Hi another for you :

2 boats sailing on port towards the leeward mark. A slightly to weather of B but clear astern.

the water condition is that the waves are big enough for boats to surf at times.

B is heading straight for the mark on her proper course to round the mark on port. A gained an overlap by surfing a wave. A is calling for room but in that time she also bore off towards the mark and touched B port side. B did not change course as he believed there was no engagement in the 4 boat lengths and therefor didn't have to leave room.

they both rounded the leeward mark heading on their beat with A calling for prostest on B. B retired due to loss of grounds.

This happens in model boat racing.

Any views ?

The last point of certainty (agreement by the two parties taking them back up the course) is that there was no overlap. In addition if there is doubt over whether an overlap was established prior to one boat entering the zone then it is assumed that it was not. There for B is first into the zone clear ahead and is entitled to mark room from A.

A would be DSQ as windward boat (rule 11) and for failing to give mark room (rule 18)

(edit, got my A and Bs the wrong way round!)

well there was disagreement as A believed he gained the engagement ahead of the 4 boat lengths where as B said no, A gained a late overlap within the 4 boat lengths and therefore was not entitled to room at the mark.

So if I get you right in the case of uncertainty of mark engagement it will be assumed at jury that the overlap was not established in time and in this case A would be dsq.

did I get this right ?

interesting stuff all the same for big boat racing but in model boat as you know the judgement call at engagements is even more difficult to the distance and the angle from where the skippers stand.

Which is why rule 18.2(d) is so important. If there is doubt then the important thing to do is avoid contact. If you are the outside boat I would suggest giving room and protesting.

RC racing has different problems. That is why they use 4 boat lengths. Everything is far easier in match racing where the umpires will make a call on whether boats are overlapped at the zone. Judges would tend to work back to the last point of certainty, often, in the absence of witnesses, the last point at which both parties agree.

Moral of the story - don't go in there if there is a doubt.

Thank you Richie and Gordon for your responses.
Still not black and white situation but I guess the best is to call no room at the 4 boat lengths to make sure there is doubt...