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Re: [PSUBS-MAILIST] concrete submarine
Wilfried schrieb:
>--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.-
This is true! Many ferro-cement boats that were built in the 60's and 70's were not built correctly. This is because the methods used for ferro-cement boat building were not fully understood. Now that there is a history of which construction technics lead to problems those problems have been eliminated. The main problems were the welded wire mesh and protruding steel. Rigging and fittings can not be welded to the internal steel matrix, this will cause many problems of corosion. All of the steel matrix and the wire mesh must be completly sealed over with the plaster. Also another problem was created by using metal floats for the plaster finish, this created a shiny hard crust which did not allow any paint systems to work properly (nothing would stick!) Sealing the surfaces too early before the chemical curing of the cement was also a problem. It takes three to four months of curing before the period of hardening and chemical action slows down enough where it will not interfear with the chemicals in the paints. A slow curing epoxy once the surface is ready is the first choice of paint but chlorinated rubber will also work. I think the smaller yachts do not perform well because at that smaller size the size to wieght ratio is not advantages to a ferro-cement system, the larger the boat the better ferro-cement can compete with other construction such as wood and fiberglass. Of coarse submarines are another matter. I'm using the ferro-cement as a superstructure and as a large soft ballast tank that will float me nicely on the surface. If built correctly ferro-cement can be bullet proof! There are a lot of successful ferro boats out there.
Brian Cox
-- Original Message -----
From: <diagroto@ibague.cetcol.net.co>
To: <personal_submersibles@psubs.org>
Sent: Wednesday, December 10, 2003 11:53 AM
Subject: Re: [PSUBS-MAILIST] concrete submarine
> 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.
> > >
> >
>