Top lights arrangement

Discussion in 'Boat Design' started by 1J1, Mar 27, 2015.

  1. 1J1
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    1J1 Senior Member

    A general cargo ship (85m lbp) has a retractable rotor (or cylinder) on the bow which can be completely raised or lowered. Does anyone know how high should be placed the aft top light? Whether it should be on a fixed height (regardless whether the rotor is raised or lowered) or on a sorta telescopic mast which would raise it along with the rotor? Gave necessary dimensions in meters if needed. :D

    Kind regards!
     

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  2. gonzo
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    gonzo Senior Member

    The lights must be visible for the required degrees. There should be no obstructions. Do you have to go under bridges or other vertical restrictions?
     
  3. TANSL
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    TANSL Senior Member

    That's like saying nothing. Navigation lights should naturally be visible. If they were not, why would serve ?. Why would ask 1J1 in relation to the telescopic mast if he did not know that?.There is an International Code for Preventing Collisions instructing (not easy to interpret) how many lights should be, how they should be and where to go each.
     
  4. gonzo
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    gonzo Senior Member

    TANSL, it may be that time of the month, but please check your bad attitude. I am quoting regs by saying what the visibility requirements are.
     
  5. 1J1
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    1J1 Senior Member

    So, from reading these, as I understand, aft masthead light should be visible as being above the forward one from the distance of 1000 meters from the stem when viewed from water level... in a way they would be still visible above the rotor. But when viewed from a shorter distance (like some 100-200m) the aft light (at his maximal height) would be obstructed by the rotor when viewed from the front...? If the rotor is retractable, then I guess indeed the aft mast should be of adjustable height in case of passing under the bridge.
     
  6. TANSL
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    TANSL Senior Member

    To pass under a bridge you can adopt the solution you want. The same solution should adopt for the funnel, even if it does not have lights.
    The code to navigate rivers, canals, below bridges, etc. I do not know whether or not there. Gonzo introduced an issue that, frankly, I do not master.
    When the boat is navigating open water, the lights must be visible at any time, with or without rotor, the grades the rule states.
     
  7. gonzo
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    gonzo Senior Member

    Yes. You can use graph paper and draw it to scale to figure out what the height above the waterline should be or you can do trigonometry. You can call the Safety Officer at the USCG and ask for clarification. The rule is not clear. I read it as saying that the separation should be clear for at least 1000 meters.
     
  8. 1J1
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    1J1 Senior Member

    There's this pic of a Japanese freighter with a big stiff folding sail at the bow: [​IMG]
    It has an enormous mast for the aft masthead light which would be visible from 1 km but as I would guess, not from a much shorter distance. So it's sorta Ok then in such case?

    "The forward masthead light, or if only one masthead light is carried, then that light, at a height above the hull of not less than 5 meters, and, if the breadth of the vessel exceeds 5 meters, then at a height above the hull not less than such breadth, so however that the light need not be placed at a greater height above the hull than 8 meters."

    That's a bit interesting. I have many GA plans of cargo vessels & I just measured on some 80-140m long ships it's placed at the height above the main deck as that ship's breadth. However, on some other ones the distance between the light & deck is much less than the breadth... :confused:
     

  9. TANSL
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    TANSL Senior Member

    1J1, in my opinion the light must be visible at a distance of 1000 m but also 100, 200, ... meters. Not sure if that answers your question.
    If in doubt, as wisely advised Gonzo, it is best to ask the competent authority. It is possible that some small blind is allowed. You can always request a waiver to the rule, in special cases.
     

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    Last edited: Mar 27, 2015
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