 4.5"
6 ft - 5.75" 13 ft - 5.25"
7 ft - 4.5" 14 ft - 8.5"
Distance from Transom to Waterline: 13"
Distance from

Width of Fouling
15" - 16"
18" - 24"
21" - 30"
24" - 36"
27" - 41"
30" - 45"
33" - 49"

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