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Re: [PSUBS-MAILIST] Sound Absorption
I've been kicking a few designs back and fourth for a while, deciding
the pressure vessel diameter is a big factor, so I made the following
table to help. It's a table rough back of napkin type thing, based
on how much sea water one foot of a cylinder of X diameter would
displace.
Diameter Displacement
3.0 feet 452lb
3.25 feet 530lb
3.5 feet 615lb
4.0 feet 804lb
5.0 feet 1256lb
(based on 1 cubic foot of sea water weighting 64lb)
The idea is multiply the displacement by the length of the pressure
hull (ideally in feet), then you have rough estimate how much weight
you need to tow around (or what size truck you need to buy).
There are more questions of bouyancy calculations answered in the FAQ:
http://www.psubs.org/faq.html
Ian.
On Fri, 30 Apr 2004 09:47:03 -0400
"Marten Liebster" <mliebster@tbteam.com> wrote:
> Erik,
>
> Thanks, that's a good idea about the mock-up. Next I'd need to find the
> formulas to determine buoyancy - weight versus air within. If someone could
> point me in that direction it would be greatly appreciated.
>
> Regardless how the plan works out ambient or 1 atmosphere, having different
> options is appreciated.
>
> With an ambient, doesn't the water level within the sub rise the deeper you
> go - as the air gets compressed?
>
> Do you plan on compensating for this - for example: releasing air from
> canisters?
> Or is your sub designed in such a way that is taken into account?
>
> Do you plan on using battery pods to isolate the batteries from water?
>
> Do you enter the sub from underneath then, while it's in the water?
>
> Thanks again.
>
> Marten
>
> -----Original Message-----
> From: owner-personal_submersibles@psubs.org
> [mailto:owner-personal_submersibles@psubs.org] On Behalf Of Erik Muller
> Sent: Friday, April 30, 2004 8:41 AM
> To: personal_submersibles@psubs.org
> Subject: Re: [PSUBS-MAILIST] Sound Absorption
>
> Marten,
> why dont you build a mock-up out of cardboard and find out the smallest
> diametre hull that you can comfortably sit in for a few hours? (or longer...
> !) Also - Dont knock the 'ambient' option!, They are the same total weight
> of course, but because the pressure differential across the hull wall is
> much smaller, you can get away with lower-strength (and usually cheaper)
> hull materials (im using perspex and fibre glass), which also dodges the
> need for owning or borrowing heavy machining equipment. In fact, I dont
> think Im planning for a single weld in my machine (except for soldering
> components, which hardly counts). I sort of think that ambients are the way
> to go for first-timers who dont have much in the way of metal machining
> skills like me, though I imagine that might be a contentious thing to say..
> !
>
> EM.
>
>
> Dan H. wrote:
>
> >Marten,
> >
> >My K-350 is 3 feet in diameter and luckily, I'm a little guy, 5'-6".
> There
> >is enough room for me to operate the sub with my head in the conning
> >tower but it's tight when working on things inside the hull. A hull
> >3'- 6" in diameter would be better but the trade off is it's gets
> >heavier to trailer around. You might want to reconsider your five foot
> >diameter design because of it's weight. Remember it has to be heavy
> >enough to dive. If your not going to transport it, displacement isn't as
> much an option.
> >
> >Dan H.
> >----- Original Message -----
> >From: "Marten Liebster" <mliebster@tbteam.com>
> >To: <personal_submersibles@psubs.org>
> >Sent: Thursday, April 29, 2004 10:05 AM
> >Subject: RE: [PSUBS-MAILIST] Sound Absorption
> >
> >
> >
> >
> >>Steven & Dan,
> >>
> >>Thanks for your responses and pointers. My sub is in the concept
> >>stage,
> >>
> >>
> >I'm
> >
> >
> >>reviewing different ideas and learning what's doable and not. I'm a
> >>fairly big guy - 6'5" - so I'd like my pressure hull to be at least 5
> >>feet in diameter.
> >>
> >>For a living I am a programmer and my experience in fabrication is
> >>purely wood working. So the thought of through hull propulsion is a
> >>bit scary for me. However, having hydraulic connections pass from the
> >>interior to the exterior seems much easier to implement.
> >>
> >>As a result, I am planning to use hydraulic propulsion, I do realize
> >>it's not as efficient as an electric motor. This is the reason for my
> >>asking
> >>
> >>
> >the
> >
> >
> >>original question, I'll have a pump running all the time. I anticipate
> >>
> >>
> >that
> >
> >
> >>with not much to absorb sound and with the shape of the hull, that
> >>would
> >>
> >>
> >get
> >
> >
> >>really annoying.
> >>
> >>Marten
> >>
> >>-----Original Message-----
> >>From: owner-personal_submersibles@psubs.org
> >>[mailto:owner-personal_submersibles@psubs.org] On Behalf Of Dan H.
> >>Sent: Wednesday, April 28, 2004 10:29 PM
> >>To: personal_submersibles@psubs.org
> >>Subject: Re: [PSUBS-MAILIST] Sound Absorption
> >>
> >>Marten,
> >>
> >>I haven't got me sub wet yet but the thrusters are up and running. My
> >>
> >>
> >three
> >
> >
> >>thrusters are in pods on the exterior of the hull. Of course I can
> >>hear them in the sub but they're not loud. If you had a hydraulic
> >>pump running all the time I'm sure that would get annoying.
> >>
> >>I like the idea of hearing noises through the hull. You can't see
> >>everything around you all the time. Hearing a noisy boat in your
> >>vicinity before you surface is a good thing!
> >>
> >>Besides, sound abatement materials against the hull is a place to trap
> >>moisture.
> >>
> >>Dan H.
> >>
> >>BTW. "Persistence" is now yellow. I finished the paint job last week.
> >>Tomorrow the trailer will be blue.
> >>
> >>
> >>----- Original Message -----
> >>From: "Marten Liebster" <mliebster@tbteam.com>
> >>To: <personal_submersibles@psubs.org>
> >>Sent: Wednesday, April 28, 2004 2:50 PM
> >>Subject: [PSUBS-MAILIST] Sound Absorption
> >>
> >>
> >>
> >>
> >>>Hi,
> >>>
> >>>I am in the initial process of designing a psub, my first. The web
> >>>site
> >>>
> >>>
> >>and
> >>
> >>
> >>>mailing list have to proven to be chock full invaluable information
> >>>to
> >>>
> >>>
> >me.
> >
> >
> >>>One thing that I haven't seen much about (perhaps I'm searching on
> >>>the
> >>>
> >>>
> >>wrong
> >>
> >>
> >>>keywords) is that of sound absorption.
> >>>
> >>>I'd imagine that a psub could be a noisy place, with all of the
> >>>motors, pumps, hydraulic and other equipment. It seems to me the hull
> >>>would
> >>>
> >>>
> >>reflect
> >>
> >>
> >>>back the sound waves, it being bare metal in a tube-like shape.
> >>>
> >>>Questions:
> >>>Is your psub a noisy place?
> >>>Do you use anything on the hull to absorb the sound?
> >>>
> >>>Thanks,
> >>>Marten Liebster
> >>>A psub newbie
> >>>
> >>>
> >>>
> >>>
> >>
> >>
> >>
> >>
> >
> >
> >
> >
> >
> >
>