Hull Markings of USS Seawolf (SSN-21)

I notice that the hull markings of USS Seawolf (SSN-21) include the word ‘PROJ’ (located above the draft marking. Can anyone suggest what this refers to?
Certain photographs show the vessel without the number ‘21’ on either side of the sail. Evidently all markings were removed (with the exception of draft marks) once the submarine was in operational service … correct or not?


I have no idea what the ‘PROJ’ refers to but it is also present on Virginia-class submarines.

Sail numbers are removed from sails once in operational service or possibly after the commissioning ceremony?

This is true, like on my Gato I made it look as if the Cobia already had some weathering before they painted it out, leaving a darker gray patch.

PROJ means that there is a projection below the keel included in the draft. (In this case probably the sonar head.) That is to ensure the draft number is adjusted before using it to calculate displacement, as otherwise it would be overestimated.
“096- Draft Marks. On ships which have projections below the keel, the Arabic draft marks designated by the letters PROJ are not suitable for use in determining the displacement without correction. The remaining draft marks, either Arabic or Roman, are for calculative purposes.”

Gary and Danie,

Thank you both for your responses … most informative.
This will really help me with completion of my Seawolf model.
I am using a 1/700-scale kit from Hobby Boss, and setting it
in an Arctic scene showing the submarine breaking through the
ice. I am using paraffin wax for the ice, heated up to a liquid state,
and poured into a picture frame base before being allowed to solidify.
A section will then be cut out (slightly larger than the shape of the
waterline). Once the submarine is in place, I will add pieces of broken
‘ice’ over and around the hull to give the impression of it having just risen
from the water. The final task will be to apply a light and patchy coat of PVA
glue, followed by a sprinkling of white silica sand, to suggest a covering
of snow.
Interesting to see how well it works …


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