Concrete submarine

[Tcubed]

Wellmer, I'm intrigued that you don't think it would be possible to plumb the 11 000 M mark with ferrocement.

This was my thought experiment; consider a solid sphere of ferroconcrete (no cavities whatsoever) now it would withstand any kind of pressure save the kind of rock liquefying pressures found beneath the earth's crust.....
Then make a very small bubble in the middle, which wouldn't weaken it very much (suppose for example wall thickness / diameter ratio = 0.49)...surely this would still hold up at the bottom of the marianas,11 000 M and have plenty of strength left over?

You know much more than me on subs and concrete so i ask you.

 

[rwatson]

Also - Wellmer, while you are at it - about the 18m prototype that is "almost done", that was on your web site a long time ago.

I am confused, aren't you now working on a much larger project in South America?

The other thing that would interest me greatly, is some financial figures on the method. The main benefit as you point out is the savings on cost.

Can you provide some indicative costings, on the prototype, or any other sub project please. Thanks in Advance

 

[wellmer]

Wellmer, I'm intrigued that you don't think it would be possible to plumb the 11 000 M mark with ferrocement.

This was my thought experiment; consider a solid sphere of ferroconcrete (no cavities whatsoever) now it would withstand any kind of pressure save the kind of rock liquefying pressures found beneath the earth's crust.....
Then make a very small bubble in the middle, which wouldn't weaken it very much (suppose for example wall thickness / diameter ratio = 0.49)...surely this would still hold up at the bottom of the marianas,11 000 M and have plenty of strength left over?

You know much more than me on subs and concrete so i ask you.

For going 11.000m (with a very small bubble in the middle) you would need a material that has a pressure resistance of at least 1100kp/cm2.

Civil engineers work with concrete resistance of some 600kp/cm2

There is experimental concrete that passes this by a factor 4 according to some studies by a factor 10 - so in THEORY could it be possible - but certainly not very practical for a sub.

At the moment there exist submarine concrete applications on large scale that resist hydrostatic pressure to some 300m.

Studies have been published with relativly small scale models for a depth of 5000feet (1660m).

http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA160232

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So i think it would be great to get to 3700m what already would make the biggest part of the ocean bottom accessible.

And best thing is - it could still be a practical sub (not a infinite small bubble in a concrete ball).

On the other hand - a submarine yacht - just diving a few dozends of meters holding a tremendous safety factor is a fairly well researched load case with no surprise to expect and still a very exiting project.

It would be bad management to try to push the technology limits to its extremes in the first round, risking too much. So i will leave deep diving for projects to come.

In any case deep divers should be based on spheres (a bit different to the submarine yacht configuration i am working with at the moment)

To give a general picture how such a boat could look like - see Deep Quest design...

...no diver chamber...

Cheers,
Wil

 

[wellmer]

concrete submarine yacht building status

Also - Wellmer, while you are at it - about the 18m prototype that is "almost done", that was on your web site a long time ago.

I am confused, aren't you now working on a much larger project in South America?

The other thing that would interest me greatly, is some financial figures on the method. The main benefit as you point out is the savings on cost.

Can you provide some indicative costings, on the prototype, or any other sub project please. Thanks in Advance

Hello rwatson,

I am Austrian and i built the prototype of 20 tons you see on the pictures below in Austria in the early nineties.

Since then i am living in colombia south america where i now build a submarine yacht that scales up the prototype by a factor 10 it is 18m / 200 tons.

It will be more or less like that:

The basic idea is to take the proven concept of the prototype which was a weekend yacht scale it up to a live aboard submarine yacht suitable for long range ocean yachting.

As you can see at my website the project was funded mid october 2007 and projected for a hull building time of one year.

As you can imagine it was not easy to get all the necessary building permits quickly so we had a building start delay of some 2 months.

At the moment the hull is almost finished and we will hold the original time shedule of 1 year building time for the hull.

The originally proyected hull building cost of 331 Euro per ton of displacement is also on shedule.

Due to my agreement with colombian naval authorities of not publishing building status fotos that could reveal details of the building method, - which could be used as a guidance for sub building by the bad guys - i can only publish fotos of the finsihed hull - which i hope will be the case in a few weeks.

Cheers,
Wil

 

[rwatson]

Thanks for that Wellmer - so essentially the hull alone for the 18 metre is around 70,000 euros by the sound of it.

Another thing that intrigues me is, none of the diagrams show bow or tail planes for diving and surfacing.

Is this just a simplification of the illustrations, or do you not use them ?

 

[harlemriverman]

As strange as it sounds, concrete is (from an engineering standpoint) a very good material for submerged, ambient-pressure structures...

...make that an excellent material for this application. technically the shape of a submarine makes for efficient use of materials, but the long term maintenance costs are going to be a killer. subs produce too much movement for my comfort zone with even the most aggressive epoxy coatings and cathodics, at least with serious dives. but if all the guy wants to do is submerge to 20, this craft might go as long as 20 years which would make for a catchy warranty phrase. but its a total junker at a major refit, it'll be cheaper to heap the shell or pour a new one compared with trying to fix it for rated serious dives.

 

[LyndonJ]

For going 11.000m
you would need a material that has a pressure resistance of at least 1100kp/cm2.

Wellmer for a supposed submarine designer you sure are full of misinformation. I am perplexed that you claim the expertise and yet misunderstand the subject to a level that leaves me cold.

Engineers work in MPa (MN/m2) for good reason, a pascal is a newton per square meter, not as you bastardize ( kp/cm2 )

The pressure at 11000m is calculated by Rho.G.h, it will be 1025(kg/m3) times 9,81(m/s/s) times 11000 (m) Which gives 110MPa of pressure.

if you want that in Newtons per cm its 110 million newtons per square meter, so divide by 100cm times 100cm (or 10000) and you get 11 kN/cm2
NOT 1100kp/cm2 as you confusedly write.

anyone interested in this should also read

http://www.boatdesign.net/forums/boat-design/submarine-yacht-project-13844-8.html and the preceding pages.

Wellemer
What is the fatigue strength and fatigue stress limit of the concrete you are using ? How many cycles/dives till the hull is derated ?

Somehow I don't think you have been there but maybe I'm being unfair, please surpise me

 

[rwatson]

Valuable link LyndonJ

Especially point 21
"It depends on how big the waves are at the surface and how deep is the submarine. During normal weather conditions, a submerged submarine will not rock with the motion of the waves on the surface. In fact, during even moderate storms the submarine stays perfectly level at its submerged depth while the waves crash above. In extremely violent storms like hurricanes and cyclones, wave motion can reach 400 feet or more below the surface. Though not as violent as on the surface, these large waves can cause a submarine to take 5 to 10 degree rolls."

I raised the point about servicability early on in this thread "Then there is the quality control. Concrete used as submarine has to be hand laid - every critical inch of it. Ferroconcrete yacht hulls have enough problems - but would you trust your life to high pressures, year after year, knowing that the hull integrity depended on carefull laying every square foot being free of voids, mis-mixtures, etc? You would be dripping sweat on every dive! especially after the first 6 months when you have no way of knowing if the steel reinforcement was being affected by salt conditions."

Now, lets consider a submarine with totally circular section, with no hydroplanes, in a moderate swell, trying to stand on a deck to .... wave to the rescue helicopter ??

 

[LyndonJ]

In my opinion its all a bit hair-brained high school project level and with the designer so far off in fantasy land that it's frightening.

That rolling when submerged is common knowledge for submariners, and 10 degree rolls lead to high levels of discomfort and dissability. For real comfort you'd want to sit on landing gear and ballast very heavily. The roll in shallower water would be far worse and Wellemer just doesn't know any of this at all.

Uboat pressure hulls were quite simple, does anyone have the scantlings?

I dont think they were all that thick and the pressur hulls were just big tubes. Steel is going to be the best material by a country mile... for a variety of reasons and yield is still a long way from collapse so you get some very visible warnings before it kills you.

Re-inforced Concrete can be really tricky, too much steel and the concrete just crumbles, you want the steel to yield before or ideally at the same time the compressive failure occurs.

 

[dccd]

Wellmer

Good god man please disreguard the preceeding, I for one retire from these forums often due to the all to common injection of uninformed jealouse opinion disguised in scientific language and a fienged moral duty to protect us from orselves or us risking the lives of others they could care less about in the jammed packed open oceans. Scarring off conducive discussion during those rare instances when somone like you actulay devotes his time, creative gifts and effort to explore and runabout in his own working creation. The moderator will start hearing from me when ever I see a bold initiative that is working for gods sake being ridiculed by lots of scepticisium with no value to the reader, designer or the writer. It is the oopsite of what this venuse is for and should be removed unless they are nessasary because they are the ones being asked to insure you. Gods speed Wellmer and I look forward to shaking your hand one day.

 

[LyndonJ]

dccd
The first duty of a thinking person is not to be conned into some belief. Skepticism is very healthy and valuable particulalry if you think you know something about the issues that apparently the 'designer' doesn't.

This person is publically advocating their commercial design on a public forum NOTE forum. He makes claims that are not just questionable but if you read all the material they are plainly based on misinformation.

Taking the high moral dudgeon just because you like the idea isn't very sensible. Make a list of the negatives that Wellemer has just sidestepped or claimed don't exist and you will see for yourself. So please read all of both the threads and the website and then ask why he sidesteps so many issues, and why he appears to have surprisingly large gaps in his knowledge.

What process would you go through if you wanted to design one atmosphere submarines?? Would you read some books on it ??

Where's a photo of this 200 tonne unit in construction ? Seeing is beleiving and something seems a bit fishy.

 

[harlemriverman]

...Steel is going to be the best material by a country mile... for a variety of reasons and yield is still a long way from collapse so you get some very visible warnings before it kills you.

Re-inforced Concrete can be really tricky, too much steel and the concrete just crumbles, you want the steel to yield before or ideally at the same time the compressive failure occurs.

not sure i agree with you, but that's as a structural engineer that knows less than nothing about concrete submarine design so i'm wide open for commentary.

what you are describing are some of the many metrics of efficient design, but these metrics are indifferent to the relative safety of steel compared with concrete for the condition you describe here. the compressive strength of concrete, its geometry and the service loads of the pressure vessel in question seem readily manageable for controlled or catestrophic failure. and as s i read these threads i'm learning that these craft are mre recreational in nature, not intended for deep commercial or military dives.

but again, i really don't know anything about concrete subs and would like to learn. does anyone know of a website or journals, perhaps a book that delves into the subject?

 

[wellmer]

...make that an excellent material for this application. technically the shape of a submarine makes for efficient use of materials, but the long term maintenance costs are going to be a killer. subs produce too much movement for my comfort zone with even the most aggressive epoxy coatings and cathodics, at least with serious dives. but if all the guy wants to do is submerge to 20, this craft might go as long as 20 years which would make for a catchy warranty phrase. but its a total junker at a major refit, it'll be cheaper to heap the shell or pour a new one compared with trying to fix it for rated serious dives.

Harlemriverman,
Are you concerned about long term maintenance cost? What do you mean with movement? You would estimate a 20 year lifetime why that short?
Let he hear your thoughts...
Wil

 

[rwatson]

Harlemriverman,
Are you concerned about long term maintenance cost? What do you mean with movement? You would estimate a 20 year lifetime why that short?
Let he hear your thoughts...
Wil

Hmm Wellmer. I was hoping *you* would give a detailed dissertation on the Coefficients of Thermal Expansion for concrete, the aggregates that form the mixture and the steel re-inforcing. How will you combat the microscopic cracks that -10 to +80 temperatures can induce in concrete structures?

Sure, concrete is considered incompressable, but we know that external pressures can have a huge impact on all materials, starting with small fractures around supporting re-inforcement, especially when combined with say engine vibration.

Perhaps you could answer HRM's request for your hull life-cycle estimates in conjunction with my interest in the precise quality control needs of laying concrete used in a high pressure hull.

You have addressed this issue I am sure, and this information will be of great interest to the potential buying public.

 

[harlemriverman]

wellmer, my perspective on this topic is as a neophyte to the application. i have more questions than thoughts.

i am concerned with long term maintenance costs, and the questions are with respect to: 1) controlled cracking; 2) fatigue; and 3) cathodic protection. we are discussing dynamic load cases, similar to stress / strain i would anticipate for seismic, wind, vehicular, etc. service loads. this raises a lot of salient questions with respect to how the hull behaves long term, which rwatson astutely points to.

20-years is not short if that is the design life cycle costing on the system, but it would very short on a submarine for recreational use. were that the life cycle of a concrete submarine, it would have virtually zero salvage value at the conclusion of its service life unless there were economic means of making major repairs to the hull without simply discarding the hulk.

i can imagine several possibilities involving skeletal alloy composites or hybrid approaches that might make a concrete shell both economical and easy to replace, thus some of my earlier questions on the approach to pouring the hull. but this is purely speculative thought on the fly, and with very little thought.

i could also develop my own model, which would take some time and i just haven't done. my guess is it will be clunky to start -- i have zero basis but could be fun. unfortunately its hunting season, and i'm headed out the door for opening day for a couple of weeks of back woods adventures. please carry on but know that i am most interested in this topic. i do see application to dry land, and for different purposes, but note that the service load issues there are considerably different.