Re: [PSUBS-MAILIST] RE: payload

[irox <irox@ix.netcom.com>]

I think you can look at it either way.  Either, the submarine is getting
lighter (less weight) or that the submarine is increasing in volume, but
the weight remains the same.  If I remember correctly, for VBT
calculations, using the "submarine is loosing weight" made the calcs
a little easier.

I'm not sure about this idea of VBT with an external bladder using
air.  I think it's going to be complex at best and most likely problematic.
The air in the bladder will compress (the reason for using oil is that
it won't compress) and the bladder volume will change with depth
making it rather tricky to maintain neutral bouyancy.  (Maybe this
wasn't VBT idea, but it seemed to have been in the context of VBTS).

Cheers,
  Ian.

-----Original Message-----
>From: Paul Kreemer <paulkreemer@gmail.com>
>Sent: Dec 5, 2006 6:05 PM
>To: personal_submersibles@psubs.org
>Subject: Re: [PSUBS-MAILIST] RE: payload
>
>Well, the weight of the sub wouldn't change.  The oil would be either in the
>bladder or the internal tank but either way it's a part of the sub and
>contributes to the weight.  Right?
>
>And air would work about the same and could be used to inflate that external
>bladder.  It's the change in displacement that's important, not the fact
>that you're using air, or olive oil or mercury to pump up that bladder.  :-)
>
>
>Paul
>
>On 12/5/06, Brian Cox <ojaivalleybeefarm@dslextreme.com> wrote:
>>
>> Hi Ray,
>>               You would still be losing the weight of the oil from inside
>> the sub.  And you would realize positive buoyancy from the oil ( in a
>> badder) in a open tank connected to the sub.  You would have to use way more
>> oil than you would just using air.    I'm not sure I am comprehending the
>> though on this.
>>
>> Brian
>>
>> ----- Original Message -----
>> From: "Ray Keefer" <psubs2001@yahoo.com>
>> To: <personal_submersibles@psubs.org>
>> Sent: Tuesday, December 05, 2006 11:15
>> Subject: Re: [PSUBS-MAILIST] RE: payload
>>
>>
>> > Hi Brian,
>> >
>> > I think the idea is to change the amount of
>> > displacement instead of changing the amount of weight.
>> > Pump the oil into the bladder and more water is
>> > displaced with the same weight of sub. Making the sub
>> > more bouyant. Pump the water out of the bladder,
>> > bladder collaspes causing less displacement for the
>> > weight, causing the sub to become less bouyant.
>> >
>> > Regards,
>> > Ray
>> >




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