Forum: The Racing Rules of Sailing
Definition of Obstruction
Jay Howell
Nationality: New Zealand
0
I have been looking more closely at the definition of an obstruction with respect to windward marks that are channel markers consisting of metal buoys and poles, as well as other convenient objects used as marks:
- Obstruction (a) an object that a boat could not pass without changing course substantially, if she were sailing directly towards it and one of her hull lengths from it;
US Sailing provides the following guidance - https://www.ussailing.org/wp-content/uploads/2020/12/Obstruction.pdf
- “In a twenty-foot boat, a course change of 10 degrees moves the bow about three and a half feet. Done when one boat-length away, a 10- degree alteration will clear a seven-foot object on either side”
- “As my general rule I would say that a course change less than 10 degrees is not “substantial;” i.e., a stationary object clearly less than one-third your boat’s length would not be an obstruction, though a moving object will require a larger alteration to get around it.”
- “An average-size channel marker is not going to require you to change your course substantially,”
The 10-degree example appears faulty as it does not appear to consider the beam of the boat. This can be checked using a standard online triangle calculator. If a 6-foot beam is assumed, then the required course change to clear the seven-foot object becomes almost 20 degrees, not 10 degrees.
When existing metal channel buoys and poles are used as turning marks, they can also be subject to strong tidal flows and can require a larger safety margin around the object to pass.
Assume a 4-foot diameter metal buoy and an additional 3-foot radius safety margin around the buoy. Also assume the 20-foot boat has a 6-foot beam and requires several feet of forward movement before it achieves its new course. In this case, the boat would need to make an approx. 26-degree course change. This size course change would seem to be substantial?
See https://www.calculator.net/triangle-calculator.html?vc=&vx=8&vy=18&va=90&vz=&vb=&angleunits=d&x=Calculate
This size course change could also require the boat to tack depending on the direction of the course change. Also, depending on the tide, the required course change could be greater.
For purposes of assessing the degree of course change, hard metal objects that have the potential to cause damage would seem to be quite different than soft marks that can be hit with no risk of damage.
Do clubs at times define these types of marks as obstructions in the sailing instructions? Or would this cause more confusion if by practice they haven’t historically been treated as obstructions?
How would a protest committee assess “substantial” when the hypothetical course change is 26 degrees as in the above example?
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A boat requires relief from. What is the safety zone. No you look at the definition you are ok. No safety zones no tide. If not an obstruction you find another way,.. if you call for room to tack when no need you get space but a possible protest. Like 18.3 Don not approach on port and make sure you lay. Port mark. Take responsibility the rule cannot at these marks save you and ruin other boats races
You are starting to mix your concepts a bit here. The idea of "finish as quickly as possible" is a concept in the rules only found in def: proper course (the word "finish" is no longer in 'proper course' and is replaced by "sail the course" .. but def: sail the course now includes "finish", so it's still there by reference).
In this thread they are discussing Obstructions and rule 19. Proper Course (how one gets to 'finish as quickly as possible') is not referenced in either Rule 19 or def's: Obstruction or Continuing Obstruction, so it is not a factor.
For kelp, we have to look at def: Obstruction .. and ask does the kelp meet those requirements.
Fundamentally it boils down to ..
Q: Is a "30 foot diameter kelp-clump" an object?
A: I think it depends upon the density of the kelp.
If you are talking about a bed of kelp .. where it's more of an area of kelp, maybe it's not an object.
If a kelp-clump is a "thing" of kelp with defined edges and visible density, then yea .. I think that's probably an object.
If we determine it meets the concept of being "an object", then as Mike B said .. it then is a ratio of the size/weight of the boat vs this object to determine if it's an obstruction (see def).. but before that, it has to first meet the concept of "object".
All that said, if there is a known kelp-bed in a racing area, def: Obstruction(c) allows a rule to define that area as an obstruction. So, an SI could ID the kelp-bed and designate it an obstruction.
Also, we have the new rule 14(c) to consider ..
Let's imagine a kelp bed, with individual stipes of kelp (yea .. I had to look-up "stipe"). Each stipe would slow the boat down a little bit when contacted, with the cumulative result that the boat will be slowed but not stopped as it passes through a bed of stipes of kelp. Also stipes of kelp might get stuck on the underwater foils and dragged beyond the bed, affecting the boat's performance past the bed.
So here are the Q's and some A's... (JMO)
Anyone else on #1-#5 above?
Rule 19 states "the outside boat shall give the inside boat room between her and the obstruction". It is reasonable to conclude that the hypothetical assessment in the definition of an obstruction of whether a course change is substantial would also take into account the room that is provided for in the associated rule. Maybe "safety zone" isn't the best terminology, but room means the inside boat can sail a course that allows for the necessary space between her and the object given the conditions and including tide.
Please don't get your nickers in a knot over the definition of Obstruction. I just had a quick look at Mary Pera's book on the 1985-88 rules and the basic rule hasn't changed since then (other than its number). My oldest reference book "Yacht Racing Rules" by L F Nalder from 1948 reveals that the basics from those times have'nt changed much at all, other than being simplified - which process is still ongoing generally.
The 1948 rules around obsructions and marks are amazingly similar as those of today illustrating the validity of their purpose. Remember that rule 20 is a safety rule requiring when a boat hails for room to tack, the hailed boat has no option but to tack. She must tack and if the hailed boat is aggrieved, believing that the hail was unnecessary, she simply hails protest, actually protests, and puts its case to the PC.
A single loose floating piece of seaweed is an object. Its not a definition, so dictionary meaning applies. I don't see how one can avoid that. However I suggest its not "an object that should be avoided" and that 14c doesn't come into play with respect to it.
There's an interesting nuance here that hadn't occurred to me before, and that's the area between "object that should be avoided" and "obstruction". The rule writers must have intended the distinction, or they would have used "obstruction". I'm just trying to think of objects that are not boats, should be avoided, but do not meet the definition of obstruction. Anyone?
It seems the definition of obstruction recognizes there will be situations that are not clear, and allows for this clarification to be provided in the sailing instructions, and seaweed is a good example. Are there any examples of designating seaweed or other objects as obstructions in various sailing instructions? Maybe guidance to race committees on when they might do so would be useful??
I submit that a clump or patch of seaweed is an object, and therefore capable of meeting the definition of obstruction looked at as a whole. Consider, if you are arguing it is not because individual plants comprising the clump or patch or whatever are not large enough to be considered an obstruction, then how do you react to a coral reef, which is comprised of even smaller animals. Anyone want to argue that a coral reef isn't an obstruction? One also gets into the ludicrous position of having to examine the patch of weed thoroughly to see whether it's a single large plant or multiple tiny ones.
Jim as far as coral, that is akin to a rocky bottom so damage to the boat is likely. Also, I'd assume often it is a protected natural resource by law in some locations. Given both of those properties, I don't think coral and kelp make a great comparison.
Also, the existence of reefs of coral might also be charted, reducing the effective depth of the water. In that way, coral is much more like a sand/rock shoal than a bed of kelp. Certainly a sand/rock shoal or shallow shore line is an obstruction.
I think that kelp, given one can traverse it and make contact with it without likely damage or injury, brings 43.1(c) exoneration into the picture as well, which makes the question a less clear as well.
Now, if the beds are protected by local law, then that could be another matter.
The rules writers have long been aware of the weakness of the definition.
A broom handle marker a boat length ahead of a slender 110 is less obstruction than one ahead of a beamy Lido or Opti.
It remains the skipper's call.
You ask the question (I paraphrase) Can a patch of weed be considered a single object.
If it is an object then whether you can push through it or not is, I submit, irrelevant in terms of the definition of obstruction.
Can an object be comprised of numerous smaller objects? In nature that is clear. It can. Your body is!
A patch of weed could be a single large plant growing from a single stem, it could be multiple stems that have grown out from a common root system, or it could be multiple individuals that have all seeded in a hospitable patch of seabed. The same is true of a floating patch of weed. It could be one individual, or it could be numerous pieces that have tangled together. In terms of RRS I claim that it is impractical to make a distinction between a single large plant and an aggregation of smaller plants and to seek to do so is at best futile.
So your answer to that is "yes"?
"Obstruction" is a defined term in the RRS, therefore we can't use the general sense of the word.
def: "obstruction" requires "an object" or an area that a rule designates so. It's not clear to me that an area of aquatic vegetation is "an object". That's just my opinion.
I can imagine that 2 boats might approach a bed of kelp differently ...
Boat A deciding, depending upon the perceived density of the kelp bed and the course-change and extra distance needed to sail around the bed, to just trim for speed & power and to barrel-through it. Where Boat B, not wanting to take a chance of getting mired-down, deciding to sail around it. That's not a physical-property of what I normally think of as "obstructions" in sailing .. where one boat could choose to sail through the middle of it.
You and others disagree. I was hoping that my #1-#5 would generate specific POV's. I'm certainly no authority on the subject.
What is clear to me however, is that an area of aquatic vegetation could be designated an obstruction in the SI/NOR in areas they are known and/or common.
From a competitive standpoint, if S and P are approaching a kelp bed or any other object, the right of way rules are very different depending on whether the object is an obstruction, so some clarity is a good thing. This can be achieved in the sailing instructions. At least kelp is soft.
"Passing" is not the same as "eventually getting past" in our context.
Assume that there is some bed of aquatic vegetation. Let's say it's 20 BL's in width (perpendicular to the boats' paths) and 5+ BL's long (direction of the boats' paths). This veg is laying directly in the path of 2 boats sailing on the same tack and overlapped.
Scenario #1: The leeward, ROW boat decides to alter course to leeward to avoid the veg.
In this scenario, I'd say the leeward boat, by her actions, has indicated that she regards the kelp-bed as an object that should be avoided. Rule 19 would then apply and she would also need to give the windward boat room to pass to leeward of the kelp-bed as well.
Scenario #2: The leeward, ROW boat decides to alter course to windward to avoid the veg.
Leeward is ROW so as long as she complies with RRS 16.1 she can make that choice. If RRS 17 applies and the windward boat claims Leeward sailed above her proper course, Leeward has a great case that, absent of Windward, she would have sailed the same course and avoided the vegetation in that direction.
Scenario #3: The leeward, ROW boat decides to hold course and blast through the kelp, but the Windward boat wants to avoid the kelp to leeward.
I don't think the Windward boat can force Leeward to recognize the kelp as an obstruction. If Leeward holds course or doesn't alter course to leeward in such a way that Leeward "passes" the vegetation, then it's not an obstruction to Leeward. If it's not an obstruction to Leeward, then both boats are not at an obstruction and RRS 19 does not apply. Windward's only choice is to either blast through as well or pass to windward of it.
Scenario #4: The boats are on a beat to windward and Leeward calls for Room to Tack under RRS 20
This is pretty clear in the RRS and Case 3 and Case 10.. A boat that is hailed for "room to tack" must either tack or reply "you tack". The arguments about the appropriateness of the hail and whether it breaks rule 20.1 can only be made in a protest hearing. Windward must act upon Leeward's judgement.
Scenario #5: The boats are passing along the leeward edge of the kelp-bed and Leeward alters course to Windward, forcing Windward into the kelp bed but escaping herself.
Out of all the scenario's, this one is the only one that I think there is any question on. If the boats got into this position to leeward of the bed because of affirmative maneuvering to avoid it, I think we are back up to Scenario #1 and it's an obstruction or continuing obstruction by the boat's previous actions.
The principle in RRS20 works universally. If a boat claims something is an obstruction, treat it as if it is, and protest if there's a dispute. If a boat claims x is an obstruction, requires another boat to manouver and then doesn't react herself it's liable to be a short hearing.
This gets back to my original post which has never been satisfactorily addressed, at least for me. The US sailing guidance on what an obstruction is seems significantly flawed.
There are always going to be edge cases. A very shallow draft boat and a very deep draft boat is the most obvious. But applying the RRS20 principle of "navigate as if it is an obstruction and protest if you disagree"
1. Always works and
2. Fails on the safe side.
Agree. That's what I wrote.