Re: [PSUBS-MAILIST] Buoyancy control

[MerlinSub@t-online.de]

Hi Alan, 

maybe because you can not open the hatches on the 
surface and needs allways a support boat with Crane ?

http://www.technovelgy.com/graphics/content09/deep-flight-super-falcon.jpg

The speed underwater if you run a psub navigating by your eyes is almost near to zero. 
Say 0-2 knots. To keep the boat underwater with this low speed 
required real big wings or very low positive bouancy - means low freeboard. 
Deep-flight is a good sample for this. And she is design to run fast in very deep water. 

MBT and HBT are not so complicate to build. And stay at zero bouancy is very helpful. 
Fact is that most psubers dive and the first work underwater is to bring the bouancy to exact zero. 

The load on a sub change after each meal, beer, other passenger..

vbr Carsten


"Alan Clifford" <Alan@nortruck.com> schrieb:
> I'm sorry if this sounds like a stupid question but here it is.
> 
>  
> 
> Virtually all submarines and submersibles have some metal ballast and
> one or more ballast tanks that are filled with water to submerge and
> cleared with compressed air to surface.  Why not just add metal ballast
> until the vessel has slightly positive buoyancy and use dive planes to
> "fly" down to whatever depth you want?  This eliminates the complexity
> of tanks, lines, valves, and compressed air.
> 
>  
> 
> I realize that the submarine would not be able to hover at a specific
> depth and could not descend vertically.  Is this important?
> 
>  
> 
> I can see that a military submarine would need to dive quickly but that
> doesn't apply to a personal submersible.
> 
>  
> 
> A submersible with slightly positive buoyancy would not have much
> freeboard.  Is that the problem?
> 
>  
> 
> If the load was changed, the ballast would have to be changed.  That
> doesn't seem to be a problem with a personal submersible.
> 
>  
> 
> Thanks for your help.
> 
>  
> 
>             Alan
> 
> 




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