Catamaran Lightning protection

[Catalysis]

We have installed Dr Thompson's Sidearcs .
We have 4 (2 port and stb of the crossbeam) and 2 port and stb under the bridgedeck from the mast step. Chainplates from shrouds would have been ideal but not practical in our case.
The goal is to dissipate the energy forward of the crew quarters.
I was impressed by Dr Thompsons articles on lightning skipping across rather than through the water . Our Sidearcs are about 2-4" above the waterline

[Falbala60]

From my experience with well grounded monohulls having a huge lead keel with the bottom not painted, those tinny electrodes and over that... not touching the water... I am a bit sceptical... very skeptical.
How to know if they really work ? Sure the manufacturer will say YES !
Many years of testing will tell that ...

I will make a design of a removable copper electrode that will be permanently installed under the hull bridge, in line with the mast with a flexible wire connecting to the mast base. For much forward mast, it will be difficult, but with the new desings, mast in the center of the cabin... this should be easy.
Will come back...

[Catalysis]

Falbala60. I'm simply sharing the results of my research into lightning dissipation. Ewen Thompson is the most credible science based source I was able to find and having spoken with him on the subject I am willing to give his system a chance. I wish you good luck on your pursuit of other options and would be interested to hear of your progress.

[Captsteve53]

Originally Posted by Falbala60

From my experience with well grounded monohulls having a huge lead keel with the bottom not painted, those tinny electrodes and over that... not touching the water... I am a bit sceptical... very skeptical.
How to know if they really work ? Sure the manufacturer will say YES !
Many years of testing will tell that ...

I will make a design of a removable copper electrode that will be permanently installed under the hull bridge, in line with the mast with a flexible wire connecting to the mast base. For much forward mast, it will be difficult, but with the new desings, mast in the center of the cabin... this should be easy.
Will come back...

Well Well, just to add a few points from above,

1) In my 40 + years as a Marine Surveyor /Chief Engineer /Vessel Captain/world circumnavigator, I have never come across an unpainted lead keel, (actually mass lead keels will dissipate electrical charges in there own mass and to the water through paint very well -hence why well bonded metal keels provide the best grounding (apart from encapsulated lead/iron keels).

2) Will like to see your design for a copper rod mounted under neath/is this in the water or not? if subject to water movement of pounding waves etc there will be enormous stresses in place here, as you know doubt realize Copper work hardens very quickly from bending stresses/vibration/impact etc then it becomes very brittle and breaks off?

Look forward to your idea's we are never to old to learn!

Cheers Steve (MIIMS-Lloyd's Maritime)

[Falbala60]

Captain,

1 - The way my berth was maid, the keel have anti-fouling paint, only the bottom horizontal surface was resting on a support that stop to paint it, and I was thinking this was adding good contact with the water.

2 - I will explore the idea. My time, some clicks, ... a rough sketch

For sure it will never be possible to have a so good contact as a monohull lead keel, I will just try to make a "real contact"... like 2 sq.ft surface. From your experience is bronze as good conductor as copper and be used for water contact ?

[Captsteve53]

FALBALA 60,

Perhaps this is the most common form of this error with the substitution of brass or bronze for copper in electrical/conductive applications. Brass is only 28% as conductive as copper. Some bronzes are as low as 7% as conductive as copper! Which dosent sit well for the above small contacts (The one in my photo's are designed to be under the water -JUST), Personally i would make any electrode or plate from Copper,

These commercial units are probably made from Bronze due to price constraints and perhaps toughness/ longevity issues,


Cheers Steve