Depth Numbers

[Goodshipvenus]

Currently building HMS Sphinx and I have a question or two on the depth numbers for the model’s bow and stern.  I’ve never seen them on a model before. What exactly were they used for on the real ships? Were they painted on or were they metal plates? Were they copper, as Chris Watton suggests, or black?

 

Just curious.

[druxey]

The depth marks were each 6" high and 6" apart, so you could eyeball the waterline to within an inch or so. The base of each number was the depth in feet. I believe that they were either carved in and painted (late 1700's and early 1800's) or cut from lead (pre copper plating days!), then of copper thereafter.

[Peanut6]

That makes perfect sense and I have a follow up question.  So what about the horseshoe shape?  What does it signify and why that shape?  

[mtaylor]

It's just a reinforcement to the connection at the stem and keel.  There's also another reinforcement, but not a horseshoe at the stern.

[Jim Lad]

Painted draught marks on the bow of HMS 'Trincomalee' (1817) on display at Hartlepool. The fore draught here is about 15 feet 5 inches.

 

John

 

[Chuck Seiler]

10 hours ago, druxey said:

The depth marks were each 6" high and 6" apart, so you could eyeball the waterline to within an inch or so.

On one hand, this could be used to calculate trim and help in moving things around to adjust same.  Also by using the fore and aft draft marks, one can consult a table to determine how much the ship and its contents weighs (load).  I don't know if that was done back then, but we did it in the 1970s.

[druxey]

That's true. In 18th century naval documents one comes across 'Sailing qualities'. These were printed forms that were filled out by the captain. One question asked for the best sailing trim of the ship, and the response gave the draught of water both fore and aft. 

[Peanut6]

thanks for the info 

[Charles Green]

I was led to believe the marks were called Plimsoll lines until your question led me to dig a little deeper.  I discovered the marks on the bow and stern are "load lines" that determine a vessel's trim.  Plimsoll lines (named after Samuell Plimsoll, 1824 - 98) came into being either in 1876 or 1884 and are located midship.  They indicate the maximum depth of the hull for an intended load/voyage depending on water density, as effected by salinity and seasonal changes.  Maby more than you wanted to know but I found it interesting.