Navigation light - horizontal arc sector test

Discussion in 'Boat Design' started by Maritimer, Aug 29, 2007.

  1. Maritimer
    Joined: Jul 2007
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    Maritimer Junior Member

    I am working on a method for assessing if existing navigation lights on vessels conform to the required light arc sectors.

    I have an old method that was completed out at sea with a small boat circling the larger vessel with lots of source of error and time involved.

    I am working on a method to be conducted the trial alonside using surveying techniques to make the trial more reliable and quicker. Anyone done anything similiar, if so did it work?
     
  2. Cangovtperson
    Joined: Feb 2010
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    Cangovtperson New Member

    Actually, this is something I have problems with myself.
    There is a method that utilizes a Theodolite mounted directly above the lamp of the light to be tested. Once it is aligned properly in relation to the centerline of the vessel, the cut-off angles can be measured accurately to within minutes of a degree. The key is to have the boat fixed as best as possible, a good sighting glass (spotting scope) on the jetty (or around the drydock), which can discern the filament of the lamp. When that filament is half visible, mark the point on the jetty or dockside, and sight back with the theodoite for your angle. Repeat procedure at each light.
    I'm looking for pointers on sea testing, myself.
     
  3. TeddyDiver
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    TeddyDiver Gollywobbler

    In the night other than navigation lights dimmed. A reverberator on the circulating vessel and measuring the running fix when the reflected light changes colour.. or incase with somewhat smaller boat just place the reverberator on the dock side and make turns with the boat to get the fixes..
     
  4. Cangovtperson
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    Cangovtperson New Member

    I'm not familiar with a "reverberator", but it sounds like a tool that would make this much easier. Can you give me more info on it, ie. supplier, function, size or what have you? WWW. link ?
    I'm doing these tests on some pretty fair sized vessels (55 m to 134 m) plus a few odd ball types. What type of distance do you find works best? I find that 1 km or more makes offset calculations easier.
     
  5. Fanie
    Joined: Oct 2007
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    Fanie Fanie

    Q please - Why does the angles of view have to be so accurate ?
     
  6. Landlubber
    Joined: Jun 2007
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    Landlubber Senior Member

    "if existing navigation lights on vessels conform to the required light arc sectors"...they either do or they don't....the manufacture has to supply certificate of compliance if they are survey type lights anyhow.
     
  7. Doug Lord
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    Doug Lord Flight Ready

    We use a goniometer, photometer and computer program in a light tunnel to test many prototype lights for major manufacturers. I'm not familiar with any "at the dock"method that would simultaneously measure angle and intensity but I do know that manufacturers are responsible for certifying(or having us or another recognized lab certify) that the lights manufactured(or used) in the USA meet USCG standards. The USCG can prevent the manufacture of a boat using lights that are not certified to their standards. A manufacturer of a neat classic boat had this happen a couple of years ago.
     
  8. TeddyDiver
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    TeddyDiver Gollywobbler

    Prismatic reflectors attached on a board.. I've used only with boats and then a single one with a distance <~20m is enough. With a ship you might need a couple of sqm covered however depends how much lightness there's around.
     

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  9. Maritimer
    Joined: Jul 2007
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    Maritimer Junior Member

    light arcs - obstructions & sidelights

    I see people questioning why a ship needs to physically determine the light arcs at the vessel if certified lights are used. This is needed as many ships have obstructions of lights and may use more than one light to get complete required arcs but mostly it is for the side lights. The side lights are actually cut off towards the centreline forward by a "shield" made of steel to manufacturer details. Often the shield is not made correctly or installed a little crooked on the ship throwing off the required cut off angle and allowing a red and green to both be visible when they should not. I don't think commercial ships worry much about this, but it is a concern on naval training vessel in particular.
     
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