I am thinking about building a sub and it seems that concrete is the cheapest, easiest and strongest. What are the advantages of steel? I know there must be some since there is very little talk here of concrete subs?
There are times when cheap is expensive. Think about how many people can you find who can actually build a submersible concrete hull. Compare that with all the thousands of certified welders who could easily build tou a hull provided that they have the proper drawings and material specifications. If you make a mistake on a concrete hull is very hard to repair whereas steel (or Aluminium) is easily repairable. I can not imagine how hard it must be to prevent electrical penetrations from leaking or getting moisture. Also you have to consider the case for submerged impact to the hull.
I would never dive a conccrete hull... that's me....
I can see your point with an impact. Concrete shatters rather than get a hole in it. Although concrete can shatter it is very stong and it would have to be some impact to shatter a thick hull. If concrete is poured correctly there should be no mositure inside the hull and as far as finding people to build a hull there are just as many people that pour concrete as weld. You are very right about the hull not being repairable. You would have to get it right the first time or start over. To drill into the hull would ruin the whole project. Still seems like a cheap alternative considering you could pour the concrete in a few days where as with metal it would take quite a bit longer. Also you are right that I don't know of anyone who has built one but some contries have built concrete subs for their navy so it is not that crazy of an idea.
Ferrocement has been used successfully for many years for ships hulls. I am not saying is a crazy idea, I just think is not practical for the application. When you have a 5 Ton mass moving at one or two knots underwater the impact forces are quite high, even though it does not appear to be so. I am sure that a ferrocement submaine has been manufactured successfully (It would be interesting to find out what is their life span), I just do not agree that is a practical material for the application. As to the cost I think that on the long term steel or aluminium is cheaper. I know of submersibles with over 30 years of service and they are still diving under ABS classification with their original hull.
Even the best financed submersibles with a full time crew to build it can take over a year to build, as it was the case of the Triton 650 which I worked on the electrical design. To me personally is about building it right the first time and not rush to build it. I rather build a sub that is reliable and economical to maintain.
I did it - concrete submarine pressure hulls are in use all over the world - the idea that there is "none" is only a perception of military sub oriented people check what oil industry, tunnel building etc... is doing.
The idea that you can not repair concrete or you can not drill it is wrong - you can do anything with a concrete hull that you can do with a structural concrete piece in a building - drilling a hole in will not make the building fall down... check (www.concretesubmarine.com)
Please post the pictures of the "Ferro-cement" submersibles from all over the World. I am anxious to see them and count how many people in many countries have them.
Can you give us details and drawings on how to do an electrical penetration on a concrete sub, and how to interface the stainless steel plumbing and hydraulic lines through the hull?
I have never worked with a cement submersible or seen one. And I have worked with submersibles since 1990. Perhaps you could educate me so I am not so biased towards the more traditional hull building technologies. How about writing an article for PSUBS on how to repair damage on a concrete hull? This will be very useful to those who are considering concrete as their hull material. Also, it would be nice if you could get an FEA model (Finite Element Analysis) of one of your designs to show that they can take the pressure (There are literally thousands of FEA models for submersible hulls built with traditional materials). How deep can a cement sub go? Can it do 100 ft, 300 ft, 600ft, 1000 ft?
My understanding from cement for underwater use is that it is ok under certain circumstances for static structures, like bridges, caissons, and shallow water tunnels. From every site I have researched on cement as a hull material, it discards it as a poor material for submersibles due to the dynamic loads to which submersibles are subjected to which cement can not survive. A good example of this is the earthquake in China... Static buildings subject to dynamic loads (The earth moving), two minutes later, 60,000 are dead and 6 million Chinese are homeless, just because the cement structures gave way. Hmmmmmmm
"If you check the photos at (www.concretesubmarine.com) you see that my sub floats - without ballast - on middle line - which means half of the displacement is hull weight. Bringing the concept to a extreme you could almost double the wall strength and still have positive buoyancy. Which brings us down to 2424m. This based on a cylinder shape. Given that my prototype is a spheric curved blimp shape it could stand -
let me guess - 3000m -
in case of a sphere shape even more - probably a lot more - this takes us down to 4000m - destruction depth - no security factor.
BUT - we are still talking about NORMAL CONCRETE - any concrete lab will tell you that special concrete as used in the core of certain record seeking buildings can increase the compression strength of concrete at least by a factor 4 compared to normal concrete. This brings us down to 12.000m destruction depth - without being limited in the size of the spheres AND still with positive buoyancy."
Wow! That is quite a claim! 12000 meters!! That is about the depth of the Deep Challenger at the Marianas Trench, the deepest spot in the world!
Wil,
I am not here to screw with anyone's business... If people want to build a sub out of recycled beer cans, and used gas cylinders that is their business. They are in their own right to kill themselves.
If you want to build concrete submarines for your personal use, that is your business. If you truly believe that your concrete sub design can dive to 3000M you are in your right to believe this and maybe you have a new formula for concrete which may well work for those depths. And if you do, you will be n fact a very wealthy man.
What bother's me is that you are trying to influence people who know very little about submersibles (No offense to anyone) by making them believe that concrete is superior in every way to steel or aluminium to build a submersible hull with absolutely no data to back-up your claims whatsoever.
If you really want to prove that a concrete hull can dive safely to those depths, may I suggest that you get sponsors to finance yourself, build a sub and take it to the depths you "guess" your concrete hull design can dive (3000m) with you as the test pilot. If you are so confident in your design you will have no problem with this. If you succeed, I will be your first advocate!
Any responsible sub builder (or potential for profit sub builder) should have a thorough tested design before offering it to the public and should have solid data to back up any innovative or untested designs.
Well i have run a concrete submarine yacht for a decade, so i hope you will understand that i am not willing to go back over and over again and discuss the question "can it be done" ... "is there sufficient data" - i already have the final answer to this...so for me this discussion is over - i understand that for some of you this may be new - so please update on my website. The questions i would like to discuss is the question of the next level - how to implement this on big scale. How far can you bring the concept. Is a "capitain nemo lifestyle" in reach for a normal pocketed person when you do it smart etc...
If somebody have not found concrete pressure hull applications for 300m waterdepth the only question to discuss is "do sub builders have sufficient capability to look over the border of their own plate..." think about it when you cross over to england in a train, have a meal at troll platform, get electricity from a concrete dam ... because concrete holds 300m water pressure.
If somebody has doubt if concrete can take dynamic loads from waves - i just can show you a picture of a concrete offshore platform - not convinced? - well there will be nothing i could do to change that right? - so what for i would enter in discussion.
If you need hard data about concrete deep diving i suggest you get a big hydraulic cylinder - pack a concrete sphere in and test it under pressure.
I would love to discuss your test series -
So i suggest we keep this a "productive discussion" or i am out. When you do something different it is just a question of efficiency to step out of discussion with people that insist in doing it the "old ways" and set facts - tomorrow i will roll out the 200 tonner i am building for Ian -
I really like the idea of concrete subs, but I'm not convinced on the depths they can reach with a 20cm thick hull, there's alot of talk about dams and tunnels etc using concrete and working, but they are not 20cm thick, the hoover dam is 200m high, i.e. it holds 200m depth of water, and the concrete at its base is also 200m thick. Obviously a lot of this concrete is needed to withstand the weight of the concrete on top of it, but look at say, the channel tunnel form england to france, I think its max depth is 60m and at that depth it has a concrete thickness of 800cm, and it runs underground. There's obviously a reason these structures use so much concrete. I'm still a student at the moment, and am just dreaming about building a sub, at first I was really hooked on the idea of concrete, I think it would be a brilliant way to build a big sub very cheaply, but until there have been some tests done to back up the safety of concrete I will probably end up opting for a metal hull.
Well that is an iteresting way to make a point. "I know it can be done and if you don't agree with me I don't want to talk about it" .....
I don't know if I learned wrong in my business classes, but my understanding is that when a potential customer asks from a vendor to prove why his product is better than his competitors, the vendor should go out of his way to demonstrate to the buyer why his product is better with as much data as possible. Not by lecturing the customer and telling him: "Because I say so, and if you do not agree with me, I don't want to talk about it".
Oil platforms and dams are a completely different ball game. They have concrete walls which are several feet thick reinforced with steel rebar (steel being the material that gives concrete most of its strength, not the concrete by itself) and are supported by steel cables or solidly attached to the ground. Dams are as stable as the ground that supports them. We all know that if a dam overflows for too long the water flow can erode the soil around it and the dam can collapse. They are also built to hold the pressure on one side.
If we are going to make a comparison to make a case we must compare apples to apples. And unfortunately, such comparison does not exist and neither Wil can provide it. Hence, the elusiveness to answer the questions.
A submersible is a completely self contained vessel, subject to compression cycles which can cause fatigue in meal and acrylic. Underwater tunnels are burried underground to keep them attached to the bottom, and are under constant pressure as they are designed to be permanently underwater (Not for pressure cycles) , and therefore they have very thick walls. The oil platforms in the north sea are designed to float and again the base is several feet of concrete thick. The same structure for metal would be about 1" steel with I beams as a frame. Again, that these are two different engineering prespectives which can not be used to make a case for concrete as a submarine hull.
The fact remains that all the engineers who have studied the matter have discarded concrete as a practical material for submarines and ship building for that matter.
Can a submarine be built with concrete? Of course! You can build one out of plywood or paper mache if you want.
Is it cheap? Absolutely!
Is it practical? No!
Is it worth the risk? That's up to each person to decide.
Now the question remains....What if a buyer purchases a submarine with a concrete hull, based on assurances by the builder that it can reach certain depth, without any data to substaitiate it. Then that person dies as a result of a hull failure at depth, I think that the lawyer for the victim will have a slam dunk if his family decides to sue the builder.
Some may argue that a dunk test will suffice to prove the depth rating.... However, even if the pressure test was done with strain gaugues all throughout the hull (A very expensive procedure) the data from this test is only valid for a single pressure cycle under extremely controlled circumstances. Both steel & Acrylic have been subject to several thousand pressure cycle tests in the laboratory and in real life. Such data does not exist for concrete.
Sorry but i really have to ask what is your personal interest in being against concrete ?
It is mankinds most used building material - the idea that "there is no data" for ANY of its technical properties is - well - not so informed...at best.
You would be surprised if you knew how many load cycles a building or a bridge can go trough in wind and traffic conditions - much more than a sub hull ever will.
A concrete dam is a application of an arch for hydrostatic pressure load - its load will change depending on fill status - not so different from a sub hull as it might look at first sight...
I don´t sell anything - i already demonstrated what i had to demonstrate - therefore i built a demonstration boat - i also have no problem if you disagree - just bring an argument that is worth a discussion...the steel cables in a platform are there to anchor the rig to the seaflor not to "support" the concrete...but of course there is rebar too in a concrete oil rig - nobody ever suggested to build a concrete hull without rebar nor to build anything structural without rebar ... so what exactly is the point ??
I am really not a friend of heated discussions so keep this on a informed and cool level - OK?
Scraps, It comes down to hull diameter versus wall thickness - the bigger the building the thicker the walls. The 20cm wall thickness on the prototype versus 2,4m Hull diameter is considerably thicker than a TROLL leg.
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