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concrete pressure vessel
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Discussion concrete pressure vessel building, what to look after, buckling, destruction depth, modelling, questions, answers, what to do, what to avoid, project setup, project cost, submarine yacht, captain nemo yacht, concrete submarine yacht, business yacht, marine headquarters, marine frontier, oceanic, network, alliance, ocean colonization, oceanic business alliance, marine cluster, caribbean, yacht, services, alliance, business network, oceanic alliance, marine cluster alliance, key player network,



 

 

 

 

I have come over to this site from psubs. i want to build a u-boat style 66 ft by 6 ft diameter sub. its big!..but want to do it this way-

create a pressure vessel using ferro-cement, but replacing the ferro-cement with fer-a-lite.

stage 1. diameter 6 ft, length 30 ft. sq ft-630 aprox, volume 848 cubic ft. (sorry for you euro guys its not metric)

2. construction

use ferro-cement techniques to create two walls- 1 outer 1 inner, spaced 3 inches apart.

3. between these walls which are used as a support mold which is integrated into the subs strength, concrete rebar is placed and holes are created in the mesh to pour concrete which will add strength and ballast. then the  outside is sheathed in 1/8 inch steel further to add strength and to provide a weldable surface to finish the hull...

 

4.  the exoshell of the sub is then welded in light guage steel to form the ballast tanks and outer hull which has free filling holes to allow the hull to submerge--an almost exact replica of the type 7b u-boat.(see the kraka as reference)

 

an optional way is to build the exoshell from fer-a-lite. (see youtube) under fer-a-lite

 

what are your opinions on this type of construction?

doing a full mold with thick concrete is an option but i prefer this method because the hull can be trasnported to a place to launch then the concrete poured. and i prefer the outer shell to be of very tough fer-a-lite.

 

sidenote: while a teardrop shaped vessel is by far easier to build--i want both good surface running characteristic and submerged characteristics...the teardrop is designed for underwater running not surface running...although there is an argument that the effect for the speed of this sub the u-boat design migh only be marginally better.

however i really love the u-boats design.  

 

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1000m depth rating possible for spheres, 500m for tubular concrete structures

...the (study) results demonstrated the feasibility of near neutrally buoyant concrete structures, having an overall safety factor of three, at depths to 3000 feet for spheres and 1500 feet for cylinders. Greater depths are possible if concretes having a compressive strenght greater than 10.000 psi are used or if negativly buoyant structures are designed.

H.H Haynes and R.D. Rail october 1986 first published sept.1976

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

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Ocean sphere fish farming:

 

http://concretesubmarine.activeboard.com/t55433095/ocean-sphere-the-next-wave-of-sustainable-fish-farming/

 

Ocean colonization gallery:

 

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Big things have small beginnings ocean colonization transition, potential:

 

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Free spirited oceanic lifestyle global mobility:

 

http://concretesubmarine.activeboard.com/t58935854/subdue-to-nobody/

 

 

 

 

 

 

 

 

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When you plan to build a pressure hull for external pressure, keep in mind that the failure depth depends most of all on the expected failure mode (buckling or non buckling).

When you build in concrete the material gives you the option to build sufficient thick walled that buckling as expected failure mode can be ruled out.

The technique you describe looks possible but sounds expensive as you are building 3 shells instead of one. (inner and outer shell to act as a form).

Keep also in mind that there are limits how deep and narrow the spaces where you cast the concrete in, can be (check concrete casting norms). If the spaces are too deep and narrow the concrete will tend to de-mix in the pour seperating the gravel in pockets.

Keep also in mind that a albacore shape has about 5 times less propulsion need than a surface vessel - this is why a whale swims below the water - not on the surface - in fact no animal swims long distances on the surface because of this difference in engergy efficiency.

Wil
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Design of Offshore Concrete Structures / Construction of Marine and Offshore Structures, Third Edition / The Dock Manual: Designing/Building/Maintaining / Plasticity in Reinforced Concrete




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Reading List:

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-- Edited by admin on Thursday 15th of March 2012 09:53:49 PM

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Hi Wil--yea, running on the surface will be to recharge the batts...but in the event of a strom ill dive, and there will be a lot of show--originally my design was a skipjack class teardrop, but realized ill be doing more surface running than diving most likely.

 doing a concrete tube would be  cheaper - if in steel i can weld--in poly--theres epoxy--concrete has some glues, but not sure how well epoxy would bond--and its expensive..

the only issue i have with concrete for the pressure vessel is how to attach the exoshell to the vessel itself. any ideas?



-- Edited by u-boatdreams on Thursday 8th of September 2011 07:19:26 AM

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Hello doug,

picture a WW2 submarine running on surface somthing like this. The beauty of the "captain nemo float out" is most of all in cruising BELOW the storm in snorkel mode and leave the coffee cup on the table while all surface ships are shaken to the border of resitance.

Snorkel is not popular in military submarines because it is absolutly NOT stealthy, especially if you stick it out some 10m above surface - but for a civil sub the snorkel mode is just perfect to cruise in calm conditions and use the diesel just as a normal surface yacht would do.

Also to benefit from the much lower drag that exists below the surface (factor 5).

 

storm.jpg . uboat_snorkel.jpg . images?q=tbn:ANd9GcR5s0Wx_XjL_z41UTebc6fHwqWGHh3AGiMxGmJIk3U5olseGvDO . submarine_yacht_18m_200_ton.jpg

When you design your sub as a surface boat with dive capability you also need to keep in mind that you will need a handling and a engine capacity similar to a surface ship.

It is for good reasons why this kind of hullform was abandoned in modern submarines.

Mother nature and submarine engineers agree on whale shapes for good reasons.

Why give away the benefit of whale like snorkel mode cruising for going back to a abandoned historic u-boat concept?

 

 The idea that a submarine should run on the surface is only understandable in the context of early submarines that where built to fit into the context of a fleet and seen as warships in the context of a surface fleet. As soon as navies became more experienced in handling submarines - the submarine started to be "a thing apart" operating apart on its own. This influenced ultimatly in its desing transforming it from a "fleet operation animal" to a "fully aquatic animal" - so in a nushell if you do not plan to have crews in gala uniform presenting fleet parade on deck - just forget surface capability and WW1/2 designs.

 

. File:Los Angeles Class submarine on surface (approaching view).png .

 

 

 




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Wil, -you sure make some convincing arguments -- i also learn everything i need to know from nature....

the teardrop shape is the best shape...but on the surface--its a rough ride in the storm due to the nose wanting to plow because the weight of the hull is not carried on the surface.

because the hull would be heavy- and nearly neutral- it wants to dive when it hits a wave. and the accounts of the albacore- they went from 9 ft to 60 ft (3m- to 20m)when they ran into that typhoon..of course- those conditions are rare...

 but you will need a very high snorkel to dive to the 40 ft needed to overcome a good gale on the surface wont you??

 

 i see what your saying--any boat/vessel would get pounded..so even a little under the surface is better than  riding the surface...hmmm- is there a way to make a tall, rigid snorkel?? without it breaking under the stress of the waves? at the top of such a snorkel the lever moment would be so intense it would caues the schnorkel to break off from the sub--i dont see a non rigid hose type snorkel working well because of the necessary power needed to push the air through it at depth...ever tried using a hose underwater to breathe??its so hard to take in air, its almost impossible and this is like 6 ft under--try 30ft!!???

so whats the solution for the snorkel if running submerged most of the time?

how do you plan to use your snorkel?

 

 



-- Edited by u-boatdreams on Thursday 8th of September 2011 06:10:53 PM

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Dough,

The fact that a whale shaped hull dived at a depth of the hull diameter in snorkel mode will not track the waves like a surface ship does, is the beauty of the concept. This leaves the coffee cup on the table and keeps the crew seasikness free.

Please check:
How deep you need to go for submerged protection

I would recommend a 10m snorkel tube, a good steel tube will work just fine. Hose snorkel workes fine too (tested that with the prototype) but i prefer a rigid tube due to the high camara point and simplicity of handling.

Snorkeling in a sub is different from a diver - a diver must breath against the water pressure that is on the lungs - so the snorkel is limited to 30cm length.

A sub does not expand lungs against the water pressure - air flows trough the hose or tube and is not affected by the pressure, just by the friction on the tube walls - so you can snorkel much deeper than a diver could.

 

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Wil- do you think that steel should be incorportated in to hull-for instance hatches?

also--I just bought another engine this time much smaller at 30 hp @ 3000 rpms.

Im guessing this would make a great engine for a sub of my size..very economical. and the right power range. my subs volume for the pressure vessel is around 800 cubic ft.

 

Your  input has forced me to reconsider my methodology for two reasons--the complexity of an inner pressure hull and an outer exo-shell seems increasingly more difficult--and costly,

secondly, the costs of a build done like a teardrop design-is much cheaper-even in more exotic materials. for this reason i am looking at a compomise between the u-boat -47 and the modern nuclear design--so ivbe settled on  the type XXI. this was the evolutionary and transitory stage between the nuclear subs and the uboats. so with this in mind i am able to design a semi-teardroped shape-which incorporates the hull form of the tube, and the bow sections of the u-47, to me a good compromise.since the bow and stern come to a vertically flat plane such as a plumb bow if a sailboat. the top of the vessel is flat but this can be molded.




 



-- Edited by u-boatdreams on Friday 9th of September 2011 05:17:14 PM

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 something like this?



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sorry the last one i treid didnt work--this is my rhino version i drew up for a skipjack copy..it will have a tower-i know there are no viewport hardware etc--but you get the picture i think...



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Dough,

I would not start with any military design. Skipyack is a design built for speed exceeding 40 knots - the type XXI is a double hull design built to resist underwater explosions used for u-boat hunting. - non of that fits the needs of a family crusing in the caribbean in a captain nemo boat.

My answer to the form question is in the fotos below. It is a autopropelled living space bubble with a living space equvalent of an 68 squaremeter apartment inside, that guarantees leave coffee cup on the table conditions in all sea states cruising at a speed of 8 knots in snorkel mode with the hull 4m submerged.

It is extremly stable at dive, can easyly hang on the snorkel, deep ballast center, high camara point on the snorkel top, a lot of natural sunlight inside due to uplooking viewports, full standing height everywhere in the boat.

Your approach may be a bit different - so best thing to go is ask yourself what you want to get and design it according to your needs - going completly away from what military sub designers do.

 

submarine-yacht-interior-design-suggestions.jpg

Videos of the 200 ton submarine yacht hull see here.



-- Edited by admin on Saturday 10th of September 2011 07:20:24 AM

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i wanted to ask--what would be best for knowing whats below you in the sub?--i.e. is there cheap depth finders??.but what about whats coming up in front of the sub ??..how do we see arouind us if its dark ??? and/or running submerged? is there an inexpensive solutions for this???...

at night or deep-its going to be dark especially in the coastal areas... not so much in the pacific islands but at night--how do you know your not approaching a hidden sand bar or reef? something not on charts??? sometimes people hit steel containers from cargo ships..they lose those in rough seas all the time --so at night--what do you use to see?



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You can run the submarine yacht as a snorkel boat - in this case you handle exactly the same navigation methods as a surface yacht. If you want to handle it as a submarine navigating below and near reefs you will need aditional navigation items like forward looking sonars that allow you getting a "picture" where the boat is and where the reef is. Keep in mind that visual orientation under water is limited to a few meters - even exceptional clear water as in the caribbean will not give you a visual of more than 20m this is very little to navigate at sight with a 20m boat. Somebody compared it to navigate a blimp in the fog in the mountains at sight. On the other hand in practice if you are drifting in the open sea with light in the viewports you will have a awful lot of sealife aproaching your viewports while hanging still.



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I'm not convinced yet that a snorkel could withstand the force of water while running submerged at or below  30 ft(10m)..

a couple issues--

1. if you are running near shipping lanes -you will want to dive under it most likely...or in emergencies.

this means you are now having to dive deeper by 10m to comensate for the snorkel.

2. the forward motion of the sub is going to create friction pressure and a huge amount of energy wasting drag--whales do no have snorkels...and that drag resistance-thats going to want to break off that snorkel... unless heavily reinforced..? this is why the uboat seems like a better idea at the moment...but its more complex--so the skipjack is much easier to build...hmm decisions..i just got the go ahead from my business partner to start the sub...we need to decide on whats the best design and materials..looking at steel for now..and FAL if its too costly...

 

 



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I understand your concerns. Just consider that the male orca fin is as high as its body diameter  and it does not bring up a drag that would slow down the male orca below the female that lacks that fin.

Imagine a snorkel boat like a orca with a tube on top of the fin - the tube would stick out in the air so would have no drag at all. Only the 4m in contact with water would create drag (comparable with the fin) when in a streamlined fairing.

What concerns submerged navigation in shiping lanes - the only good advice is do not look for ways "how to do it" - just avoid shipping lanes like any other yacht,  handle such sea areas surfaced. Always keep in mind that a ship needs kilometers to stop due to inertia and has no way to change course while navigating a narrow channel- never plan to dive under it - iwould recommend to just stay out of the way like anyone else does.

For a good impression how rigid a snorkel is, check a flag mast  - also keep in mind that drag appears on the foot of the mast - not on top - while snorkeling. If you still not comfortable consider a forestag or a snorkel built like a airplane wing.

 

images?q=tbn:ANd9GcSSCM8MvJiV0HfCddznJVp8rv-Mu2Pi-YRFmLFBw3RaJHt6rw5PtP-uPhF6Bw



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Yes that makes sense- but arent you going to want to dive deeper than snorkel depth?..how will this affect the drag on the long pipe snorkel?

Your idea of using a flexible tube  seems like an option - what would you use to keep it on the surface? a hose could work perhaps with a bouy to keep it from sinking or taking in water--then it trails along when 30 ft down ???..the only problem is how to keep water out of it...??? On one of youir larger designs on your web page i noticed a two snorkels, one on each end of the sub(unless my memory fails me)...?? an intake and a exhaust im guessing...? how did you set up those systems--im thinking a flange with steel webs -four like rocket ship tail configurations welded to the flange for support?? this could work but again--the drag really sucks..

Wil, have you heard anything from the idiot harboumaster who wont let you launch??...

is the walls of your sub 30 inches thick i cant rememeber??- i loved the inside--and --(laugh) is that you doing the walkthrough?i also noticed a shaft for the prop..please explain your systems for that..what seals have you used??..simmering??...o-rings?

 

 I just had an idea-if you made a 30 ft wiong section snorkel- i.e. you could use wood and make it the simple shape of a wing(symmetrical so as not to create lift)using small chords say the wings seciton was 6 inches then ran a tube through that as the snorkel- this could work to reduce drag and be more efficient like the whales fins..



-- Edited by u-boatdreams on Thursday 15th of September 2011 07:27:47 AM



-- Edited by u-boatdreams on Thursday 15th of September 2011 07:38:38 AM

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The hose snorkel worked very well when i tested it with the prototype. You might go for a detachable hose. At the end of the hose you need a buoy and a automatic close valve if the end goes under.

Keep the connection of the snorkel with the hull as strurdy as possible - (cast in) - and put a valve on the inside of the hull for easy valve off when snorkel takes damage .

The two snorkel design you see on the pictures allows a simple automatic ventilation sistem. The boat will tend to have the nose in the wind direction while hanging on a mooring so if you put a 90 degree knee and a funnel on the bow snorkel you force air down the snorkel into the hull leaving it trough the aft snorkel.

This kept the hull absolute condensation and moist free - much better than i have seen it on sailing yachts in the same climate and mooring conditions.

 11468d1170881663-dealing-pirates-ad.jpgbg-deckcon1.gif



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....is that you doing the walkthrough...

I asume you refer to that video of the walktrough (video).
The guy walking is Alvaro - i am the one with the camara.

Wilfried Ellmer

concretesubmarine.com



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Wil--yes thats the guy--his langauge sounds like dutch to me?..but im guessing he must be local. The size of that hull is amazing..when its fitted out it will be beautiful.

 

I have a thoerneycroft 30 hp for my sub..its a 60 tonner i believe(the one in project status)

total immersed volume 1127 cubic feet. so that makes it a 60 tonner i bleieve? displacement about 69000lbs fresh water. concrete will be used to fill the entire rear portion and some of the bow section to bring it down. the rest will be open space ...

the 30 hp -i hope thats big enough or not too big..i chose this because it seemed about right if i needed a bit of emergency power up river ina current or such.

Its running here...

http://www.youtube.com/watch?v=VjUBwsdeR-k



-- Edited by u-boatdreams on Thursday 15th of September 2011 10:57:52 AM

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http://www.youtube.com/watch?v=egp1_ypxNlk

wil, you might want to see this...its me in the vid showing what this can do...it doesnt show compressive yield strength but im going to build a test model to see how far down i can go before it implodes....

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I also want to note to others reading--that the first post for a pressure vessel was not a final decision

we might do it that way or--not...

concrete will be used but likely for ballast. I still acknowledge Wil for his contributions to my project and his influential and pioneering ideas...



a decision on the actual sub method will be made by end of two weeks from today--

i have a business partner and we are going to build it to see what can be done----not to "mass" produce subs(no worries there Wil- not competing with you at all) -but to see what interest there is and to sell one to leapfrog to a better one...I wont be doing concrete that i know of..either steel or FAL which is a ferrocement synthetic morter...different than using standard concrete forms--as in Wils methods.

my goals are to go to the arctic and great alkes -such as superior, and make voyages in it in order to prove what they can do...and to show off a little--yea a bit of ego there maybe-

since i cant wait to pull up in my sub at the boat shows....



-- Edited by u-boatdreams on Thursday 15th of September 2011 11:53:30 AM

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u-boatdreams wrote:

http://www.youtube.com/watch?v=egp1_ypxNlk
.... vid showing what this can do...


The material looks quite impressive, i would take it for the super structure, the saddle tank, the sail, the snorkel tube fairing, the rudders, the propeller ....

The pressure hull itself needs a LOT of material - talk dozends of tons - also keep in mind that you need forseeable results in thick walled application.

How is the cost?



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Wil when using saddle tanks- there are issues as i am learning-

 1. where do the viewports go?

2. how does the saddle tank interface with the side of the pressure hull?

3. by what mechanism can you open the induction valves for the MBT's?(in ths case saddle tanks?)I was thinking a kingston valve--or t valve but this must reach through the pressure hull..?

fal has the advantage of also forming to complex surfaces like a uboat design..of course concrete is cheaper--so concrete could make the inner pressure hull surrounded by two 1/2 inch thick walls of fal.

 

 

FAL- yes its  expensive but less  than steel.- would make a good form --you can apply it in patches it sticks to itself so cold joints are no worry. Its about the same as fiberglass in costs  but stronger...and rigid. I would love to know the compression yield of it at 1 inch thickness...hmmm ill likely do a drop test with a small model and see how it goes...



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When the hull is outfitted it will look  like that:

. . . . . . . . . . . . . . .

 

 

Dough,
I prefer uplooking viewports in the upper part of the hull due to the massive amount of light they bring into the hull. - this leaves space for a saddletank in the upper part of the hull.

When thinking of attachments to a concrete structure you will find plenty of solutions in a hardware store. Cast in rebar pieces is also frequently seen in concrete engineering to make connectors. Epoxy bonding, grouting, etc... all will work well.

You should be aware that when having a saddletank have it divided in sections to avoid airbubbles shifting your trim.

I am not a big Fan of big amounts of pressure air and battery banks in submarine yachts. Those elements have proven to be a cause of nasty accidents. Military subs run them for military reasons.

In a submarine yacht - if you insist in emergency blow out manouvers - you can have better ways to produce the necessary amount of gas - you can have sistems that can only work once (in an emergency) and then needs a chemical refill. Sistems like the fill sistem for airplane lifeboats can be a guide. Those are much safer than compressed air tanks rusting in your bilge waiting to produce an accident.

Fal is a nice material - quite expensive if you want to use it as form material.

Wil



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So you suggest to have an emergency saddle tank blow out manouver - without compressed air - on the base of chemical generation of gas like in a car airbag.

http://www.lemurzone.com/airbag/inflate.htm

The car industry went away from compressed air due to the higher long term reliability of a chemical gas sistem. Maybe for a submarine it would be fine to have a smoother and less explosive (dangerous) way to generate the gas. (different chemicals)

Although such a sistem would share the downside of drop weights (use only once) it could be built with very little cost and risk of operation.

A gram of chemical can produce half a liter of gas - means 2 kilo of chemical can produce a ton of emergency buoyancy force.



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hello tornado--my sub would not have a static dive system, and therefore would not need an emergency blow...if a sub gets caught in a netting or snagged it is still not going to resurface even with a blow or drop weight system.  a dynamic system, using dive planes is much simpler and easier and more cost effective than a combined system of dive planes and a static system.

however my choice would be to use a divers air tank--the reason being is it would be rare for a divers tank to explode. if the tank was  mounted securely it would be fine --stowed in  a small vented concrete box-  to house it should it explode. 

a chemical system..im not sure what chemicals would work or where to get them which one are you talking about? the problem would be--to engineer a system to use and where to get that much of the product...its easier to just go buy a tank -store it in a concrete box once a month inspect it--refill it..etc...this is easier(less expensive too?) than buying sodium azide- and nitrogen. divers tanks can be refilled almost anywhere... 


 



-- Edited by u-boatdreams on Friday 23rd of September 2011 06:53:24 PM

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dive planes are lift mechanisms that can fail in many ways, for example block in a collision, and they fail completly to create lift when the boat stops. Drop weights depend on release mechanisms that left allone in marine ambient during a decade probably will not work when you need them.

A scuba tank can explode with the force of a granade, if you ever saw such a event you would probably not think about the possibility to store such a tank in a way that makes his explosion non-lethal i would assume that a scuba tank explosion inside a sub hull is a sure kill for the complete crew. Scuba tanks need regular inspections to avoid such events, they are expensive, they have expensive valves to control the extreme pressure inside and a scuba tank only contains a gas volume the size of a telephone cell which creates 2 tons of buoyancy on the surface but only a few kilogram of lift in critical depths where you probably will need the emergency sistem most.

So if you relay on blow out sistems you need a LOT of gas to create lift at depth due to the compressibility of gas. This means you need several dozends of scuba tanks each of them with a tight inspection shedule each of them expensive, each of them a kill hazard. So a sistem based on scuba and compressed air is probably more hazard to safety than addition of safety.

Military subs use compressed air as they have such sistem on board anyhow to launch torpedos - so it is not a additional sistem that creates a additional hazard it is a second use for a sistem that is already on board anyhow for military reasons.

Engineering a chemical sistem can be as easy as filling Alka Selzer tablets into a glass bottle and put it into the saddle tank. As soon as the boat goes below a certain depth the bottle will crack water comes in contact with the tablets and produces a amount of gas compareable with a scuba tank. The sistem is simple, free of inspection, free of explosion risk, full automatic, cheap. And you can design it for lots of gas that still give a reasonable lift in considerable depth.

M6350014-Alka-Seltzer-SPL.jpg



-- Edited by tornado on Saturday 24th of September 2011 06:23:16 AM

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the beauty of this type of diving is that the sub remains positively bouyant all the time... if the subs dive plaes get damaged--you rise to the surface...if the dynamic sub cannot resurface- in a given crisis(nets or snagging etc)-chances are a static diving sub couldn't resurface either...the downfall of this is- you cannot view wrecks at 0 knots.--sleep in it while submerged etc..however--the complexity of a static dive is greater--you need air- compressed air to control the tanks unless you use pumps. compressed air -the very thing you mentioned that you didnt want-

 

 however another simpler solution for a static diving sub is pumps--simple 12/120 volt high pressure pumps-a pressure pump from a pressure washer could do the trick--but how are you going to power 120 volts??..you could use an inverter..but again this would drain very fast..then you have to resurface much more to recharge your batts costing much fuel..

simpler--is to use a simple dynamic diving system...no need for  120 volts-compressors attched to engines shafts(although a good idea) or finding rare items such as 100 lbs of alka seltzer..not saying you aren't correct..it is a great idea to use the chemical system..like baking soda for example--but it is for a one time blow--what will you use to control your static  dive -i.e. trim etc on the 90 tonner? for me the solution to ballast water mbt's...is high volume pumps on the surface-then drain the  MB tanks while running on the surface or  you would use pumps connected to the drive shaft and drain them to float higher in the water--this allows you to be unstranded from a grounding etc. in an emergency--althouhgh it will be hard on the ears--provided there is a bulkhead with doors for the engine room-you could run the engine for five minutes-while running pressure washer pumps off the engine...this could put a few gallons out of the tanks --but probably not enough for an emergency blow...if i were to build a static diving sub--id use pressure washer pumps to control trim and diving.but now that i think of it--using a small air compressor--attched to the shaft into a small tank could work...

 

  also-- it is very difficult -at least when i built my models--to get the sub to stay at any given certain depth-the sub wants to go up or down but very hard to keep it level and at a constant steady depth...this is likely why military subs rely on both static and dynamic diving capabilities...



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One other thing i wanted to mention- i have dabbled in steam engines and boilers- these days fire tube boilers are very safe--it is because they use blow off valves. the pressure in aboiler is much higher than a compressore tank. so it would be easy to set the blowoff vlave at say 200 psi...or evben 150 psi--that way it is sure not to explode. if you put two valves on the tank this is a almost a guarantee it is safe...fact: there have been no marine accidents in the steamyachting world for over 50 years now...no boilers exploding...that i am aware of...to me the tank is the way to go--of course scuba tanks are something like 3000 psi rating i think...they use very high pressure compressed air--i believe around 600 psi...probably not good then if it explodes--

also sadly thje other day i priced concrete prssure pipe- the costs were about 1800.00 u.s. per meter of 6 diameter tube...steel was less expensive at about 9500.00 compared to 15000.00 for the pressure pipe--wil--is concrete going to to not crack under the pressure? if not done like a prssure pipe??? ok i know your sub is 30 inches or somehting like that thick- but whats to keep it from a crack that can make its way through the hull???hairline cracks

 

- but pressure cracks?? don't they go right through the entire pipe?



-- Edited by u-boatdreams on Saturday 24th of September 2011 08:32:50 AM

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Dough, the concept of positive buoyancy and diveplanes is similar to the deepflight concept.  Two drawbacks for a yacht submarine, the reserve buoyancy is low and the hull can not rest on a sandy lagoon bottom.

Steam engines (turbines) are present in nuke subs - so obviously this could work.

You might consider a heat deposit of liquid salt as it is used for solar energy plants to keep operating during night time. It might be possible to run the steam turbine surface independent - with no need for battery banks that way. Check solar two molten salt heat technology



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Hey Wil- actually i wasnt thinking of using a steam plant for propulsion although the idea has crossed my mind- because the fuel: wood, could act  as ballast--but the space requirements are too much to hold  the large amount of fuel--

of course a smokestack is a bit of a problem because of the diameter needed and the extra drag created

and the heat generated from the boiler- up the smokestack would melt the rubber valve seal.

 

ill look at the salt concept you mentioned... i used steam boilers as an example;

 i was trying to inform people that pressure tanks, if safety valves are installed, are safe. and can be used for ballast blows.

 

 I thought if running  a compressor off the main shaft and as well a generator head too. this would give me electricity and also ballast blow in an emergency. for battery recharge--ill use windmill dc generators.- the  more rpms- the more charge power they create. they create a lot of voltage and current at low rpms about 500 produces about 24 volts.  so idling my 30 hp would give lots of charge power.

 

  I am quite happy not staying on the ocean  floor too long--i prefer short dives. im not claustrophobic but a 6 ft diameter tube is not my idea of a fun time..the uc3 nautilus is the same diameter. ill need lots of viewports to not feel couped up...but 6ft dia. is as large as i want to go....too costly-other wise-

 

 

presently my business partner and i are making negotiations for a 6 ft dia. x 40 ft(aprox 12.7 m.)long used propane tank. rated at 200 psi-of course this is a safety factor..and i bet itll go to 1000 psi at over 1/2 inch thick..its solid! cost less than 2500.00 euros. about 4700.00 u.s. or about 4500.00 cdn.should this pan out--this will become the pressure hull..ill reinfoce it..--i did look at concrete--im very fearful that it may crack under pressure...it wont buckle, but cracking -and cyclic loads my weaken it..the mold process is beyond my understanding in concrete....im not prepared to build a 90 tonner, so my goal is 67 ft x 6 ft diameter. max, i did think that ferro-cement would be a great alternaitve with impact resistance over 20 000 psi. and high compressive strength--again cracking the problem is:

i dont want to go down in the pressure hull, the hull cracks- and when water starts to come in fast under pressure- i lose very quickly the subs positive bouyancy of course this is where the mergency blow comes in--but if the water coming in is too fast--then its catastophic failure--the 1 atm is lost and i get the bends even if it does resurface..

how did you reinforce your walls wil?..i suppose that a layer of fiberglass and epoxy might solve cracking issues--but how then do you know there is a crack?



-- Edited by u-boatdreams on Saturday 24th of September 2011 12:23:21 PM

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There are probably many ways propulsion for a submarine yacht could look like. As it looks you take it for given that you will have a diesel engine, batteries, a compressor, - i would be concerned that the concept could be a "overengineered" concept in the end. Full of "sistems" that can fail and create their own safety hazards when doing so.

I would tend to have a submarine yacht with a simple propulsion compareable to a yacht but several times smaller, and a bilge pump with an aditional trim function - thats it. But like in yachts you can go for the most simple and you can stuff out the boat with tons of mechanics and electronics toys - it is most of all a question of taste of the yacht owner.

I would see a submarine yacht more as a submerged living space bubble habitat - with a low machinery component - almost contrary to the military submarine concept.

Probably there will not be a lot of people that voluntaryly adopt submarine confinement as a desireable style of living.

It may be one out of hundred who really would like to live disconnected from the surface, producing oxigen from the seawater wandering submerged and seperated from mankind trough the worlds oceans Captain Nemo style.

The typical owner would handle a submersible living space bubble habitat (i avoid the word submarine due to the misleading coffin perception) as a simple yacht that is in almost all of its aspects a yacht, just absolute storm safe, seasickness free, burglar safe, and maintenance cost free.

Like other yachties you would not be the whole day enclosed inside your boat. You would form part of a yachtie community anchored in the bay of a caribbean island.

In the morning you would row over to the beach meet with people from the other boats, have a beach grill, a coconut, a island adventure - you would only return to your boat to have a pleaseant night sleep in a king size bed and a freshwater shower.

There are differences in lifestyle to other yachties. For example when you leave your boat in the morning (all of your family - nobody wants to stay and watch the family home) you just close the hatch - so your living space becomes absolute burglar safe.

The other yachties always live a bit preocupied about their boat, is somebody breaking in to steal your nav equipment?, is the weather on the anchorplace changing smashing the boat against the reef?, - so they tend to live in sight of the boat.

You on the other hand, when get an offer for this dream one week trip - take it - when you return you will find your stuff well protected inside your living space bubble - just exactly as you left it there - breaking in trough a hatch is like breaking into a banksafe - nobody can deploy the necessary (heavy industrial) tools on a anchorplace.

Another situation where your life is really different to a yachtie is when you are together with several sailing and motor yachts anchored in front of this pristine beach of a unhabitated island. Somebody has a radio and spreads the news that tropical cyclon Bertha category 4 is closing in. Now it becomes clear why this beautiful island was uninhabitated in first place - no save harbor miles around.

Some yachts rush out into the dark of the night to make it by the speed of their expensive engines to the next safe spot - just to find that it is cramped with poorly anchored industrial barges that tend to come loose in a storm and grind everything in their way to pieces.

Smaller yachts send the kids for the nearest hotel to be safe and go for the mangroves to bring out several lines to the trunks and fight it out. They can make it as long as the storm surge is moderate.

You on the other hand just close your hatch drink a coffee watch TV - no need to leave the anchor place. If things become bumpy flood your ballast tanks and lay your bubble some 5m down on the sandy lagoon bottom until the storm has passed over you. You and your family are safe as in a underground bunker.

You could take advantage of the **** weather and the sudden absence of all your yachtie friends and make a few miles to visit the next spot. You sail out directly into the storm - trim your living space bubble at snorkel depth - you leave the coffee cup on the table, you watch the weather the sea and ship traffic with your snorkel top camara - but your comfort is not affected by the storm.

Your live will also be a bit different when aproaching a cramped marina with no space for "another boat" - you will always be the "most exotic boat" that draws the attention and marina owners will love to asign you a nice place to stay - maybe for free. While it may be difficult to have privacy in a cramped marina on a surface boat - you close your hatch and you have it.

Your living space bubble will also be different in terms of aircon, comfort electrics, and loading capacity.

For example a yacht in the caribbean can spend dozends of dollars a day in aircon to make the climate below a sun heated deck just bearable. The seawater around your hull maintains the inside at 22 degee with no aircon need.

Yacht owners sometimes go crazy with the vibrations and noise of the small generator that keeps the battery and freezer alive. Noise dampening and vibration is most of all a function of bulkhead weight - bad news for "leight weight yacht outfitting" - you have your generator behind 20cm concrete - complete silence guaranteed.

Yachties are always short of loading capacity for freshwater food, tools, equipment.

You on the other hand have dozends of tons loading capacity this gives you not only the freedom of a much longer range compared with similar sized surface yachts - it also allows you to make a living as a trader - moving cold beer in hotel quantity to remote locations.

So in general i would see a submarine yacht along the lines of a yachtie lifestyle or in a use similar as a business jet that allows travel worldwide and stay in you office at the same time...

10ac_20f3.jpg?c=819c



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...presently my business partner and i are making negotiations for a 6 ft dia. x 40 ft(aprox 12.7 m.)long used propane tank. rated at 200 psi-of course this is a safety factor..and i bet itll go to 1000 psi at over 1/2 inch thick..its solid! cost less than 2500.00 euros. about 4700.00 u.s. or about 4500.00 cdn.should this pan out--this will become the pressure hull..ill reinfoce it..--i did look at concrete--im very fearful that it may crack under pressure...it wont buckle, but cracking -and cyclic loads my weaken it..the mold process is beyond my understanding in concrete....im not prepared to build a 90 tonner, so my goal is 67 ft x 6 ft diameter. max, i did think that ferro-cement would be a great alternaitve with impact resistance over 20 000 psi. and high compressive strength--again cracking the problem is:

i dont want to go down in the pressure hull, the hull cracks- and when water starts to come in fast under pressure- i lose very quickly the subs positive bouyancy of course this is where the mergency blow comes in--but if the water coming in is too fast--then its catastophic failure--the 1 atm is lost and i get the bends even if it does resurface..

how did you reinforce your walls wil?..i suppose that a layer of fiberglass and epoxy might solve cracking issues--but how then do you know there is a crack?

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

Dough, you must be aware that the pressure rating for a propane tank is for inside pressure - its capability for taking compression force is almost cero - as it will fail in buckling mode.
What you should fear in compression load is the arch failure in buckling mode not cracks.
Cracks even if there is one filtering a bit of water on the surface will stop filtering under compression they will not lead to a early unexpected failure in a thickwalled (buckling free) concrete hull where the compression strength of the material and wallthickness versus hull diameter geometry are the important factors.
On the other hand in a thin walled hull that can not stand as an arch but fails in buckling mode - the failure point is almost arbitrary and unexpected early almost inpredictable.
Please keep in mind that before going to make design decisions that you have a clear picture what you should fear, what you should not fear, how compression load is different to inside pressure, and why pressure vessels must be completly different designed when taking inside or outside pressure.
A good way to understand how a propane tank will fail is to watch the following video - this is just 1bar ( =10m depth) pressure (video) - this is a failure by buckling ! from atmosphere perssure of a tank. You can avoid this only by a internal rib structure as military submarines have. Even so failure by buckling remains a serious problem. A thick walled concrete hull solves this elegant - it is thick enough to stand as an arch.
default.jpgarch3.jpg
Wil
concretesubmarine.com



-- Edited by admin on Saturday 24th of September 2011 01:13:12 PM



-- Edited by admin on Saturday 24th of September 2011 01:16:40 PM

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Concrete tunnels recieve external pressure and they are lined out by segments - the pressure resistance of the structure is NOT compromized by the fact that it is segmented.

img1663.pngimage.cfm?id=173558



-- Edited by tornado on Saturday 24th of September 2011 01:35:27 PM



-- Edited by tornado on Saturday 24th of September 2011 01:36:57 PM

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wil, can you send the video link please?



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video link of buckling failure is:
http://www.youtube.com/watch?v=2WJVHtF8GwI&feature=player_detailpage



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You have catastrophic buckling failure for a tank in 10m depth - and you have 1430m destruction depth for a concrete cylinder (see study below).

This paints the picture ...

---------------------------------------
Paper Number 3011-MS
Title OCEAN IMPLOSION TEST OF CONCRETE (SEACON) CYLINDRICAL STRUCTURE
Authors Roy S. Highberg and Harvey H. Haynes, Civil Engineering Laboratory
Source

Offshore Technology Conference, 2-5 May , Houston, Texas
Copyright 1977. Offshore Technology Conference
Language English
Preview ABSTRACT

An ocean implosion test was conducted on a pressure-resistant concrete cylindrical structure to obtain the depth at implosion. The structure was a reinforced concrete cylinder with hemispherical end caps, twenty feet (6.1 m) in overall length, ten feet (3.05 m) in outside diameter, and 9.5 inches (241 mm) in wall thickness. The structure was near-neutrally buoyant having a positive buoyancy of 12,000 pounds (5.4 Mg) for a hull displacement of 85,000 pounds (38.5 Mg). The implosion depth of the cylinder was 4700 feet (1430 m). A predicted implosion depth, using an empirical design equation based upon past test results, was 16 percent less than the actual implosion depth.

INTRODUCTION

A pressure-resistant, reinforced concrete hull was constructed in 1971 as part of a Seafloor Construction Experiment, SEACON I. The structure was placed on the seafloor at a depth of 600 feet (180 m) for 10 months. Figure 1 shows the SEACON I hull prior to its ocean emplacement. Since its retrieval in 1972, it has been located in the open air about 150 ft. (50 m) from the ocean. In the summer of 1976, the structure was returned to the ocean for an ultimate load test, that is, the structure was lowered into the ocean until implosion.

SPECIMEN DESCRIPTION

The cylindrical structure was assembled from three precast, reinforced concrete sections. The straight cylinder section, 10.1 feet (3080 mm) in outside diameter by 10 feet (3050 mm) in length by 9.5 inches (241 mm) in wall thickness, was fabricated by United Concrete Pipe Corporation. The concrete hemisphere end-closures, 10.1 feet (3080 mm) in outside diameter by 9.5 inches (241 mm) in wall thickness, were fabricated in-house. Tolerances on the sections conformed to concrete pipe standards of not to exceed to ±0.75 inch (19 mm) for the inside diameter or minus 0.5 inch (13 mm) for the wall thickness.

Steel reinforcement in the amount of 0.70% by area was used in both the axial and hoop direction. Reinforcing bars of 0.6 inch (15 mm) diameter were employed throughout the structure. A double circular reinforcement cage was fabricated for each precast section; the concrete cover on the outside and inside reinforcing cage was 1 inch (25 mm). For the cylinder section, hoop rebars had a spacing of 27.25 inches (692 nm) and 31.25 inches (794 mm) for the inside and outside cages respectively.

The hemispherical end-closures were bonded to the cylinder section with an epoxy adhesive, no other attachment besides the epoxy bond was employed (Figure 2). The gap between the mating surfaces of the hemisphere and the cylinder was less than 0.13 inch (3 mm) for 75% of the contact area. Prior to epoxy bonding, the concrete surfaces were prepared by sandblasting and washing with acetone.

Source: http://www.onepetro.org/mslib/servle...011-MS&soc=OTC

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Hi will--yes i watched this and a few others on  vacuum implosions. That tank was not a pressure vessel it was a storage tank. albeit probably 3/16th steel...and not reinforced.

the shape does not matter--its the reinforcing that makes the difference. take 1/4 inch steel roll it- put rings inside and you have a strong - pressure vessel- the kittredge uses 1/4 inch pipe, reinforced. the uc3 good to 300 ft.  the nautilus uses 1/2 inch plate rolled. and 1/2 inch frames spaced quite a distance apart. 100 meters s.o.d...

Of course i have sene the paper on  the conxrete spheres.impressive--but thats a lot of concrete and - i dont plan to go so deep.....however --are you saying if i built a concrete pipe using rebar and standard mesh that it could go to 4700 ft?

 

perhaps your right--but try molding hemispherical caps...steel however is easy for me to work..but ill look into this more..im not convinced its cheaper to build in concrete..after a mold and  such--am then the technical ability --steel comes prerolled ina 1/2 inch propane tank. and then i cna just add rings for strength..another way to strengthen steel is to use half pipe wrapped around the whole pipe...

 



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Wil--these sections would be a great way to build a sub--the thing that would be hard would be- how do you make all those sections watertight??

 

i am guessing you would use pipe installed into the mold to give holes to connect them...

is it possible to do a hull this way and make it watertight and one solid monolithic structure?



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Dough - i just want to make sure that you take the right design considerations for the right reasons - the thickness of the plating - does matter very little for a hull that fails in buckling - what avoids the buckling failure in a steel sub is not the thickness of the plating - it is the compression resistance of the underlaying frame structure ... and this underlaying frame structure is completly absent in a propane tank so if you do not put a framework in in a secondary process - the tank will fail very early in exactly the same way as the video shows - ANY plating that is not thick enough (talk several inch) to work as compression arch will fail in buckling.

The idea of having a hull that can go very deep is most of all to have abundant safety factors in place.

As said before you seem to be concerned about the wrong issues - be concerned about buckling when you design a hull - not about water thightness between segments. This is a imaginary issue - the idea that more and more water would come in trough a crack or between segments the deeper you go is wrong.

The space between segments will get smaller as the pressure presses the segments together - a segment union leaking on the surface will be bone dry in 11.000m - check the story of the TRIESTE on this. Triestes pressure hull had 3 segments with the separation gap leaking on the surface when little pressure was on the hull, but it was bone dry at 11.000 m depth, when the pressure pressed the segments together and sealed the gap completly.

"are you saying a concrete pipe could go 4000 feet" - the study is saying that - my own test results confirm that.

"try molding hemispherical caps " - have been there have done that - not a big deal - but try to form a sphere from a 36cm thick steelplate that is challenging.

The danger is that you are concerned so much about imaginary issues that you end up not viewing the real issues (buckling failure). The best way to get a feeling for reality under external pressure is to get a hidraulic cylinder and test all kind of model structures inside of it.











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thanks Wil, i had planned to reinforce any steel pressure vessel i bought...the deal  may or may not go through--and my biz partner and i are going to look at concrete as an alternative. wanted to ask you what youi think of shotcrete???

 

 my idea of a splithull--seems to be the best way to go..but we will make three models if we don't get the 6 ft x 40 ft tank--the problem  is that the tank might not be 6 ft dia. so if not its a no go. the other way in steel is 5/16 th steel wrapped around 1/2 inch rings and then 1/4 inch stringers spaced 6 inches apart..this makes a strong matrix.

 

 but we will want to investigate-within one month-  three small scaled test models:

they  will be:

 

 65 inches long (1.8   meters?) and 6.5 inches wide all are scaled models

 

1. a pressure cylinder using concrete full thickness conventional at about 1 or 2 inches thick (scaled)

2. a ferro-cement cylinder with 4 layers of mesh and steel rebar. the full hull is 8 layers.

3.  fer-a lite cylinder made same as 2. but using FAL instead.. this might act the same as cement--

OH YEA! what is the best mix to use for high strength concrete? im guessing here but

 need at least 30 mpa ?  would i use  stone aggregates?..plastisizers? glass fibers? air entrainment?

 

in all cases they will be reinforced. but we will do a vacuum test on each to see what happens --or a drop test in a neaby lake--depth 600 ft or 100 fathoms. The split mold might work really well-- it is the whale shape--or teardrop shape..two halves are made--then joined. im guessing again here but 6-8 inches of concrete??? would be a good operating thickness for 200-300 ft?

let me know your thoughts on that?

 



 



-- Edited by u-boatdreams on Monday 26th of September 2011 06:20:50 AM

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Dough, if you buy a tank have deep toughts about the frame structure that you will put into it to make it compression resistant - consider the compression strength of the plating itself as it is in a tank, as near cero, no matter how thick it is, no matter how solid it appears. Rule of a thumb : if it is thin enough that it can be rolled or bent to form a tank it will buckle almost inmediatly similar to the video under compression.

- shotcrete - it does little matter for the compression strenght of concrete what is the method how you bring the concrete in place. Shotcrete is concrete as any other concrete. The problem of shotcreate is that it is concrete full of voids frequently as all depends on the personal skill of the nozzleman. This is why shotcrete is not frequently used in structural applications.

- splithull - Trieste had a "split hull" if you do the split right the weakening will be near cero for compression load. On the other hand the craning manouver to get the 2 halfs together might cost you more than the hullbuilding. I would check on that before going for such a design.

-reinfrocements - the way how you focus on "reinforcements" seem to indicate that you take for given that your planned reinforcements will strenghten the hull in compression load. That is not the case - you do not put rebar into the concrete to improve the material for compression loads - you put it in to enforce the material for tension loads - tension loads in a sub hull are no big consideration - appearing only in drydock and in waves . (hog/sag/torsion forces) - so the strong focus on reinforcement (tension load measure) looks like a basic misunderstanding of the load case.

You should consider that excessive rebar and meshwire in the concrete although it will improve the not needed tension load behavior will WEAKEN the much needed compression load capability not increase it.

So the idea that "more is better" has strict limits in a submarine hull.

- special concrete - consider that what you want to avoid at all cost is that your hull fails surprisingly at "unexpected depth". Every element that you add (glass fiber, mesh wire, special aggregates, admixtures) - that gets you away from good old proven concrete engineering and its tested and predictible compression load behavior. Is not a step forward but a step backward instead. It adds "surprise factor" and surprise factor is what you do not want.

So if you want to go away from the proven engineering to "avoid imaginary problems" you will probably get real unexpected problems. It is better to have a known problem with a know material and a known way to deal with it, than a unknown problem with a unknown material, and no idea how to deal with it.

You have seen from the study that normal concrete is perfectly capeable to reach 1400m depth - so if you have no plans to beat that mark - i see no good reason to go away from proven ground and venture to unproven ground - especially if you do not have the means to do systematic testing and research and development on new materials.

So if you want to use FAL do it as "forming auxiliary material" and asign a strength factor 0 to it to be on the safe side. Do not use it for structural parts where life depends on predictibility of the part.

Wil
concretesubmarine.com





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Hi wil- wow--once again you are right--i talked to an engineer today- i asked him about the steel pressure vessel and forces exerted externally- and then on a side note- i asked him about concrete as a pressure vessel...--he insisted that it makes a great pressure vessel because- it handles compressive forces exceptionally well-- he cited that thats why they use it for pillars and other structural uses. so the result of this is-forget steel-costly and complicated and i dont want to fear the buckling--(after i saw how easily it buckled in those vids--i didn't feel comfortable) so i am going to build the pressure hull out of concrete. in fact i calculated a 6 ft i.d. pipe to be 1700.00.0 cdn, using 40 mpa and 32 mpa was 10.00 less per cubic meter. the pressure vessel in steel was -for the same diameter-- $10,000 in 5/16th inch! about 8x's the price of concrete-

and now i am certain its stronger due to the fact  i have had it confirmed by engineers more than once.and yea -other strucures... I once did beleive a concrete vessel could be used--

 

and after today its how i will be building the pressure hull. now this does bring up other problems-

 

1. how to attach things to the hull-- how to attach thru hulls, etc, and attaching the exo-shell to the concrete pressure hull... will epoxy work to add the sail??..i.e. could i prefab a concrete or fc. sail and attach it to the pressure hull for entry using epoxy?? what about hatches????

 

what would you suggest as the mix ratio? and reinforcing? i dont have the concrete civil eng. handbook--could you provide a link? i thought if i followed the concrete scientific paper you sent me--made the hull to those parameters i.e. use the same ratio of reinforcemnts and concrete type etc..then it should be able to handle a 200 ft s.o.d.?? any help is appreciated here Wil-- you are right about concrete though--im now convinced. so if i understand correctly--concrete just compresses more and more under pressure making it elastic in a sense?



-- Edited by u-boatdreams on Monday 26th of September 2011 11:33:34 AM



-- Edited by u-boatdreams on Monday 26th of September 2011 06:04:03 PM

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http://www.concreteconstruction.net/Images/Ferrocement%20in%20Construction_tcm45-340846.pdf

compressive strength of 2 inch thick ferro-cement- 10 000 psi, 69 mpa or failure depth at 21,768 ft !! its crack resistant. formable and does not need molds....2 inch thick would be perfect...then the whole hull could be formed and a integrated pressure vessel built right into the whole hull...thoughts?

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i get it now--this is why cold joints are not an issue--they compress into themselves under pressure....water cannot penetrate ...aha light bulb just went on...

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The specific compressive strength of the material you use has only indirect influence in the compressive strength of the hull you build. In the video of the buckling failure the material (steel) has not failed in compression nor has it failed tension load - it has been neither "pulverized by pressure" nor "ripped apart by tension" - so the material itself has not "failed" yet after the form change it just flexed quite a bit. It is probable that the tank still does not have a single leak.

So the idea that a hull is safe when you build it from a tough material is not necessaryly true. It depends more on how you place the material and what is the expected failure mode. If you build the tank above from titanium it will fail in exact the same way at a not very different depth.

The fact that you talk about a 2 inch thickness in a 6 foot diameter hull (and seem to assume that 2 inch bring you out of the range of deadly buckling) concerns me quite a bit. Have a look at the thickness versus diameter geometry that is handled in tunnels - to get a better idea what buckling free arch load structures require.

It will also be helpful if you check on the building history of gothic cathedrals - they pushed arch construction to the extreme and learnd why you can not make an arch extremly thin the hard way - a very good lesson to understand the basic priciples of arch and buckling.



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One of the problems of thick concrete walls is EXACTLY the weight.  if the sub runs aground and you have a type of submarine that can raise itself up to 1/3 hull diameter, then this can release it from the grounding. if the subs weight from the hull is so inherently heavy-then if the sub get stranded on anything such as a reef, then its not going to dislodge easily--if the shell is lighter--say 1/4 the weight of neutral--then you at least can dislodge it...this is one of my big problems with thick walled subs..

 

as seen in scientific papers ferro-cement is very crack resistant and its compressive strength is huge--no buckling issues--yes its a little more costly to make--but then you just ballast the hull with two walls of concrete inside the hull. i.e the bow section and stern seciton would be filled  completely with cheap concrete mix and scrap steel for ballast. the tanks will be big enough to float the sub at her lines 1/3 of it being freeboard.

the other issue- as mentioned is that few cranes can lift heavy hull sections. there currently are-to my knowledge no trucks that can haul a 58 ft x 120 000 lb load. the hydraulic trailer maxes out at 50 000 lbs. these are serious issues in practicality.

 

of course you could make smaller sections--but you still have to have them moved and everytrip costs. plus there is an added technical challenge in assembling them.

 

 why dont i  just use fc. its proven--they use it for watertight tanks all the time. and there  was talk using them for pressure boilers in steam applications. i would prefer to build one hull install engine and hatches etc on land then -launch and add ballast as required.



-- Edited by u-boatdreams on Tuesday 27th of September 2011 11:17:31 AM

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http://www.fer-a-lite.com/pdf/arevolutioninferroconstruction.PDF

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weight is only a problem if you plan a lighweight surface boat - in a submarine enough weight to overcome bouyancy is a reqired feature - not a problem.

I doubth that your "ran aground scenario" will work - according to my stranding tests i prefer a strong hull that works itself into the reef and refloat at high tide over a light hull that allows that the reef works itself into it.

The crack resistance of a material is a function of its elastic features - elastic is something you do not want - elastic is exaclty what the tank plating in the video above has and brings up the buckling.

Why would you make the walls thinn and light to invite buckling - and then have a structurally useless weight casted in front and stern - why not distribute the material into the wall where it is double useful - as ballast and as anti buckling measure.

I understand that weight can be a transport issue - and you have to create a viable compromise. Instead creating the hull according to your land transport capabilities, i would try to find a way to skip the land transport and heavy lifting need.




Reading List:

Basic Concrete Engineering for Builders with CDROM / Design of Concrete Structures / Strength Design for Reinforced - Concrete Hydraulic Structures Engineering Manual on CD / Design of Offshore Concrete Structures / Construction of Marine and Offshore Structures, Second Edition (Civil Engineering - Advisors) / The Dock Manual: Designing/Building/Maintaining / Theory and Design of Concrete Shells / Thin Shell Concrete Structures / design procedures of reinforced concrete shell structures (JGJT 22-98) / Understanding Structures / Concrete Planet: The Strange and Fascinating Story of the World's Most Common Man-made Material / Concrete Construction Manual (Construction Manuals (englisch)) / Large Wind Turbines: Design and Economics / Dynamics of Offshore Structures / Offshore Technology in Civil Engineering / Design of Offshore Concrete Structures / Concrete in the Marine Environment (Modern Concrete Technology)

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Wil--in the paper- the scientific journal on the cylinder implosion. what is meant by a "cage" is this simply a layer of mesh?

would a 5 inch thick wall be too thin? i can go 6 inches tops for weight.

 

waterfront property to rent or buy then  build is not cost efficient...so thats not an option. and trucking is the only other way. so it must be light enought to move...



-- Edited by u-boatdreams on Wednesday 28th of September 2011 01:26:02 PM

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Wil it would be impossible for a ferrocement hull to buckle--what would happen is- first the concrete would start to crack and let in water--this would relieve the stress on the hull...true the  water would be the end for the crew- but it would still be able to surface because of the diveplanes. it would not take long to do an emergency run to the surface to relieve the pressure. its highly unlikely though that at 2 inch thick concrete and 12 -18 layers of mesh that the wall would be breached. If i can build the sub in manageable sections using the pour method--such as in the tunnel type of construction it might work ...i could use cheaper transportation and then epoxy the peices together. using small hoists. but ferro-cement or fer-a-lite--has a higher compressive strength and a theoretical implosion depth of 20 000 ft! so 200 ft doesnt seem to be at least to me- a big issue. the build must not only be strong but also practical for me...thick hulls -not easily transported are not viable...

Wil- do you have another project request after this one? if so how large is it?

Concrete Floating Structures

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