Concrete submarine

[MikeJohns]

Originally Posted by Knut Sand

If we'd assume that the aft bulkhead is supposed to hold against surrounding pressure? I'd not even consider that one, If I understand you correctly; A circular internal wall subjected to pressure? ...........

From his drawings it was a big solid ring frame in concrete presumably with reo tied to the hull mesh, I would expect to see some nasty shear stress in the bulkead- hull interface and I'd expect an early crack failure of the matrix in this area.

Earlier in this or the other thread some tried to impress on Wilfred the importance of safety and also the fast emergency surfacing for one atmospehere subs. Even a small crack or seal failure spurting water will quickly overwhelm the fish bladder type depth control. Was there even the slightest indication of significant emergency ballast release?

I'd like to see the suggested engineering systems design (or lack thereof).

[hoytedow]

Originally Posted by Submarine Tom

Would you care to guess at the crush depth?

Tom

I believe apex1 is on the right track. It will seep full of water through the cracks and voids in the hull before it crushes. Eveyone inside will get nitrogen narcosis and slide peacefully into unconsciousness. Hull failure in that sense, probably 45 meters

[oralpiskin]

how hydrodynamic resistance and stability of submarines are calculated?

[Submarine Tom]

Hey, finally, a hard number out of hoytodow 45 m, great!


Catstrophic failure depth of Willy's c-sub destructive test wager board:

bntii: 85 m

watson: 0 m

s-tom: 312 m

KnutS: 74 m

Apex: 60 m

gonzo: 16.3 m

hoytodow: 45 m

That's an average of ~99 m (excluding watson who doesn't think the sub

will ever get wet). And ~56 m if you throw out my optimistic 312 m.

Lets go diving Willy!

[rwatson]

Oh yeah - and scuttling it to make a wave break or an artificial reef voids all bets - like a race scratching!!

I am keeping an eye out in the Columbian Real Estate ads for a really cheap but bullet proof egg shaped beach hut right at the waters edge - as is!

[Knut Sand]

Originally Posted by rwatson

I am keeping an eye out in the Columbian Real Estate ads for a really cheap but bullet proof egg shaped beach hut right at the waters edge - as is!

Placed vertically, nose up, it'll look kind of cool...

MikeJohns:

"From his drawings it was a big solid ring frame in concrete presumably with reo tied to the hull mesh, I would expect to see some nasty shear stress in the bulkead- hull interface and I'd expect an early crack failure of the matrix in this area."

I do believe I typed something about a behaviour like a cork.... Also because a wall cross section will have shear stress along the inside of the hull, if I understand the shape correctly...

For steel like materials allowable shear stress is, well: Yield stress, divided by the root of the number 3. (and to that again mulytiply by 2,3,4, 4,5, 6, or divide by the same numbers, or use the tensile strength, pick your choice, but check your figures and choose the one you're most comfortable with... Make it safe). When something starts to happen, well there will remain less cross section to handle tha same stress. Stainless steels, and some other types of steels have "deformation" hardening, I.e as the metallic structure in the steel is squeezed, the internal strength increases, and in some cases; enough to hold.... (a kinda of strange behaviour that's hardly never ever seen upon as an unpleasent thing, not allowable to calculate into the structure though).

Well, concrete hardening, Willner is correct about concrete continues to harden, increase the ability to handle stress, as the time goes, but when designing a hull like that, there should be some specified numbers;
Cure time, samples, samples tested, (and spare samples saved, just to prove you were right at a later stage....). And stress values, material properties documented for all the loads in the same design;

Those values should be there for a hull, like 3 - 6 months from the layup, (example). Noboby can be expected to buy a hull that's not fully hardened until a couple of decades have passed.... Or? (or how do you then document that there's still something left of that reinforcement steel inside...?).

I've said earlier;
tension and
compression, now I'll add;
shear stress properties too....

I'd expect thet the material properties for concrete exposed for shear stress is pretty low...


Waiting for some numbers...

[bntii]

Originally Posted by Knut Sand

Waiting for some numbers...

You are being difficult Knut!

Wellmer has repeatably provided his 'numbers' on this craft and his prototype:

"Let me start with the facts : troll platform is based on concrete legs that reach down 303 meters with 24 m diameter and 1m wall thickness. Including usual security factors i assume that it could have a destruction depth of some double of this. Which places a positive buoyant cylinder similar as troll at 606 m destruction depth.

My submarine prototype - which i obviously did not test to destruction depth - has almost exactly the double diameter / wall thickness as troll - means it is double as strong and may have a destruction depth of 1212m"

He doubled the thickness from a know structure and therefor has to his mind a known strength.
You have to keep in mind:

"As i said before i am not a static engineer, i am not a material scientist, i have listened carefully to some experts on my advisor board, so i believe i can understand "a little bit" of what is the basics."

You won't get any numbers from Ellmer past the above- that's all he has...
Wellmer is not an engineer. He is a salesman selling a "concept".
Our Wellmer is simply smitten with a material. I think he fails to understand that each structure is a unique and must be engineered as a discrete entity. He also fails to understand the limitations of the material and how well it is already understood in the engineering community:

"I am not sure why US navy is not building in concrete - most probably it has to do with the fact that a warship is part of a sistem - it holds weapon sistems that are normally part of a steel ship, it goes to shipyards skilled for steel building, it has a crew trained on steel repair and maintainance, etc. etc."
Wilfried Ellmer 2008

Perhaps apex also has "missed the boat" and will start to build concrete vessels in his yards!

[wardd]

can i mention my wicker submarine concept?

it has unlimited diving depth by equalizing the pressure inside with that outside

[peter radclyffe]

now how about a plastic sub

[Knut Sand]

Originally Posted by bntii

You are being difficult Knut!"Let me start with the facts : troll platform is based on concrete legs that reach down 303 meters with 24 m diameter and 1m wall thickness. Including usual security factors i assume that it could have a destruction depth of some double of this. Which places a positive buoyant cylinder similar as troll at 606 m destruction depth.

My submarine prototype - which i obviously did not test to destruction depth - has almost exactly the double diameter / wall thickness as troll - means it is double as strong and may have a destruction depth of 1212m"

I'm never difficult...

(though my wife have mention sometimes that I don't alway seem to play the "hard to get" type, more the "hard to want" type.. Don't know what she means by that...)...

Ok he says 606 m/ 24 m dia/ 1 m thickness. _Troll....

Soooo.... Let's assume:

4 m dia / 60 cm thickness/ that would give something like ..330 mm..?

IF:

You have similar layup; one pour...., same concrete (or better), scale up the reinforcement in a similar way, NO WINDOWS...

I know for sure that any engineer suggesting windows somwhere on the legs of the Troll platform would have got the puzzled look, then if they were judged to be not joking, would be immedeately relocated to other work tasks...

I don't know the layup/ reinforcement/ process... So I assume I'm around here for the information....

Curious, not difficult...

Edit: THAT one I screwed up... "4 m dia / 60 cm thickness/ that would give something like ..330 mm..?"
I meant; 4 m diameter 330 mm hull thickness...

[Knut Sand]

"My submarine prototype - which i obviously did not test to destruction depth - has almost exactly the double diameter / wall thickness as troll - means it is double as strong and may have a destruction depth of 1212m"

Hmm, what about a test (DNV/ Lloyd witnessed...?) to 1200 m? That would stop the arguements..

I'm not that morbid, so I'd prefer an unmanned test, but I'd like to have a camera aimed at the designer/ builders face.... just in case to load on the wire suddnly alters rapidly, one way or the other...

[bntii]

The 18 meter sub has a diameter of 4.3 meters and a shell thickness of 34 cm.

[Submarine Tom]

Knut Sand wrote:

"Hmm, what about a test (DNV/ Lloyd witnessed...?) to 1200 m? That would stop the arguements..."

-and lets have it live in "real time" on the Internet for all to see!

Tom

[gonzo]

An unmanned test would spoil all the betting. Someone shoot that party pooper

[Knut Sand]

Originally Posted by bntii

The 18 meter sub has a diameter of 4.3 meters and a shell thickness of 34 cm.

I stand corrected. I was seriously out of depth with my post yesterday.

BUT that implies identical layup, reinforcement, curing time, same concrete...
or better.....

And no windows, that weaken the strength of the hull.... No opening for any hatch, too... which makes it a bit impractical...?