I don't have a case reference or dictionary definition to back this up, but in my opinion:
- Draw an imaginary line down the centerline of your boat.
- Draw another imaginary line (or curve) representing the position of the sail.
- Draw an imaginary arrow representing the direction of the wind.
Now, if the sail is in line with the wind, you are not backing it.
If the sail is not in line with the wind then the wind is exerting pressure against it. If that pressure is on the side of the sail facing aft (pushing the boat forward) then you are not backing it. If the pressure is on the fore side of the sail (pushing the boat backwards), then you ARE backing the sail.
It doesn't matter which side of the boat the sail is on or how you hold it out - by hand, with a sheet, or a pole. You're still backing it.
One can back a jib to help get through a tack, or to help turn the bow down to get out of irons. As long as it does not make you move astern, rule 21.3 does not apply. If you back a sail and back up, you must keep clear of boats that are not.
Regards,
Eric
