Super resiliant nav lights  - Page 1
Forum section: electronics / projects

author: towlerg
author_rank: Contributor
timestamp: July 18, 2018, 01:13:47 pm
content: I own a small sailing boat which has nav light at masthead and on the bow. The bow mounted lights are very vulnerable to being squished between the pier an 2 ton of poorly handled boat. Even with really expensive polycarbonate ones the lens pop out when deformed.I thought that several ultra bright LEDs in casting resin would survive. If I can reduce the width they will get a little protection from the pulpit (pipework mounted on the bow acting as a handrail amoung other things).There will be a voltage drop due to length of wires (approx 20ft). In the same cuircuit will be trickle charge from small PV controller and a diesel engine. In theory these lights should not be on while the engine is running but if there are big ships close you turn on every light you have.I have no idea how to wire the LED's, serial parallel, with individual limit resistors or a single one? Any suggestions.One more thing does anyone have a reason why it is better to use coloured LEDs or tint (obviously red and green) in the casting resin?

author: Ian.M
author_rank: Super Contributor
timestamp: July 18, 2018, 01:53:00 pm
content: You'll have great difficulty complying with the IMO navigation lights standard, specifically cut-off angles for the visible sectors, and probably the uniformity of luminous intensity, and chromaticity requirements.If you are involved in a collision at night, the use of navigation lights that are not type approved by your national navigation authority, or a recognised foreign navigation authority may void your insurance.The correct lights for small craft less than 12m under power are red and green sidelights (which may be a combined fitting), white stern light, and an elevated white 'steaming' light covering the same sector as both sidelights. It may be possible to use sidelights and an elevated all-round white with no separate stern light to meet the requirements, but that increases the risk of an overtaking vessel not seeing your stern light against a background of shore lights. The use of combinations of lights that don't meet the regulations should be avoided as anything that causes even brief confusion of the other vessel's watch officer (because they do not recognise the combination or because from their angle of view it resembles the lights of a different type of vessel) may either slow their response or cause them to take inappropriate avoiding action, increasing your hazard.You may be able to find type approved LED lights that are sufficiently low profile that they wont be the first point of contact, otherwise you may have to rethink the mountings to move the lights inboard a bit.I've lost a few bow light lenses myself to lock and quay sides, and its now my standard practice to lash a pair of grossly oversized fenders horizontally with a lanyard on each end, just below the gunnels from the stemhead fitting to the rear legs of the pulpit if I am shorthanded or in adverse conditions and am approaching pilings, quays or ship-locks.

author: DaJMasta
author_rank: Super Contributor
timestamp: July 18, 2018, 02:40:48 pm
content: Is it possible to change the mounting point at all to just keep the lens from being the point of contact? Or is it possible to use some other material to build up areas near it to at least share the pressure?I guess my first instinct would be to try to lessen the blow on the sensitive parts rather than just trying to strengthen the part itself, at least in the case of something that's already small and fairly durable on something so large.

author: dmills
author_rank: Super Contributor
timestamp: July 18, 2018, 05:11:31 pm
content: I am having some trouble envisaging how any of the normal nav lights should be that close to the bow?Normally I would expect to see red and green sides probably mounted about where the foremast chain plates are located, a white steaming light up the foremast and a white stern light, only the stern light seems to be to be likely the only vulnerable one and by the time that hits you have probably lost the steering gear.Regards, Dan.

author: Ian.M
author_rank: Super Contributor
timestamp: July 18, 2018, 05:34:36 pm
content: Sloop rigged sailboats that fly overlapping low footed genoas typically have bow mounted nav lights - either a single fitting on the centerline under one of the pulpit rails, or port and starboard lights typically just in front of the forward pulpit stanchions, again under a pulpit rail. They cant be mounted inboard aft of the forestay or they'd be obscured by the genoa on the lee side, and most modern sloops don't have suitable shrouds to mount a light board to that would clear the genoa leach.

author: JS
author_rank: Frequent Contributor
timestamp: July 18, 2018, 07:04:41 pm
content: I have LEDs on my nav and position lights, reversed polarity so 2 conductors manage both lights. Many of the LEDs were burned over the years so it was coming time to fix that, the whole assembly was quite expensive as most things on boat shops but I got a bag of LEDs for 1/50th of the cost and rewired the thing.It had 3 led in series with a limiting resistor for each 3 lights, is what makes the most sense anyway. I tried a few experiments running individual LEDs with it's own resistors so when one goes bad only that one get's off but didn't worked, it was too much heat inside and the things burned because of the heat. I wanted to add zener diodes in parallel with each LED so when it burns, the others in the serie remains on, but two problems there, one is the working area to solder them on the air as the whole assembly originally was and the second one would be when the other polarity is selected the current would be forward in those zeners, that could be fixed with two diodes, one for each light. IIRC white LEDs where 2 in series, red and green 3.The whole assembly was a piece of PVC pipe with two lines of holes all arround, one for each LED, PVC caps, the bottom one had an electrical tube for screwing and taking wires out, the top cap two LEDs for the wind indicator, when the nav light is on. Luckyly for me I don't hit too many things with my mast, but the wind indicators (one mechanical and one electronic) and the VHF antenna would hit first and are more expensive so I can't advice much on resilience. You could pot the whole thing but it's tricky to get some potting compound that conducts heat, doesn't contract while setting, takes nice the thermal cycles and don't break connections, etc. I guess using a sturdy metal pipe and use a similar construction to mine should do, I would have to see if I have the photos somewhere but it seems like a pretty common type of light since LED are around.JS

author: towlerg
author_rank: Contributor
timestamp: July 19, 2018, 11:53:22 am
content: @JS Thanks for the practical advise. Given that both lights are on and off togther I don't understand "reversed polarity so 2 conductors manage both lights." Could you elaborate.

author: Ian.M
author_rank: Super Contributor
timestamp: July 19, 2018, 12:36:15 pm
content: If I'm reading that correctly, JS rebuilt an existing LED nav light with new LEDs. If it was a type approved light, that's pretty dodgy because the beam angle of the new LEDs may not be close enough to that of the old ones, leading to an uneven illumination pattern with intensity variations exceeding the factor of 1.5 permitted by the IMO standard. The reason that intensity variations exceeding that factor are not permitted is the risk that the light will be mistaken for a fixed flashing or occulting one.The odds of a home-built nav light ever contributing to a serious incident other than due to it failing are very small, but do you wish to be personally liable for possibly multi-million dollar damages, serious injury or loss of life?In the event of an incident JS would probably get away with it, unless he's been dumb and blogged about it somewhere that can be traced back to his real identity, as long as his modifications aren't noticed by the incident investigator or any party's insurance investigator.Build a nav light from scratch and the odds are an investigator *will* notice if there is any question raised about the lights your vessel was actually displaying. Your only chance of getting out of that with your skin intact is if you can prove that your home-built light met or exceeded the IMO requirements.The polarity reversal thing is because JS must have wired his masthead tricolour and all-round white in anti-parallel. That saves one wire down the mast. Use a DPDT center off switch, with the lights wired to the moving contacts and power and ground each wired to a pair of diagonally opposite fixed contacts, and it will light the Tricolour when set one way and the all-round white when set the other way, off in the middle. If you want to do this with conventional lights you need to add a pair of beefy Schottky diodes to steer the current through the light selected by the polarity.

author: JS
author_rank: Frequent Contributor
timestamp: July 19, 2018, 09:15:09 pm
content: Quote from: Ian.M on July 19, 2018, 12:36:15 pmThats about it. All around white 3mm leds in one polarity, tri colour 5mn in the other, nice high brightness LEDs l, repair was cheap enough, I didn't used cheap LEDsFor sure the dodgy repair was much better than the one with many leds down, it has quite a lot of LEDs, I don't remember but at least 6 each color, covering 120° it's 20° each, enough overlapping between lights to be pretty smooth with almost any LED, certainly the ones I used. I've seen it from other boats a few times and looks fine to me, pretty clear where all goes.Also, the last time the boat went to a high transit night trip was well before the repair and no plans to do so again for now, if any long journey would be planned I'll note this into the safety checks before leaving. It's mostly used to go to the beach 20' away.I don't know what rules are applied here, I should check and would be interesting to check the one I repaired against this rules.I also built an auto pilot remote control for a friend but let's not start on the safety for that, writing on the seatalk bus.JS

author: towlerg
author_rank: Contributor
timestamp: July 19, 2018, 09:36:59 pm
content: Ian.M I appreciate your dire warnings but with all due respect and with no intention to be rude but the whole sea lawyer thing is getting a bit old. If you think that type approval is going to make you visible to a couple of hundred feet of container ship, then thats fine. They wouldn't see you if you had a lighthouse strapped to the bow. Modern vessels keep radar watch , and not even that sometimes.Realistically, the chances of a guy on the bridge 200 feet up, with the nearest mile or so hidden by the bow, spotting a 5 watt bulb 18 inches off the waterline just about zero.I think it's better to have working lights than broken IMO approved ones, but thats just me.If my insurance company want to avoid a claim , I'm sure they could find a whole bunch reasons.as for "uneven illumination pattern with intensity variations exceeding the factor of 1.5 permitted by the IMO standard." I'm sure a handful a LED's will acheive that goal better than a single incandescent bulb.

author: Ian.M
author_rank: Super Contributor
timestamp: July 19, 2018, 10:35:47 pm
content: Anyone who ever knowingly puts their vessel in the position where that large ship watch officer cant see them because of the line of sight from the bridge over the ship's bow, then they are an <expletive> fool. Most large vessels are entirely predictable, generally have higher standards of watchkeeping than many small commercial and recreational vessels, and it is generally easily possible to avoid situations that would require avoiding action on their part except when being overtaken in a restricted channel, by operating on the assumption that they have *NOT* seen you and have lost your radar return in the clutter. The biggest hazard is usually smaller recreational powerboats with inexperienced and/or impaired operators, and the second biggest hazard is usually fishing vessels, due to their tendency to manoeuvre unpredictably due to the nature of their work.If you want to build your own lights at least study the IMO standards. IIRC Annex 1 of the COLREGS has the details you need.You are going to have an *interesting* time developing lights to meet your stated requirements that would be standards compliant if tested, as the casting resin will affect the optics on the individual LEDS, so the beamwidth wont be as per datasheet.Its actually very easy to meet the IMO standards with an incandescent bulb as long as it has a precision vertical filament powered within its rated voltage range. All it needs is a properly designed Freznel lens that's either a complete cylinder or a section of one concentric to the filament. Its *MUCH* harder to get the required illumination pattern with LEDs, especially in a small form factor. As an experiment, try taking a bunch of identical LEDs wired in series, a suitable PSU and current limiting circuit, and a block of Plasticine (to support the LEDs while letting you easily reposition them), and attempt to get even illumination of a white surface a couple of meters away, then see if you can get an effective cutoff over an angle of no more than three degrees, which is what is required when the port and starboard nav lights are viewed from near dead ahead. If the overlap of the red and green sectors is excessive it vastly increases the risk that the operator of the other vessel will think you are headed straight at them when you aren't, resulting in them taking avoiding action that you do not expect, and increasing the risk of collision.The other issue is, as JS has pointed out, reliability. His commercial lights had many failed LEDs. As they weren't potted he was able to fix them. Your proposed design however is going to be essentially unrepairable once potted in casting resin, and the first significant impact is likely to micro-crack the resin enough that moisture can reach the LED leads which will then rapidly corrode and fail.

author: Ian.M
author_rank: Super Contributor
timestamp: July 20, 2018, 05:02:31 am
content: Other issues to consider if designing an IMO standards compliant nav light is voltage and temperature range, and LED aging. Its got to meet the luminosity requirements at minimum voltage, with enough margin to still meet them after at least five years of the LEDs weakening due to ageing. Its also got to stay within the LEDs maximum current rating at maximum voltage, and , to survive accidentally being left on on a hot day, not exceed their thermally derated power dissipation in high ambient temperatures.Coping with a voltage range of 11V to 15V, at an ambient temperature of up to 50 deg C, without using active components to regulate the LED current is difficult. If you do use active components, then they have to be capable of surviving the transients that may be present on the vessel's 12V system during engine start and running, so you need to design to automotive specs with similar transients to ISO 7637.

author: towlerg
author_rank: Contributor
timestamp: July 21, 2018, 11:54:24 am
content: @Ian.M I probably should let you have the last word as you are clearly both knowledgeable and passionate but I can't resist.QuoteI'm sure you've sailed busy waters at night and know that between the height of the sides of the vessel and deck lights it's almost impossible to know what the watch may or may not be able to see. I've only passed down the Channel once at night and I'll never do that again, I ended up hugging the coast relying on depth sounder and not giving a damn about whether that was IMO or MCA approved. I now day sail on the west coast of Ireland, where I rarely see more than 10 other boats in a day and not one of them bigger than 30ft.BTW I like the lashed fenders idea and if I can find fenders fat enough I'll certainly give it a go.George

author: Ian.M
author_rank: Super Contributor
timestamp: July 21, 2018, 12:32:12 pm
content: Quote from: towlerg on July 21, 2018, 11:54:24 amYeah, and then you hear the horror stories about the only sober watchkeeper being the captain's dog, or the whole crew watching a football match.If you cant clearly see the top half of the front of their superstructure, you can bet the ship's watch officer cant see you. Avoiding conflicts is mostly a matter of whenever possible avoiding entering a moving 'box' extending a few miles ahead of the ship and about a quarter of a mile either side, and a ship's length astern. Unless there are hazards that will affect a vessel of your draft adjacent to the channel, stay out of busy deep water channels, TSSes etc. except to cross them as quickly as possible, and if you have to use a deep water channel or TSS stay near the edge of it.That's just a slightly more formal statement of how you worked your way down channel. However trying to stay in shallow water doesn't help much when there are steep-to hazards like rock pinnacles or some sandbanks in areas with fast tidal streams, and if the weather turns adverse, and you cant seek shelter or at least get in the lee of some shoals that will damp the sea state, then you need as much deep water searoom as you can get, and standing off-shore till the storm blows itself out may be your only option. I therefore don't like sailing along coasts with very few ports of refuge or only ones with difficult approach channels or limited tidal access.As I said the fenders are *grossly* oversize for my 26' vessel - they are about 3' long and 16" diameter. As the flair of the pulpit puts the nav lights about 6" outboard anything thinner just wouldn't work. I salvaged them from a marina skip, where a motor-boater had chucked them because they looked too scruffy due to diesel soot buildup. That came off pretty easily by scrubbing them with neat washing up liquid + a dash of petrol, using green panscourers, then pressure-washing them. There's no feasible place to stow them on deck so they either live in the tender lashed cross-ways under the thwarts, or if I expect to need them on that passage, on a forward berth.

author: dmills
author_rank: Super Contributor
timestamp: July 21, 2018, 12:37:45 pm
content: Top tip for busy waters at night, rig a reasonably powerful flood up at the cross trees or such so that it illuminates the sails, MUCH more visible then the nav lights (Which of course must also be present).A 400W metal halide onto reasonably white knock staysail or t'gallant is visible from a long, long way, and if you set it up carefully does not have to destroy a lookouts night vision.Personally, particularly when sailing (but in fact even when motoring) I dislike running close to shore, especially a lee shore with nowhere to go, sea room is very much your friend.Regards, Dan.

author: towlerg
author_rank: Contributor
timestamp: July 22, 2018, 03:20:44 pm
content: I guess it depends on how close is "close to shore". And lets not forget, we have charts so some hidden danger is going to suddenly materialize.Much as I agree that seeking searoom in the even of a storm is appropriate and given that forecasting is not perfect, I wouldn't allow myself to be in the Channel at night in a storm either as skipper or crew.Those big ass fenders sound perfect. How do you stop them "rolling" up onto the deck in the event of mishap?

author: Ian.M
author_rank: Super Contributor
timestamp: July 22, 2018, 03:54:17 pm
content: I've been out in some fairly heavy weather in the channel. Nothing much over force 7 but plenty enough to make you think "Why the **** am I out here, and why haven't I traded the boat in for a caravan?". Part of the problem is that the Met Office Shipping Forecast tends to overstate the expected wind strength, then on the rare occasions when its actually as strong as forecast, if one is caught out, one gets a very unpleasant surprise. The Gull stream inside the Goodwin sands between Dover and Ramsgate can be rather nasty in a blow, to name but one passage that was more pain than pleasure. Unfortunately, the great British summer being what it is, most years you don't get a weather window that will let you make a passage the length of the channel in fair conditions, and unless you want to get stuck in expensive ports for days at a time, you have to take the rough with the smooth.The aft fender lanyards pass through drain holes in the toe rail, and the forward ones go under the bow roller, and there is just enough slack that they cant jam above the rail against the pulpit stanchions. Yes they can ride up, but as they only have to fend off occasional impacts rather than the continuous pressure if fending off amidships when moored, they tend to drop back if they do get knocked above the rail. I suspect they wouldn't work so well if the vessel was pitching a lot, but OTOH if its that rough in the lock or alongside a quay you probably shouldn't be there in the first place and will be happy enough if the damage is only smashed nav lghts and a pulpit bent into a pretzel.

author: towlerg
author_rank: Contributor
timestamp: July 24, 2018, 12:49:27 pm
content: QuoteOn my bit of the world, it's wind over tide over fresh water flow in the mouth of the Shannon especially around Loop Head. I quess if you asked a local they could give you chaper and verse, but I have no idea and spin a coin.