Lightning Arresotr For Solar Boat

Discussion in 'OnBoard Electronics & Controls' started by ashwinnaique, Sep 25, 2015.

  1. powerabout
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    powerabout Senior Member

    how do you get a contact on a carbon mast that should be sealed?
     
  2. BertKu
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    BertKu Senior Member

    I always have had deep respect for Naval architects and boat builders. I am now getting worried that the design of a carbon mast is not thought through. Off course , one can make round clamps (outside around the mast pole) and have the 20 mm 2 copper wire brought down via the outside or even better down to the outside of the boats, directly to the waterline. What statistics are available on the number of yachts damaged by lightning per year?. If that is only 5 boats per year, around the world, this whole thread is then a complete waste of time. If there are damages running in the 10.000's then the designers of those carbon mast have done a lousy job.
    Bert
     
  3. gonzo
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    gonzo Senior Member

    When I did accident investigations for insurance companies, I would inspect more than 5 per year.
     
  4. BertKu
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    BertKu Senior Member

    Thank you Gonzo, can we assume that there are some 1000 surveyors like you in the world ? That would mean some 5 - 10000 boats per year and that means, a designer should look at a solution for his mast. Bert
     
  5. powerabout
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    powerabout Senior Member

    I have raced on many boats that have had multiple hits over the years or electrical damage from close-by hits.
    Its common out here in SE Asia
    but some yachts seems to get hit and or damaged more than others?
     
  6. BertKu
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    BertKu Senior Member

    Yes, it totally depends on what the resistance is from the highest top of the mast to water level. One cannot predict in how far wet masts and sails are contributing to getting a strike or not. Or that the one mast has a very high resistance and not very attractive for a lightning surge and the other has a lower resistance but not good enough to reroute the current easy to the water level and therefore get damaged. Unfortunately I cannot assist you here, there are too many variables. Bert
     
  7. powerabout
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    powerabout Senior Member

    Hey thats interesting, would an isolated mast offer better strike protection?
    I guess that might only be possible till its got seawater on it?
     
  8. BertKu
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    BertKu Senior Member

    That is correct. But you forget all the stainless steel wires from the top of the mast to bow, transom and all sides. You need to use than maybe nylon ropes. Bert
     
  9. BertKu
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    BertKu Senior Member

    Hi Powerabout, there are two philosophies. The one say, don't protect, but make sure that there are no conducting metals on the boat to close to the waterline, to make a better path for a strike to the earth then via the air.

    Others say. if you do have conducting metals close of the waterline, protect it properly and ensure your resistance is then from top of the mast to the waterline less than 0.01 Ohm i.e. at 50.000 Ampere, this means only 500 Volt or maybe 0.05 Ohm, if you accept 2500 Volt sparks up to 2 cm and maybe somebody can live with that. Provided you do it in such a way that it protect you and the boat. But I stick to 0.01 Ohm.
    I believe in the second, because in the first philosophy, you have always some metals on a ship/yacht/booat.
    Bert
     
  10. BertKu
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    BertKu Senior Member

    Hi Powerabout,
    Would you be willing to tell us a little bit more about all your lightning strikes you had on the boats you sailed on? Like whether you felt the energy in your body, with a shock as off you received a large current flow through your system? Or you felt nothing, what was the damage and where. Were you blinded for some time, were you deaf for some time?.
    We love to read about your experiences.
    Please, please do us a favor!!!!!!!!
    Bert
     
  11. powerabout
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    powerabout Senior Member

    Only hits I have had are the risers when it is waiting to strike and I made the earth connection, short sharp shock, the bigger shock to teh system is where it actually hits next usually up to 1000m away luckily a few seconds later.
    Have spoken to plenty of crew with direct hits and they witnesses pink and purple glow on the stauntions and wires, got tingley, hair stands up they all say
    Only kit to survive was one where they put the vhf in the microwave everything else even disconnected was blown up.
    Been on board when the strike is somewhere else but close, electronics blown up on board several times, those are the boats I call magnets for the stuff.
    Definable never the tallest object
    Sitting in the yacht club open dining room and a direct hit on a coconut tree 5m away from me, several people closer, just massive bang and light, tree caught fire
     
  12. BertKu
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    BertKu Senior Member

    Hi Powerabout, Very interesting, Yes, electronics is quite sensitive to induced surges. But like you said, there are solutions. Indeed the one is that you have a metal box, with or without holes like a microwave oven and have some filters for the input and for the DC side and your equipment will survive. )*** That is the Faraday cage concept. One could make a yacht to a semi-Faraday cage by having a couple of more wires coming from the top of the mast to the bow, transom and sides, which you make like a curtain, you open with blue sky and close it, when there is lightning strikes in sight. That is also one reason why the one boat gets more damage then the other. Not that they having a curtain, but their construction and metal is more protecting the boat then others. Most electronic equipment is not properly protected against close surges and induced energy. However it can be done. It needs more money as usual, it may increases the weight and a manufacturer needs to be competitive. Thanks for your response. Bert
     
    Last edited: Oct 7, 2015
  13. powerabout
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    powerabout Senior Member

    yes as I posted previously all commercial kit is isolated earth and all in (Faraday cage) steel boxes

    Would just 4 wires from the mast head make a faraday cage and how would you test that?
     
  14. BertKu
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    BertKu Senior Member

    No sadly not, you need quite a number. I am trying to find my notes of the seminar I have given, donkey's years back. One of the subjects I presented was the protection of thatched roof houses. The principle there is similar as for a boat. Will do my best to find them
    Bert
     

  15. gonzo
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    gonzo Senior Member

    Faraday cages are usually made of tight metal mesh or plate. If you were to use wires, they would have to be very close to each other; very difficult to do.
     
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