While I haven't thought through all the implications, I suspect that you are making a bad problem even worse.  What is the reason for doing this?  Is it really a problem?

What about boats that come in on starboard tack on the layline to #3 and tack onto port there?  Or are on starboard and cross the line and tack onto port.

What if there are no boats coming in on starboard?

If you define #3 as a mark then rule 18 applies there.  If it is just the end of an obstruction line, then 19 and 20 apply and you have to not only define it that way but also make it a rule that you can't cross the line and tell people what, if anything, you can do if you do cross it.

there's some decent limiting mark verbiage here: https://yachtscoring.com/event_documents/6135/Circle%201%20Appendix.pdf

You appear to be a have overlapping zones. Move mark 3 so it is 7-8 boat lengths to leeward of the windward mark and eliminate the other mark. 

 

NYYC has been y=using the limit mark for a number of years with good success. The setting of the mark in the correct location is critical to accomplishing your objective. We found 8 lengths work the better.

Here is the description used in the NYYC SIs (don’t mind the color.

Limit Mark
a) The Race Committee may set a pink inflatable limit mark approximately 6-8 boat lengths to leeward of the windward mark.
b) The limit mark shall be left to port on both the upwind and the downwind legs.
c) In the event of a change of course to the windward mark after the first windward mark
rounding in that race, the limit mark will not be set.
d) The location of the limit mark or the failure of the Race Committee to set the limit mark shall
not be grounds for a boat to request redress. This changes RRS 62.1(a).
e) The Race Committee will display flag “Third Substitute” if the limit mark is a mark of the course.

Matthew - the limiting language doesn't really help at all.  It just gives you two places where you can have problems.  The limiting mark is still a mark with everything that goes along with it.

I suggest simply define all: 1, 2 and 3 as port rounding marks.

Putting a mark at position 3 will move traffic to the right , so do you still need an offset?
Making the line an obstruction would activate a right to tack, and to compel others to tack, inside the four length circle. That could cause chaos.
Perhaps you might require mark 3 to be passed to port only on upwind legs.
How many boat lengths from mark 1 are you putting mark 3?
It would be interesting to hear from anyone who has used this technique as to how effective it is.

John

The language I posted has been used for years in the IC37 class at major events.  Seems to work for them.  I think the obstruction language you have in there would cause major issues.  

Very interesting especially for radio sailing on the first beat after the start, the pileups sometimes can massive. I have been thinking about this for several years after see the "Windward Inner Mark" (WIM)used in the TP52 Series. My thoughts that the WIM should be at least 7 to 8 boat length downwind of the Windward mark so any port tackers are outside the 4 boat length circle when they meet the starboard layline boats. If a port tacker wants to tack at the WIM he will do 2 extra tacks.

Iceboats (and particularly the DN Class) use a limit mark (called a Darling Mark in iceboat parlance) at both windward and leeward marks for safety following an update to the NIA (National Iceboat Authority) rules in 2018.  Neither iceboat classes nor the NIA are affiliated with World Sailing so there are significant differences from the Racing Rules of Sailing, including no zone at a mark to muddy the waters.  :-)  The relevant NIA definitions are:
MARK: Any object, which a yacht must round or pass on a required side to properly round the course.
DARLING MARK: A MARK that is positioned in line with and between the windward MARK and the leeward MARK.  The imaginary line between the MARK and its accompanying DARLING MARK is considered part of the MARK.
The use of Darling Marks is considered a good way to move port-starboard interactions away from the marks, but Darling marks are generally something like 75 to 100M away from their associated marks.  Seven to eight metre, or even eight boat length separation is ineffective at 30+ knots. 
If you are curious, the NIA rules can be found at www.iceboat.org/nia/ 

In Kiteboard we have used this mark for more than 10 years and never had a problem. No extra wording in RRS and NOR/SI only a adapted drawing in the Course Diagram(s)

Keep it simple as Bruno points out. that solution will cover you all  the way ;-) This is how Club Swan 50 does it: 

Agree, stay away from the obstruction language and other language that restrict/penalize a boat for crossing the line between the limit-mark and the mark.  

We've had several different threads in the past trying to deal with how to both declare a line as an obstruction and also something that a boat is not allowed to cross (which are 2 separate items) and what implications that has relative to those boundaries and if/how a boat that crosses the line can exonerate themselves (you'd have to write-in an exoneration path if you wanted one).

Also, consider that if you state that a boat can not cross that line and it is an obstruction, and it is say 8 BL's long .. now we may be talking about a continuing obstruction and one might argue Rule 19 applies at both marks instead of 18, depending on where these boats are.

Ang

Thanks everyone for your comments.

I agree that the concept of an obstruction is not the way to go.

I think the simplest option is just to give it a required side, like any other mark.

Regards 

John

You don't need the 3rd mark. But you have to make sure that the two marks are at least 6 hull lengths apart. At 3 hull lengths apart Yellow passes through head to wind in the zone. At 6 hull lengths Blue passes through head to wind on the edge of the zone.8-10 lengths is better.

     

The issue is: "to reduce/discourage late port tack approach to windward mark."

Starboard tack boats should possess protest flags and the fortitude to follow through with a protest.
Seems the problem would thereby resolve itself in time - without pink marks.

@Phil Hubbell I tend to agree with you.  I can't really see what's wrong with a port tack approach to the windward mark - if it infringes, then people protest, surely?  If there really is an issue, sit the protest committee members near the windward mark.  If you want to prescribe the precise way around the course, set hundreds of marks so there's only one way to go - but that defeats racing - seems this would too?  I have to admit I can't see the problem that this is trying to solve.  (Though if it really is a problem, then the >6 boat lengths between them makes more sense than < 6).