Non-Vitriolic Concrete Submarine Thread

Thanks, Stumble, for a fascinating thread.

Well before the days of the internet while I was still in high school I recall a neighbour building a submarine in his front garden.

I pestered that poor man every day of 1983 and 1984. He indulged me and often let me believe I was of some assistance to him and his build.

I do recall the submarine being craned onto a truck in the late 80's so I presume he finished it.

I'll put the work out in the old neighbourhood with the hope of finding him. He might have something of value to add to the thread if he's so inclined.

 

That was cool reading.

 

This is particularly enlightening from the above attachment, thanks.

 

Here is another:

FEASIBILITY STUDY FOR CONCRETE SUBMARINE

"A feasibility study was conducted by utilizing classical analysis techniques and state of the art construction methods. Prestressed concrete was found to be a viable material for shallow to medium depth submersibles. A replica of an existing steel-hulled submarine was used in the calculations to enable both economic and performance characteristics to be analyzed and compared. It was found that both longitudinal and circumferential prestress must be used in the construction of the pressure hull. To facilitate this, a modular-segmental construction was employed. It was also found that concrete offers both performance and economic advantages over steel. The performance advantages include: freedom from maintenance, durability, readily-available materials, superior performance under impact and accident conditions, non temperature-sensitive, easily formed into compound curvature, and concrete has good insulating properties. Economic analysis has indicated that the concrete pressure hull would cost between 50% and 60% of the equivalent steel hull."
http://trid.trb.org/view.aspx?id=28767

The paper is hard to find, I have it somewhere.
I will see if I can find it.

 

As always with F/C, "hull" costs are reduced 40 to 50 percent.
The hull/deck is usually figured by builders as one third of the cost of the boat in expense, so the saving is half of one third or about 16 percent overall.
And the other costs of penetrations etc?
Looking forward to reading that paper if you find it.
I love this stuff.
In Sausalito CA they started building F/C 'monolithic pour' houseboat flotation barges in the early 70s and I watched them float in saltwater for 30 years, kind of like a three story house that floats on its basement/foundation.
Some lasted well, others cracked from mooring loads and re-bar too close to the surface.
I don't know of any that actually failed as to not be repairable.

 

I will look Bataan - I think it is on my other computer.

Take a glance at my post #242 on other thread- or perhaps its not best to turn over some rocks...

 

The original poster has an attitude not unlike I see on F*** "News", which is "I can make up any reality I want and it's just as valid as yours".
Maybe I let this bother me too much.

 

Oh, non-vitriol. Got it.

 

Wait, I have that attitude Baatan? Or the OP on the other thread? I honestly don't know anything about using concrete at depth, but I am curious. However the other thread... Well it's the other thread.

One of the interesting things I came across was a cycle loading test that was done on concrete. At http://www.quakewrap.com/frp papers...nedwithDifferentFRPLaminateConfigurations.pdf which indicated that cycle loads of less than 60% of nominal yield strength were considered too low to produc results, as concrete is assumed to cycle infinitely as these loads. Since the paper Bntii posted indicated a minimum safety margin of 3:1 for manned submersible concrete structures the maximum cycle loading should be no higher that 33% well below the minimum cycle stress needed to damage concrete (testing was done up to 20,000 cycles).

This seems to indicate that assuming a safety margin of 3:1 the cycle stresses are a non issue over the life of the structure.


Bataan you raised the issue of penetrations. I roughly priced some out, and from what I can see it would be possible to use standard T and Y taps already used in the pressurized concrete industry. These have a nominal cost of around 4-500, which does not include the metal hatch door, just the joint. The preassure doors I found rand around $1200 when rated at over 1,000psi. Which should far exceed the nominal operating range of the sub.


As for smaller hull penetrations, the same paper Bntii posted discussed them, and indicated that if joined properly they were not the source of failure. I was able to source high preassure penetrations at McMaster Carr for around $12, for brass fittings rated to 1,000 psi at 72 degrees F, and operational at -65f through 250f. http://www.mcmaster.com/#8682T23

 

The original poster had the attitude, and sometimes so do I.

 

As a former marine contractor/engineer, the concrete submarine idea is valid. Use highest density, use corrosion additives. You can also look into using fibers instead of rebars for reinforcement. Make sure you have a good single pour and you should be ok. The biggest problem is pressure cycling and sealing door and windows. I would build a few RPV before I would ever get in one. Figure the concrete hull of an 80' submarine might cost $50,000 to build. It will weight about 100tons. The molds would be tricky and it would have to be made in one piece. A lot of this stuff has been discussed before. Wellmers idea was solid, it just happen that he really wasn't building it right.

 

Those colombian smugglers might get ideas from these threads.

 

Hmm, perhaps you mean that the idea of using concrete for high pressure underwater applicatons is valid. That is not necessarily a submarine.

Now we are talking about submarines - and that point has been raised ad-infinitum.

That is the crux of the matter - untested processes. "This might work, that might work ..." but until an engineer of sufficient status is confident enough to put his tender parts on the block, no insurance company or port authority will have anything to do with a concrete sub.

No, Wellmer's concept MAY have been workable, but he coulds only guess what processes were required - unluckily he chose to carry out method 132, which didnt work.

By the time we get to method 516, we may have some useful data.

Now, all we need is some rich enthusiasts to get the other ~ 300 methods tested.

 

Is that FCNN News?

I noticed my neighbor's window sill made of concrete had a big piece of concrete missing due to swelling of oxidized re-bar reinforcement.

 

Well it wasn't his ideal.
The concept is proven, dates back to WWII and working examples have been built:

"A feasibility study was conducted by utilizing classical analysis techniques and state of the art construction methods. Prestressed concrete was found to be a viable material for shallow to medium depth submersibles. A replica of an existing steel-hulled submarine was used in the calculations to enable both economic and performance characteristics to be analyzed and compared. It was found that both longitudinal and circumferential prestress must be used in the construction of the pressure hull. To facilitate this, a modular-segmental construction was employed. It was also found that concrete offers both performance and economic advantages over steel. The performance advantages include: freedom from maintenance, durability, readily-available materials, superior performance under impact and accident conditions, non temperature-sensitive, easily formed into compound curvature, and concrete has good insulating properties. Economic analysis has indicated that the concrete pressure hull would cost between 50% and 60% of the equivalent steel hull."

"he didn't build it right"

Well yes you could say that.

This concrete sub mania seems like a repeat of the ferro hull craze of the 70's
The odd bit is attributing the hull material as being the driver for the up and coming 'submarine yachting revolution'

Coming to a harbor near you- a half awash hazard to navigation. Built on the cheap and poorly equipped, these submersibles are going to be a game changer.
I can't wait.