One actually does not need a ruler to measure the first bit. The distance between frame 155 (shown but not labelled on the
deckplans here) and the forward perpendicular can be found by subtracting all the known lengths from the LBP (850’0”), using the numbering and frame spacing to perform the subtraction piecewise. From frame 155 to the forward perpendicular, the distance is 3’8”.
From forward perpendicular to bowsprit, 2’6” (this difference comes from the fact that the Board of Trade measured LBP from the bowsprit, giving 852’6”, where the builders measured from forward perpendicular, giving 850’0”). The extra expanse beyond frame 155 is therefore 6’2”.
From frame 80 (the frame aligned with the bridge front) to frame 95, 45’0”. From frame 95 to frame 107, 33’0”. From frame 107 to 119, 30’0”. From frame 119 to frame 134, 33’9”. From frame 134 to frame 155, 42’0”. From frame 155 to bowsprit, 6’2”.
From bridge to bowsprit the full distance was 189’11”.