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[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.
------