Hello Carsten,
Euronaut has a operation depth of 250m - Troll Platform legs (concrete hollow) are operating at 303m as we speak - and operated during construction at 350m (security factors included).
Troll platform legs have 24m diameter and 1m thickness - so a hulldiameter / wall thickness ratio of 1:24
So a sub hull needs a hulldiameter / wallthickness ratio of 1:24 to go for 350m - in real world - what is a bit far from your numbers - my prototype had 2400mm outer hull diameter and 18mm wall thickness - it is twice as troll in thickness - (and very similar in internal space to a steel sub if you count the lost space by the stiffeners in steel subs.)
Your conclusion is right if you compare thick walled steel hulls (like TRIESTE) with thick walled concrete hulls - where in both cases BUCKLING is ruled out as expected failure mode.
It does not apply if you compare massive concrete (buckling ruled out) to steel plate material (fails long long before the steel compression strength limit due to buckling).
In conclusion concrete is similar in space distribution (incl.stiffeners) much cheaper, much less maintainance, and dives deeper . Building cost 331 Euro/ton of displacement as executed in the prototype and Ians 200 ton submarine yacht.
See the support of that arguments at my website - reading list section - with the respective studies about concrete marine and deep sea applications.
Wil
concretesubmarine.com
2009/5/16, MerlinSub@t-online.de <MerlinSub@t-online.de>:Hi Brian
Typical steel has a pressure strength of 500 N/mm2 but
typical concrete has around 20 N/mm2.
Means if you put the same outside pressure on the sub the concrete
hull needs about 500/20 = 25 times more tickness.
Euronaut has a 22 mm strong steel shell means in
concrete should be around 500 mm thickness to get equal dive deep.
Imagine a sub with 2 meter internal diamter - you can just stand upright.
The steel sub has a outside diamter of 2000 +22+22 = 2044 mm
the same depth diving sub in concrete has 2000 + 500 + 500 = 3000 mm diamter.
In other words a 15 meter long steel sub has a volume 50 m3 = 50 t in fresh water
in concrete it has 107 t! For the same speed it needs a
bigger diesel, bigger e-motor, more batteries, less space inside because of this.
You change cheap steel against expensive batterys to get the same result..
Imagine you have to made an additional eletrical troughull (or 10) in 500 mm material..
I have even not a single drill for that..
Concrete needs even as cylinder a mould to get a nice flush surface - steel not.
Concrete is nice for bridges and oilriggs were power, speed and volume
do not matter as item - but for vessels ?
The highest skyscraper of the world are all made from steel..
In concrete the bottom levels can not take the load - or the
walls get much to strong to get practical.
ps: human bones have 150 N/mm2 pr.strength
vbr Carsten
"Brian Cox" <ojaivalleybeefarm@dslextreme.com> schrieb:
> Hi Carsten,
> What would your assesment of the pros and cons of building a
> large sub like yours using steel for the hull, like you are doing, as
> compared to using concrete for the hull? If I were to build a large sub
> like your size out of concrete I would build it in sections that would bolt
> together. Probably 10' sections that could be individually sealed. They
> would all be made using the same mold except for the two end pieces. And
> then just keep adding section after section. You would definately have some
> different issues using concrete.
>
> Brian
>
> -----Original Message-----
> From: owner-personal_submersibles@psubs.org
> [mailto:owner-personal_submersibles@psubs.org]On Behalf Of
> MerlinSub@t-online.de
> Sent: Friday, May 15, 2009 2:59 PM
> To: personal_submersibles@psubs.org
> Subject: Re: [PSUBS-MAILIST] Submersible Cost and Time to Build
>
>
> Alan you need more than 1000 hours.. and about 20K.
>
> Less material cost means more hours.
> More material cost for the SAME sub means less hours.
>
> Sample :
> You purchase a ready to play dome: high cost but less hours
> You made the dome yourself : less material cost but many hours.
>
> Another item is what kind of workshops and tools you have.
> More workshop and better tools lower your hours and material costs..
>
> You need at least a good grinder, much better two, a small and a big
> drilling machine, a good welder
> and a garage. A plasma cutter helps also a lot. If you miss one of this
> items you have to put it one the money list for the project. And two 2-3
> overalls, 10-15 pair of hand gloves and, and..
>
> My figures shows that you have to add to the material cost about 4-5% for
> tools and about 9% for other cost (like transport, repair the welder
> etc..)and it takes you 1-2 hours a week just to clean up..
>
> If you work each weekend 16 hours on the sub and that maybe
> 40 weeks a year you can spend just 600-700 hours per year and you need one
> and a half year.
> I build Peppers in a year, a small one man single seater. But Emile spent
> another year to refit
> and upgrade it.
>
> Make a exel sheet with all figures helps a lot. And dont worry about the
> high figures.
> Just start- if you finish it you will forget all the hard money and hours
> very fast
> - and a good build and maintance sub can stay very very long.
> My one mann is twenty years old now and still operational.
>
> So divided the
> 1000 hours to build by a operational time of
> 30 years and you get just 33 hours a year to get a sub.
>
> I think I have much over 10.000 hours on Euronaut now..
>
> vbr Carsten
>
>
>
> "Alan Clifford" <Alan@nortruck.com> schrieb:
> > Assuming I do most of the work, will $16K buy the materials for a dry,
> > one atmosphere, two person submersible with a trailer?
> >
> >
> >
> > Does it take 200, 300, or 400 hours to build one?
> >
> >
> >
> > Alan
> >
> >
>
>
>
>
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