Author Topic: VIIC/41 - Schematices drawing  (Read 512463 times)

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Offline Pat

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Re: VIIC/41 - Schematices drawing
« Reply #390 on: 28 Feb , 2010, 09:12 »
Simon, you're correct that there would be "galvanic corrosion" between lead and steel.

Galvanic corrosion occurs when two dissimilar metals connect, especially when immersed in a conductive liquid such as sea water.  The baser metal (the lead in this case) corrodes, not the more noble metal (the steel).

However, it's actually preferred that the lead WOULD corrode, rather than have the lead protected.  The reason is that there are many different kinds of metal used on any ship, and a submarine might have some specialized metals not found on most ships, and since they take water into ballast tanks and have all sorts of piping inside not found in surface ships, there's probably more different metals than surf-side.

So the idea is to have lots of the baser metals available for corrosion, so that it won't go on to attack the next metal up the scale.

All boats with any metal in contact with the water have what's called "zincs" or sacrificial anodes in several places to save the more expensive , vulnerable and important pieces.  These are just what they sound like, a piece of zinc, bolted to the sides of metal parts because if there's any stray electtrical current in the water, it will corrode the less noble metal (the zinc in this case) first and ignore the more noble metal.  The zincs have to be inspected once in a while and replaced when getting thin since as soon as the zinc is gone, the galvanic action will attack the next least noble metal.

On my own boat, there is a zinc inside the raw cooling water inlet before it gets to the engine, to protect the inside of the engine.  There is also a zinc on either side of the hull beside the propellor shaft to protect the shaft and propellor.

I've seen pictures of type VII's under water with a zinc on either side of both rudders, up near the top of the rudder close to the shaftand another zinc on each side of the propellor shaft struts, just by the hub that the shaft goes through.  These zincs are rectangular and 2-3 inches thick. 

The exact size and placement of the zincs would not be the same on each boat since they would use whatever was available at the time from whatever manufacturer had stock, and the location is not precise, just "close to where something needs protection".  On different years of my own boat, the zincs are always there, but could be as much as a foot different in location.

There would almost definitely be zincs somewhere around the diesel engines as well, and possibly somewhere near the electric motors to protect against stray current there.

One other point, the zincs should NEVER be covered over with the anti-corrosive paint.  The whole idea is that if there IS any corrosion, it would be the zinc that gets it.

The zinc itself is a dull silvery-grey colour, perhaps with some whitish corrosion on it.  You could make zincs for your model out of a strip of plastic, perhaps 1/4 mm thick, 1/2 mm high and 1.5-2 mm long.  The long axis is parallel to the motion of the boat.  Some zincs have rounded edges, some squared.

Offline NZSnowman

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Re: VIIC/41 - Schematices drawing
« Reply #391 on: 28 Feb , 2010, 11:07 »
Thanks Pat for the information  :) :)

Offline SnakeDoc

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Re: VIIC/41 - Schematices drawing
« Reply #392 on: 28 Feb , 2010, 13:11 »
Hello Simon

Going back to the keel ballast question. Would the lead blocks be painted with anything, e.g. like anti-corrosion?

According to
http://www.ubootarchiv.de/dieboote/farben_maerz_1940.html
http://www.ubootarchiv.de/dieboote/farben_juli_1944.html
keel ballast was painted grey.

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Maciek

Offline Pat

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Re: VIIC/41 - Schematices drawing
« Reply #393 on: 28 Feb , 2010, 13:43 »
Did a bit more research and see that I had one thing wrong about the galvanic corrosion.

http://en.wikipedia.org/wiki/Galvanic_corrosion

Anodic index (edited)
Gold, solid and plated, Gold-platinum alloy 0.00
Silver, solid or plated; monel metal. High nickel-copper alloys 0.15
Nickel, solid or plated, titanium an s alloys, Monel 0.30
Copper, solid or plated; low brasses or bronzes; silver solder; German silvery high copper-nickel alloys; nickel-chromium alloys 0.35
Brass and bronzes 0.40
High brasses and bronzes 0.45
18% chromium type corrosion-resistant steels 0.50
Chromium plated; tin plated; 12% chromium type corrosion-resistant steels 0.60
Tin-plate; tin-lead solder 0.65
Lead, solid or plated; high lead alloys 0.70
Iron, wrought, gray or malleable, plain carbon and low alloy steels 0.85
Aluminum, cast alloys other than silicon type, cadmium, plated and chromate 0.95
Hot-dip-zinc plate; galvanized steel 1.20
Zinc, wrought; zinc-base die-casting alloys; zinc plated 1.25


From the above chart, lead is more 'noble' than iron/mild steel, so the lead in ballast will not corrode.  Zinc is the lowest one on the scale (higher number means it corrodes faster), so that's why it's used as a sacrificial anode.  You can see from the chart why stainless steel (high chromium) is used in so many marine applications, and why brass was used in the old sailing ships, before stainless steel was invented. 

Powdered copper and tin are what is put into anti-fouling paints to keep barnacles, algae and marine life from attaching to the hulls.  Why it changes colour to slate grey/black after it's been in the water for a while, I don't know.  But it's because of that I suspect that even though at launching the hull of a U-boat might be dark grey, I think it will probably get darker with immersion.

Offline NZSnowman

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Re: VIIC/41 - Schematices drawing
« Reply #394 on: 28 Feb , 2010, 18:42 »
Hello Simon

Going back to the keel ballast question. Would the lead blocks be painted with anything, e.g. like anti-corrosion?

According to
http://www.ubootarchiv.de/dieboote/farben_maerz_1940.html
http://www.ubootarchiv.de/dieboote/farben_juli_1944.html
keel ballast was painted grey.

--
Regards
Maciek

Thanks Maciek. Great link :) :) I had forgotten about these pages.

The information on the 1944 version was great :) :) Ballast keel inside = 3 layers of tar varnish :) So they may have just put the lead blocks straight in without painting them.

Offline NZSnowman

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Re: VIIC/41 - Schematices drawing
« Reply #395 on: 28 Feb , 2010, 18:46 »
Did a bit more research and see that I had one thing wrong about the galvanic corrosion.

http://en.wikipedia.org/wiki/Galvanic_corrosion

Anodic index (edited)
Gold, solid and plated, Gold-platinum alloy 0.00
Silver, solid or plated; monel metal. High nickel-copper alloys 0.15
Nickel, solid or plated, titanium an s alloys, Monel 0.30
Copper, solid or plated; low brasses or bronzes; silver solder; German silvery high copper-nickel alloys; nickel-chromium alloys 0.35
Brass and bronzes 0.40
High brasses and bronzes 0.45
18% chromium type corrosion-resistant steels 0.50
Chromium plated; tin plated; 12% chromium type corrosion-resistant steels 0.60
Tin-plate; tin-lead solder 0.65
Lead, solid or plated; high lead alloys 0.70
Iron, wrought, gray or malleable, plain carbon and low alloy steels 0.85
Aluminum, cast alloys other than silicon type, cadmium, plated and chromate 0.95
Hot-dip-zinc plate; galvanized steel 1.20
Zinc, wrought; zinc-base die-casting alloys; zinc plated 1.25


From the above chart, lead is more 'noble' than iron/mild steel, so the lead in ballast will not corrode.  Zinc is the lowest one on the scale (higher number means it corrodes faster), so that's why it's used as a sacrificial anode.  You can see from the chart why stainless steel (high chromium) is used in so many marine applications, and why brass was used in the old sailing ships, before stainless steel was invented. 

Powdered copper and tin are what is put into anti-fouling paints to keep barnacles, algae and marine life from attaching to the hulls.  Why it changes colour to slate grey/black after it's been in the water for a while, I don't know.  But it's because of that I suspect that even though at launching the hull of a U-boat might be dark grey, I think it will probably get darker with immersion.

Pat, the Wikipedia page on galvanic corrosion was the start thing I did after your late post ;D

Offline NZSnowman

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Re: VIIC/41 - Schematices drawing
« Reply #396 on: 28 Feb , 2010, 19:39 »
Turbo blower for the Port Diesel Engine


Offline Greif

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Re: VIIC/41 - Schematices drawing
« Reply #397 on: 01 Mar , 2010, 01:01 »
Nice picture Simon.  I wanted to build a turbo blower for my engine room interior, but I just could not gather the spare parts to build a realistic looking one.

Ernest

Turbo blower for the Port Diesel Engine



Offline Rokket

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Re: VIIC/41 - Schematices drawing
« Reply #398 on: 04 Mar , 2010, 04:15 »
Not very submarine-ie but my solar hot water heater (and apparently most hot water heaters) has an anode that is designed to decay. It gets used up and prtoects the tank. has to be replaced every 5 years. Same principle.
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Offline Pat

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Re: VIIC/41 - Schematices drawing
« Reply #399 on: 04 Mar , 2010, 07:00 »
Well, at least your anode IS under water all the time rokket.  That's sort of submarine-ie.

And yes, it's definitely the same principal.

Offline NZSnowman

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Re: VIIC/41 - Schematices drawing
« Reply #400 on: 05 Mar , 2010, 12:56 »
I was reading Iron Coffins by Herbert A. Werner yesterday. The date is 1st June 1943 and U-230 is about to go to sea. Herbert state:


Offline Rokket

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Re: VIIC/41 - Schematices drawing
« Reply #401 on: 06 Mar , 2010, 16:52 »
Interesting point, NZ, but then, the Germans were looking at a lot of almost sci-fi stuff, maybe it wasn't very secret. I think it's also ironic that the Metox lead Allies directly to it!
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Offline NZSnowman

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Re: VIIC/41 - Schematices drawing
« Reply #402 on: 06 Mar , 2010, 19:23 »
Yes lots of talk about secret sci-fi stuff!! Herbert talks a lot about a 'Secret Dead Ray'  ;D ;D

I have been doing a lot reading about Metox and I think the new thought about it is.

Yes the Metox did emitted a weak signal and the Allies could detection this sign. However, it now believe that the signal was so weak that it could not be used to track U-Boats. About this time the Allies started to hear rumor that the Germans were starting to think that the Allies were homing into the Metox. So the Allies started a rumor that they could detection the Metox sign. I think they did this by telling Bombing crews, know that a few of them would be shot down over Germany. As soon the Germans hear that Allies could detection the Metox sign they toll all U-boat to stop using them. This was just what the Allies wanted. Now the Allies could used there radar with good results.

Offline Rokket

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Re: VIIC/41 - Schematices drawing
« Reply #403 on: 07 Mar , 2010, 17:35 »
Clever! Intrigue! Like the "man who never was" - Brits put fake invasion plans on a dead body, dumped in the ocean with plane debris, and let it be discovered in Spain. Great triple twists!
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Offline Pat

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Re: VIIC/41 - Schematices drawing
« Reply #404 on: 07 Mar , 2010, 18:17 »
That's an interesting story about the Metoz and the bomber crews Snowman.  What year was that happening and was it ALL Allied bomber crews or just the ones of one nation?

I've been tossing around the idea of writing a book about what I know of my father's war, and it might be something that he was involved in.  He was shot down in Feb '44, over Germany and as a Pathfinder, he would have been involved in radar and radar detection and electronic navigation (Oboe) before it was common among the RAF crews.