There is no case to my knowledge. I would take the plain reading of the rule and agree that the leeward boat cannot "heat up." 

If the windward boat overtakes to windward from astern then surely Rule 17 does not apply and the leeward boat can sail as high as she like to fill her spinnaker.

What a good question.  First let's assume rule 17 applied to the leeward boat.  The likely scenario is leeward approached from clear astern, established an overlap and then became blanketed.  Leeward would not luff in the absence of windward, therefore leeward would be sailing above her proper course.  I see there is a counter argument but it would be tough to persuade a protest committee.  Especially since if leeward was not constrained by 17 her move would be to luff the boat trying to pass to windward.

After establishing an overlap from leeward, the leeward boat may jibe and then jibe back onto the original course, which eliminates the restriction created by RRS 17. The jibe needs only be completed with the mainsail. This is a common maneuver with non-spinnaker boats like Lasers. Once done, the leeward boat can sail as high as they choose. A simpler option for spinnaker boats is to establish the overlap from greater than 2 BLs. 

Jim, there are a lot of issues at play here, as much depends on sym v asym, other boats around that might influence the leeward-boat's decisions, wind conditions or changes.  

What I'm saying is that "proper course" is not a static, singular thing, especially for asym boats.  Even sym-spin boats have a range of angles that produce very similar VMG's (depending on the conditions), so even under normal circumstances sailing alone, an asym or sym boat will "wobble" downwind to maintain a good head of steam.

Also, a boat overtaking from behind might actually sail below their proper course to establish overlap to leeward and then once overlapped, head back up to their proper course range.

Rule 17 says "above her proper course" .. so when we are talking about a range, that would be above the upper-range of her proper course. 

If your premise is that:

If the above is all true, then .. no .. L can't "luff up" W to clear her air.

I think if in the absence of another boat you would go hot then you can. 

Thanks for the replies everyone. Yes I understand about approaching from outside the two boat lengths and gybing the main and such, I was trying to keep the scenario as simple as possible, that is, the windward boat blanked the leeward boat while leeward is subject to proper course limitation. I was thinking primarily about asym boats when I posed the question.  

This did not come from an actual incident, it's just a thought exercise. It seemed to me that the leeward boat would not be permitted to heat up to fill her chute, but I could not find a case. I'm surprised there is not a case, as it seems this (1) would be a common occurance and (2) it's really not an obvious restriction given the circumstances.

I say it's not obvious because as we know, a tactician has a lot of latitude on selecting his proper course. Is there current? What sails do I have up? Did the wind velocity change? None of these things of course involve the windward boat but I think it's a distinction many sailors miss.  

I would say that the leeward boat is not allowed to sail above her proper course if the reason for the sail collapsing is the presence of the windward boat.  If she could then what would be the point of having rule 17 in the book?  If leeward can justify luffing a windward boat up simply because her spinnaker collapsed, which is at the point in time when she most wants to luff windward to pass beneath her, it really defeats the purpose of rule 17.

Simply put, the leeward boat's proper course is what they would sail in the absence of the other boat...So, yes...a Leeward boat with an asymmetric sail may sail higher than a windward boat with a symmetric spinnaker as long as this is the angle they would be sailing in the absence of the windward boat. But no...they cannot sail higher than their proper course to clear their air that was blanketed by the windward boat. 

Is this a match race, fleet race, or team race? In match racing, rule 17 is turned off. 

OP, might you have a diagram, please?

Well I was thinking it's the context of a fleet race, but really it does not matter, it's only important that I stipulate that the leeward boat is subject to the proper course limitation. I don't think it needs a diagram, I tried to describe it as simply as I could, but Andrew is there something missing from my description that a diagram would address? 

Hi Jim,

I'm trying to understand and learn from the scenario you've painted and facets of it that might be clear to some, aren't yet clear to me.

In the scenario the leeward boat has her spinnaker collapsed by a windward boat.  I infer from that description that the windward boat takes an action that causes the leewards boat to collapse and not that the leeward boat has caused their own spinnaker to collapse.

I'm curious how the scenario comes about that the windward boat causes the collapse, and at the same time the leeward boat is limited by Rule 17.  How are these boats overlapped and how did the overlap come about? 

Andrew, read my implied play-by-play above.  It happens all the time. 

 I do not know how to post question re; windward, leeward at the start line?  That said following is my question.
 Question is; coming  to the start line, pin end both boats on starboard tack A is windward B is leeward boats are slightly overlapped behind start line B tries to luff A, A responds by heading up does not touch the pin as both boats cross start line B continues to luff A after the start and is well beyond head to wind with sails luffing, A responds by coming up and hails B sail your proper course B continues to luff A then comments if we have contact I will protest you A tells  B again to sail a proper course B abruptly goes bow down A goes bow down almost same time trying to avoid contact with B,  B stern just misses hitting A amidships by inches but no contact occurred. .  Question is who had right way and when?  Seems to me poor sportsmanship by B to apparently try and make contact and not make an effort to avoid contact.  If B had made contact with A could B have been protested by A for trying to make contact and not avoiding a collision and also for not sailing a proper course?

Thanks, Jim

Hi Andrew, I'll explain. I'm speaking in general, so please everyone, let's not play gotya.

Picture two boats racing downwind. Very often, they are not going dead downwind, even boats with symmetric often sail a bit above dead downwind. Boats with asymmetric rarely if ever go dead downwind (qualified because of the wing on wing trick - forget that for now). This is more of an issue in mixed fleet racing, where some boats are faster than others but it can happen in any type of fleet. So for now, as is very often the case, assume these boats are not dead downwind. 

Now, let's say boat A catches boat B and chooses to go below her (perhaps to prevent being taken up). Boat A will establish a leeward overlap under boat B. Remember, for whatever reason A is the faster boat. As she passes B to leeward of her (so long as it's within two boat lengths side to side) boat A becomes subject to the "proper course" limitation and may not head above her proper course.

"Proper course" is the course boat A (the faster, leeward boat in this case) would sail to get to her mark as quickly as possible in absence of the windward boat she is passing. So if there is current, boat A may steer a course that takes current into account. She may sail her fastest point of sail for the sails she has up. Stuff like that. 

Now, as she passes under boat B and is close, at some point the sails of boat B are probably going to block the wind from boat A. At this point boat A is likely to experience her spinnaker collapsing. Boat B didn't do anything but sit there, but her sails create a wind shadow. When a spinnaker collapses, a driver will often head higher, to fill that spinnaker again and keep the boat moving. But in this case, boat A may not do that because doing so (absent another reason) would mean that she is sailing above her proper course. Remember, proper course is the course she would sail ABSENT the windward boat. But the spinnaker collapse was caused by the windward boat, it would not have happened in the absence of boat A, so boat B may not use this as reason to head up.

Now, if the two are sailing happily along and the wind shifts or dies, impacting both boats, then boat A may in fact claim her proper course is to head up, because this is probably what she would do when the wind dies whether the other boat is there or not.

Does this help? 

PS - The lesson learned is, unless you're much faster and can roll right under the windward boat, don't pass below her too close. 
  

Jim Honey, that is a more complex question and there is much to address, such as what does "well beyond head to wind" mean? I suggest you start a new thread with this question and people, including me, will address it. In the new question it will be important to know when the start gun went off and where the boats were at that time. I can tell you that, regarding rule 17, it's important to know how the overlap was created, even if it was created before the start gun. But please, make a new thread with those considerations in your question. 

Many commenters are inventing rules and definitions when the existing rules suffice.
"In the absence of the other boat" does not include the absence of the other boat's wind shadow, turbulence, or wake,
The spinnaker may collapse from yet a third boat's position or natural causes.
Proper course may be to luff to fill the spinnaker.
RRS 16.1 suffices to protect the keep clear windward boat from the leeward boat's proper luff.

If you remove the other boat you must also remove the effects of that boat as there is nothing to cause those effects, i.e. if the boat is absent then so are her sails and hull; no sails therefore no wind shadow, no hull therefore no wake and no turbulence, etc.  This is not inventing any rules or definitions.  It's common sense.

Under your interpretation the only thing the leeward boat can't do while limited by Rule 17 is sail a course where it tries to occupy the same space as the windward boat, i.e. only the other boat is absent but not the effects of that boat.  This makes no sense whatsoever.  Why have rule 17 at all if this is the reasoning?

If a third boat, with which the leeward boat does *not* have a rule 17 limitation, causes the spinnaker collapse then the leeward boat can luff to fill her spinnaker or even to prevent that boat from passing her.  But that is an entirely different situation than the simple one we are discussing here.  AND this does not remove the leeward's boat's limitation under rule 17 w.r.t to the windward boat, it only changes what is considered to be the leeward boat's proper course.

A boat sails in the wind she sees.
Take away the windward boat from the picture and the boat still sees a velocity header.
Her proper course of action is to react to it.
And who can prove which boat is causing the blanketing, i.e., the overlapped windward boat or a third boat astern.
It makes no sense to allow a course change from a third boat's impact, which the windward boat might not anticipate, yet not allow a course change that the windward boat precipitates and expects.

Perhaps some day we'll have a case on this. 

Case 7, Case 14, case 46 all refer to this scenario.  Regardless of the way the overlap occurs the windward boat must keep clear once given time (rule15)to do so. In some instances they cant be luffed but it doesn't mean they couldn't be required to do a substantial alteration of course.  Remember the windward boat's course is irrelevant when overlapped to leeward.