Copper sheet on the hull?

[Faithless Nomad]

G'day, I'm looking at a small sail boat to buy for day trips around the bay. It's a 28' 1974 Hong Kong yacht, with a fibreglass hull. She has a unique feature I haven't seen on a sail boat before and I'm hoping someone on the forum can help. The feature is a 3'x2' thin sheet of copper fixed to the underside of the hull (below the water line). The hull has an indent to accommodate the copper sheet. The current owner doesn't know what it is or what it does.
Also, while I've got your attention, the deck seems to be covered with a bituminous compound painted over. It look as though they pulled up a teak deck and put this down as a cheap waterproof seal over plywood. Is this common practice? Thanks.

[dennismckim]

Originally Posted by Faithless Nomad

The feature is a 3'x2' thin sheet of copper fixed to the underside of the hull (below the water line). The hull has an indent to accommodate the copper sheet. The current owner doesn't know what it is or what it does.

Is it possibly a ground plate for lightning protection?

[AiniA]

Or a ground plate for a SSB radio.

[Steadman Uhlich]

Howdy Faithless Nomad. I see this is your first post on CF. Welcome Aboard CF! :

Photos always help in diagnosis of odd things on boats.

Take some photos and post them here in the thread.
If you are unsure how to post photos here, There is a youtube video that shows an easy way to upload photos to a thread like this when you post.

Good luck on your boat hunt.

[mogulskibum]

This one is easy: it's 19th century anti-fouling.

[fstbttms]

Originally Posted by mogulskibum

This one is easy: it's 19th century anti-fouling.

It's a single 2' X 3' sheet. I don't think anti fouling is the goal.

[mogulskibum]

Originally Posted by fstbttms

It's a single 2' X 3' sheet. I don't think anti fouling is the goal.

[fstbttms]

Originally Posted by mogulskibum

Yeah? Don't quit your day job.

[sck5]

does it have a lug passing thru to the inside of the hull? if so it is very likely a ground plate for a marine hi frequency (ssb) radio

[GordMay]

Greetings and welcome aboard the CF, Nomad.

[Scot McPherson]

yes it is fairly common practice to protect decking with pitch or asphault....even the decks of wooden ships were swabbed with tar to preserve them.

[Kita]

I have done considerable research on lighting & boats, it's possible for a strike to hit mast & travel through boat to ground or in the case of a boat,water... some fiberglass boats have metal through hull fittings that have been blown off in a strike,end result is a hole & down she goes! In my research I found that navy boats are all metal and they are struck often with no damage.. a fiberglass boat makes like a big resistor with a very small metal ground and all that voltage will blow that small metal piece right off the boat. But in the Navy's case they get no damage from a direct hit And the reason for that is that the whole ship makes for a wonderful ground. The lightning goes right through the ship and into the water and dissipate. Now a fiberglass boat doesn't even have to be hit to be a problem, the emp from a nearby strike can fry Electronics. The point to all of this is like one of the other fellows mentioned it's possible that somebody had the idea to dissipate a lightning strike through that plate. It's just a theory. But one that I find fascinating because the great big metal ship gets struck and has no damage. But a small fiberglass boat will take a lot of damage in a lightning strike. Lightning is funny stuff. It is always been a concern of mine because I live in one of the lightning hotspots in the world. If you find that it is something else please let us know I would be very interested. Thank you!

[buzzstar]

Originally Posted by fstbttms

Yeah? Don't quit your day job.

That from a guy who appears to clean foul bottoms?

[Cadence]

I would guess a ground for lightening. If the whole hull was covered maybe 18 century any fouling and I can't see a 74 28ft. boat constructed with SSB in mind.

The pitch on deck was probably some ones cheap fix. If it works, live with it. I can see one long messy job to remove it.

[Jesse]

It is a ground plane with an "n" instead of a "t". They were common lotsa years ago and worked very well. No idea why they fell out of favor, perhaps too pricey. There will be a lug to connect your radio's and it should be an excellent ground for GPS and the like.