On the ISAF Olympic micro site under the requests for information section, an interesting issue was raised today by the Danish Laser sailor:
"A boat is approaching the start line on starboard tack 30 seconds before the start. An upwind current is carrying the boat toward the start line. She backs her sail still carrying the main on her port side and as a result of that she: 1) Is beyond doubt moving "backward" trough the water looking at her hull and rudder. 2) She is still moving "forward" over the ground physically approaching the start mark and beyond doubt decreasing the distance to the mark.
Is the boat "moving astern" with regard to RRS 20.3, yes or no?
Does this boat have to keep clear of other boats approaching from astern?
No answer has been provided as of yet and I started thinking how I would answer this.
In a body of water that is displaced because of current, all movement is influenced by that current if you look at relative position to the "ground". However, if you disregard that movement and go only with the speed/movement relative to the ground, no sailor will be able to accurately judge speed any more. All movement trough the water must be relevant in my opinion. So I would answer that this boat is "moving backward" by backing her sail and subject to rule 20.3.
What do you think?