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Catalina/Capri 25/250 Sailor's Forums

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Lightning Hit my Masthead

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KD4AO
Navigator

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USA
202 Posts

Response Posted - 03/06/2009 : 13:05:56

Doesn't the diffuser depend on a path to the water through the mast and bonding to the keel or other metal in the water? From what I think I have read about the C250WK, the mast is not bonded to anything in the water. Or maybe I just don't get it yet because of what Arlyn said "use an ionizing diffuser on top of the mast and keep the mast from getting a supply of electrons to build up a charge by not having it grounded".
In my limited experience with 2 meter and 450mhz repeaters and base stations, we used grounded antenna's on top of a watertower or other metal tower. In my own case I had a 10, 15, 20 meter beam below the vhf antenna on the tower, in Dallas area and in the Atlanta area where plenty of lightning existed. I never got hit. Lucky maybe.

Edited by - on

Arlyn Stewart
Master Marine Consultant

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2980 Posts

Response Posted - 03/08/2009 : 10:33:56

Hey Bob, likely many mast not thought to be grounded... are from incidental electrical grounding rather than intentional lightning protection grounding and even if the mast is not grounded, there may be grounded structures aloft on the mast.

That ground could be made by a lighting, radio or instrument fixture installed on the mast in conjunction with the electrical system being grounded.

On a 250, because it uses an outboard there is no electrical system ground and thus potential for mast or fixtures aloft grounding unless the boat is equipped with shore power charging where the grounding is made via the line grounding.

Do you recall if your boat was hooked up to shore charging when it was hit?

You are correct to point out that an ion diffuser would be of little value to an ungrounded mast.

A few thoughts on vhf and uhf vertical antennas. Some have a stinger whip that is grounded and some don't. The very popular Ringo Ranger had a grounded stinger, which of course meant that the stinger had a source to build up a capacitive charge potential. The very popular Metz base loaded boat antenna also has a grounded stinger so its use on a boat with either an inboard or shore power charging means that it is fully capable of sending up leaders and increasing chances of being struck.

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KD4AO
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USA
202 Posts

Response Posted - 03/09/2009 : 11:39:04

I am sure the boat was not connected to shore power at that time, I tend to charge the batteries for a couple of days and then disconnect the power. All my shore power does is power a charger. I do not think the mast is grounded to any electrical components except the lights through the deck connector which promptly blew apart and probably prevented further damage. All is fixed now and the mast is back up.

I rearranged the "A" frame to a fixed configuration, leaning about 25 degrees forward and it worked quite well raising the mast. I must say though that I now have a new respect for all the trailer sailors that do this regularly. It is just plain a JOB.

I used a Ringo Ranger for years on my tower and it was a very good antenna, especially above a beam. Several years ago I put a 2 meter antenna at the top of the mast on my 32 Hunter. It worked very well but caused an unexpected ground between the mast, keel and other bonded items, back to the DC common. This resulted in shaft zincs being used at a rate of about 1 a month. Took me a long time to realise what I had done but I finally proved it by simply disconnecting the antenna from the back of the radio while the boat was not in use. Zinc usage went back to 6 or more months.

Thanks Arlyn, for all your comments and help.

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aeckhart
Master Marine Consultant

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USA
1709 Posts

Response Posted - 03/20/2009 : 11:44:06

I once read that a coil of line, swinging and rubbing on something like the stern rail, can cause enough ionization to attract a lightning strike. Part of my "leaving-the-boat-prep" is to ensure that anything that may cause an ionization build-up, is fixed - that is, everything I can see and fix. Basically this includes making sure the panel master switch or all electronics are turned off, and there is nothing on the boat-inside or out, that swings free and rubs on the boat.

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Notice: The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.