Submarine Exterior Surface Rubberized Coatings

[Higgler]

Knowing the sensitive nature of the subject, can someone provide me with approximately what type material is used to coat submarines. No classified details please, but maybe some ballpark thickness range and material type.

example: 0.25 inches of dense neoprene.

As an antenna engineer, I would like to calculate some RF energy loss parameters of a material.
Unclassified reference material would also be appreciated.
Thanks,
kch

 

[GregLocock]

Much thicker than that, I think there are photos showing something like 200 mm thickness.

I'm sure we are paying for a fortune for whatever compound is used.

Cheers

Greg Locock

 

[Higgler]

That's huge, and good news too.
Hopefully the material stops penetration of sea water (or else the sound would just penetrate it) and it is similar to the caulking we use around our tubs and sinks, i.e. low rf loss and dielectric of about 3,5-4.5.
Thanks Greg,
kch

 

[IRstuff]

Why does the RF loss matter?

The RF transmission of sea water is quite poor.

TTFN

 

[Higgler]

I plan on propagating RF energy in the rubberized layer, using the reflection of the rubber/sea water interface.
kch

 

[GregLocock]

What about the steel hull underneath?

Cheers

Greg Locock

 

[wsmith]

The coating varies between the classes of submarines as well as across the sub itself. For some subs, the only coating you will find is paint. Others will have some type of rubber against parts of the steel hull, which is interrupted by numerous fittings, the sail, and the casing.

I am curious why and how you would pump RF into this coating. If you are trying to develop something to be installed on the sub, not only do you have to convince skeptics that it will work underwater, you also have to convince them that it won't increase the magnetic signature, interfere with the degaussing system, or induce galvanic corrosion.

 

[Higgler]

To communicate across the face of the sub, one obvious way is to string lots of wires, that's very awkward. I believe the coatings do propagate RF energy, how much loss is in them is tbd. For future sub designs, the coatings could have a metallic layer added/sprayed on to optimize the loss characteristics of the propagation.

The concept is to duplicate normal wireless communications simlar to a wireless bluetooth setup. Very low power milliwatts) battery operated transmitters. The rubber layer would act as a parallel plate waveguiding section. The loss in RF propagation is much less for 2 dimensional divergence than it is for 3 dimensional propagation, hence you could allow some loss in the material and the reflection off the seawater (or added propagation metal boundary) and still communicate quite well.

Since sub's have high power antennas on them, I'm guessing there is no affect on the magnetic signature, degaussing system and galvanic corrosion by adding an antenna signal 10,000 X weaker than the normal sub's antennas. How can I be sure of that though? What levels RF energy affect these parameters.

Thanks all,

kch

 

[mshimko]

Three considerations to provide:
1. The "most exterior" coating on all Naval vessels is an antifouling coating to keep marine growth to a minimum. These coatings are all currently copper ablative types, and their use will remain a requirement into the future.
2. All marine vessels also employ cathodic protection systems, and will do so as long as steel remains the primary construction material.
3. Anything even possibly related to the signature of a submarine is classified; it wouldn't suprise me if the specs for a coffee pot on a sub were classified

 

[Higgler]

mshimko,
Thanks for your input,
Let me try to restate your item #1, if the layering of the sub starts with a metal hull (titatium), added to that is some sort of rubber/silicone coating, then the outer coating that contacts the seawater is copper ablative.
I realize ablative means it would flake off as it corrodes, so I'd expect it to be many layers of copper. Hence if I propagate rf energy inside the rubberized layer, it should repeatibly reflect off the copper and Hull metal in a low loss parallel plate waveguiding mode (energy bounces off top/bottom/top/bottom....etc).
sound correct to you?
kch

 

[GregLocock]

No, I'm pretty sure, from the photos I've seen, the rubber is the outer layer.

Also very few subs, and no USAn ones of any operational significance, have Ti hulls. They are mostly HY100 steel I think.




Cheers

Greg Locock

 

[mshimko]

Higgler:
I need to provide a better explanation of the copper ablative antifouling system:

These are organic coatings that typically contain very fine particles of cuprous oxide (metallic copper could be used in theory, but I'm not aware of any current examples). "Ablation" does not refer to the corrosion of copper, but to the almost erosion-like wearing away of the outermost layers of paint when the vessel is in motion. This ablation serves two purposes; (1) fouling that does attach to the coating (as these coatings are not sufficently toxic to prevent all fouling) will fall off as the paint itself ablates, and (2) "fresh" particles of cuprous oxide are exposed. Last, this antifouling coating is the "outermost" item on the boat.

Also, by "layers" I do not mean coats of paint; "layers" is simply a term used to refer to a "very thin film" of paint. These coatings are typically applied in two coats and allowed to dry/cure just before the vessel is put back into the water. (Not sure if this is any clearer, if not just ask and I'll try again).

I won't get into the hull materials, other than to confirm that they are steel. A few Soviet Union subs have titanium hulls, but that's it.

 

[Higgler]

Thanks mshimko,
A coworker was explaining similarly to me that the coating is not layers of metal but probably a powder. He says it's a bit environmentally non friendly in the application process. I can probably buy some at my local marine shops I would think.

Regarding the "cathodic protection systems"; I just read something from google on it at

http://www.mcpsltd.co.uk/mcpscatalogue/iccp.html.

If this is the way the sub would be layed out, how many anodes are needed on the sub? Does the material on the anodes actually flake off with use?

Thanks,
kch

 

[ssreese1500]

Really good info here, this is my first post! When talking about cathodic protection, there are two types, sacrificial anodes, nowadays made of aluminum, and induced current. The advantage of the induced current is that it is, in theory, non-sacrificial. What you will find however is that due to just normal use there is going to have to be maintenance performed and parts replaced when the vessel is drydocked.

Regarding rubber coatings, I have experience using a product from International Coatings (not sure of the website) that is commonly called PRC. It is applied most usually in .125" thickness and is truly a fantastic product. It is tough and flexible will deaden sound in a steel decked interior. There are a few downfalls though, it has a relatively short working time and doesnt adhere all that well to vertical surfaces. I know this product is used for various applications in the US Navy Surface fleet, but dont know about subs. Probably a high tech version of this stuff that is proprietary.

Regarding copper ablative coatings, check here

http://www.ameroncoatings.com/products/pdf/ABC3_PDS_AI.pdf

 

[wsmith]

Higgler,

You can find out much more about submarine construction, operation, and history from books such as "The Complete Idiot's Guide to Submarines". There you will find that American hulls are HY80 or HY100 steel, and that during normal operations the hull and the conning tower are almost always completely submerged.

Even if your antenna were to be implemented on the top of a submarine on the surface, then regardless of power levels it would only be ably to communicate with aircraft or satellites directly overhead: without any antenna height above the water, multipath propagation will kill communications in all other directions.

 

[mshimko]

For ssreese - PRC is actually a name of a company/product line (former company now, I believe). The product I'm familier with is a decking material that is literally poured onto a deck and allowed to harden forming a smooth, cosmetically pleasing, and durable deck surface. Also, while some sacrificial anodes in the marine industry are aluminum, zinc is by far the most common material. Regarding Impressed Current Cathodic Protection (ICCP) versus sacrificial, the coatings on the anodes are designed for a very long service live, such as 20 years. As someone else mentioned above, their service life is limited more from damage such as being smashed by a tug or log than anything else.

For Higgler - powder coatings are merely coatings without solvent, provided and applied in the form of a powder, then cured, typically by heat. Most uses of powder coatings are limited to relatively small items that can placed in a furnace or oven for cure. I know of no large scale application of powder coatings, but it's use is epanding. The AF coatings on marine vessels are your typical solvent-borne coatings typically applied by airless spray.

 

[ssreese1500]

mshimko,

thanks for responding. Zinc used to be the most popular, but not anymore when concerning large cargo vessels. Aluminum gives off a higher discharge voltage than zinc, thus better protection with the same amount of anodes. They also "turn on" faster than zinc, which is very important for vessels travelling between fresh water and salt water enviroments.

Regarding the impressed current systems, sometimes you will see the forward anode banged up, almost never the aft ones. they are generally placed on areas of the ship with a sharp rake well below the waterline making them less vulnerable to damage from floating debris. Mostly what I have seen with these is that either the bolts holding them against the hull become corroded, or the insulating material starts to peel off the hull.