Coast Goard hovercraft hits unlit anchored sailboat with no radar reflector.

[desodave]

Originally Posted by Macblaze

Well, when there is a state of emergency in the province and even the military resources are being deployed, well, you take what you can get.

[StuM]

Originally Posted by team karst

Define "nm". nautical meter??

A nanometre is one billionth of a metre. (A metrer is 39.37 inches, or slightly longer than one yard.) The prefix “nano” means “one billionth”, or 10-9, in the international system for units of weights and measures. The SI abbreviation for nanometre is "nm"


I guess you would pickup a periscope that is 30 nanometres away.

[Adelie]

Originally Posted by team karst

Define "nm". nautical meter??

In SI units it means nanometer.

In the context of a discussion about marine activities is means nautical mile.

I could explain more about why the nautical mile exists and why it continues to be used in navigation despite the near ubiquity of the metric system but I’m tired and the wife is about to make me figure out what dinner is going to be and either make it or go get it.

[bcboomer]

Originally Posted by team karst

A huge hovercraft was a ridiculous choice for this mission.
Reminds me of a hook and ladder truck responding to a fender bender. At least there, its effective to block traffic

Given the circumstances, what would you have sent?

[bcboomer]

Originally Posted by Lodesman

Do you have a link to the video?

It's on a Facebook group: BC Coastal Mariners.

Sorry, I don't know how to share it.

It shows the hovercraft from maybe a hundred yards away, cruising slowly by.
One thing I do see is that the radar antenna is quite far back and the huge fan ducts would obscure quite a bit of the forward area close in.

[TrentePieds]

Lodesman (and all others who understand what's going on in this corner of this 'ere colony):

Not the clip you asked for. Nevertheless, while this clip is a commercial for a firm specializing in "heavy moves", there are many, many worthwhile views of Siyay's sister Moytel, and a good deal explanation of her principles. There are also some shot of her "bridge" while she is underway, as well as a good shot of her spewing spume and corruption right left and centre while making very little way.

Scroll through it till you find the interesting bits :-)

https://www.youtube.com/watch?v=nwkWUZbvZdY

TrentePieds

[Hugh17]

Originally Posted by jackdale

A Canadian Coast Guard hovercraft sustained damage after colliding with a sailboat near Salt Spring Island on Monday evening.

The hovercraft CCGS Siyay was transporting advanced life-support paramedics to Ganges Harbour to medevac a patient to Vancouver around 5:45 p.m.

Coast guard officials say the craft was travelling at eight knots – approximately 15 km/h – in the harbour when an unlit sailboat that was anchored outside the common anchorage area suddenly appeared in front of the vessel.

"The captain of the Siyay was able to perform an emergency maneuver and avoid direct contact with the sailboat," coast guard spokesperson Kiri Westnedge said in a statement Tuesday.

"However, there was contact on the starboard side of the hovercraft and the bowsprit of the sailboat (a spar that extends from a sailboat’s bow)," she added.

Westnedge says the sailboat was not detected on the hovercraft's radar.

No one was aboard the sailboat when the vessels collided. The paramedics and the seven-person hovercraft crew were uninjured in the crash, according to the coast guard.

The rescuers were able to complete the medevac to Vancouver.

https://www.iheartradio.ca/cfax-1070...ast-1.16549765

When a moving vessel strikes an object not moving it is an allision not a collision. A collision requires both vessels or objects to be moving.

[Lodesman]

Originally Posted by Hugh17

When a moving vessel strikes an object not moving it is an allision not a collision. A collision requires both vessels or objects to be moving.

I'm not a marine lawyer, but I always understood an allision to be a vessel striking a fixed object, such as a pier, bridge, piling, etc. A vessel striking another vessel is a collision whether or not both are moving. That leaves some ambiguity, as I would consider a vessel tied up at a pier to be, in effect, part of the pier, therefore striking it would be an allision. A vessel at anchor, while technically fixed to the ground, is still moving, albeit in a small area - so I suppose one could argue that it is either a collision or an allision.

[Lodesman]

Originally Posted by Davidla

I have thirty years plus of operating radars in the marine environment. I once picked up a submarine periscope at 30nm in a sea state 2. (Believe me they don't have radar reflectors.) I picked up yachts at that range and they did not have radar reflectors. A colleague picked up a fishing vessel cooler (esky) at about 20nm. This was completely made of plastic and had no radar signature at all! How did it get detected? It was carrying two refugees and it was lower in the water. Radar can detect a hole in the water easily. Thats why I can see whales in the great barrier reef at 30nm.
The problem with radar is it needs to be scanned continuously to be effective at dealing with issues such as this, by a competent operator who knows the area.

I guess Davidla doesn't want to answer. Submarine periscopes usually give a pretty good return, because they create a "rooster tail" of water as the submarine moves through the water. However, only sticking up a couple metres means the radar antenna would need to be mounted nearly 600 feet above sea level. I'm doubtful that any ship is that tall. I suppose that a rare super-refraction event could have potentially extended the radar horizon significantly - but not likely to be repeated as much as the poster suggested. As others have suggested, then visually identifying what the blip is, would not be possible at the ranges alleged. I call BS.

[Hugh17]

Originally Posted by Lodesman

I'm not a marine lawyer, but I always understood an allision to be a vessel striking a fixed object, such as a pier, bridge, piling, etc. A vessel striking another vessel is a collision whether or not both are moving. That leaves some ambiguity, as I would consider a vessel tied up at a pier to be, in effect, part of the pier, therefore striking it would be an allision. A vessel at anchor, while technically fixed to the ground, is still moving, albeit in a small area - so I suppose one could argue that it is either a collision or an allision.

I am also not a marine lawyer. It is however, an interesting point you raise. Referenced below is a link. Here's the introductory comment. "What is an Allision? The nautical definition of an allision is “the running of one ship upon another ship that is stationary.” The distinction between it and a ‘collision’ is that in the latter, both ships are moving."

https://naylorlaw.com/blog/allision/

Based on this information it is clear that "allision" can pertain to two vessels. I think the operative word now is "stationary." I would assume a vessel at anchor would be stationary by legal definition, but like all legal matters I'm sure that can also be argued.

[TrentePieds]

You will note, please, that Chuck Naylor is an AMERICAN attorney based in Long Beach, California.

This prolonged discussion arose from an incident that occurred in CANADIAN waters. It would be quite wonderful, I think, if forum members not acquainted with Canadian Law, Canadian conventions and Canadian mores, let alone Canadian locations characterized by very particular and somewhat exceptional conditions, would perhaps start a thread of their own where Americans may engage undisturbedly in discussion of circumstances that they may be expected to have a far higher probability of being acquainted with :-)

All the best,

TrentePieds

[Lodesman]

Originally Posted by Hugh17

I am also not a marine lawyer. It is however, an interesting point you raise. Referenced below is a link. Here's the introductory comment. "What is an Allision? The nautical definition of an allision is “the running of one ship upon another ship that is stationary.” The distinction between it and a ‘collision’ is that in the latter, both ships are moving."

https://naylorlaw.com/blog/allision/

Based on this information it is clear that "allision" can pertain to two vessels. I think the operative word now is "stationary." I would assume a vessel at anchor would be stationary by legal definition, but like all legal matters I'm sure that can also be argued.

If we just want to take random links for reference, I can throw up:

https://www.attorneystevelee.com/fre...ssel-allision/

https://www.funnel2tunnel.com/answer...n-and-allison/

https://www.offshoreinjuryfirm.com/m...-an-allision-/

https://www.malleylawfirm.com/mariti...s-an-allision/

[Boatyarddog]

Originally Posted by Adelie

In SI units it means nanometer.

In the context of a discussion about marine activities is means nautical mile.

I could explain more about why the nautical mile exists and why it continues to be used in navigation despite the near ubiquity of the metric system but I’m tired and the wife is about to make me figure out what dinner is going to be and either make it or go get it.

Because the earth, to most, isn't flat.
NM is used in latitude calculations....1 NM is ...1 minute Latitude!
1NM is 1.151, SM (statute mile)
Boatyarddog

[jackdale]

Originally Posted by Boatyarddog

Because the earth, to most, isn't flat.
NM is used in latitude calculations....1 NM is ...1 minute Latitude!
1NM is 1.151, SM (statute mile)
Boatyarddog

To get pedantic:

The Earth is not a perfect sphere but is an oblate spheroid with slightly flattened poles, a minute of latitude is not constant, but about 1861 metres at the poles and 1843 metres at the Equator. So we split the difference. The international nautical mile is defined as exactly 1852 metres (6076 feet; 1.151 statute miles).

We still use the latitude scale on Mercator projections as it is close enough.

[Lodesman]

Originally Posted by jackdale

To get pedantic:

The Earth is not a perfect sphere but is an oblate spheroid with slightly flattened poles, a minute of latitude is not constant, but about 1861 metres at the poles and 1843 metres at the Equator. So we split the difference. The international nautical mile is defined as exactly 1852 metres (6076 feet; 1.151 statute miles).

We still use the latitude scale on Mercator projections as it is close enough.

With the standard I grew up with, a nautical mile is 6080 feet. This discussion on how this was derived takes up a fairly significant portion of Chapter 1 in the Admiralty Manual of Navigation, Vol III.