[PSUBS-MAILIST] (no subject)

Fri Aug 28 07:57:26 EDT 2015

I'd be inclined to link the two systems, such that you catch a trim with the VBT upon initial submersion, drive down with thrusters, and then at your operating depth, have a controller (PAC or PLC) maintain that depth automatically using thrusters, but simultaneously auto-adjust the VBT level to bring the required thruster output back to zero.  That way they're never fighting the vessel's buoyancy and you maximize battery endurance.

Sean

On August 27, 2015 5:15:52 PM MDT, Alec Smyth via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>Just two cents on this. I've actually changed my MO over time.
>Initially I
>liked diving heavy. It was an effortless way to descend, and I would
>get
>neutral with the VBT once at depth. If slightly heavy then you can use
>the
>thrusters to hover, but they will be pointing down and that ruins the
>visibility. I used to surface on air.
>
>These days, I just weigh myself and passenger and I have a little table
>on
>my clipboard telling me how many buoys to load. Once you've figured the
>payload of the sub once, the method nails the buoyancy every time, and
>I
>mean to within 5 lbs or so. I both dive and surface on thrusters,
>although
>it is true I have to blow a little bubble in the MBTs on deep dives due
>to
>hull compression. I find thruster dives make for better control and use
>way
>less air. Thruster movement has less "momentum" than buoyancy driven
>motion, meaning that you can shut off the propulsive power instantly
>whereas, if your propulsion is coming from a tankload of air, it takes
>longer to vent or flood the tanks. Its also handy that the sub just
>hovers
>if you stop paying attention for any reason.
>
>
>Best,
>
>Alec
>
>On Thu, Aug 27, 2015 at 4:13 PM, hank pronk via Personal_Submersibles <
>personal_submersibles at psubs.org> wrote:
>
>> Alan,
>> I agree, I need to dive slower, I have a video from yesterday with a
>very
>> nice touch down.  As a rule I have been going down fast and using the
>> vertical thrusters as breaks.  When I dive fast, there is  a bit to
>much
>> momentum built up, thats all.  The video I posted shows what not to
>do :-)
>> I did not put the brakes on.
>> I will get my lead weight situation sorted out.
>> Hank
>>
>>
>>
>> On Thursday, August 27, 2015 1:14 PM, Alan via Personal_Submersibles
><
>> personal_submersibles at psubs.org> wrote:
>>
>>
>> Hank,
>> you said you know the bottom is soft & sink fast.
>> I am a bit concerned as I have read of subs getting temporarily 
>stuck in
>> the mud
>> on the bottom. Haven't heard of any getting permanently stuck but
>there is
>> always
>> a first time. Have also heard of them picking up a lot of weight in
>the
>> form of mud.
>>    Would be good if there was a quick easy lead transference system.
>> Maybe Alec's buoy system is the simplest & easiest to use!
>> Just clip on a number of buoys that account for the weight of the
>> passenger.
>> With lead it has to be placed low, so when doing dive ops it would
>need to
>> go
>> in through the hatch to the hull bottom.
>> Alec's system has the buoys in a tube, but I am thinking that they
>could
>> all have
>> short cords on them, with clips to attach to various points on the
>top of
>> the sub.
>> Alan
>>
>> Sent from my iPad
>>
>> On 28/08/2015, at 2:27 am, hank pronk via Personal_Submersibles <
>> personal_submersibles at psubs.org> wrote:
>>
>> Sean,
>> This is the big debate, VBT or no VBT.  I used to like the idea of no
>VBT
>> and that is the way the Nekton subs operate, just not sure eanymore. 
>I
>> have to admit, my regulator idea is riddled with potential problems. 
>I am
>> just being lazy, if I keep the sub with in 15 lbs (as per the
>operating
>> manual)  or less of buoyant with tanks flooded, and I pay attention,
>it is
>> easy to operate.   I can sink as slow as I want and hover at any
>depth if I
>> take my time.   I need to correct a bad habit  that I have.  I know
>the
>> bottom is soft, so I sink fast.  I need to practice what I preach and
>> always sink as if there is a hard hazard below.
>> Hank
>>
>>
>>
>> On Thursday, August 27, 2015 7:26 AM, Sean T. Stevenson via
>> Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>>
>>
>> Hank, your best bet is to arrange your MBTs such thatrou they flood
>> completely every time with no residual bubble(s), at which point you
>should
>> have very slight positive buoyancy when correctly ballasted. Add a
>small
>> VBT, either internally or externally in a hard tank (you could blow
>this
>> with HP air instead of pumping, but would need to valve it to isolate
>it
>> from ambient pressure changes), to compensate for minor crew weight
>> differences, and compensate for the major ones by adding or removing
>lead.
>> You want to avoid a situation where a depth change creates a buoyancy
>> change, except in the sole case where you have blown your tanks to
>ascend.
>> Sean
>>
>>
>> On August 27, 2015 7:13:27 AM MDT, hank pronk via
>Personal_Submersibles <
>> personal_submersibles at psubs.org> wrote:
>>
>> Alan,
>> It won't work unless there is a check valve between the second stage
>> regulator and the ballast tank. Okay to complicated, bad idea.
>> Hank
>>
>>
>>
>>
>> ------------------------------
>>
>>
>>
>> * From: *
>> hank pronk via Personal_Submersibles ;
>>
>>
>>
>> * To: *
>> Personal Submersibles General Discussion ;
>>
>>
>>
>> * Subject: *
>> Re: [PSUBS-MAILIST] new video
>>
>>
>>
>> * Sent: *
>> Thu, Aug 27, 2015 11:36:09 AM
>>
>>
>>
>>
>> Alan,
>> I am not sure if my idea will work .  When I sink Gamma, there is an
>air
>> bubble remaining in the ballast tank, the size  is determined by the
>weight
>> of the sub.  If I have a first and second stage regulator feeding air
>to
>> the ballast tank, the regulator will feed air into the ballast tank
>as I
>> sink keeping the bubble the same size while I sink.  Right now it is
>> completely manual and takes practise but it works.  I can use both
>systems
>> ( manual or regulated) by simply turning the air supply on or off to
>the
>> external regulators.   With the regula! tor system, I would not have
>to
>> worry about keeping the sub at an ideal weight.
>> Hank
>>
>>
>>
>> On Thursday, August 27, 2015 12:03 AM, Alan via Personal_Submersibles
>> wrote:
>>
>>
>> Thanks Hank,
>> must be this one, the umbrella dive.
>> https://m.youtube.com/watch?v=sflIEnkTth4
>> Sent a reply to your post about using a second stage attached to your
>> ballast tank, but it didn't come back to me.
>> not sure how it would work!
>> Alan
>>
>> Sent from my iPad
>>
>> On 27/08/2015, at 1:30 pm, hank pronk via Personal_Submersibles
>> personal_submersibles at psubs.org> wrote:
>>
>> made some dive
>> video's today, posted one on youtube under Hank Pronk
>>
>> _______________________________________________
>> Personal_Submersibles mailing list
>> Personal_Submersibles at psubs.org
>> http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
>>
>>
>> _______________________________________________
>> Personal_Submersibles mailing list
>> Personal_Submersibles at psubs.org
>> http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
>>
>>
>>
>>
>>
>>
>>
>> ------------------------------
>> * From: * hank pronk via Personal_Submersibles <
>> personal_submersibles at psubs.org>;
>> * To: * Personal Submersibles General Discussion <
>> personal_submersibles at psubs.org>;
>> * Subject: * Re: [PSUBS-MAILIST] new video
>> * Sent: * Thu, Aug 27, 2015 11:36:09 AM
>>
>> Alan,
>> I am not sure if my idea will work .  When I sink Gamma, there is an
>air
>> bubble remaining in the ballast tank, the size  is determined by the
>weight
>> of the sub.  If I have a first and second stage regulator feeding air
>to
>> the ballast tank, the regulator will feed air into the ballast tank
>as I
>> sink keeping the bubble the same size while I sink.  Right now it is
>> completely manual and takes practise but it works.  I can use both
>systems
>> ( manual or regulated) by simply turning the air supply on or off to
>the
>> external regulators.   With the regulator system, I would not have to
>worry
>> about keeping the sub at an ideal weight.
>> Hank
>>
>>
>>
>> On Thursday, August 27, 2015 12:03 AM, Alan via Personal_Submersibles
><
>> personal_submersibles at psubs.org> wrote:
>>
>>
>> Thanks Hank,
>> must be this one, the umbrella dive.
>> https://m.youtube.com/watch?v=sflIEnkTth4
>> Sent a reply to your post about using a second stage attached to your
>> ballast tank, but it didn't come back to me.
>> not sure how it would work!
>> Alan
>>
>> Sent from my iPad
>>
>> On 27/08/2015, at 1:30 pm, hank pronk via Personal_Submersibles <
>> personal_submersibles at psubs.org> wrote:
>>
>> made some dive video's today, posted one on youtube under Hank Pronk
>>
>> _______________________________________________
>> Personal_Submersibles mailing list
>> Personal_Submersibles at psubs.org
>> http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
>>
>>
>> _______________________________________________
>> Personal_Submersibles mailing list
>> Personal_Submersibles at psubs.org
>> http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
>>
>>
>> ------------------------------
>>
>> Personal_Submersibles mailing list
>> Personal_Submersibles at psubs.org
>> http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
>>
>>
>> _______________________________________________
>> Personal_Submersibles mailing list
>> Personal_Submersibles at psubs.org
>> http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
>>
>>
>> _______________________________________________
>> Personal_Submersibles mailing list
>> Personal_Submersibles at psubs.org
>> http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
>>
>>
>> _______________________________________________
>> Personal_Submersibles mailing list
>> Personal_Submersibles at psubs.org
>> http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
>>
>>
>>
>> _______________________________________________
>> Personal_Submersibles mailing list
>> Personal_Submersibles at psubs.org
>> http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
>>
>>
>
>
>------------------------------------------------------------------------
>
>_______________________________________________
>Personal_Submersibles mailing list
>Personal_Submersibles at psubs.org
>http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.whoweb.com/pipermail/personal_submersibles/attachments/20150828/50a45768/attachment-0001.html>