Case 145 touches on this topic.  Probably most equitable to use existing channel/shoal markers in the course description instead of "the island" if possible .. or drop a few for the race at specific Lat/Log around the island. 

If it is "too shallow" or otherwise not navigable, then I might have to think about it being an "obstacle".

It's not the best worded case in the book is it!
A boat’s string,... when drawn taut, is to lie in navigable water only.
When I first looked at that I thought it meant that if, when the string is drawn taut, the string passes over land or unnavigable water then the RC has made an error. The rest of the case makes it clear that there's an implied "and constrained to navigable water." after "when drawn taut" in the definition, but it's hard to see where it comes from. 

1: If OA set a course that cannot be sailed by all boats in the race, it screwed up and the race should be tossed on redress
2: Nope - that one is the case in almost ANY race that has land/reef features within the course area

Fastnet Rock comes to mind. A mark and a continuing obstruction.

Jerry ... u read my mind. 

2.  No redress. Buy a smaller boat.

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1.  This is more complex.

Case 145 appears to apply, but I don't believe is actually relevant to Question 1.

Case 145 is taken from the RYA casebook, and answers the question of 'direction from the last mark' and how that may be affected by the navigable waters vs headlands, rivers etc...  It is NOT about the race management's wisdom or lack of in setting a course which cannot be sailed.

Here's what I think...

If a race course is going to be restricted in depth for a vessel who may reasonably be expected to enter, then it should be made clear enough in the NOR. (See Appendix J1.3(4)).  The boat can then look at the charts and decide whether to enter or not.

If it is in the NOR, then the boat cannot seek redress for such a course.

However, if the RO sets the course which surprisingly cannot be navigated by all boats, then it could be an improper action, since that would not be a fair race.

If the course is sailable by all boats (by virtue that all marks are surrounded by water which is eventually navigable to all boats) then it would not be considered a 'restriction'.  (See point 2 above!)  That's life - small boats can round islands tighter!!!

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I sailed one race where a difference in keel depth of 1m equated to being able to sail about 1-2 miles closer to the coast.  This meant massively out of the current for the smaller boats compared to the bigger boats.  Tough luck for us.

Ben re: "it could be an improper action, since that would not be a fair race"

RRS 32.1(d) states that an RC may abandon a race for any reason affecting fairness, but is there an RRS that requires the OA to offer, or the RC to setup, a "fair race" in the first place?

RRS 2 only applies to boats and is about how they compete against each other. The RC is not "competing".

RRS 5 ties the OA/RC to the rules but is there a rule that applies?

Without a "will" or "shall" in a rule someplace, where is the improper action?

PS: We had a thread where a mark was laid in the shallows and boats could not "sail the course".  It seems this is quite different, where all boats could "sail the course" as described.

(I'll reiterate my first comment. Marks around the island should be used/laid to put all boats in deep enough water).

PS2: US118 has an interesting discussion of "improper" .. maybe there is a nail in there to hang a hat on.

Many thanks for your comments.
Let me be 'hypothetically more specific' - the course goes through a channel - lets say 100m wide. The 'channel' is between rocks that some boats can pass over (so no real channel for them) and others have to sail very accurately between the rocks to make the course or take the safe option and sail a long way around. In most conditions steering accurately between the rock would be 'navigable' but if it were upwind or in strong winds then there would be significant risk (ie. low probability, but high consequence). The course is in the SSI's and so you could enter before you know the course.

Mark,

The OA/RC (may have) screwed up.  If this was the only option for a race course - it is what it is and boats can choose to race - or not.  If better options for a fair course were available - fire the clowns that laid the course and have better fun next time.  Having sailed some challenging courses (see Tjörn Runt as an example) everybody knows there are a few tight passages that can get a bit on the edgy side if it blows, one has to make a conscious decision to race or not as it can involve some potential expensive kisses with rocks to go through these. 
For a major championship this is naturally not a good choice of venue/course.  For a traditional race, where the challenge is a part of the tradition it is fine. we all choose to race or not - that is the privilege and the responsibility of the PIC

Horses for courses

Folks
I learn a lot by reading the comments and following the logic. 
With this topic I am reminded that we are participating in a 'pastime and not a profession' and we rely on many willing and able volunteers to run races. The challenge we all have is that we have such a broad range of competitors from 'great to be out there' through to maybe 'win at all cost', the stakes are proportionate to the attitude and thus the expectations vary considerably. This is a situation where the competitors are predominantly 40' ish and anything like a TP52 (or above) has a hard time getting around a course that has some lumps and bumps at 4 - 4.5m depth. 
Be humble, enjoy the privilege and carry on! :)

Mark,

A nice summary to your own questions.

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Ang,

You're right - there is nothing in the RRS which requires an RO to run a 'fair' race - it would be impossible for the RRS to do that.  Probably no race can give all boats equal chance to win (especially not mixed fleet racing).

My reference to 'improper action' then I suppose is probably more accurately in relating to the RC failure to 'describe' the course in the NOR as per J1.3(4) so that the boats could make a decision whether or not to enter based on their draught.