With all due respect to Wayne, RRS 13 does not define tacking. Indeed the rule is very careful to avoid using the word tack in any form. What RRS 13 does do is define when a boat that has passed head to wind (thus changing tack) must keep clear of other boats.

Our match racing colleagues have written a definition of tacking in MR Call N6.
For the purpose of taking a penalty, tacking is to change course from close-hauled on one tack, through head to wind, to close-hauled on the other.
This appears to be an (yet another?) attempt to introduce a new rule or definition without having to pass through the long process required to change the rule book.
Disappointingly, the call then goes on to apply  in a way that has no need of this defintion. In the incident, Yellow passes head to wind and does not then bear away, but passes head to wind in the opposite direction, before bearing away.
The call would be exactly the same without the superfluous first sentence. According to RRS C7.2(a)(2) Yellow must pass head to wind and then bear away as soon as reasonably possible . She does not bear away as soon as reasonably possible but instead reverses her change of direction, passes back on to starboard and only then bears away.
So in the only instance I have found in an authoritative  text approved by WS that defines tacking, the definition is irrelevant to the call. 

Which will convince me better that you were anxious.

"I hailed Starboard. They ignored me. I hailed louder again shouting you need to tack too. They ignored me. I altered course"

"I wasn't sure if they saw me and I was anxious so I altered course"

Can you expand on this?

John, I am glad that the WASZP rules are working in practice.  I think that the wingfoils will go a different direction, with little or no limitations, at least in part because they are always in the standing position.  I think that should be up to the fleet decide and adopt in their class rules so we shall see as the class matures.

I'm with Phillip, in the definition its a measure, and that measure should be consistent. A less than competent crew is not entitled to more room than an expert one, and would be breaking a rule if they require it (lets leave room made freely available out of it for now).  Similarlty an expert crew is allowed the same room as a competent one, even though they may not need it,

John, I agree with you about reasonable apprehension and skill level, but I think its a red herring in the context of Room and Case 103.