I remember witnessing the 'accurate' track of the blades using the chalk and flag method on a Wasp back in the 80's at Portland.
What amuses me is that the blades continued to be marked with the same colours as the chalk even when the method died out.
The inaccuracies were mainly down to the most junior 'bod' being the poor sap with the pole. In his ensuing panic the pole was rarely held steady! It was difficult to achieve on board as the rubber strip would often be flung into the sea! Added to the above problems the boat (I was never a ship driver!) movement added its own problems. As the old beasties were so damn clunky and could put up with far more abuse than the 'sensitive' choppers of today the 'belt and braces' approach worked rather well.
The chalk was then replaced by a 1 inch square numbered flag on each blade tip with a strobe light connected to a microswitch on the head which gave a 4R/5R (dependant upon the number of blades obviously) flash that enabled the Grubber to see 'static' numbers with track and lead lag and write down the adjustments to each blade based on how high the flags were relevant to each other or how far forward or back. The blade adjustments still used the colour code from the chalk days though! E.g. 'Blue blade 1 flat down'. Was great fun at night, just like being with John Travolta in the disco!
Finally they were all replaced with some sort of electronic blade and track gizmo that even took the tail and the battery balance into account!
Various straight and level flights at differing speeds gave the reading. Nowhere near as much fun but it did seem to work.
Sorry, no pictures, just reminiscing!
