Re: [PSUBS-MAILIST] concret submarine, hatches, connectors, viewports, bubbles, classification

["Brian Cox" <ojaibees@ojai.net>]

Wow,   My hat is off to you my friend !!!!  That is an extraordinary achievement to actually build a concrete sub in the face of so many saying that it can't be done!  Somebody should bring that sub back up form the bottom of the lake !  By now it is probably even stronger than it was when it was first built !

Brian Cox

----- Original Message ----- 
From: <diagroto@ibague.cetcol.net.co>
To: <personal_submersibles@psubs.org>
Sent: Monday, September 29, 2003 1:41 PM
Subject: [PSUBS-MAILIST] concret submarine, hatches, connectors, viewports, bubbles, classification


> (concret submarine, hatches, connectors, viewports, bubbles)
> 
> Wilfried Ellmer
> 
> Ah...some carsten was visting me when i had hull recenly in water...anyway.
> 
> To answer carsten and warren at the same time.
> 
> You guys seem to be very concerned about viewport, bugs, bubbles, connectors.
> You are completly right with that concern as it comes to steel and alu hulls 
> that are in deed a kind of
> thin (some millimeter skin) over a skeleton of ribs.
> Between the ribs you have the steel skin on TENSION - not under compression 
> force.
> putting a hole in such a thin skin under tension is like putting a hole in a 
> ballon.
> a major failure starts on little woles bubbles etc. (needle-baloon) and bang !
> You have to use rings to lead forces around the hole.
> On a massive concrete hull you (massive is 18cm wallthickness at 2.5m hull 
> diameter) hull will not be on tension.
> It will also not "fold in" on one point as thin steel alu hulls do - when it 
> fails.
> A massive thick concrete hull stands more like an arch in a gothic cathedral.
> It will not move nor fold nor be under tension over ribs...pure compression 
> force resistance is the limit.
> To understand what i say take an egg(paint to make waterproof-suck liqid out) 
> and a beer can under water. You will see beer can folding far above the egg 
> shell breaks.
> Then put hole on both - you will see beercan (stiffen it with ribs) getting a 
> cut starting on hole (need a enforcement ring to stop it).
> You also will see egg is influenced very little in its strucktural integrity by 
> a little hole.
> 
> Test it on a brick in a hyraulic press. If brick stands 10 tons compression 
> force, it will still stand 9.9 tons with a little hole, bubble, in it.
> If you make the hole that big that it is half of the bricks diameter brick will 
> stand 5 tons (half).
> Compression forces go around hole like in an arch. Weakness comes from "lack of 
> material" in the hole standing against compression force.
> So if you have a little hole or bubble in a massive wall weakening is very very 
> little. (completly differnt to tension skin over ribbs - baloon needle little 
> hole bang !).
> To fabricate concrete that consist half of bubble (hull will collaps at 500 m 
> instead of 1000m still far below security limit discussed) you must have quite 
> drunken construction workers.
> 
> So the most important thing on a concrete hull is that you can make it 
> incredibly thick so that you have a pure compression force situation no 
> folding, no tension, standing like an arch.
> Which makes holes, bubbles, impurities etc. relativly irrelevant.
> You have holes bubbles impurities in each concrete building in the colums - no 
> construction worker is perfect. Who cares ? as long as compression force is at 
> work imperfections (holes, viewports) weakens LINEAR not catastrophic.
> 
> This has a big impact how you design viewports connectors etc.
> 
> Remember you have rings to guide tension forces around the hole in thin skins.
> You also need a ring to stabilize "environment" of your viewport the twisting 
> in a thin hull under moderate pressure will create uncontrollable tension in 
> viewport and make it crack.
> So you make a big stable ring to have viewprort seat in a "non moving 
> environment".
> 
> Massive concret hull does NOT move until it reaches destruction depth. So you 
> can form viewort seat directly in the hull no steel ring necessary.
> 
> If you don't believe me, make a concret cylinder (thick wall) put one of the 
> viewports on it (as it would be in hull) and test it on depth.
> Make it with a expensive complicated steel ring seat and yust form it the 
> concrete without special ring around hole.
> You will find that destruction depth (as well for concrete hull as for the 
> port)  is nearly IDENTICAL !
> You even might find that steel ring interrupts the uniformity of compression 
> force flow around the hole so that a construction with steel ring collapes 
> silghtly EARLIER !
> I did it...
> 
> This leads to carstens approach - i found that a massive concret hull is that 
> strong that you will have trouble to find sufficient depth to bring it to 
> destruction.
> Even if you have test zylinders with "special weakened concrete" (less cement) 
> tested - did it.
> 
> Destruction depth will be limited not by the hull itself (it stands and stands -
>  can't say exactly how deep...but VERY deep...) - limit will be what your 
> acrylic viewports can take.
> 
> So testing the viewport including a seat as it will be on sub, habitat whatever 
> can be a good aproach to come up with a test depth for classification if you 
> want do it NON destructive.
> 
> On the other hand massive concrete hull is that cheap that you can make 3 hulls 
> destroy 2 to convince classification organisations.
> Cost of 3 complete hulls still will be small cost factor in comparation to full 
> equipped sub cost.
> 
> What concerns that russian c-sub - if you think in a military sub lets say 12 m 
> hull diameter this would have massive concrete walls of 1m (bunker size) can be 
> a headache not only to detect but also to design a handsome torpedo to break 
> THIS...
> 
> That brings me to last point. (ever sold a hull) - no.
> 
> Back in 1994 concrete submarine hull was that unusual that you would not have 
> got a classification engineer even to DISCUSS the problem.
> 
> If you want sell hulls on that base - hard to do... also didn't have financal 
> power to make big promotions or do a kind of lobbying for that material.
> 
> So i did it to enjoy my personal sub - moved later to south america (now living 
> here) - no way to bring a 20ton sub at reasonable cost. So i took out 
> machinery, left hull behind on lake.
> Years later somebody broke the (plexiglass) hatch to look that "extraordinary 
> thing" from inside. Water came in over broken hatch over time and hull sank.
> 
> It still is there on the bottom. Enjoying local dive club.
> 
> If that idea of concrete subs now comes up from military field maybe it is time 
> to aproach it again.
> Classification organisations now might be on the point to listen, to discuss 
> it, or give you a certificate with an extreme security margen like: test it to 
> 1000 m classifie for 50 m ...
> 
> If anybody is working on such an approach - if you have a project that can 
> work - want me on board - want my advise - i am ready.
> 
> In my opinion it is not so difficult to make work a concrete sub, habitat, 
> etc...
> 
> Have it done before, all problems long solved in tunnel, dam, oilrig, 
> construction !
> 
> What is DIFFICULT is to get work peoples imagiation when it comes to 
> (appearantly) new things as concrete subs.
> 
> Could get work the concept - enjoyed my sub - could not get buyers, projects, 
> etc... all serious sub manufactures work (and think) in steel, alu, acrylic -  
> so started doing other things.
> 
> At that time it was harder to connect worldwide - internet did not exist - and 
> find local support - impossible.
> 
> So i really enjoy this forum .
> 
> 
> Kindest Regards,
> 
> Wilfried Ellmer
> 
> 
> 
> 
> ------
> 
> > Hello Carsten,
> > 
> > You are the guy that visited me on lake Atter right?
> 
> No - I never saw it in real - just a bad photocopy of a picture from a
> diveshop
> shows the plain hull without sail or rudders during lauching into the
> lake. 
> And swimming with the waterline on about centerline - so probably
> complete
> without interior equipment. 
> 
> > Will do my best to get a couple of pictures online.
> > Had some tube connections in molding process (complicated) but found out that
> > this is not necessary in practice.
> > If you just hammer a hole trough the wall (remember 18cm not a delicate work
> > no risk of cracks) and pop a tube cable whatever trough, close the hole
> > (around tube, cable) with the kind of rapid binding cement used for fixing
> > screws in concrete and later cover the whole thing with bitumen or silikon it
> > will not leak and it will hold.
> > Just imagine a tube fixed with cement in a 18cm wall - what is the force you
> > need to push it trough - if you applie 10kp force it will not move (100m
> > depth) if you applie a ton probably also will not move (1000m depth) so
> > special connectors are not necessary as long as wall is that thick. Make hole
> > big enough to have place for rapid binding cement around it.
> 
> The problem seems the same as on GRP hulls - how calculate this bugs,
> bubbles
> and small mistake and errors.. Classification might be a problem.. 
> You can have two hulls, more or less indentical GRP hulls build by two
> different 
> guys on two different days - and you get two differnet destroy pressure
> hull result. 
> 
> The best way to meassure what this hull can hold - is build three and
> destroy test for two - if the two get the same results - number three
> get the label.. :-O 
> But in general this material is intressting for P-subers because you can
> form it to more or less any configuration including keel,
> rudderbasements etc. An Russian Alpha style midget submarine will be
> easy to make with this material. And it is a cheap material.  
> 
> Have you ever sold a hull as you offer in 1994 ? 
> Best regards Carsten
> 
> 
> ------
> I am curious about viewports and hatches in your hull.
> I want to build an underwater "habit" (read house).
> And
> have looked into quite a few materials. The problem
> with
> concrete has been related to view-ports promarilly. I
> haven't been able to find any information on that. If
> you have any further information of this, or other
> construction methods, you certainly have my attention.
> 
> Warren.
> 
> ------
> 
> I looked into that extensively. It does work, but
> takes
> a lot more current then you might be lead to believe.
> Unless you have free electricity it is more expensive
> then just buying concrete.
> 
> Warren.
> ------
>