Strobes again

bilbobaggins

bilbobaggins

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Remembering the heated spat on here some time ago about the use of strobes - and the original post was AIR about offshore use - this appeared in the news....

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In his blog, Pete ( Goss ) writes: "Last night had an odd boat pass us by about a mile away in that it had a strobe light high up and we were wondering if it might be a Vendee Boat. Perhaps someone could compare web sites and let us know."


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Personally I think strobes are damned useful when used well offshore. It would be good if the Colregs guys could re-appraise the use of strobes and come up with some acceptable guidelines or rules to prevent confusion. I don't see the use of strobes going away, but quite the reverse, as they attract attention, and that has to be a good thing, providing that others are not confused in the process.
I suppose it's inevitable that Colregs will always be playing 'catch-up' where technology is concerned (like, there hasn't always been electric lighting, or radar ...), and that there really needs to be some form of regular re-assessment of technical developments and their deployment at sea.
 
Seems to me to be pretty simple :

Rule 34 (d) allows the classic five short blasts to be supplemented by an equivalent light signal, if someone would come up with a 'black box' that would automatically flash an all round LED (existing anchor light ?) in quick or very quick flash mode as groups of five with an appropriate pause in between, then problem solved.

It would not be confused with any buoy. The regs will not have to be changed.

Any electronic designers out there ?
 
Don't get stressed about it, they will continue to be used by people who think they are usefull and fullfill a purpose.

I will continue to use my blue srobe when I think the situation demands it. It does get you noticed when you need to be seen - even in the middle of Biscay.

As for the Col' Reg's issue, when I'm told by a responsible officer of the MCA (or similar) to move it I will. And put it back when I've cleared out.

As I said "it works, therefore it stays".
 
[ QUOTE ]
Seems to me to be pretty simple :

Rule 34 (d) allows the classic five short blasts to be supplemented by an equivalent light signal, if someone would come up with a 'black box' that would automatically flash an all round LED (existing anchor light ?) in quick or very quick flash mode as groups of five with an appropriate pause in between, then problem solved.

It would not be confused with any buoy. The regs will not have to be changed.

Any electronic designers out there ?

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It's a good idea in principle, although there are at least 2 lighthouses which flash 5 shorts, Casquets and Dungeness. There might be others, especially overseas.

From an engineering point-of-view, a single flash every 30 secs or so would be favourite (lower power requirement and longer tube life), but unfortunately there are lots of lighthouses with a single flash.
 
I have found strobes on the water very difficult to get a "fix" on. Yes, they are visible and yes they attract attention but I found it difficult to actually know how far off they were.

You think that they are some way off and you are approaching slowly, then suddenly realise that you are actually going past the light right then. Which, of course, makes them far from ideal for nav lights.
 
I see that that our Pilots safety gear includes strobes on their lifejackets.

So we have a conundrum. Do we keep away from them, or head towards?

Perhaps the best thing to do is report the strobe sighting to Coastguard and ask for guidance.
 
I'm all for introducing a masthead strobe for yachts and maintaining the conventional nav lights.
A small strobe on a bike can clearly be made out even on a wet dark night on the roads. Therefore to intially bring attention to a craft and to then identify it as a yacht by conventional means should be a good thing surely?
A problem arises when individuals take things into their own hands and start using a strobe outside the colregs. In the event of an incident, the user could well be deemed as acting illegally and also nullify any insurance on the vessel.
 
Absolutely nrottocs.

Following a collision, each party will be looking to show evidence of fault in the other. I for one will be sure to mention the other's non regulation lights causing my confusion.
 
" It's a good idea in principle, although there are at least 2 lighthouses which flash 5 shorts, Casquets and Dungeness. There might be others, especially overseas. "

Fair enough - however if the strobe was producing, say, either a Very Quick ( 2 / sec.) or Ultra Quick (5 / sec.) with , say, a 10 sec. pause I don't think it would be confused with any other light .

I'm sure someone will dig out a lighthouse in China or somewhere that has this characteristic !!!
 
Oddly enough, in aviation we have to use both conventional nav lights and also white strobes when on the active runway or airborne. They're darn good at catching the eye then yoiu look for the reds / greens to work out if you're about to hit each other. Admittedly, there is a dearth of lit bouys or lighthouses up in the big blue yonder, but we also use strobes as airfield and even runway markers (the "running rabbit" lead in lights) and again these supplement identification lighting. Why not in the marine use as well? Downside is strobes are utterly blinding in close quarters!
 
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I have found strobes on the water very difficult to get a "fix" on. Yes, they are visible and yes they attract attention but I found it difficult to actually know how far off they were.

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A real 'strobe' light (i.e. one used as a stroboscopic flash to stop motion) looks almost like a steady light, and is quite easy to get a fix on. A single flash repeated at intervals of a few seconds is more difficult; it's too short to be able to get a fix with a bearing compass, and no matter how carefully you hold the compass the next flash will come up in an unexpected place. Some years ago Trinity House had an experimental buoy with an electronic flash in their experimental area off Harwich; superbly visible but the devil's own job to get a bearing from.

But why do we need lights? I reckon that they do four jobs. Firstly, and most importantly, they draw attention to the existence of a hazard; secondly, they show the direction of the hazard; thirdly they identify the type of hazard; fourthly they help to distinguish stand-on from give-way vessel and may give some indication of the direction in which the hazard is moving.

Viewed in that way, most of our discussion about lights is based on the poor performance of our present lights in performing their first task; drawing attention. Provided that we are warned of their presence, the existing lights perform their other tasks quite well. The flash, on the other hand, is very good at drawing attention, but relatively poor at the other functions.

The human peripheral vision is very good at detecting rapid changes, but less good at detecting slowly changing or steady things. So let's add a periodic flash as an option to our present lights, perhaps in the same housing as the masthead anchor light.

How big a light would we need? Take as a starting point the sort of flash used in a disposable camera. I've just dismantled one. The storage capacitor is 80 microfarads at 300 volt working; assuming that a fully charged capacitor like that is discharged into the flash tube then each flash takes about 7 joules of energy. My bet is that they wouldn't work that close to the limits, and 5 joules is probably more likely.

How often would it need to flash? Imagine that you are looking forward when something catches your eye on the beam. You turn to look at it, but there's nothing there. How long would you stay looking in that direction before turning back? My bet is that 10 seconds is too long, but that a flash every 5 seconds should be OK.

How much battery power would that need? 5 joules every 5 seconds is 1 watt. The charging process can't be more than 50% efficient, and with other inefficiencies we'd probably draw about 3 watts. At 12 volts, that's about a quarter of an amp; compared with the other lights, that's negligible.

You would still need the other lights, to fulfil the other functions. You can imagine the mental processes; "What was that?" .... "There's a flash!" .......... "There's a red light! Must be a sailing boat."

Yes, there are a few lighthouses that are Fl 5s. But I don't think that the normal lighthouse light, with its rotating loom, could ever be mistaken for a short electronic flash lasting a millisecond or so. Certainly none of the IALA buoys flash Fl 5s.

What do you think?
 
Rule 36 quite specifically says "the use of high intensity intermittent or revolving lights, such as strobe lights, shall be avoided."

If you decide that you are going to ignore Rule 36, why shouldn't anyone else choose to ignore Rule 5? or 6? or any other that they find inconvenient?

Rule 25c specifically gives sailing vessels the option of displaying "at or near the top of the mast, where they can best be seen, two all-round lights in a vertical line, the upper being red and the lower green".

Having been lucky enough to skipper a boat that had them, I can say that they are great ship-scarers, and perfectly legal.

Why bother with strobes?
 
Peter - thank you for that , good information.


"Why bother with strobes? "

because :

"The human peripheral vision is very good at detecting rapid changes, but less good at detecting slowly changing or steady things."

!!!!
 
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Rule 36 quite specifically says "the use of high intensity intermittent or revolving lights, such as strobe lights, shall be avoided."

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No it doesn't.

It reads: Rule 36: Signals to Attract Attention

"If necessary to attract the attention of another vessel, any vessel may make light or sound signals that cannot be mistaken for any signal authorized elsewhere in these Rules, or may direct the beam of her searchlight in the direction of the danger, in such a way as not to embarrass any vessel Any light to attract the attention of another vessel shall be such that it cannot be mistaken for any aid to navigation. For the purpose of this Rule the use of high intensity intermittent or revolving lights, such as strobe lights, shall be avoided."

So - it doesn't say you can't use strobes, only not to use them as a means of 'attracting attention' - the meaning of which I infer as being a method of establishing some form of one-to-one communication.
As Colregs is concerned with the minimum lights to be displayed, and not additional lights (as shown by cruise liners, fishing boats etc), as long as a strobe is used in addition to nav lights, it could be argued that they are permissible.

Afaik, cruise liners do not have a rule which prohibits the use of flash photography on deck during the hours of darkness ?
 
I was doing my NMs the other night. Ok so it's been deleted but it was a north cardinal - "GfU" is the code for the north cardinal icon.

L5703/08 SCOTLAND — Firth of Clyde — Dunoon Bank — Buoy.
Source: Clydeport Estuary Control
Chart: SC5610·2 ETRS89 DATUM
Delete GfU Fl(5)Y.20s 55° 56' ·83N. , 4° 54' ·25W.

So, yes, lights do flash 5.

Night vision - when dark adapted the eye tends to scan to utilise the rods more than the cones - this is why the occasional flash appears to move about.
 
SAE140, I don't follow your logic. Surely the reason strobes are being discussed here is because their proponents do see them as a means of attracting attention. In which case the Rules clearly prohibit their use.

Possibly the day might come when ColRegs are modified to include strobes, but until then we have to accept the rules as they are. As has already been said, we should not make personal selections of which rules we choose to obey and which we choose to disregard.

On a practical note, I have posted on a previous occasion that I once made a long offshore passage on a boat whose owner insisted on displaying a quick flashing strobe. Arguably it got us noticed by other traffic on those increasingly rare occasions when anyone bothers to maintain a visual look-out, but I felt very uneasy when we closed a coast and started giving other vessels a convincing imitation of a northerly cardinal. The only time it could arguably have been of some benefit was in fog. Unfortunately the light pulses radiate back from the fog around the boat, totally ruining the watchkeeper's already limited range of vision.
 
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