Hum thought I knew the rules ( inside 3 boat lengths)
 
So am clear rounding a windmark to port you   can't come in on port and bang a tack in front of a starboard boat making that boat have to avoid you
 
But if the course  is a starboard round windward mark what are the rules if a starboard  boat come in,  can that boat tack in front of a port boat and be ok even if the port boat has to avoid it 
 
Also in this particular incidence the protesting boat waited until he saw the offending party hadn't done his turns then shouted protest.  Is this ok 
 
Not me in this situation but interested in views  

What a palaver!
 
Rule 18, specifically, rule 18.3 does not apply
 
best way to understand is to remove the mark
 
Port has to keep clear.  Rule 10
But a tacking boat has to keep clear.  Rule 13
There is no problem tacking from starboard onto port in the zone provided you keep clear.  Once tacked the tacking boat could stop and force the other boat to avoid.  This would be ok provided it has room to do so.  Rule 15
 
any boat who wants to protest needs to hail immediately.  Rule 61.1. The reason that you cannot wait for a boat to exonerate itself (or not) is that they don’t know that they need to do it...
 
 

It is a tricky one, however the Starboard boat can't just tack where it wants.  The trick as the port boat is to come in a little high, slow down so that the Starboard boat crosses you and then duck his transom.  As the Starboard boat is the right of way boat he could force you to tack if you are crossing ahead, but if you are taking avoiding action around their stern then they are not able to throw in a tack to keep ahead of you.

Ok that's clear

Guess starboard round windward Mark's are uncommon

So in this case as John says it's just like tacking anywhere on the course

As long as the starboard boat completes his tack then that's ok 

It's just somebody coming in on port that cant tack making starboard boat avoid

This is why team racing has starboard hand rounding.  The rules are very interesting and when two boats arrive at the mark close to each other neither has a clear advantage and both can manipulate the situation to slow the other.  In the situation above where the port tack boat is looking to duck the starboard one, the starboard tack boat can slow down, and certainly in team racing there is no obligation on the starboard tack boat to tack onto port promptly after passing the mark.

Very interesting 
 
Still learning after all these years
 
Think quite a misunderstood rule. As previously I thought (wrongly) whatever tack you were on within 3 boat lengths the rules were different when tacking in front of a boat 
 
Thinking this was to avoid big slam tacks right in front of people  

Colin 

Until this iteration of the rules you were correct. 
The other point to bear in mind, when tacking  in the zone on a port rounding, making the starboard boat avoid is fine as long as 
1. You have completed your tack rule 13
2. They do or have to go above close hauled. Rule 18.3
3. If they go to leeward, you are able to give them room at the Mark. 

This seems to be a very misunderstood rule. 
Of course when someone tacks in front of me in the zone and I have to avoid, the jib always flaps.

Tricky team racer

Colin 

Until this iteration of the rules you were correct. 
The other point to bear in mind, when tacking  in the zone on a port rounding, making the starboard boat avoid is fine as long as 
1. You have completed your tack rule 13
2. They do or have to go above close hauled. Rule 18.3
3. If they go to leeward, you are able to give them room at the Mark. 

This seems to be a very misunderstood rule. 
Of course when someone tacks in front of me in the zone and I have to avoid, the jib always flaps.

Tricky team racer

However, if you are coming in on port to a crowded port-hand rounding, the logic of this is that you can either tack below the line of starboard tackers if they are all sufficiently above the lay-line that they do not have to go above close-hauled to avoid you (unlikely in a Merlin fleet) or you cross and tack sufficiently above them to be able to give room at the mark.  Your rights close to the mark on port are slight.