Concrete submarine

[ancient kayaker]

I have some pros and cons on this one.

Cons first:

I can't argue with LyndonJ's math. I'm bothered by apparent lack of propulsion means and control surfaces in what I assume to be photos. I'm also bothered by Wellmer's failure to respond to these questions. I'm also bothered by the fact that, according to the site provided by Welmer, this project has been going for 14 years, but I have the impression there has only been one sub actually completed so far.

Pros:

I'm fascinated by the concept. Concrete is a well established material for making big things, it's relatively cheap and well understood, it easily casts into any weird shape you want, it's waterproof and withstands compression. That's practically a definition of what you need to make a sub.

What is the problem with having a concrete hull with no rebar to avoid problems with corrosion? Why would you use reinforcement in an application that is pure compression? I can understand why steel is needed in a concrete surface vessel, there's much more dynamic stress there. For relatively shallow use the pressure forces on a concrete hull are negligible; buildings with deep basements in soil with high water levels can withstand such pressures for centuries; they have rebar, sure, but that's to handle the dynamic loads transmitted by the building on top. Roman buildings did not use metal much as a structural element except for a few exceptions like the dome over the Parthenon.

I don't see this application as a stressful situation for concrete provided there is no risk of collision with something big: and let's face it, subs don't often come out the winner in that scenario. For anything smaller, I would wish it good luck hitting a few tonnes of concrete; try attacking a dock with your boat.

Maintenance? About the same as for bridge footings I imagine, which is to say, check it yearly and usually find nothing to do. The biggest problem would be freezing, so just sink the sucker for the winter.

If I wasn't so chicken I would try it myself.

 

[rwatson]

Why would you use reinforcement in an application that is pure compression? I can understand why steel is needed in a concrete surface vessel, there's much more dynamic stress there.

I don't see this application as a stressful situation for concrete provided there is no risk of collision with something big:

Maintenance? About the same as for bridge footings I imagine, which is to say, check it yearly and usually find nothing to do. The biggest problem would be freezing, so just sink the sucker for the winter.
.

Are you not reading the previous postings at all ?

Both HRM and myself have identified a lot more than just compression forces at work here on the concrete structure.

Temperature changes alone will create severe expansion stresses - forces that destroy great basalt monoliths, let alone a couple of truckloads of aggregate with a hole in the middle.

The comparison to Bridge footings is totally unsuitable, despite Wellmers attempts at his website by quoting huge concrete structures as a basis for the viability of his project.

I have come across papers on the internet that discuss failures in even glass fibre re-inforced concrete structures due to vibration and moisture penetration.

As a skeptic, I at least can change my mind when the concept is proven, but it sounds like Wellmer and maybe others have quite a bit of time and money invested, and cannot possibly admit the possibility of failure. Certainly the silence on a lot of points about the project ( as you observed) dont build my confidence.

 

[ancient kayaker]

Are you not reading the previous postings at all ?

Both HRM and myself have identified a lot more than just compression forces at work here on the concrete structure.

Temperature changes alone will create severe expansion stresses - forces that destroy great basalt monoliths, let alone a couple of truckloads of aggregate with a hole in the middle.

The comparison to Bridge footings is totally unsuitable, despite Wellmers attempts at his website by quoting huge concrete structures as a basis for the viability of his project.

I have come across papers on the internet that discuss failures in even glass fibre re-inforced concrete structures due to vibration and moisture penetration.

As a skeptic, I at least can change my mind when the concept is proven, but it sounds like Wellmer and maybe others have quite a bit of time and money invested, and cannot possibly admit the possibility of failure. Certainly the silence on a lot of points about the project ( as you observed) dont build my confidence.

I read the previous postings. Again. There is no consensus that I can form, just a lot of conflicting opinions. I don't know the contributors so I don't know who is informed and who like myself, is looking at something new and wnating to learn more.

I accept your refutation of my remarks about bridge footings, I should have made my lack of knowledge clear and trust you are speaking from knowledge, but I would have thought the main challenge there would be undercutting by the current.

Failures due to vibration: is that relevant here? It is hard to imagine a slow-moving tube of concrete floating in the water having a vibration problem. A bridge deck or support is quite another matter.

You mentioned failures due to moisture penetration and also expansion stresses resulting from temperature changes, which sounds like you are concerned about repeated frost cycles. My concrete basement handles a temperature difference of 60 deg and a range of 80 deg on one side, and it didn't seem too bothered when it leaked for a couple of seasons and I'va had no further problems since slapping on a bit of hydraulic cement 25 years ago. Extreme temperature cycles are easy to prevent in a submersible craft not used in the winter, just add enough ballast to sink it when you let the air out of the tanks; pump 'em up in the spring. That assumes access to sufficiently deep water, but seems reasonable if you have a submarine

The thought behind my suggestion for using unreinforced concrete was this: the modulus of elasticity of concrete is 1/10 that of steel; placing a hollow ferro-concrete vessel under considerable pressure could therefore result in the steel imposing tensile forces on the concrete from within, with predictable results. Unless, that is, the steel was pre-stressed, but I haven't seen that mentioned yet. I don't have relevant data for fiber reinforcement.

I can't change my mind, it's not made up yet. I agree that Wellmer has not yet made his case; I think that we both are inviting him to do so.

 

[ancient kayaker]

I have a question for Wellmer:

Wil, how many concrete submarines have you built? I have searched through the forum for all your posts in a total of 9 threads to date and have found refences to these:

1 tonne personal sub
9m/20 tonne sub
18m/200 tonne currently under construction

 

[wellmer]

I have a question for Wellmer:

Wil, how many concrete submarines have you built? I have searched through the forum for all your posts in a total of 9 threads to date and have found refences to these:

1 tonne personal sub
9m/20 tonne sub
18m/200 tonne currently under construction

Hello ancient kayaker

Those are the 3 funktional subs i built - the first 2 dived for decades - the big one raw construction finishing. Plus hundreds of concrete test models...

 

[wellmer]

...control surfaces in what I assume to be photos. I'm also bothered by Wellmer's failure to respond to these questions...

Ancient kayaker

Control surfaces for dynamic diving are a military concept born form military need of quick diving - please check on BEN FRANKLIN and all tourist subs that fowllow you will not find dynamic dive operation and asociated control surfaces.

Sorry for my retirement from forums that still discuss questions like "is concrete a suitable material for a submarine pressure hull" - when the answer is given by hundreds of working concrete pressure structures as i point out on my website - there are still people that discuss questions like "took evolution ever place" - and you surley understand the reasons why i am not discussing about that...

Please check the "studies" link on my website that features key studies on that theme. On the other hand i am always interested in discussing new and exciting questions count on me ...

 

[brian eiland]

Ben Franklin sub & Gulf Stream drifting project

Been away from the forums for quite awhile and missed this subject of submarines.

I do remember being quite fascinated with the Ben Franklin Gulf Stream Project as I was involved with submarines at the time, and also very interested in the field of oceanography. I've see it mentioned a few times on this subject thread, but no direct web-links to the subject....so I offer a few here:

http://www.sub-find.com/historical.htm

http://www.bosunsmate.org/benfranklintour.php

http://www.unexplainable.net/artman/publish/article_1006.shtml
"In mid-July of 1969 the whole world was focused on NASA's Apollo 11 moon landing. But some people at NASA were focused on something else.

On July 14, just two days before the Apollo launch, the PX-15 deep sea submarine Ben Franklin was towed to the high-velocity center of the Gulf Stream off the coast of Palm Beach, Florida. With NASA observer Chester "Chet" May on board, the sub descended to 1,000 feet off of Riviera Beach, Florida and drifted 1,400 miles north with the current for more than four weeks, reemerging near Maine.

In addition to studying the warm water current which flows northeast off the U.S. East Coast, the sub also made space exploration history by studying the behavior of aquanauts in a sealed, self-contained, self-sufficient capsule for NASA. The mission is the focus of a program airing on the Science Channel"

Lots of other reference sites:
http://seawifs.gsfc.nasa.gov/FRANKLIN/HTML/franklin_links.html

Popular Mechanics article:
http://seawifs.gsfc.nasa.gov/FRANKLIN/IMAGES/POPULAR_MECHANICS/popular_mechanics.html

 

[ancient kayaker]

Ancient kayaker

Control surfaces for dynamic diving are a military concept born form military need of quick diving - please check on BEN FRANKLIN and all tourist subs that fowllow you will not find dynamic dive operation and asociated control surfaces.

Sorry for my retirement from forums that still discuss questions like "is concrete a suitable material for a submarine pressure hull" ...

I don't know much about subs but I am open-minded and have no problem believing that the idea can, and indeed has already worked, I think it is a good idea. I just have some questions that are obvious to anyone with a little knowledge. I would note that BEN FRANKLIN had a steerable pod at each corner, but I don't think they were intended for continuous use. It had trim tanks and carried a lot of ballast low down in the form of massive batteries, and drifted in the Gulf Stream. The batteries were, I assume, mostly for life support systems.

For a commercial or recreational sub drifting along in that manner would not be attractive; you have to be able to move the thing along at least, and aim it where you want to go, so I expected to see drive pods or a prop and rudder in your photos. I suppose trim tanks could take care of attitude and depth once you have dived, but depth control would be a never-ending dynamic thing without external vanes or pods unless you can rest on a cold layer.

Diving needs main tanks. Air is compressible so you either fill the tanks completely to dive, or you close off the water intake which leaves the tanks under external pressure. Otherwise every change of outside pressure can move water in or out of the tanks and destabilize the depth. Also you need a tank on each side I think, unless you have a single tank high up, or you might turn turtle when surfacing. In a non-military sub not required to perform a crash dive, I imagine the main tanks could be completely flooded leaving a small amount of reserve bouyancy, followed by a slow dive performed using trim tanks. Is that how it's done? Of course one could tow a stabilizing float to control depth but that would be very risky.

I am interested in how you have dealt with these issues. Hopefully you can find time to answer my questions; I have been curious about these aspects of subs for some time.

 

[wellmer]

drifting not attractive

...
For a commercial or recreational sub drifting along in that manner would not be attractive; you have to be able to move the thing along at least, and aim it where you want to go...

ancient kayaker,
I agree with you completely on that point - what makes BEN FRANKLIN so important is, that it pointed out the POSSIBILITY for a sub to just hang perfectly balanced with a non compressible hull in a current and do tremendous voyages without paying a cent for fuel - Jacques Piccard is always talking about the similarity with a ballon ride. This is of course a VERY different operating envelope compared to a military sub. I would take the best from both worlds - like a airship - you can handle it like a ballon - but still moving the thing along - this is why my hulls have streamline shape on contrary to BEN FRANKLIN.

For more on Ben Franklin i recommend:
Piccard, Jacques: Tauchfahrt im Golfstrom, Wiesbaden 1972
http://www.buchfreund.de/productListing.php?used=1&productId=34779381

This is the german version - but there must exist a english verson too...

 

[wellmer]

depth stabilize

... rest on a cold layer...destabilize the depth... stabilizing float to control depth but that would be very risky...

Ancient kayaker,
I see you have that idea in mind that holding a certain depth is a "never ending dynamic" thing - suceptible to destabilize - and risky - and you are right ! - again- for military subs. Most military subs are not designed to have a full stop under water, they are designed for dynamic diving - and for good reasons. On the other hand - it is Piccards merit to show that there are also very DIFFERENT designs possible - BEN FRANKLIN is one of them - my yacht subs are too. What is a hell of a risky maneuver at least with a old style military sub - like rest on a cold layer or "hang the boat on the snorkel tube" to stabilize it. Is natural and easy for BEN FANKLIN - and my hulls. Just to give you a clearer idea the amount of ballast water to shift in my 20 ton prototype to invert floatablility was 1liter - the content of a bottle - the key to stability is a not compressible hull - and ballast sistem.

 

[rwatson]

Hi Ancient Kyaker.

Thanks for the valued input, and the valid responses from Welmer they are producing.

Just on your comments though, I would like to make one point from your own personal experience re concrete footings, and the cracking caused by temperature variations.

At 1 atmosphere, the cure was some waterproof film, and voila, dry basement. As a submarine, about to descend to much higher pressures, the implications are a bit more intense. Not only would the repair need to be waterproof at 1 atmosphere, but you would need to bet your comfort if not your life on it being safe at much higher pressure. Likewise, what if the leak occurred while at significant depth ? Wellmer is saying that he is not using a ballast system (1 litre of differential), and that rapid descent and ascent are not in the purvue of his design, so would you be facing an agonizing wait as more than 1 litre of water seeped into the hull?

What if we also add the problem of your house varying in weight from X to X x 10 on a regular basis, (simulating diving pressures) make the incoming water salt, and place openings in the footing for hatches and portholes. Lets also put an operational 50 hp diesal engine on the bottom floor, as a vibration source, and simulate some hard jetty or bottom landings with few nudges from a backhoe. How many dives would you personally make, and how many with your children as crew, in your basement?

Another observation, based on Welmers latest comments, fast dives are not just for military reasons. The commander of this sub, finding himself in front of a fast moving steel tanker (who cant see the low profile of a slow moving, uninsured concrete vessel in the whitcaps ) might suddenly wish they had the rapid descent capabilities of the old U boats.

While I still have my black hat on, have you wondered why Welmer went to South America to build submarines? Have you also wondered why he is building inside a naval base ?

The last adventure story I read that had these elements was a second "Kon Tiki" expedition, wanting to use the currents along the coast of South America. They also got wonderfull help from the Navy, right up until they wanted to put to sea. Lack of deposit for rescue activity, insurance problems and a whole lot of "last minute" red tape nearly stopped the whole project, and they had to resort to clever subterfuge to get underway. I think the navy was using the old "keep your close to your friends and even closer to your enemies" approach. Navies have spent a fortune on rescues over the years since Thor Heyerdahl set a trend, and their treasurers are very, very sensitive people.

Whatever the engineering challenges of this project are, the regulatory requirements are going to be as big a hurdle. Its one thing to let 20 balsa logs float way into busy shipping lanes, ( and balsa rafts have had some close calls), but tonnes of slow moving, slow submerging concrete has got to be a much bigger cause for concern.

Obviously, Welmer is not giving too much away, as he has a right to the intellectual capital and effort invested. However, I am sure that if the design goes commercial, all these concerns will be addressed in this forum or in the sales documentation.

Its only an interesting source of speculation to me, I wiould be very happy to send a congratulatory telegram to Welmer - I look forward to the ongoing story.

 

[ancient kayaker]

I assume the 1 liter compensates for water density variation although it seemed incredibly small to me at first, but it works out given the compressibility of water is about 5 x 10^-5 at 1 atmosphere or 10 m depth for a 20 tonne displacement or 20 cu m.

However it ignores hull compression. My reference has a modulus value of 20,000 MPa linear for concrete or 7,000 volumetric. For 20 cu m at 1 atmos we get 0.3 L, but that is for a solid hull!

To get a more realistic value for hull compression, I'll assume ordinary concrete stressed to 10% of its ultimate strength of (from my reference book) 1,500 psi. At 150 psi the concrete is under about 10 atmos pressure so that 0.3 L figure rises to about 3 L. That would correspond to a skin thickness about 5% of the diameter, say 10 cm for a 20 tonner, sounds about right. A bit less than my basement but that does not benefit from a curved shape.

So the amount of water to shift in or out to stabilize depth at depths up to but not exceeding 32 ft is about 4 L. Still very small; at 1 atmos, pumping that amount in, say 10 sec amounts to only 40 W, even allowing for reasonable inefficiency that's a modest battery; less than the motive power needs.

surfacing is another matter of course, but even a small portable pressurised tank would be able to handle several dive/surface cycles from 10 m.

RWatson: you're correct, but you've stretch my analogy far beyond its elastic limit. I think it is reasonable to expect the material and manufacturing standards of a sub to exceed those of a basement by a wide margin but enough.

How would I build it? Not sure, but I would investigate the use of pre-cast tubular structures like those I see construction crews burying underground from time to time, probably stronger than anything I could make.

For the cases above how much would I trust my own putative home-made sub? Not at all until after I test it. Sink it under remote control 3 times to twice the max depth of the lake I plan to use it in for a start. Have the design reviewed by people who know what they are doing. have the prototype surveyed for integrity (ultrasound?). Establish an appropriate "pre-flight inspection" process and follow it rigourously. Then, yes, I'd be about as comfortable as I personally am ever likely to be in a (deliberately) submerged craft.

Salt water? Not on your (or my) life. How deep? I would want to design it for more than 10 m!

Why would I need a 50 HP diesel, I would not likely need remotely that much power for underwater. Definitely have a towboat around for moving on the surface but if it is shaped properly a trolling moter is probably enough to get a few knots out of it submerged. no way I would want to go faster than that. Collision is the uncontrollable risk; you need a safe place to surface which means you have to navigate accurately underwater. For emergency surfacing you would have to take what you can get, but if you have a minute to spare a hydrophone would pick up any rapidly moving power craft.

I have acquired more confidence in Wellmer's claims as a result of doing some math.

 

[rwatson]

Valid points AK, and in an ideal world, the theory does hold (out) water.

The basement anology actually isnt too wild. Basements are built with huge engineering redundancies, unlike a weight sensitive pressure vessel like a submarine.

Though, we have yet to hear how Welmer assures the quality control of all that hand laid concrete. Even in totally professional ferro hulls, some cracking is expected. With his thicker hull, the control of voids, mismixes and the like is even more of a problem.

The ultrasound test would need to be carried out before *each* dive to assure my satisfaction - and even one ultrasound inspection on a hull that size would be a major operation. I am not even sure they have machines that big. maybe some of the technologies used by customs would work, but an expensive option.

For a 10 metre , up to 50 metre depth, all the worries of using concrete would barely cover the very slight savings in hull cost compared to a steel hull I suspect. I think I would rather a 6 monthly layup to chip rust and barnacles from a steel hull than the uncertainty of concrete.

 

[Boston]

well having worked with concrete for about thirty years

Rwatson came up with some great questions
I worked my way through school as a contractor and gotta say a few things about a concrete submarine

its nuts

cant you buy an old Russian diesel sub for about the cost of getting it out of there hair

Im all for crazy ideas
but yikes
might as well carve your name and birthday into that thing and maybe a little something they can remember you by

 

[wellmer]

...its nuts..

...buy an old Russian diesel sub...

Please tell this to the guys that built Troll A
Check :
http://imulead.com/tolimared/concretesubmarine/anuncios/ac
Check also the following studies:

source:
http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA160232
surce:
http://cedb.asce.org/cgi/WWWdisplay.cgi?5012561
source
http://www.hydroports.com/underwater03.htm


etc...etc...

----------------------------

Studies overall conclusion:

...The data have shown that concrete exhibits good behavior for ocean applications. High quality, well-cured concrete can be expected to gain and maintain strength when submerged in seawater under high pressure. Concrete is a durable material in the deep ocean; neither deterioration of the concrete matrix nor corrosion of reinforcing steel are problems, even though the concrete becomes saturated with seawater. Uncoated concrete has a very low rate of premeation of seawater through the concrete and even this small flow can be prevented by a waterproofing coating...

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- as said before the question "is concrete a suitable material for submarine pressure hulls" was in discussion in the early forties - ist is NOT really in discussion today - please look around and check all those APPLICATIONS sourrounding you...so if it is still in discussion for you - please update -

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old russian sub for a yacht - probably as good as a conversion of an old destroyer to a sailing yacht - i would not do it...

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Cheers,
Wil