Angela directed me to this thread as she knows I love me some racin' - especially in the Solent which has crazy tides and tidal gradients.
I thought I would throw my two cents in, but want to clarify a bit about difference between tactics and strategy.
Tactics is the use of boat on boat actions to create advantage. An example of this would be when you are in the lee position very close to another boat you could pinch up to try to force them to tack away or to try to put them into bad air and slow them down. This can also be when you are not close to boats. If you feel that even though you are on an advantageous tack and are in the lead and you see the rest of the fleet, or boats that are in contention, go the opposite direction you might consider that abandon your current strategy and "cover the fleet" by tacking over - even if you feel this is not the optimal direction. You have kept yourself between the fleet and the mark and will experience the same wind and current as the fleet so no advantages can be gained be a mistake in your strategy.
Strategy is the use of a sum of vectors to sail the shortest distance and the highest VMG to a given mark. The vectors are Wind Direction and Speed, Current Direction and Speed, and most importantly the ΔT (change over time) of these vectors - which brings me to the reason of my post.
If a course is static (which doesnt exist in real life) and there is perfectly constant wind direction and speed and current direction and speed across the whole of the course for the whole of the race
then there can be no gains found for any boat with any strategy that give it an advantage over another boat.
i.e. The lee bow effect does not exist.
Boats A,B and C all sail the exact same distance and spend the exact smae amount of time on each tack.
1. In an environment
where there is no change in vectors over times all boats sail the same distance and time on each tack
and therefore would all benefit equally. Regardless of where they go or how many tacks they make they are all equal (taking out any loses made during the tack itself in large boats or gains made by roll tacking in smaller boats)
2. There is no "current" - you are sailing through still water
. All boats are moved the same distance by the current regardless of sailing angle or tack. This was covered very well by the "Tablecloth" analogy in the other thread
3. All boats experience the same amount of header and lift
effect with the wind due to the current since they spend the exact amount of time on each tack.
4. Pinching up to get the "current" to push your lee bow isnt possible. The "current" doesnt push your boat. You are sailing through still water and the whole body of water (including all the other boats) is moving as a single
mass over the ground. You are decreasing your VMG by slowing the boat down by pinching.
5. There is no benefit gained by staying on a given tack longer to take advantage of the lift
caused by the current as all boats have to sail the same distance on the same tack - on a race
course with marks where there are no changes in wind and current over time or geography every boat will spend the same amount of time over a given leg on starboard and port tacks
whether you sail to the layline on a long tack or short tack up the middle it is irrelevant - smae distance and time for every boat.
Once you introduce ΔT to the equation then you are no longer talking about the mythical "lee bow effect" but instead discussing Wind and Current Strategy. Once there are differences in wind and current on the location of the course (one side has a stronger tidal stream gradient) or based on time (there is a fixed period 30degree wind oscillation) then various strategies work - but not the lee bow effect.
I dont know anyone personally who believes in this effect, they would be more proponents of Positioning and Strategy which is planning for and estimating the change in location and time of these vectors and planning how to be in position to take advantage of them.
In fact I would venture to say those that do believe in it and claimed to have won races with it are actually merely benefiting by placing themselves in the right place at the right time benefiting from the right combination of vectors of force.
edit: for clarity on the image attached i am assuming the following:
1. These are race boats with a tacking angle of 70°
2. The boats have a STW of 6kts
3. The current of 2kts is coming parallel to the starboard layline and add ~33% to the Port Tack layline - meaning to lay the mark your COG on Port Tack would be 35° + 33% = 46.55°