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RE: [PSUBS-MAILIST] Reserved buoyancy
I posted a photo of this on moki.
Regards,
Marius
-----Original Message-----
From: Greeff, Marius (M)
Sent: 11 March 2004 07:39
To: personal_submersibles@psubs.org
Subject: RE: [PSUBS-MAILIST] Reserved buoyancy
Thanks Carsten,
The mid section where my conning tower is located is 21mm thick steel,
grade of steel I am not sure of so drop testing will be no1 on list of
tests. This already with the first section of coning tower displaces
close to 1 m3 and weighs 660Kg. This section is 1.35m long. Adding the
rest of the hull and conning tower will take it to 1.85 m3. Here I will
use 1/4" thick steel where view ports will be placed. I would like my
buoyancy correct on paper to cancel out any other parts still to come
like the motors and battery pods. I will ammend my design to a point
where it will work before I make another hasty buy.
PS. Erik Muller, fun experiment: raw egg floats in salt water and sinks
in fresh water.
Kind regards,
Marius
-----Original Message-----
From: Carsten Standfuss [mailto:MerlinSub@t-online.de]
Sent: 10 March 2004 10:35
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Reserved buoyancy
Yes thats right - the body displace stil the same 1cm of something.
But the density of something is different - and there with on a planet
with constant gravitation - the lift force - bouancy.
A sub of a volume of excat 1 m3 and a weight of 1 t or 1000 kg
in freshwater with a density of 1,0 will just be in dive trim.
It displace excat 1000 kg of water.
Saltwater has an higher density = about 1,025 t per m3 (or 1025 kg)
So you can build the sub 0,025 t or 25 kg heavier and it will be still
dive trim.
Put your 1m3 sub in mercury with a density of 13,595 t per m3
and you have to add 12,595 t of lead or something into your sub before
it dive.
If you dive with a 1m3 and 1 t heavy sub in petrol tank to inspect a big
oil raffinere from Shell.. it will sunk strait to the bottom of the tank
-> Petrol = 0,68 -0,75 t per m3 means negative lift of 0,25-0,32 t
Real sample :
Euronauts weight is about 57 ts.
Baltic sea has about 1,000 t per m3 density.
North Sea has about 1,025 t per m3 density.
If I leave the baltic on dive station via the Kategatt way -
the lift of the water will increase of 1,025 x 57 = to 58.425 t
and the boat will be force on the surface with a lift of 1,425 t - the
weight of a Kittredge size sub..
It is a bad idear to dive with a militar high sea sub from the South
Atlantic into the Amazonas river delta in dived condition..
A 8000 ts boats "lost" about 195 ts of lift -> bouancy ;-)
Sorry about my poor english language.. Carsten
Erik Muller schrieb:
>
> Hello Carsten,
> I am just following up on that calc.
> I am unclear why the displacement is different for salt and fresh
water.
> I know that the boyant force will be different, but surely if I put a
> 1cm cube of metal into a cup of liquid, I still displace 1cm,
regardless
> of anything else disolved., Do you mean to write that the boyant force
> is 1 5323 kg (i.e. rather than m^3) in fresh and 1 5706 kg in sea?
> Thanks Carsten,
> EM.
>
> Carsten Standfuss wrote:
>
> >Show us the general weight calculation of your boat here..
> >
> >I estimate that :
> >
> >A.1) Estimate bouancy calculation :
> >
> >0,921 by 0,921 x 3,1415/4 x 2,3 m = 1,5323 m3 displacement in
freshwater
> >(1,5706 in seawater) without endcaps and outside displacement parts.
> >
> >B.1) Estimate weight calculation :
> >
> >hmm...
> >Which tickness has the pipe ? Mild steel or stainless ?
> >
> >regards Carsten
> >
> >
> >Steven Mills schrieb:
> >
> >
> >>Ouch ! Marius,
> >>
> >>What grade and standard of steel did you get?
> >>
> >>--Steve
> >>
> >>On Wed, 10 Mar 2004 15:58:33 +0200 "Greeff, Marius (M)"
> >><Marius.Greeff@sasol.com> writes:
> >>
> >>
> >>>Howdy,
> >>>I think I bought the wrong piece of steel to start my pressure hull
> >>>with. I end up calculating about 700kg buoyancy reserved on the
> >>>design before motors, batteries and all the rest are added. I wish
> >>>to get this right before I buy the rest of the steel needed to
> >>>build. My design have the hull already 2.3m long and a diameter of
> >>>921mm(36").
> >>>
> >>>Kind Regards
> >>>Marius
> >>>
> >>>
> >>>
>
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> >
> >
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