Nav Light Conundrum?

[dom]

Boat light regulations hark back to the days of incandescent lamps, puny batteries and wheezy charging systems (Part C Colregs: <12m requires sidelights vis at 1m, sternlight 2m; 12-20m sidelights + sternlight 2m). The advent of better alternators, solar power, LED technology, etc. has however completely changed the game.

My boat used to sport 25W incandescent bulbs delivering 350-400 lumens each. The vast majority of upgrades ones sees are of c.3W LEDs with a slightly higher lumen output, which naturally save the vessel a few Ah overnight.

I decided to split the power gain (so to speak) and fitted 15W LED lamps delivering c.900 lumens each. A bit more power (c.20Ah) over the night, but the payoff is that I'm much more visible.

Why don't more people go this route? Or perhaps they do?

 

[lw395]

The gain in being seen from a brighter light is not proportional to power.
Having brighter nav lights than anybody else might mean other boats are not seen. Or people may mis-judge your distance.
A 15W LED lamp in a typical nav light fitting might run quite hot and not last very long?
On many yachts, the nav lights illuminate the waves to some extent. Other times they illuminate the rain. There is a chance you will be limiting your own night vision at times.

 

[awol]

Many years ago when NiCd batteries came available I popped a 3W bulb into my rear EverReady Nightrider bike light instead of the usual 0.3W. I stopped at a pedestrian crossing and a Ford Escort shot past nearly hitting a pedestrian. I caught up with the car at the next stoppage and his excuse? "Blinded by my red light!"
Try not to blind too many mobo drivers!

 

[Elemental]

My boat used to sport 25W incandescent bulbs delivering 350-400 lumens each.
...
I decided to split the power gain (so to speak) and fitted 15W LED lamps delivering c.900 lumens each. A bit more power (c.20Ah) over the night, but the payoff is that I'm much more visible.

Presumably you changed the lenses at the same time ? Do they not carry maximum power / brightness recommendations?

 

[bedouin]

Have you actually checked to see whether the increase in power does make you visible from further away?

Irrespective of that these days I don't think of nav lights as being the main method of being seen by other vessels except at comparatively short range (< 1NM) so I am not sure that pushing up your visibility from 2NM to 3(say) has a massive impact on visibility.

That said I am about to replace my old nav lights with new LED ones and will install those intended for larger boats so I will be doing much the same as you.

 

[dom]

Presumably you changed the lenses at the same time ? Do they not carry maximum power / brightness recommendations?

Interesting comments all:

@ lw395: yes you're right, the reflection on the water esp from the stbd light can be annoying. I might buy some 5/10W lamps for comparison purposes. The fittings are rated higher, so not a prob.

@awol: wrt blinding other vessels, I don't think this is a massive problem, but will follow up

@Sea Spray: great point, checked but lenses not marked!

@ Bedouin: no tests, but I asked a shipping co.'s advice and they 'thought' (subject to size/lens) that 1000 lumens wld be visible at 5-6m assuming average atmospheric transmissivity (K factor of 0.8).

Looks like I have a lot of work to do . FWIW, said shipping co. pointed out that larger ships like to make course alterations in advance of 4m. Then there are the endless stories of small boat vessels being too dim to see.

Might be worth a yachting mag doing some proper tests, though for all I know they already have.

 

[cueball]

A word of warning, I installed really good LED NAV lights, resulting in me having to gaffe tape all of the pulpit stainless as the bright reflection was ruining my night vision.

 

[Giblets]

......but the payoff is that I'm much more visible.

Sadly the same can't be said for your AIS (unless you keep turning it on and off!).

 

[bedouin]

I think visible distance increases with the square root of Lumens, so if 1000 Lumens is visible at 6 miles then 500 is visible at 4 - which sounds plenty far enough to me

 

[DJE]

15W LED sounds huge. I have 13.5W lamps in my office and they are brighter than the 100W incandescent lamps that they replaced. They are rated at 1520 lm. I suppose the output of coloured lamps is less for the same power as white?

 

[dom]

Sadly the same can't be said for your AIS (unless you keep turning it on and off!).

Lol! I have been working off my backup antenna again (stern rail) this year with a splitter as I had lent a component to another forumite!

All sorted now and transmitting back from the masthead with a VSWR of 1.25 following a trip up to the masthead Sun before last. Also purchased a horrendous looking orange Echomax passive reflector for when its foggy.

Seriously though, I saw a plot of two 'typical' yachts in a 5-6m sea on the simulator of a big shipping co. One had a radar reflector, the other not. Massively powerful system could not detect the yacht without a reflector. The other showed up fine at 3 miles (this was a simulation but based on real data). Apparently any unexplained bip will trigger the watch to look with the binos and they'll see even a small light ok.

A quick visual - according to them - will not reliably pickup a 10W incandescent light at 1.5-2m or a 25W light at 2-3m in grotty conditions.

 

[dom]

I think visible distance increases with the square root of Lumens, so if 1000 Lumens is visible at 6 miles then 500 is visible at 4 - which sounds plenty far enough to me

The formula I was given was:

I = 3.43 x 10^6 x T x D^2 x K^D
​

I: luminous intensity in old money (candelas) under pre-defined service condition
T: threshold factor 2 x 10^-7 lux
D required luminous range in nautical miles (D^2 relationship is as you say)
K: atmospheric transmissivity

Using this you shld indeed be seen at c.4.5m with a normal K factor of 0.8.

But hey, I notice your lamp is getting steadily brighter

 

[Roberto]

I was once hailed by a warship at about 5-6miles (saw them on radar, no visible lights), "sailing vessel ... ... switch on your navigation lights", it was minutes after sunset and I was fighting with the odd tuna fish, they often decide to commit suicide just before dinnertime. Funny how the warship could spot me without lights from such a distance.

 

[Topcat47]

My masthead sailing lights are leds and far brighter than the incandescent lamps that preceded them. A word of warning, however, I have noticed that LED indicators on cars are only visible from ahead or astern (yes I know they're not boats but you get the sense). Standing at the side of a road, waiting to cross, it's often hard to see them until a vehicle actually turning towards you. I didn't realise how "directional" they were.

My masthead lights are a string of LEDs around a cylinder, justo in case you might think otherwise.

 

[prv]

Funny how the warship could spot me without lights from such a distance.

A warship presumably has image intensifiers and/or infrared cameras.

Pete

 

[sarabande]

Height of lights above sea level is a factor in visibility. It also diminishes the effect of 'back scatter' (total internal reflection of light by water particles [rain, fog, spray] in the air).

A really bright stern light would be best above the plane of the crews' eye level.

 

[weustace]

A warship presumably has image intensifiers and/or infrared cameras.

Pete

I suspect they also have radar which is rather more sophisticated than that you might find on a merchant vessel—not to mention the fact they will probably have more people dedicated to monitoring radar etc. at one time than the average container ship might have in the whole crew... I do wonder whether this might be a bigger factor, actually, now I think about it!

 

[black mercury]

Please remember the lumens output is measured at source not at a distance so hard to compare. Led light output has a far narrower band in the light spectrum compared with incandescent bulbs. This may explain why I have found at night yachts with led nav lights are harder to spot at a distance than ones with older incandescent bulbs. From a distance the incandescent light tend to glint at you and catch your eye, with led lights you see a dot of light. You can still see the light from a distance, but you have to search for it. Its to do with what the human eye can detect. Look at the conversions of light houses to led. The led light is rubbish, it may have the range, you just can't pick it up unless you are looking for it, it doesn't catch your eye. Might be talking rubbish, but this is what I have seen. Maybe a future test would be a good idea.

 

[prv]

I suspect they also have radar which is rather more sophisticated than that you might find on a merchant vessel—not to mention the fact they will probably have more people dedicated to monitoring radar etc. at one time than the average container ship might have in the whole crew... I do wonder whether this might be a bigger factor, actually, now I think about it!

All true, but they wouldn't know that Roberto was a sailing boat without sighting him visually.

(I'm assuming he wasn't transmitting AIS or there would be no mystery.)

Pete

 

[prv]

I have found at night yachts with led nav lights are harder to spot at a distance than ones with older incandescent bulbs.

How do you know what type of lights other passing yachts have fitted?

Pete