I realized today that I was unclear when I talked about resolving the vector into southward and eastward components, although that’s correct when the vessel is headed east. What I should have said is to resolve the vector into one component parallel to the heading of your hull and another at right angles to that.
(And I see that in my ‘knots vs mph’ post above, I scuttled a letter from the word ‘stated’. Scurvy lubber!)