Re: [PSUBS-MAILIST] shapeable incompressable filler..any ideas?

[Erik Michael Muller <emm03@uow.edu.au>]

Dear CAARRO@ and all.
I suppose I should tell the full story, which I was loath to into in
the past in an effort to conserve email space etc. But...here we go
My grand plan:
ambient press dry sub, very small, slightly over 1 ton disp (prelim
calcs..lots of assumptions..if anyone REALLY wants to see some plans,
calcs etc. let me know..). 

The shapes of curved hull, the batteries, tanks and the like cause a
lot of deadspace in the cabin that would ordinarily need to be
compensated on the way down.  I am trying to displace air occupying
the deadspace with some incompressable material. It will be a kind of
formed shape with specially shaped holes into which I can slide in and
out the tanks and batteries to replace, repair or whatever. I intend
that the entire displacing material will also be removeable from the
boat to facilitate maintainance etc.

So the filler will be INSIDE the boat, displacing air volume (and
since it will be non-compressable, will reduce the amount of air
needed to compensate).
I should say that I am still trying to figure if I should try to
displace as much air as possible, or as little as possible, since the
less air volume I have, the harder any scrubbers have to work (does
anyone have some empirical knowledge..or actual figures on this?).
In any case I still need at least a little bit of some sort of filler,
just to hold the batteries and tanks in one place, so they cant move
around during use.

To answer your concerns directly:
1)Since the filler will be removable, corrosion from lack of draining
wont be a problem (at least not in the short term, during a dive)
2)The filler will be inside the boat, and (hopefully!) wont be filled
with water (although this is an option, but not one of my favourites)
3)Lack of Floation is not really concern..more the opposite! I hope to
have a very light hull. The ballast will be sealed concrete laid in
the bottom of the cabin (v. low center of mass, good compression
strength, low porosity, durable and waterproof!)

So there we go, sorry for the verbosity!, I tried to keep it small.
thanks for the tips and ideas too!
E.

-------------------
> I am concerned about corrosion occurring between your 
> structure and filler material.  Small voids under 
> pressure are going to fill with water and not drain 
> out well.  Further, I'm not sure why you want to fill 
> these voids, as they would weigh nothing out of the 
> water and be filled with neutral buoyancy in 
> compressible water when in use.  If you need extra 
> flotation why not make a few ridged air canisters?  
> Please excuse me if I haven't grasped the situation 
> correctly.
> --- Original Message ---
> From: Erik Michael Muller <emm03@uow.edu.au>
> To: personal_submersibles@psubs.org
> Subject: Re: [PSUBS-MAILIST] shapeable incompressable 
> filler..any =?us-ascii?q?ideas=3F?=
> 
> >Hello Marcus, and everyone.
> >Thanks for your ideas..once again, the combined brain 
> power of this
> >mailing list has awe-inspired me!
> >It is interesting, Marcus, I had a major revelation 
> last night duing a
> >bout of insomnia, and it occured to me that 
> superballs were not very
> >compressable (high resitituion too).  
> >
> >My brain rambled on and  I thought it might be 
> possible to either use
> >a big slab of neoprene rubber (not the foamy 
> compressable wetsuit
> >kind, but the solid rubber variety). although I think 
> this might be
> >expensive, so I thought I might be able to mix up a 
> plaster+granulated
> >neoprene conglomerate.  Some serious work would have 
> to go into
> >checking exactly what ratio would be the most 
> durable, though even an
> >integrity (sp) failure here wouldnt matter (i.e. it 
> has no airspaces
> >and cant crush, even if it cracks I wouldnt like it 
> too, just because
> >it looks messy), since the only function of the stuff 
> is to fill
> >volume. 
> >
> >The reason a conglomerate might be more useful is 
> that rubber is less
> >dense than water, whereas plaster (which IS 
> waterproof) is more dense.
> > The combined mix (depending on the ratio) might be 
> at a similar
> >density to water.
> >Although the durability is not a safety concern, I 
> would still like to
> >vary the rubber/plaster ratio and test it out (since 
> I suspect that
> >plaster IS slightly porus!)..anyone with a boat who 
> wants to sink a
> >few test bricks of this stuff to a few atms?