Metal in Bulkhead Mystery

[HR]

While cutting through the plywood bulkhead between the cockpit and the cabin on our boat to remove some rot, I hit something hard.

On further investigation, I found a piece of metal, about 1/2" thick and about 10" high embedded in the bulkhead, running from about 8" inboard of the cabin side to the companionway (and perhaps right across, I stopped drilling test holes at the companionway). The bulkhead is made up of several layers of plywood, and space was left for this metal plate. The plate itself seems to be covered with a cellophane-like material.

This photo shows the bulkhead - the metal plate is in the area to the right of the opening and extends down to the countertop (at least) and over as far as the drill holes indicate (at least)...

http://im1.shutterfly.com/procserv/47b5d702b3127cce940a53aba59500000016109AcuGzRs0bU

Here's a closup...

http://im1.shutterfly.com/procserv/47b5d702b3127cce940a5396249800000016109AcuGzRs0bU

As background, the boat is a 40' pilothouse ketch built in the Bahamas in 1965. Anybody have any ideas on why this metal plate is there?

Thanks.

Howard

Edited to fix typo in heading

[ 09-23-2005, 08:26 AM: Message edited by: HR ]

[Thad Van Gilder]

um, maybe someone thought it would reflect radar beter?

-Thad

[Dan McCosh]

You don't say what kind of metal, but it looks like soundproofing material to me. This is usually a sandwich of lead or other soft metal and some composites. !/2 ins. is awfully thick for structural reinforcement.

[ssor]

Look below deck and see if anything is hanging from it. As was asked before what kind of metal?

[StevenBauer]

Hi Howard, any progress tracking down the rigging problems? Here's a Chuck Paine designed boat we sailed past on Sunday:

http://www.imagestation.com/picture/sraid188/peb163236f0ed4f19f23da9f3563e61ac/f22d432f.jpg

Steven

[Peter Malcolm Jardine]

My suspicion is that it would be a stiffener of some kind, perhaps put it while the hull was assembled. Just a guess, but that's a big piece of steel. Where do the shrouds come down? could it be attached to the plates and run across?

[kc8pql]

Originally posted by HR:

On further investigation, I found a piece of metal, about 1/2" thick and about 10" high embedded in the bulkhead,At least now you know why the compass always points north. :D

[HR]

Thanks for the suggestions.

The consensus among local boatbuilders is that it some sort of stiffener for the bulkhead, although none of them have ever heard of that being done before.

I'm going to investigate further and see if it extends across the bridge deck and continues on the other side of the bulkhead. If it is a stiffener, I can't imagine why it doesn't extend all the way to the outside of the bulkhead?

I prefer the suggestion that it is bulletproofing from a previous life as a rumrunner - much more interesting story!

And yes, it certainly does explain why the forward compass reads much differently than the aft one!

By the way, the metal seems to be iron. Any other ideas would be appreciated.

Thanks for the photo Steven - haven't heard anything from them yet. Today we're off sailing on our friend's Crocker Gull in the Lunenburg classic boat race. Looks like a nice day ahead!

Howard

[John E Hardiman]

If it is iron and she's is/was a shallow centerboarder, I would say ballast/trimming weight.

[kc8pql]

Originally posted by MIke:
In some requirements in the long range radios, they would require a metal style mess to be installed. Possable, but would be an odd way to do it. A radio counterpoise needs surface area, not mass. That's why copper foil or screen work well. RF current travels mostly on the surface of a conductor rather than through it.

Ken

[StevenBauer]

Howard, which bulkhead is that we're looking at? Is that where the galley was? What're you planning to do?

Steven

[HR]

After some more prodding, I have found no sign of wires or other connections, but I have determined that the iron plate runs across the boat under the bridge deck.

I have sent a note to a previous owner who has known the boat since she was built and maybe he'll be able to shed some light. Otherwise, unless someone comes up with a better idea I'll have to assume it was to add rigidity to the bulkhead.

Steven, it's the bulkhead on the starboard side of the companionway in the area my wife calls the "starboard galley" and I refer to as MY workbench area (not settled yet, but I know I'll lose). There were shelves on it which I removed to access the bad wood. I'm cutting out the rotten wood and replacing it with new. I'll leave the iron in place, at least for now.

Howard

[John B]

I just can't imagine its there for strength HR. John Hardiman has it..... ballast/roll inertia etc.
The only other reason , the only other way I've seen this done is for class boats that have been built too light or with too much righting moment for the class rules. Some I know of carry weights screwed up under the side decks and or bulkheads for those reasons.Yours doesn't sound like a racing class design though?

[pipefitter]

Maybe in 1965 in the Bahamas they didn't have an expansive choice of material to use and although ½" plate may be overkill they might just not have had anything else on hand nor wanted to wait to order something else or found they were short of ballast material.

[Hughman]

This wouldn't be ballast material if it's above the waterline. (?)

[HR]

John, she's definitely not a racer of any sort, nor a class boat. She's a one-off, heavy displacement (15 ton) cruiser. As Hugh suggested, if it was for ballast, wouldn't it be lower down? This iron is about a foot above the waterline and 3 feet or so above the top of the ballast keel.

Mike, I know that the boat did have a SSB radio and the fellow who owned the boat for most of her life (from '66 to about '92) was the president of an electric equipment company and had all kinds of electrical gear on board. Maybe there's something to that?

[Peter Malcolm Jardine]

There was a requirement years ago for the old AM based ship to shore radios to have substantive grounding requirements, but that was usually series of long copper tubes under the water.

[TimothyB]

I'll toss in a guess...

The cellophane material may have been put there to prevent rot. Wood/Metal connections are reknowned for that.

My guess is that if it wasn't for electrical/electronic purposes, it may have been to dampen roll inertia. Perhaps upon launching the boat was rolling too snappy for the owner and he had the plate put in above the WL to dampen the roll somewhat. It would explain why it is so massive, and why it looks like a retrofit.

EDIT: Whoops. JH already suggested this smile.gif

[ 09-26-2005, 10:37 AM: Message edited by: TimothyB ]

[DJM]

Iron Smuggler?

[John B]

'iron smuggler' :D

you're absolutely sure its iron ,right?

[ 09-26-2005, 06:19 PM: Message edited by: John B ]

[ssor]

Does anybody have a magnet?? :D