Re: [PSUBS-MAILIST] concrete submarine

[diagroto@ibague.cetcol.net.co]

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).
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.
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

Mensaje citado por: Carsten Standfuss <MerlinSub@t-online.de>:

> In any way this is a brand new idear.. 
> 
> ..a wet 1 atm boat. You have just to open a small 
> vale - the pressure inside increase to ambinet and you can go out. 
> Later you pump some water out and the pressure reduce to 1 atm. 
> But maybe this depresure process has to be very carefully.. 
> 
>  I understand that right ? carsten
> 
> Michael Edwards schrieb:
> > 
> > Hello Wilfried:
> > 
> > I do want to pressurize this hull, only with water in it. Less weight
> to sink
> > the boat is less weight to pull on a trailer.
> >
>