I'd say treat it the same as "Propper Course" except in this case the proper course is upwind, best VMC. The point of sail you would be on in the absence of other boats.  In waves you would be cracked off a bit, in heavy wind maybe you are feathered up and pinching a bit in flat water.  Substantially you're close to luffing if you turn much more into the wind.  If you're footed off 10 degrees to cut off a competitor for instance, you are not close hauled. Same thing if you overstood a windward mark and are reaching in, you could be forced to head up by a boat tacking below you, until you are once again, "close hauled". 

In RRS 13 the rule refers to reaching a close-hauled course. This refers to the heading of the boat, not the sheeting of the sails.
There is no hard and fast rule for defining when a boat has reached a close hauled course.
Umpires will often observe boats before racing and agree between themselves when, in those boats in those conditions, a boat has reached a close-hauled course.
When umpiring and observing radio sailing I would usually work on the assumption that a boat has reached close-hauled when she stops turning! Unless it is clear that she has borne away below close-hauled.

Rule 18.3 refers to sailing above close-hauled. The commonly used indicator is does the jib lift. Once again this is less useful in radio sailing with stiff sail-cloth and small sails. This is one of the many reasons why RRS 18.3 des not work well under AppE

For the purposes of rule 13 and 18.3, I’d say close-hauled for a J/70 is 33-35 deg TWA (hard to distinguish and based on the polar).  Close-hauled is also used in rule 20 and 42, but I think those applications of the term are not so finely inspected. 

Of course the problem with applying close-hauled in rule 13 is that the tacking boat is turning and the sails are changing sides at the same time.  If there is a boat of the same make sailing close-hauled close by, I think that’s a pretty good gauge. Before the start behind the line when boats are running the line … it’s a tougher call as the boat will tack from one side to another and pass through close-hauled before stopping her turn and the other boats around are reaching, so they are not a useful guage. 

For 18.3 it’s tricky in another way, as often the boat that has been on starboard may have overstood and eased their sheets for speed into the mark. The front of starboard’s jib luffing is therefore an inconclusive indicator that she was forced above close-hauled. 

I had the above happen in our championships last fall where I was on starboard and a boat tacked in the zone.  I was eased a bit and though I altered course to windward to avoid contact and luffed my jib a bit (after they completed their tack) I knew I wasn’t above close hauled (as I explained to a couple of my crew who got vocal and upset about it). 

PS: It’s a hard thing in the heat of the battle to remind crew that I’m the only one on the boat allowed to call out to other boats, unless there is an emergency or imminent collision.  Certainly, I’m the only one allowed to hail “protest” or call for room to tack. 

PS2: Just conferred with a friend who is a top J70 sailor and he confirmed that tacking through 70 deg is a good number. 

On RRS 13: I do not think judges/umpires or other sailors can establish whether a J-70 has reached a course 33° from the TWA! Umpires use the last point of certainty: a boat is between head to wind and close-hauled until the umpires are certain that the boat has reached a close-hauled course.
As a judge, including when judging RRS 42 on the water, a boat is subject to RRS 13 until she is clearly close-hauled. This may well be slightly later than the moment at which the crew of the tacking boat think they have reached close-hauled.

In the same way, for RRS 18.3, the boat has to clearly sail above close-hauled before the PC will find as a fact that she is doing so. I suspect that it becomes clear that a boat is above close-hauled somewhat closer to the wind than the 33-35° mentioned above.

Gordon,  I agree with that general sense. We do however have those instances where a boat does not stop to establish themselves sailing on the close-hauled course. Once the boat reaches that angle, even if her sails are in flux and she continues to turn, rule 13 ends (Case 17 and US 35).

It’s useful to have those numbers if they are knowable. 

Definitely depends on the boats and conditions. For Lasers/ILCAs, we sail at about 37 degrees off the wind in fully powered-up conditions (~8-12 knots), but in lighter conditions, but more like 40-45 degrees off the wind when it's lighter and apparent wind is more a factor. It's easy to see these angles when sailing with a digital compass.

I'd combine Gordon's and Angelo's comments above to use "when a *properly trimmed* sail luffs (has a bubble)" is when a boat is above close-hauled. So, an eased jib or eased main luffing will, of course, luff prior to reaching close-hauled.

My apologies for adding a complication:
Many keelboats  need to come out of a tack low then 'wind' up as flow is established over the sails and keel. This can be especially noticeable in light winds. Boats with narrow keels (FF15s) will also make considerable leeway until the accelerate.

I  will usually assume that the boat has reached a close hauled course when she reaches this initial lower course before she 'winds up', accelerating and sailing higher.

Gordon re: “lower end wind-up angle”… that’s interesting …

I have always thought the opposite actually. That, coming out of a tack, a boat reaches a close-hauled course at the tighter angle to the wind where she could trim her sails in fully while sailing to windward (the higher-slower upwind mode a boat might take to make a mark they are just barely fetching).

A close-hauled course is not a fixed angle, but a compromise. It varies with the conditions, and can vary frequently, as when a boat is sailing in big waves.
When sailing  some keel boats, a close-hauled course  - the compromise course allowing a boat to make progress to windward -  can be very different when a boat comes out of a tack than when she is fully powered up. Both are close-hauled courses, the closest the boat can sail at that moment to make progress to windward.

Gordon re: “the closest the boat can sail at that moment to make progress to windward”

Yea .. that’s good wording.  That’s what I’m saying. Depending on the boat and conditions, there can be a less than optimal angle that is tighter .. like if a boat misjudged adverse current at the windward mark and comes out of the tack tight to make it. 

'Stuffing' to make the mark is the closest the boat can sail at that moment to make progress to windward!
Sailing a few degrees lower to accelerate out of a tack until the flow on the sail is and keels is established is also  the closest the boat can sail at that moment to make progress to windward. 

Just to explain my vocabulary:
- 'stuffing' sailing close-hauled as close to the wind as possible, to the detriment of boat speed. Sails are trimmed in consequence. 
- 'footing' sailing close-hauled favouring speed against  heading. There may only be a few degrees of difference in the heading, but the behaviour of the boat is very different. Often observed in dinghy classes that can plane to windward. In marginal conditions some boats (heavy crews) will be sailing close-hauled in displacement mode while other boats are planing. Both are 'close-hauled'. 
- 'shooting' pointing the boat above the heading in which the boat is powered by the sails, using the inertia of the boat to work to windward. Heavy keelboats may approach the windward mark below the layline then luff above close-hauled (often furling the jib) to fetch the mark.

Writing this leads me to a working definition of 'close-hauled': a course on which a boat is seeking to gain to windward and on which the boat adapts to changes in wind direction and strength by changing course and not by trimming the sails.

So, a boat 'stuffing' or 'footing' (high mode/fast mode?) is sailing close hauled, a boat sailing 'full and by' is not close hauled, neither is a boat that is 'shooting'

Gordon re: “full and by” ..

You keep adding new terms each time you define the previous one! LOL

This is all great to get on the same page on what we mean by what we say.  Also, thanks for sharing your working definition.

My issue with your working definition however (as applied to rule 13) is Case 17 .. adapting to changing etc … when 17 states it’s regardless if or how the boat is even moving through the water. 

PS: This is why I’ve always thought of the “stuffing angle” as the point a boat has reached close-hauled in rule 13. Sure a boat can continue down to her “best VMG”, her “footing angle” or below to her “acceleration angle” (slightly below footing), but I’ve imagined she’s reached a close-hauled course once she gets to that tightest “stuffing” angle, even if she doesn’t stop turning there. 

I think what Gordon calls "stuffing" is generally called "pinching" in Sydney, Australia.
Gordon, please let us know if you use both terms and if so the difference in meaning.
IMO "close hauled course" is the highest the boat can sail without the jib cloth fluttering/starting to backwind at the luff, with the sails set for working hard to windward (not caring about speed or VMG) in the prevailing conditions.
Once a tacking boat reaches that course, even if she chooses to sail below it, she regains her rights lost when she passed "head to wind", even if her sails re not yet trimmed. The test is about the hull course, not the actual trim of the sails.

I can't get my head around this.  Boats on anything above 90 degrees to the wind are gaining to windward and can adapt to wind direction by changing course - I can't see it helps define close-hauled.

I think you could allow close-hauled to be above the 'no bubble' in a tightly sheeted main because of a high-and-slow mode.  I'd consider the closest close-hauled to be when a boat can continue to make way to windward through the action of wind on sails.  i.e. pinching is allowed, if it can continue; shooting the mark is above close-hauled because it relies on momentum.

But all these are still judgements.  Close-hauled is. in practice, taken from the behaviour of similar boats heading to the same mark n the vicinity of the boat in question - there's a few degrees of variation in the VMG choice they take.

I like the 'closest you can sail to make progress to windward' but it's not a momentary thing (e.g. stuffing) - it requires ongoing progress.  As Angelo says

On the keelboat coming round and setting up lower and them coming up, I agree it's optimal for their speed, but I'd be happy with them being 'close-hauled' when they first get to the angle they end up at - going lower is at that point a choice and an optimisation, but they could stay at that other angle and suffer side-slip for longer if they really wanted to - and as they are sailing and continuing, I'd say they were close-hauled.  They are also close-hauled at the lower angle as they seek to establish flow, too - these are essentially low and fast/high and slow versions.  So in my view, the keelboat gains rights before perhaps Gordon would give them.

" until she is on a close-hauled course"
 I would not infer the word "maintain" into the rule. Once she momentarily gets to close hauled course her rights are regained even if she goes below, or back above, close hauled immediately..
The heading is "While tacking". IMO the tack is completed the moment she acquires, however briefly, a close hauled course.
Having momentarily gained "close hauled" she regains (subject to the various rules and exceptions) rights to luff a windward boat, over a port boat if on starboard, over a boat (even barely, but with "room") clear astern.
To get to "footing" from tacking you pass through "close hauled"
Any course equivalent to "shooting" is not close hauled and does not complete a tack and restore rights.

So the grey area is a few degrees between the course heading that would hold a tightly trimmed jib with the first say 10-20cm not in the perfect curve and the course heading where it would be in such a perfect curve.
 
So is the course where the jib would not be 100% in the perfect curve "close hauled"? If yes, how much of the front of the jib might not be in the perfect curve? 10%? 20%? 30%
IMO "close hauled" is where the jib first would form the perfect curve when tightly trimmed, front 5cm ignored.

Given that the sails's actual trim is irrelevant to the boat's actual course it is a judgement call that we rely on PC's and umpires to make and the actual position of the sails is merely a consideration, unless it is shown that they were trimmed to a perfect curve.

So it gets down to burden of proof, reasonable probability, last point of certainty, reliability of witnesses and judgement of the PC or umpire.

    Writing this leads me to a working definition of 'close-hauled': a course on which a boat is seeking to gain to windward and on which the boat adapts to changes in wind direction and strength by changing course and not by trimming the sails.
I can't get my head around this.  Boats on anything above 90 degrees to the wind are gaining to windward and can adapt to wind direction by changing course - I can't see it helps define close-hauled.

I would argue that this is a pragmatic definition

An illustration: on a beat to windward a boat is approaching the mark slightly below the lay line. The sails will be trimmed to suit the wind speed. The helm will react to any change in wind direction by changing course to maintain the optimum angle to the wind direction. The boat is on a close-hauled course.

Another boat is approaching the same mark a short distance above the lay line. The crew will react to any change in the wind direction by trimming the saila in order to maintain the optimum speed while maintaining the course to the mark/ The boat is NOT close-hauled.

This definition respects the reality that the crew may choose to sail higher and slower or slightly lower and faster. This can be seen in dinghy classes that may plane to windward. In marginal conditions there may be a noticeable difference in the heading of a boat planing to windward and one still in displacement mode. Yet both are close-hauled.

Does this definition from the pre 1995 RRS help:

Close-hauled A yacht is close-hauled when sailing by the wind as close as she can lie with advantage in working to windward.

John re: "Close-hauled A yacht is close-hauled when sailing by the wind as close as she can lie with advantage in working to windward."

I think so ... it's basically what I'm saying but the distinction we are talking about (I think) is "can lie" vs the imaginary "could lie" in the situations where a boat's hull is reaching that angle before any sails are trimmed or the boat is effectively making way in that state (or has no intention to make way on a close-hauled course).