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Vessel detectors - radar visibility of your own vessel
RichH wrote in message ...
Ive often wondered for those situations where the approaching vessel has lost your boat's radar image in the sea state clutter and you have the god awful intuition that they CANT see you ... that a flare shell filled with the appropriate aluminum 'chaff' and sent skywards would be in order. Just imagine being on the bridge of freighter when suddenly what appears on the radar screen in front of you is the size of an aircraft carrier... and to be repeated several times. THAT would certainly get someone's attention. Even if the bridge were unattended, such an 'event' would most certainly set off a few automatic alarms .... if indeed the radar scope was even on on that bridge. Just an exercise in 'mental masturbation' but perhaps relevant to this discussion. Perhaps a cheapa/simple radar emitting device that would give such a false image could be another possibility. Such a device already exists. A few years back, I asked Pains-Wessex if such a device wouldn't help in SAR operations and their reply was that they manufactured the equoivalent of a parachute flar, but woith chaff. The only propblem was that, duue to its costs, the only market was the military... OTOH, before I left for a transatlantic cruise, I fastened a second radar reflector ( s mall 9" HYE model) close to the masthead on the starboard side of the mast whilst I had the DAvis "Echomnaster" hanging from the starbord spreader. All the shiops I spoke to on VHF said they had seem me at "beetter than 10 miles distance" and the captain of a Hapag-Lloyd container ship with whom I had quite a chat (he must have had a Philipino crew to be so happy to encounter somedody who understood German...) told me "You have a very good echo, not a ship's echo, mind you, but a very good one for such a small boat.." When I returned from Europe, I had taken off the masthead reflector that had been damaged, and the reports said that I was only seen at around 6 miles. It gave me confidence that even if my radar went on the blink, I still had a chance to be seen, IF somebody was looking at the screen... john |
Vessel detectors - radar visibility of your own vessel
Shen44 wrote:
SG If these ships are so big and easily seen and well lit and a small boat is maintaining a good helmwatch and obeying the rules ..... how does one get themselves soo close to one that they get "run down" by the ship ...... kinda like "I was driving down the road and this 80 story skyscraper reared up and hit me!!" With respect, your question makes me wonder exactly how many nights you have spent well offshore in a small cruising sailboat. Things sometimes just happen. If you are maintaining a good watch, you should see him LONG before he sees you. At sea, never approach a ship closer than 2 mi. if you have the room. Splendid advice. See above. -- Good luck and good sailing. s/v Kerry Deare of Barnegat http://kerrydeare.tripod.com |
Vessel detectors - radar visibility of your own vessel
"Jack Rye" wrote
two pairs of binoculars 20x60 . . . night vision 5x magnification with an illuminator Although two pairs is a good idea (breakage), 20x magnification would be useless on a boat. A pair of lightweight 8x25s for daylight bouy reading, guests, etc., and a pair of good 7x50s for dawn dusk action. They're not gonna work when it's dark, though. No need for magnification on the NV device; it's a shape detection tool. And the illuminator also isn't needed when boating, in that a "million candlepower" searchlight serves better. NV is for loom detection, shoreline observation, etc., distant viewing applications. Neither does what radar does: penetrate fog, snow and rain. But then radar requires a trained (according to the Coast Guard) operator on station and good reflectance on the observed vessel, a step away from directly "looking" at something using binos or NV. Surely doing your part by hoisting a good reflector (inexpensive too) is proper seamanship. |
Vessel detectors - radar visibility of your own vessel
Subject: Vessel detectors - radar visibility of your own vessel
From: "Armond Perretta" Date: 08/24/2003 11:36 Pacific Standard Time Message-id: Shen44 wrote: SG If these ships are so big and easily seen and well lit and a small boat is maintaining a good helmwatch and obeying the rules ..... how does one get themselves soo close to one that they get "run down" by the ship ...... kinda like "I was driving down the road and this 80 story skyscraper reared up and hit me!!" With respect, your question makes me wonder exactly how many nights you have spent well offshore in a small cruising sailboat. Things sometimes just happen. G Those nights existed in my past around N.E., but what has happened more, in many areas was seeing a close aboard, dimly lit cruising sailboats, sometimes at a point where my options are limited, and wondering how HE could let himself get so close. You're right, in that sometimes "chit" happens, and it happens on both sides of this coin ..... just DON'T expect a ship to see you and/or react to you as you might expect or want him to, or G you may hit that ship, and he won't have a clue that you did. Again .... never approach closer than two miles at sea, and if you miss the ship and it's close aboard or within that distance, figure it's up to you to avoid .... worry about some rule later. If you are maintaining a good watch, you should see him LONG before he sees you. At sea, never approach a ship closer than 2 mi. if you have the room. Splendid advice. See above. -- Good luck and good sailing. s/v Kerry Deare of Barnegat http://kerrydeare.tripod.com |
Vessel detectors - radar visibility of your own vessel
Subject: Vessel detectors - radar visibility of your own vessel
From: "Armond Perretta" Date: 08/24/2003 14:04 Pacific Standard Time Message-id: Shen44 wrote: Again .... never approach closer than two miles at sea, and if you miss the ship and it's close aboard or within that distance, figure it's up to you to avoid .... worry about some rule later. Always a sound approach, but consider this. I have a 4 to 4.5 knot sailboat. Offshore the commercial traffic I encounter (neglecting for the moment commercial fishermen) typically maintains 16 to 24 knots. Even should I pick up a target at 8 miles on radar (or otherwise), there is in a practical sense very little I can do to _insure_ a CPA of 2 miles or better. I am speaking only from the perspective of quite a bit of offshore cruising in a small sailing boat, which is not to say I don't realize that "big boat always wins." Oh, fiddle faddle. To begin with, not all ships you see out there will be heading directly at you, so, for the most part, even at 4k, you will have plenty of time to adjust. Secondly, on a clear day you should be able to see a ship at 8mi plus and have a good idea as to it's heading, which means you can take appropriate action to give it as wide a berth as possible. Hey, if you don't make 2 mi., you tried..... at least you worked to maximize the passing distance. From my own standpoint, the "small" boat has a better chance of seeing the"big" ship sooner (especially at night) and starting to maneuver to maximize the passing distance .... especially, considering your slower rate of speed. Don't get me wrong, I don't condone poor watch keeping on ships (visual and radar) any more than I do so for small boats, but varied experience has taught me that both have things which must be dealt with/ worked around, when dealing with the other, and overall, small boaters should always act as if they are not seen and maneuver accordingly ..... use the radio, shine a bright light on your sails, use a strobe (short periods) .... do what it takes, never assume. Shen |
Vessel detectors - radar visibility of your own vessel
Single-handed - and asleep?
Brian W On 24 Aug 2003 17:40:35 GMT, (Shen44) wrote: SG If these ships are so big and easily seen and well lit and a small boat is maintaining a good helmwatch and obeying the rules ..... how does one get themselves soo close to one that they get "run down" by the ship //// |
Vessel detectors - radar visibility of your own vessel
x-no-archive:yes
(Shen44) wrote: Subject: Vessel detectors - radar visibility of your own vessel From: "Armond Perretta" Date: 08/24/2003 14:04 Pacific Standard Time Message-id: Shen44 wrote: Again .... never approach closer than two miles at sea, and if you miss the ship and it's close aboard or within that distance, figure it's up to you to avoid .... worry about some rule later. Always a sound approach, but consider this. I have a 4 to 4.5 knot sailboat. Offshore the commercial traffic I encounter (neglecting for the moment commercial fishermen) typically maintains 16 to 24 knots. Even should I pick up a target at 8 miles on radar (or otherwise), there is in a practical sense very little I can do to _insure_ a CPA of 2 miles or better. I am speaking only from the perspective of quite a bit of offshore cruising in a small sailing boat, which is not to say I don't realize that "big boat always wins." Oh, fiddle faddle. To begin with, not all ships you see out there will be heading directly at you, so, for the most part, even at 4k, you will have plenty of time to adjust. Secondly, on a clear day you should be able to see a ship at 8mi plus and have a good idea as to it's heading, which means you can take appropriate action to give it as wide a berth as possible. Hey, if you don't make 2 mi., you tried..... at least you worked to maximize the passing distance. There are some boats, particularly off the FL coast which do not have a heading that is stable. They are well lit so we can see them (better than the little fishing boats which may be anchored at random with no lights at all), but they don't maintain any kind of heading. We used to think they got their kicks by heading for any small boat they saw. Actually I think they are gambling ships out just beyond the requisite mile limit and aren't going anywhere particular. Bob's method of dealing is to head for them at which point they seem to veer off. We'd never catch them so that's probably safe. From my own standpoint, the "small" boat has a better chance of seeing the"big" ship sooner (especially at night) and starting to maneuver to maximize the passing distance .... especially, considering your slower rate of speed. Don't get me wrong, I don't condone poor watch keeping on ships (visual and radar) any more than I do so for small boats, but varied experience has taught me that both have things which must be dealt with/ worked around, when dealing with the other, and overall, small boaters should always act as if they are not seen and maneuver accordingly ..... use the radio, shine a bright light on your sails, use a strobe (short periods) .... do what it takes, never assume. How long does it take a large ship going at the rate of speed that they normally go at to get from a blip on the horizon to the observer? (8 miles? 12 miles?) If the ship is going 24 knots 8 nm would take 20 minutes. The small boat going 6 knots will take an hour and 20 minutes to do the same distance if I'm correct (and math isn't really my thing) and will be able to separate from the larger ship's course (if accurately determined) by two miles in that length of time.. You'd think that would be enough time to get out of the way, but that assumes you can accurately tell at that distance what their course is, that you are correct in the action that you take, that they maintain the course and also that you see them 8 nm away by whatever means. If you don't see them until they are 4 nm away, they will be at your boat in 10 minutes, and in that length of time you can only get a mile. There was a case here in the bay where a cruising boat running up the western shore at night saw a ship on his radar and saw something else that he couldn't ID, and apparently went down into the cabin to look at a chart or get a cup of coffee or something, and he ran between a tug and the tow and his boat sank within a couple of minutes. So it isn't as clear-cut a problem as wanting each ship to keep proper lookout IMHO grandma Rosalie S/V RosalieAnn, Leonardtown, MD CSY 44 WO #156 http://home.mindspring.com/~gmbeasley/id2.html |
Vessel detectors - radar visibility of your own vessel
Subject: Vessel detectors - radar visibility of your own vessel
From: Brian Whatcott Date: 08/24/2003 18:07 Pacific Standard Time Message-id: Single-handed - and asleep? Brian W Yes .... well, that's a chance you take when doing this, and a whole nuther argument. |
Vessel detectors - radar visibility of your own vessel
Subject: Vessel detectors - radar visibility of your own vessel
From: Rosalie B. There are some boats, particularly off the FL coast which do not have a heading that is stable. They are well lit so we can see them (better than the little fishing boats which may be anchored at random with no lights at all), but they don't maintain any kind of heading. We used to think they got their kicks by heading for any small boat they saw. Actually I think they are gambling ships out just beyond the requisite mile limit and aren't going anywhere particular. Bob's method of dealing is to head for them at which point they seem to veer off. We'd never catch them so that's probably safe. The one advantage to these types of ships, is they are normally well lit. Problem is in seeing their running lights and narrowing down their heading at night (and except for dead ahead, I wouldn't give you much chance of being visually seen by them). Hard to give good advice on these .... fraid you will have to take each case as it comes, but still figure you are your own best solution. How long does it take a large ship going at the rate of speed that they normally go at to get from a blip on the horizon to the observer? (8 miles? 12 miles?) If the ship is going 24 knots 8 nm would take 20 minutes. The small boat going 6 knots will take an hour and 20 minutes to do the same distance if I'm correct (and math isn't really my thing) and will be able to separate from the larger ship's course (if accurately determined) by two miles in that length of time.. You'd think that would be enough time to get out of the way, but that assumes you can accurately tell at that distance what their course is, that you are correct in the action that you take, that they maintain the course and also that you see them 8 nm away by whatever means. If you don't see them until they are 4 nm away, they will be at your boat in 10 minutes, and in that length of time you can only get a mile. The 2mi, is a number to strive for .... it's NOT written in stone. Also, once again .... how many ships that you meet are heading directly at you? That is only ONE case. In many, if not most cases, they will be heading in a direction that crosses your path, and here, it's important to figure out their "relative motion". BTW, if you don't see a ship until it's 4 mi from you, on a relatively clear day, you're not keeping a very good watch. Normally, from the moment you spot the ship, it should take no more than one to two minutes to get a good feel for the ship's basic heading and whether the bearing is steady, opening, or closing .... at which point, your work begins. Naturally,if you've got radar, this is easier, but if not, you need to do some "eyeball" calculations, and these need to be watched closely to see if you are getting the results you wish (probably means a greater course change than if you had radar) There was a case here in the bay where a cruising boat running up the western shore at night saw a ship on his radar and saw something else that he couldn't ID, and apparently went down into the cabin to look at a chart or get a cup of coffee or something, and he ran between a tug and the tow and his boat sank within a couple of minutes. Two errors here (well a bunch, actually). A tug and tow, is normally an easy radar spot (kinda like a triangle small target leading a larger one, close together, maintaining a same distance separation) so poor radar interpretation on his part..... and never leave the radar, till you KNOW what you are seeing and what it's doing. So it isn't as clear-cut a problem as wanting each ship to keep proper lookout IMHO It's a clear cut problem with BOTH vessels keeping a proper lookout, but not clearcut as how you should respond for varying conditions .... I'm saying try to stay at least 2 mi. clear. Well, we all know that's not always possible .....it's a goal and one which can be attained, frequently, only by very early, substantial action. Shen |
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