Re: [PSUBS-MAILIST] concrete submarine

[diagroto@ibague.cetcol.net.co]

Hello Michael

My experience is that a small sub of 1-2 tons is to heavy to trailer,
need cranes to bring it to water, need surface ship to bring it to dive place,
is so uncomfortable that dive time is very limited.

In a concrete sub it makes little difference if it is 2 tons or 20 tons. (hull 
cost) machine engineering in a 2 ton ship is complicated (all on outside) in 20 
tons easy (all inside - motor, tanks etc. very similar to yacht).
Once in water 20 tons boat can stay in a normal harbour for years. No crane no 
surface ship. Minimum size is same as you see for autonomous yacht. Can be done 
with some 5 m (complicated) but is nice with some 10m.

Built the hull standing, from material was wood, the only problem is the cone, 
shape. You can solve it by using a combination of paralel and triangular wood 
pieces in the slip form fixed on their place with wire. The more cone shape the 
more triangular pieces you use. All other is same as normal forming.

Greetings
Wilfried



Mensaje citado por: Michael Edwards <me@sustainkauai.org>:

> Hello Wilfried:
> 
> diagroto@ibague.cetcol.net.co wrote:
> 
> > Hello Michael, curtis, brian, Gene, Carsten, everyone interested,
> >
> > In my opinion to do a sub you can get in and out are two proven
> concepts.
> > A simple wet sub at ambient pressure, or a bigger dry sub with diver
> chamber
> > like carsten did. Altough i think that anything else is possible i
> would be
> > careful not to combine disadvantages of various different and proven
> concepts.
> > (water in sub, pressure regulation-complicated, floating regulation,
> etc.)
> > Anyhow i agree with carsten that this is a new idea worth to
> explore.
> > Would not do it with a concrete hull. (sensible to internal
> overpressure).
> 
> Thank you Wilfried, for pointing out the "fatal flaw". You were clear in
> your
> earlier threads
> that concrete shines in compression, not with pressurization. I guess I
> presumed
> that like water tanks, the material could stand a certain amount of
> pressurization/
> tension?
> 
> > You also should be aware that there is a BIG difference between
> ferrocement
> > construction (meshing glue cement in...) and massive concrete
> construction.
> > Ferrocement is a concept that is used in yacht building only (not
> other
> > engineering ) had a LOT of problems especially rusting of mashing and
> crackling
> > due to not optimal use of concrete and lack of proper compactation. It
> also is
> > specially problematic for small yachts below 10m due to thin walls
> while it can
> > be used with relative good results for bigger yachts.
> > Massive concrete is widly used in submarine tunnels (salt water under
> pressure)
> > in drilling platforms (wave action) and offshore oil tanks and dam
> building in
> > same or more severe conditions than it would be in a sub.
> > In all this conditions concrete is compacted as in normal construction
> what
> > limits it to walls of 5cm minimum. - You need 2cm of concrete above
> steelbars
> > as minimum to avoid rust and distribute forces. You need space in your
> mold to
> > bring concrete in and compact it properly.
> > I had a double mold (kind of gliding mold as used for television
> towers or
> > bridges, boat consists in cone shape rings with variable diameters -
> no secret)
> > This means i did a cone shape ring every week and form was made to be
> recycled
> > and to adapt to any ring diameter and wall thickness on both ends.
> 
> I have a million questions here. How many days did this "pour" take?
> Were the cones added on to an "internal" male mold? Or were cones
> used for both the inner and outer forms? Was the hull formed on it's
> side or standing upright? What material did you make the forms out of?
> I have seen slip forms in cast buildings but nothing anywhere near
> this
> complex of a form in concrete.
> 
> > You are completly right, if you do not compact your concret properly
> during
> > construction (as in many ferrocement constructions) you will have a
> poor
> > crackling water barrier, endless rusting of steelbars - final failure.
> If you
> > do it right you will have your steel completly protected (2cm below
> surface).
> > Every building material has its limitations. And one of the
> limitations of
> > concrete is wall thickness below 5cm. This makes it little ideal for
> small
> > trailerable wet sub. But it can be used with excellent results for
> bigger thick
> > wall pressure standing dry sub.
> > Greetings
> > Wilfried
> 
> Wilfried; do you feel in retrospect, that the small 2 meter sub was the
> wrong
> material
> for this small size? As a practical matter, what is the minimum size
> you
> would recommend for a "dry" concrete sub?
> 
> Thank you
> 
> Michael
>