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  • 11 Jan 2022 18:51
    Reply # 12255244 on 12250597

    hi jan

    fortunately i don't have my own experience with lightning strikes. but i have seen photographs of a grp hull holed below the mast. it was impressing just to see those pictures. i'm quite sure the antifouling wouldn't be an issue. i think it would either be burned or blown off…


  • 10 Jan 2022 21:15
    Reply # 12253042 on 12250597

    I'd been intending to ask the following questions so now seems appropriate. Having read the advice in PJR I'm not clear on what happens under the boat in relation to anti-fouling? Is the plate not antifouled and does it it then get fouled? If your lightning conductor was connected to the keelbolts of a cast iron keel would it conduct through the anti-fouling (which does have a metal content but looks quite isolating and plastic), would the lightning just blow the anti-fouling off? Anyone have theories or better still, practical experience? 

    Last modified: 11 Jan 2022 00:48 | Anonymous member (Administrator)
  • 10 Jan 2022 17:31
    Reply # 12252549 on 12250597

    hi curtis

    Curtis Mangess wrote:

    –I'm sure I read something recently about how to ground a mast, including a specification of the size of the grounding plate needed on the underside of the boat. Was that in PJR?

    yes, the writers of pjr recommend a submerged metallic area of at least one square foot.


  • 10 Jan 2022 16:46
    Reply # 12252446 on 12250597

    I read the topic title and thought it would be about reducing weight ... there's no 'e' in the kind you're talking about.

    But I'm sure I read something recently about how to ground a mast, including a specification of the size of the grounding plate needed on the underside of the boat. Was that in PJR?

  • 09 Jan 2022 20:17
    Message # 12250597

    Lightning is always a potential threat.   The number of boats hit in Florida is enough to be a bit scary....... though I'm not in Fla.   It often knocks out all your electronics, and frequently will blow holes in the side or bottom of a boat.   A metal free standing mast would seem to provide a straight path to the keel, and through the bottom of the boat, making a case for having the mast step built in a way that you could easily stop water from an adjacent hole.... it's own compartment in the bilge that could be isolated and sealed easily.    I'm reminded of a farmer who was having trouble with a chain on a feed grinder breaking regularly, and wanted me to upgrade to a heavier chain.   I refused, explaining that the best solution was a set of "weak links" ...master links that were filed so they would be the breakage point, and could easily be replaced.  He upgraded anyway, and soon was breaking drive shafts.... as I had predicted, upgraded those, and then tore out the gearbox.    A weak link is often the best solution IMHO.    I've even contemplated the rather outrageous idea of putting the masts on a biplane catamaran rig outside the hulls with a streamlined cover, running in the water, and a sort of lower V strut brace, the whole designed to fold aft using a forward beam above deck level as a pivot point.   This would lead the energy of a lightening strike right into the ocean..... but that was not the idea. It was to preserve space in the narrow hulls.  Not a practical solution, but an interesting mental exercise.  There are all sort of "snake oil" solutions out there.   Where I live many homes and other buildings have lightening rods with heavy aluminum cables going to the ground...... a 50's & '60's era scam I think.  None have suffered lightening damage, but I don't now of any others that have either  ;-)

          I found this today on Apple News (Ipad), and it might be of interest, though not particularly useful:

    Detailed Footage Finally Reveals What Triggers Lightning The first detailed observations of lightning's emergence inside a cloud have exposed how electric fields grow strong enough to let bolts fly.


    Last modified: 12 Jan 2022 15:36 | Anonymous member
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