Operative word is "MAY" have passed close ahead. S altered course to avoid a possible collision. P violated the Keep Clear rule.

Indeed, 'May have' is operative. If S filed a valid protest and in the finding of facts phase of a hearing declared she is uncertain that P was avoiding her, she should not win such a protest.
In the spirit of the of the sport there is nothing wrong with playing safe, whatever the conditions.
On the topic of weather, the RRS are agnostic.

I would strongly encourage every official to first look at the cases for an interpretation...

Indeed. "Reasonable apprehension" is the concept here (Case 50).

I couldn't find a case that covered the situation....... if S bears away to avoid a POSSIBLE collision, that's not the same as bearing away to AVOID A COLLISION. especially as S agrees that P MAY have passed clear ahead if she had held her course.

As I said, R10 says P must KEEP CLEAR (def), nobody has to GIVE ROOM (def) ..... but S agrees that P MAY have passed clear ahead.

mmmmmm......

Based on the discussion it sounds like no flag was flown and no protest was filed? Is this the case?

If S thinks that they may be clear but alters incase both are misjudging and is extremely cautious that is in her right to sail as she's entitled to.
If she flagged and filed she is stating that it was too close in her opinion. I think the other details are just as important in this case and its also
why discussing a situation in the abstract may be very misleading in comparison to the full situation.

Do you have more that you can add to clarify?

Thanks,
Brent

From Case 50:
" At a protest hearing, S must establish either that contact would have occurred if she had held her course, or that there was enough doubt that P could safely cross ahead to create a reasonable apprehension of contact on S's part and that it was unlikely that S would have "no need to take avoiding action" (see the definition Keep Clear). "

Yet again, it is a question of the credibility of the evidence given by the parties and any witnesses as to whether the protest committee accepts that S had a reasonable apprehension.

The problem is that if the S's never succeed, then the P's keep pushing to the point of gaining advantage by breaking the rules. I would tend to have a slight bias in favour of the right of way boat as that encourages keep clear boats to be clearly seen to have kept clear and discourages P's from creating dangerous situations when they are the "keep clear" boat.

Thankyou. I think that part of case 50 helps. "reasonable Apprehension of a collision" seems to be the point to prove.

I disagree that Case50 is entirely applicable - there is a lot to parse in the Case. I'd say that it doesn't even satisfy the intent of Cases.
Considering the 'Principle Aim' clause: to clarify an important meaning in a rule or to increase the understanding of a complex rule
Rule 10 is not complex, so does 50 clarify Rule 10?

Starting with Facts found -On a windward leg, P met S and sailed a course to cross ahead of S
Is it generally accepted that 'cross ahead' precludes collision? I think so.

Case 50 states that the wind was Force 3, this incident states heavy weather.
Should 50 be discounted because of differing conditions - not entirely clear?

A genuine and reasonable apprehension of collision?
S surely had apprehension, yet doubted herself.

'. . .satisfied that S did change course, that there was reasonable doubt that P could have crossed ahead'
Does reasonable doubt cut both ways?

Later in the Decision it is written, 'safely crossed ahead'.
Is there a distinction between cross ahead and safely cross ahead?

Case 50 foundation is accepting one diagram over the other.
Diagrams are not evidence, rather, they are subjective testimony from interested parties.
Lacking witness supporting one over the other, all the the Case has accomplished is justification of bias that P has onus of proof over S.
But in this instance, isn't it just as reasonable to decide that S was overly cautious?

Getting back to the principle aim question, did the Case add clarity to the Rule?
I'd say that the only thing its accomplished is to set precedent that S's claim (however flimsy) outweighs P's.
If that is the purpose of Rule 10, why not expand on the definition of Keep Clear by adding the 'genuine and reasonable apprehension' language?

IMHO, this is actually pretty easy -- if the protest committee keeps to the knitting.

Definition of "Keep Clear" says P keeps clear if S "... can sail her course with no need to take avoiding action ...". When does S have a need to take avoiding action? Case 50 gives great guidance. S "... need not hold her course so as to prove ... a collision was inevitable. ... At a protest hearing, S must establish either that contact would have occurred ... or that there was enough doubt that P could safely cross ahead to create a reasonable apprehension of contact. ..."

I know I left a lot out. The point is to define the knitting. Judges on the protest committee need to first listen for, and if not forthcoming in the testimony, ask questions, enough information to determine whether S had a genuine and reasonable apprehension of collision. Those facts probably include wind and sea state, type of boats, distance from P when S altered course, how much S altered course, how close the boats were at their closest point. (It does not include the experience of the sailors. That's covered in a different case.)

In the end, whose opinion whether there was an expectation of a collision matters? The majority of judges on the protest committee. (to be cheeky). But having the right facts to support that conclusion and decision encompasses both the art and science of judging.