Exactly. You never want the tank to contain stored energy in the form of gas pressure. The only part of the system that would see constant pressure is the line between the PD pump discharge and the discharge isolator valve. When the pump is operating, the tank should be relieved by a process air line at 1 atm or some other low pressure to maintain some positive suction head against the pump inlet. The only time the VBT would see internal pressure is when the inlet isolator valve is open, and in that case for safety's sake you would probably have an orifice or something to throttle that flow to something manageable at the deepest operating depth. If the VBT is a hard tank, as it fills the gas cap above the water inside will compress, and will need to be vented off. This can either be done continuously or discretely, but at the end of the addition operation, the VBT should be returned to LP internally. If it is a soft tank, that is a non-issue.<br><br>Sean<br><br><br>-------- Original Message --------<br>On Aug. 17, 2023, 10:41, Cliff Redus via Personal_Submersibles < personal_submersibles@psubs.org> wrote:<blockquote class="protonmail_quote"><br><html><head></head><body><div class="ydpfb5508bdyahoo-style-wrap" style="font-family:times new roman, new york, times, serif;font-size:16px;"><div></div>
<div dir="ltr" data-setdir="false">Jon, if I am understanding Sean correctly, he is advocating using a PD pump with a check valve to move water out of the VBT instead of air pressure so issue of in rush of water when the flood valve is opened goes away.</div><div dir="ltr" data-setdir="false"><br></div><div dir="ltr" data-setdir="false">I do agree "<span><span style="color: rgb(38, 40, 42); font-family: times new roman, new york, times, serif; font-size: 16px;">working out the dynamics in actual practice would require a bit of time". Constants for PID controller would have to be experimented with.</span></span></div><div dir="ltr" data-setdir="false"><br></div><div dir="ltr" data-setdir="false">Cliff</div><div><br></div>
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On Thursday, August 17, 2023 at 10:51:19 AM CDT, Jon Wallace via Personal_Submersibles <personal_submersibles@psubs.org> wrote:
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<div dir="ltr">Conceptually it's a great idea for automation and likely not a big deal to implement via software code. I think working out the dynamics in actual practice would require a bit of time. Assuming you wanted more buoyancy the biggest issue would be the description Cliff gave of adding air to the VBT without the inrush of water because of the pressure difference at depth. The only solution I see to that is adding a pressure sensor to the VBT and adding air first to counter the outside water pressure, then opening the outside valve to the VBT. That means another sensor, more software code, and more potential things that could go wrong, which is why I like the simplicity of removing the VBT entirely and just relying on weight control to obtain neutral buoyancy. BUT...it would be a good project if somebody wanted to implement it.</div><div dir="ltr"><br clear="none"></div><div dir="ltr">Jon</div><div dir="ltr"><br clear="none"></div><div><br clear="none"></div>
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On Thursday, August 17, 2023 at 10:25:56 AM EDT, Cliff Redus via Personal_Submersibles <personal_submersibles@psubs.org> wrote:
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<div dir="ltr">Sean, I think this control strategy could work. To utilize, you would need a PLC or microprocessor to implement a PID loop. It would be easy to test by putting the sub in shallow test tank to test depth station keeping capability. You could then upset the system by adding some lead ballast to the boat and see how well the VBT/Thrusters handle the upset.</div><div dir="ltr"><br clear="none"></div><div dir="ltr">My guess is that those in our group that like the KISS strategy would deems this as too complicated while those that like this kind of approach would see some nice benefits of this control strategy. My experience with Psubs is that someone try's something new and if it works incrementally better than what they were using, they adopt. For me it would have to be modified as I don't have a VBT, i.e., I could implement a depth/altitude station keeping PLC function with a PID loop controlling either depth or altitude with vertical thrusters alone.</div><div dir="ltr"><br clear="none"></div><div dir="ltr">Cliff</div><div><br clear="none"></div>
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On Wednesday, August 16, 2023 at 10:59:28 PM CDT, Sean T. Stevenson via Personal_Submersibles <personal_submersibles@psubs.org> wrote:
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<div><div id="ydpac39dabdyiv3438947984ydpad76c273yiv0413517991ydp64f5db12yiv3536991157"><div>I think I may have offered this the last time the VBT discussion came up, but I always thought that a good control scheme for the VBT would be to automate it within a slave loop to the vertical thruster control. So, for example, you have a position setpoint in the vertical direction which is either auto-depth or auto-altitude, and have your vertical thrusters programmed to respond accordingly to maintain that setpoint. Separately, you monitor the instantaneous output to the vertical thrusters that results from that control loop, filtered on a longer time base, and operate one of two valves via a slower acting control loop to either admit water to the VBT, or open the pump discharge to let water out, as necessary in order to null out that thruster input. This way, external disturbances such as vertical currents, or buoyancy changes due to hull deflection at depth etc., would be compensated for automatically, and the system would also act to conserve energy by minimizing power consumption to the vertical thrusters, by always dialing the boat to neutral.<br clear="none"><br clear="none">When not holding an altitude or depth, the system could also activate whenever the manual thruster command was saturated at 100% in either direction, in order to hasten a long ascent or descent, or possibly to respond to the condition where the available vertical thrust is insufficient. The only caveat would be to make sure that you don't allow so much VBT volume that you couldn't manually counter the resultant buoyant force with opposing thrust in an emergency.<br clear="none"><br clear="none">Such an embodiment would require a check valve based reciprocating pump, like a Sprague, that could be deadheaded against the discharge valve at full outlet pressure. Opening the discharge valve would cause it to stroke, while closing the discharge valve would deadhead it again. This is possibly a safety feature, because as as long as the pump is not stroking with the discharge valve closed, you know it can develop pressure, and again, having a pump that just stops when pressure builds downstream will conserve the HP air or electrical power used to drive it, in contrast to a pump that must be explicitly run.<br clear="none"><br clear="none">Just a thought.<br clear="none"><br clear="none">Sean<br clear="none"><br clear="none"><br clear="none">-------- Original Message --------<br clear="none">On Aug. 16, 2023, 21:18, Cliff Redus via Personal_Submersibles < personal_submersibles@psubs.org> wrote:<blockquote class="ydpac39dabdyiv3438947984ydpad76c273yiv0413517991ydp64f5db12yiv3536991157protonmail_quote"><br clear="none"></blockquote></div><div id="ydpac39dabdyiv3438947984ydpad76c273yiv0413517991ydp64f5db12yiv3536991157yqt09167" class="ydpac39dabdyiv3438947984ydpad76c273yiv0413517991ydp64f5db12yiv3536991157yqt0290428532"><div><div style="font-family:times new roman, new york, times, serif;font-size:16px;" class="ydpac39dabdyiv3438947984ydpad76c273yiv0413517991ydp64f5db12yiv3536991157ydpc1e70a7byahoo-style-wrap"><div></div>
<div dir="ltr">Hugh, I understand the attraction of using VBT for QSub. With a mission profile to be able to do long ocean surface transects to a dive location, submerge, dive, surface and then transect back. It is not practical to haul excess ballast since the Qsub is operating more like a submarine than a submersible. If you can find a positive displacement pump that does not have a lot of slippage at your maximum depth, then the issue I mentioned about opening the VBT at depth and getting negatively buoyant goes away because the pump itself is preventing a large inrush of water. When this happened on my boat, I had already switched to air for blowing VBT. I would, as you note, adjust the water in the VBT just below the surface after flooding the MBTs. This was the NOP but sometimes the unexpected happens and you need to add buoyancy at depth with the VBT. I was diving the R300 about seven years ago at Lake Amistad on the border between Mexico and Texas. I submerged to about 150 ft in old river bottom. When I lifted of the bottom to start the ascent using my vertical thrusters at an altitude of about 10ft, the boat stopped ascending even with full vertical thrusters. I was watching the depth gage and I was just going up. I did not realize it but I was being dragged along by a 5-knot current and was not accenting at a rate I was comfortable with. The boat at the time was neutrally buoyant. To increase the rate of ascent, I decided to blow the VBT at depth. The depth was about 140 ft at the time. When I opened the motorized ball valve on the vent side of the VBT, the boat started descending even though air was being introduced because of this sudden influx of water. Eventually, the water in the VBT was displaced with air and the boat started to ascend. When I surfaced, I was about a mile downstream from the tender vessel. Because the water visibly was so bad, I did not realize I was being dragged by the current so much. </div><div dir="ltr"><br clear="none"></div><div dir="ltr">Cliff</div><div dir="ltr"><br clear="none"></div><div><br clear="none"></div>
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On Wednesday, August 16, 2023 at 09:25:55 PM CDT, via Personal_Submersibles <personal_submersibles@psubs.org> wrote:
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<div><div dir="ltr">Hi Cliff,<br clear="none"></div><div dir="ltr">I am interested in your comments re the pump slippage etc and operation of<br clear="none"></div><div dir="ltr">the VBTs when you were using them.<br clear="none"></div><div dir="ltr">My approach, untried and purely theoretical, was that most of the VBT<br clear="none"></div><div dir="ltr">adjustment would be done just below the surface and only minor adjustment<br clear="none"></div><div dir="ltr">for compression of vessels etc would be done at depth. <br clear="none"></div><div dir="ltr">I do appreciate that weight balance appears more foolproof. Regards, Hugh <br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">-----Original Message-----<br clear="none"></div><div dir="ltr">From: Personal_Submersibles <<a shape="rect" href="mailto:personal_submersibles-bounces@psubs.org" rel="nofollow" target="_blank">personal_submersibles-bounces@psubs.org</a>> On<br clear="none"></div><div dir="ltr">Behalf Of via Personal_Submersibles<br clear="none"></div><div dir="ltr">Sent: Thursday, August 17, 2023 1:02 PM<br clear="none"></div><div dir="ltr">To: <a shape="rect" href="mailto:personal_submersibles@psubs.org" rel="nofollow" target="_blank">personal_submersibles@psubs.org</a><br clear="none"></div><div dir="ltr">Subject: Personal_Submersibles Digest, Vol 120, Issue 40<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">Send Personal_Submersibles mailing list submissions to<br clear="none"></div><div dir="ltr"> <a shape="rect" href="mailto:personal_submersibles@psubs.org" rel="nofollow" target="_blank">personal_submersibles@psubs.org</a><br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">To subscribe or unsubscribe via the World Wide Web, visit<br clear="none"></div><div dir="ltr"> <a shape="rect" href="http://www.whoweb.com/mailman/listinfo.cgi/personal_submersibles" rel="nofollow" target="_blank">http://www.whoweb.com/mailman/listinfo.cgi/personal_submersibles</a><br clear="none"></div><div dir="ltr">or, via email, send a message with subject or body 'help' to<br clear="none"></div><div dir="ltr"> <a shape="rect" href="mailto:personal_submersibles-request@psubs.org" rel="nofollow" target="_blank">personal_submersibles-request@psubs.org</a><br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">You can reach the person managing the list at<br clear="none"></div><div dir="ltr"> <a shape="rect" href="mailto:personal_submersibles-owner@psubs.org" rel="nofollow" target="_blank">personal_submersibles-owner@psubs.org</a><br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">When replying, please edit your Subject line so it is more specific than<br clear="none"></div><div dir="ltr">"Re: Contents of Personal_Submersibles digest..."<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">Today's Topics:<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr"> 1. Re: Re VBT Pump (Cliff Redus via Personal_Submersibles)<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">----------------------------------------------------------------------<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">Message: 1<br clear="none"></div><div dir="ltr">Date: Thu, 17 Aug 2023 01:01:56 +0000 (UTC)<br clear="none"></div><div dir="ltr">From: Cliff Redus via Personal_Submersibles<br clear="none"></div><div dir="ltr"> <<a shape="rect" href="mailto:personal_submersibles@psubs.org" rel="nofollow" target="_blank">personal_submersibles@psubs.org</a>><br clear="none"></div><div dir="ltr">To: via Personal_Submersibles <<a shape="rect" href="mailto:personal_submersibles@psubs.org" rel="nofollow" target="_blank">personal_submersibles@psubs.org</a>><br clear="none"></div><div dir="ltr">Subject: Re: [PSUBS-MAILIST] Re VBT Pump<br clear="none"></div><div dir="ltr">Message-ID: <<a shape="rect" href="mailto:2137621386.758356.1692234116222@mail.yahoo.com" rel="nofollow" target="_blank">2137621386.758356.1692234116222@mail.yahoo.com</a>><br clear="none"></div><div dir="ltr">Content-Type: text/plain; charset="utf-8"<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr"> Hugh, thanks for update on QSub.? I am looking forward to her dunk test in<br clear="none"></div><div dir="ltr">your new test pool. I quite enjoyed sitting in her pressure hull in your<br clear="none"></div><div dir="ltr">shop in New Zealand a few years back.? She will be quite something when<br clear="none"></div><div dir="ltr">complete.<br clear="none"></div><div dir="ltr">Best<br clear="none"></div><div dir="ltr"> On Wednesday, August 16, 2023 at 06:43:41 PM CDT, via<br clear="none"></div><div dir="ltr">Personal_Submersibles <<a shape="rect" href="mailto:personal_submersibles@psubs.org" rel="nofollow" target="_blank">personal_submersibles@psubs.org</a>> wrote: <br clear="none"></div><div dir="ltr"> <br clear="none"></div><div dir="ltr"> Thanks, Cliff, Alec, Vance, Jon.<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">The model I was looking at, correction, was the Oberdorfer 994 which is same<br clear="none"></div><div dir="ltr">as a 2000 series but 3/8" - 1/2"? and direct mounted not foot mounted as per<br clear="none"></div><div dir="ltr">the 2000 series.<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">The other pump I liked was the Wanner D10 which is diaphragm and can do no<br clear="none"></div><div dir="ltr">slippage and 250 -300 psi etc but it is not bidirectional.? However that can<br clear="none"></div><div dir="ltr">be fixed with valves.<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">I am making some progress with my Q-Sub but made the mistake of going too<br clear="none"></div><div dir="ltr">complex and trying to do everything.? I? have had issues with --- 1. BMS<br clear="none"></div><div dir="ltr">systems for the LiFePO4 batteries and had to replace these.<br clear="none"></div><div dir="ltr">2. Precharge systems for the 72 v and 144 volt electrics and voltage spikes.<br clear="none"></div><div dir="ltr">3. Gear cable kinking for the mercruiser sternlegs.<br clear="none"></div><div dir="ltr">4. Inaccessible fuses and not motor rated.<br clear="none"></div><div dir="ltr">5. Mechanical seal leakage on the hydraulics.<br clear="none"></div><div dir="ltr">6. Joystick pot issues.<br clear="none"></div><div dir="ltr">7. Canbus systems at different voltages.<br clear="none"></div><div dir="ltr">8. Rotary sensors too coarse required op amp addition to amplify signals for<br clear="none"></div><div dir="ltr">small rotary movements with steering.<br clear="none"></div><div dir="ltr">9. Port Engine starting issues.<br clear="none"></div><div dir="ltr">10. Oil compensation line fittings leaks.<br clear="none"></div><div dir="ltr">11. Software issues.<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">Still plugging along.? IN the meantime I have built a test pool same-same<br clear="none"></div><div dir="ltr">Hank 8 ft deep 12 wide x 27 long, and another gantry crane for PVHO removal,<br clear="none"></div><div dir="ltr">as well as a shed just for the sub.? This year it has to be finished.? Has<br clear="none"></div><div dir="ltr">not even been in the pool yet!!<br clear="none"></div><div dir="ltr">Regards,? Hugh<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">-----Original Message-----<br clear="none"></div><div dir="ltr">From: Personal_Submersibles <<a shape="rect" href="mailto:personal_submersibles-bounces@psubs.org" rel="nofollow" target="_blank">personal_submersibles-bounces@psubs.org</a>> On<br clear="none"></div><div dir="ltr">Behalf Of via Personal_Submersibles<br clear="none"></div><div dir="ltr">Sent: Thursday, August 17, 2023 3:21 AM<br clear="none"></div><div dir="ltr">To: <a shape="rect" href="mailto:personal_submersibles@psubs.org" rel="nofollow" target="_blank">personal_submersibles@psubs.org</a><br clear="none"></div><div dir="ltr">Subject: Personal_Submersibles Digest, Vol 120, Issue 36<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">Send Personal_Submersibles mailing list submissions to ???<br clear="none"></div><div dir="ltr"><a shape="rect" href="mailto:personal_submersibles@psubs.org" rel="nofollow" target="_blank">personal_submersibles@psubs.org</a><br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">To subscribe or unsubscribe via the World Wide Web, visit ???<br clear="none"></div><div dir="ltr"><a shape="rect" href="http://www.whoweb.com/mailman/listinfo.cgi/personal_submersibles" rel="nofollow" target="_blank">http://www.whoweb.com/mailman/listinfo.cgi/personal_submersibles</a><br clear="none"></div><div dir="ltr">or, via email, send a message with subject or body 'help' to ???<br clear="none"></div><div dir="ltr"><a shape="rect" href="mailto:personal_submersibles-request@psubs.org" rel="nofollow" target="_blank">personal_submersibles-request@psubs.org</a><br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">You can reach the person managing the list at ???<br clear="none"></div><div dir="ltr"><a shape="rect" href="mailto:personal_submersibles-owner@psubs.org" rel="nofollow" target="_blank">personal_submersibles-owner@psubs.org</a><br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">When replying, please edit your Subject line so it is more specific than<br clear="none"></div><div dir="ltr">"Re: Contents of Personal_Submersibles digest..."<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">Today's Topics:<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">? 1. Re: FW: VBT pump (Cliff Redus via Personal_Submersibles) ? 2. Re: FW:<br clear="none"></div><div dir="ltr">VBT pump (Alec Smyth via Personal_Submersibles) ? 3. Re: FW: VBT pump (Jon<br clear="none"></div><div dir="ltr">Wallace via Personal_Submersibles)<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">----------------------------------------------------------------------<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">Message: 1<br clear="none"></div><div dir="ltr">Date: Wed, 16 Aug 2023 13:29:07 +0000 (UTC)<br clear="none"></div><div dir="ltr">From: Cliff Redus via Personal_Submersibles ???<br clear="none"></div><div dir="ltr"><<a shape="rect" href="mailto:personal_submersibles@psubs.org" rel="nofollow" target="_blank">personal_submersibles@psubs.org</a>><br clear="none"></div><div dir="ltr">To: via Personal_Submersibles <<a shape="rect" href="mailto:personal_submersibles@psubs.org" rel="nofollow" target="_blank">personal_submersibles@psubs.org</a>><br clear="none"></div><div dir="ltr">Subject: Re: [PSUBS-MAILIST] FW: VBT pump<br clear="none"></div><div dir="ltr">Message-ID: <<a shape="rect" href="mailto:536726240.403633.1692192547749@mail.yahoo.com" rel="nofollow" target="_blank">536726240.403633.1692192547749@mail.yahoo.com</a>><br clear="none"></div><div dir="ltr">Content-Type: text/plain; charset="utf-8"<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr"> Hugh, on my original design for the R300 I had a hard VBT just aft of the<br clear="none"></div><div dir="ltr">pilot. At the time I had a small HPU in the boat.? My plan was to use a<br clear="none"></div><div dir="ltr">Oberdorfer Bronze gear pump driven by a small hydraulic motor to move water<br clear="none"></div><div dir="ltr">in and out of the VBT.? I don't remember the specs on the pump.? I had<br clear="none"></div><div dir="ltr">motorized ball valves on the vent and flood side of the VBT.? Prior to using<br clear="none"></div><div dir="ltr">this set up, I did some testing of this gear pump which I still have.? What<br clear="none"></div><div dir="ltr">I found was an unacceptable amount of flow slippage at my max design depth.?<br clear="none"></div><div dir="ltr">There was so much slippage that the pump could not blow the VBT at max<br clear="none"></div><div dir="ltr">depth.? At that point I abandoned using a pump and vent to blowing the VBT<br clear="none"></div><div dir="ltr">with air.? I eventually abandoned the VBT altogether for operability<br clear="none"></div><div dir="ltr">reasons.? When I used this hard VBT to get neutral on the surface, the<br clear="none"></div><div dir="ltr">pressure in the tank was low.? When at depth if I ever tried to use the VBT,<br clear="none"></div><div dir="ltr">water would rush in until the pressure equalized with ambient water<br clear="none"></div><div dir="ltr">pressure.? This made the boat nega!<br clear="none"></div><div dir="ltr"> tively buoyant until air was added.? The other thing that bugged me was I<br clear="none"></div><div dir="ltr">had a float style level sensor in the VBT.? The water level in the VBT was<br clear="none"></div><div dir="ltr">always moving around so you never trust the reading.? I eventually abandoned<br clear="none"></div><div dir="ltr">the VBT and now just add ballast at the boat CG where the VBT was located.?<br clear="none"></div><div dir="ltr">I find this works great.? The other issue is the VBT restricted access to<br clear="none"></div><div dir="ltr">equipment aft of the VBT so to work on any of this equipment, I had to<br clear="none"></div><div dir="ltr">remove the VBT.? ?All in all, I found the VBT to be a pain in butt.<br clear="none"></div><div dir="ltr">Cliff<br clear="none"></div><div dir="ltr">Oberdorfer 944 Bronze<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">? ? On Sunday, August 13, 2023 at 04:57:24 PM CDT, via Personal_Submersibles<br clear="none"></div><div dir="ltr"><<a shape="rect" href="mailto:personal_submersibles@psubs.org" rel="nofollow" target="_blank">personal_submersibles@psubs.org</a>> wrote:? <br clear="none"></div><div dir="ltr"> <br clear="none"></div><div dir="ltr"> <br clear="none"></div><div dir="ltr">Hi Guys<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr"> ?<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">What make of pump is best for VBT water transfer in/out for 250 psi 1.5 kw.<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">I am looking at a gear pump 1.5kw Oberdorfer 944 Bronze.? These are only<br clear="none"></div><div dir="ltr">rated for 10 bar.? I tried an hydraulic gear pump 30cc where I had a<br clear="none"></div><div dir="ltr">stainless and bronze gear set made up but the aluminium body corroded form<br clear="none"></div><div dir="ltr">the trials and I just found that they had used steel backed sleeve bearings.<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr"> ?<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">Regards,<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">Hugh<br clear="none"></div><div dir="ltr">_______________________________________________<br clear="none"></div><div dir="ltr">Personal_Submersibles mailing list<br clear="none"></div><div dir="ltr"><a shape="rect" href="mailto:Personal_Submersibles@psubs.org" rel="nofollow" target="_blank">Personal_Submersibles@psubs.org</a><br clear="none"></div><div dir="ltr"><a shape="rect" href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" rel="nofollow" target="_blank">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a><br clear="none"></div><div dir="ltr">? <br clear="none"></div><div dir="ltr">-------------- next part --------------<br clear="none"></div><div dir="ltr">An HTML attachment was scrubbed...<br clear="none"></div><div dir="ltr">URL:<br clear="none"></div><div dir="ltr"><<a shape="rect" href="http://www.whoweb.com/pipermail/personal_submersibles/attachments/20230816/" rel="nofollow" target="_blank">http://www.whoweb.com/pipermail/personal_submersibles/attachments/20230816/</a><br clear="none"></div><div dir="ltr">b13a39c1/attachment-0001.html><br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">------------------------------<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">Message: 2<br clear="none"></div><div dir="ltr">Date: Wed, 16 Aug 2023 09:41:53 -0400<br clear="none"></div><div dir="ltr">From: Alec Smyth via Personal_Submersibles ???<br clear="none"></div><div dir="ltr"><<a shape="rect" href="mailto:personal_submersibles@psubs.org" rel="nofollow" target="_blank">personal_submersibles@psubs.org</a>><br clear="none"></div><div dir="ltr">To: Personal Submersibles General Discussion ???<br clear="none"></div><div dir="ltr"><<a shape="rect" href="mailto:personal_submersibles@psubs.org" rel="nofollow" target="_blank">personal_submersibles@psubs.org</a>><br clear="none"></div><div dir="ltr">Subject: Re: [PSUBS-MAILIST] FW: VBT pump<br clear="none"></div><div dir="ltr">Message-ID:<br clear="none"></div><div dir="ltr">??? <CABECYQ7JnW3k0Jz+wtvG64tx4pApp=vj5vkF9yWW2NN0fQMU3Q@mail.gmail.com><br clear="none"></div><div dir="ltr">Content-Type: text/plain; charset="utf-8"<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">I second that (getting rid of VBT). I got rid of the VBT in my K250 years<br clear="none"></div><div dir="ltr">ago to make space and turn it into a 2-person and to try and to simplify,<br clear="none"></div><div dir="ltr">and it worked so well I never thought of using any other method on the<br clear="none"></div><div dir="ltr">current sub. The only difference with Cliff's method is that I add or remove<br clear="none"></div><div dir="ltr">floats, while he uses ballast. But either way, once you have a reference<br clear="none"></div><div dir="ltr">point for how much ballast/buoyancy you need for a given crew weight, you<br clear="none"></div><div dir="ltr">just make incremental changes and it never fails. You may be off neutral by<br clear="none"></div><div dir="ltr">just a few pounds, but if you have vertical thrusters they're usually just<br clear="none"></div><div dir="ltr">ticking over at slow RPMs to compensate.<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">Best,<br clear="none"></div><div dir="ltr">Alec<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">On Wed, Aug 16, 2023 at 9:30?AM Cliff Redus via Personal_Submersibles <<br clear="none"></div><div dir="ltr"><a shape="rect" href="mailto:personal_submersibles@psubs.org" rel="nofollow" target="_blank">personal_submersibles@psubs.org</a>> wrote:<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">> Hugh, on my original design for the R300 I had a hard VBT just aft of <br clear="none"></div><div dir="ltr">> the pilot. At the time I had a small HPU in the boat.? My plan was to <br clear="none"></div><div dir="ltr">> use a Oberdorfer Bronze gear pump driven by a small hydraulic motor to <br clear="none"></div><div dir="ltr">> move water in and out of the VBT.? I don't remember the specs on the <br clear="none"></div><div dir="ltr">> pump.? I had motorized ball valves on the vent and flood side of the <br clear="none"></div><div dir="ltr">> VBT.? Prior to using this set up, I did some testing of this gear pump <br clear="none"></div><div dir="ltr">> which I still have.? What I found was an unacceptable amount of flow <br clear="none"></div><div dir="ltr">> slippage at my max design depth.? There was so much slippage that the <br clear="none"></div><div dir="ltr">> pump could not blow the VBT at max depth.? At that point I abandoned <br clear="none"></div><div dir="ltr">> using a pump and vent to blowing the VBT with air.? I eventually <br clear="none"></div><div dir="ltr">> abandoned the VBT altogether for operability reasons.? When I used <br clear="none"></div><div dir="ltr">> this hard VBT to get neutral on the surface, the pressure in the tank <br clear="none"></div><div dir="ltr">> was low.? When at depth if I ever tried to use the VBT, water would <br clear="none"></div><div dir="ltr">> rush in until the pressure equalized with ambient water pressure.?<br clear="none"></div><div dir="ltr">> This made the boat negatively buoyant until air was added.? The other <br clear="none"></div><div dir="ltr">> thing that bugged me was I had a float style level sensor in the VBT.?<br clear="none"></div><div dir="ltr">> The water level in the VBT was always moving around so you never trust <br clear="none"></div><div dir="ltr">> the reading.? I eventually abandoned the VBT and now just add ballast <br clear="none"></div><div dir="ltr">> at the boat CG where the VBT was located.? I find this works great.? <br clear="none"></div><div dir="ltr">> The<br clear="none"></div><div dir="ltr">other issue is the VBT restricted access to equipment aft of<br clear="none"></div><div dir="ltr">> the VBT so to work on any of this equipment, I had to remove the VBT.<br clear="none"></div><div dir="ltr">All<br clear="none"></div><div dir="ltr">> in all, I found the VBT to be a pain in butt.<br clear="none"></div><div dir="ltr">><br clear="none"></div><div dir="ltr">> Cliff<br clear="none"></div><div dir="ltr">><br clear="none"></div><div dir="ltr">> Oberdorfer 944 Bronze<br clear="none"></div><div dir="ltr">><br clear="none"></div><div dir="ltr">> On Sunday, August 13, 2023 at 04:57:24 PM CDT, via <br clear="none"></div><div dir="ltr">> Personal_Submersibles < <a shape="rect" href="mailto:personal_submersibles@psubs.org" rel="nofollow" target="_blank">personal_submersibles@psubs.org</a>> wrote:<br clear="none"></div><div dir="ltr">><br clear="none"></div><div dir="ltr">><br clear="none"></div><div dir="ltr">> Hi Guys<br clear="none"></div><div dir="ltr">><br clear="none"></div><div dir="ltr">><br clear="none"></div><div dir="ltr">><br clear="none"></div><div dir="ltr">> What make of pump is best for VBT water transfer in/out for 250 psi <br clear="none"></div><div dir="ltr">> 1.5<br clear="none"></div><div dir="ltr">kw.<br clear="none"></div><div dir="ltr">><br clear="none"></div><div dir="ltr">> I am looking at a gear pump 1.5kw Oberdorfer 944 Bronze.? These are <br clear="none"></div><div dir="ltr">> only rated for 10 bar.? I tried an hydraulic gear pump 30cc where I <br clear="none"></div><div dir="ltr">> had a stainless and bronze gear set made up but the aluminium body <br clear="none"></div><div dir="ltr">> corroded form the trials and I just found that they had used steel <br clear="none"></div><div dir="ltr">> backed<br clear="none"></div><div dir="ltr">sleeve bearings.<br clear="none"></div><div dir="ltr">><br clear="none"></div><div dir="ltr">><br clear="none"></div><div dir="ltr">><br clear="none"></div><div dir="ltr">> Regards,<br clear="none"></div><div dir="ltr">><br clear="none"></div><div dir="ltr">> Hugh<br clear="none"></div><div dir="ltr">> _______________________________________________<br clear="none"></div><div dir="ltr">> Personal_Submersibles mailing list<br clear="none"></div><div dir="ltr">> <a shape="rect" href="mailto:Personal_Submersibles@psubs.org" rel="nofollow" target="_blank">Personal_Submersibles@psubs.org</a><br clear="none"></div><div dir="ltr">> <a shape="rect" href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" rel="nofollow" target="_blank">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a><br clear="none"></div><div dir="ltr">> _______________________________________________<br clear="none"></div><div dir="ltr">> Personal_Submersibles mailing list<br clear="none"></div><div dir="ltr">> <a shape="rect" href="mailto:Personal_Submersibles@psubs.org" rel="nofollow" target="_blank">Personal_Submersibles@psubs.org</a><br clear="none"></div><div dir="ltr">> <a shape="rect" href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" rel="nofollow" target="_blank">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a><br clear="none"></div><div dir="ltr">><br clear="none"></div><div dir="ltr">-------------- next part --------------<br clear="none"></div><div dir="ltr">An HTML attachment was scrubbed...<br clear="none"></div><div dir="ltr">URL:<br clear="none"></div><div dir="ltr"><<a shape="rect" href="http://www.whoweb.com/pipermail/personal_submersibles/attachments/20230816/" rel="nofollow" target="_blank">http://www.whoweb.com/pipermail/personal_submersibles/attachments/20230816/</a><br clear="none"></div><div dir="ltr">b5338913/attachment-0001.html><br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">------------------------------<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">Message: 3<br clear="none"></div><div dir="ltr">Date: Wed, 16 Aug 2023 15:20:44 +0000 (UTC)<br clear="none"></div><div dir="ltr">From: Jon Wallace via Personal_Submersibles ???<br clear="none"></div><div dir="ltr"><<a shape="rect" href="mailto:personal_submersibles@psubs.org" rel="nofollow" target="_blank">personal_submersibles@psubs.org</a>><br clear="none"></div><div dir="ltr">To: Personal Submersibles General Discussion ???<br clear="none"></div><div dir="ltr"><<a shape="rect" href="mailto:personal_submersibles@psubs.org" rel="nofollow" target="_blank">personal_submersibles@psubs.org</a>><br clear="none"></div><div dir="ltr">Subject: Re: [PSUBS-MAILIST] FW: VBT pump<br clear="none"></div><div dir="ltr">Message-ID: <<a shape="rect" href="mailto:1959084270.469930.1692199244774@mail.yahoo.com" rel="nofollow" target="_blank">1959084270.469930.1692199244774@mail.yahoo.com</a>><br clear="none"></div><div dir="ltr">Content-Type: text/plain; charset="utf-8"<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr"> I'll chime in here...I removed the VBT from the K600 because it was fairly<br clear="none"></div><div dir="ltr">well rusted inside and needed to be replaced, however I am planning on using<br clear="none"></div><div dir="ltr">the ballast/float method instead and forgoing the VBT altogether for many of<br clear="none"></div><div dir="ltr">the reasons Alec and Cliff cited.? I will say that it can be challenging to<br clear="none"></div><div dir="ltr">change ballast on-station since the weight/floatation has to be transferred<br clear="none"></div><div dir="ltr">somewhere and by somebody, however I see the K600 being trimmed for specific<br clear="none"></div><div dir="ltr">missions prior to launch and not being trimmed dynamically on-station to<br clear="none"></div><div dir="ltr">embark/disembark passengers or equipment.<br clear="none"></div><div dir="ltr">Jon<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">? ? On Wednesday, August 16, 2023 at 09:43:35 AM EDT, Alec Smyth via<br clear="none"></div><div dir="ltr">Personal_Submersibles <<a shape="rect" href="mailto:personal_submersibles@psubs.org" rel="nofollow" target="_blank">personal_submersibles@psubs.org</a>> wrote:? <br clear="none"></div><div dir="ltr"> <br clear="none"></div><div dir="ltr"> I second that (getting rid of VBT). I got rid of the VBT in my K250 years<br clear="none"></div><div dir="ltr">ago to make space and turn it into a 2-person and to try and to<br clear="none"></div><div dir="ltr">simplify,?and it worked so well I never thought of using?any other method on<br clear="none"></div><div dir="ltr">the current sub. The only difference with Cliff's method is that I add or<br clear="none"></div><div dir="ltr">remove floats, while he uses ballast. But either way, once you have a<br clear="none"></div><div dir="ltr">reference point for how much ballast/buoyancy you need for a given crew<br clear="none"></div><div dir="ltr">weight, you just make incremental changes and it never fails. You may be off<br clear="none"></div><div dir="ltr">neutral by just a few pounds, but if you have vertical thrusters they're<br clear="none"></div><div dir="ltr">usually just ticking over at slow RPMs to compensate.<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">Best,Alec<br clear="none"></div><div dir="ltr">On Wed, Aug 16, 2023 at 9:30?AM Cliff Redus via Personal_Submersibles<br clear="none"></div><div dir="ltr"><<a shape="rect" href="mailto:personal_submersibles@psubs.org" rel="nofollow" target="_blank">personal_submersibles@psubs.org</a>> wrote:<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr"> Hugh, on my original design for the R300 I had a hard VBT just aft of the<br clear="none"></div><div dir="ltr">pilot. At the time I had a small HPU in the boat.? My plan was to use a<br clear="none"></div><div dir="ltr">Oberdorfer Bronze gear pump driven by a small hydraulic motor to move water<br clear="none"></div><div dir="ltr">in and out of the VBT.? I don't remember the specs on the pump.? I had<br clear="none"></div><div dir="ltr">motorized ball valves on the vent and flood side of the VBT.? Prior to using<br clear="none"></div><div dir="ltr">this set up, I did some testing of this gear pump which I still have.? What<br clear="none"></div><div dir="ltr">I found was an unacceptable amount of flow slippage at my max design depth.?<br clear="none"></div><div dir="ltr">There was so much slippage that the pump could not blow the VBT at max<br clear="none"></div><div dir="ltr">depth.? At that point I abandoned using a pump and vent to blowing the VBT<br clear="none"></div><div dir="ltr">with air.? I eventually abandoned the VBT altogether for operability<br clear="none"></div><div dir="ltr">reasons.? When I used this hard VBT to get neutral on the surface, the<br clear="none"></div><div dir="ltr">pressure in the tank was low.? When at depth if I ever tried to use the VBT,<br clear="none"></div><div dir="ltr">water would rush in until the pressure equalized with ambient water<br clear="none"></div><div dir="ltr">pressure.? This made the boat nega!<br clear="none"></div><div dir="ltr"> tively buoyant until air was added.? The other thing that bugged me was I<br clear="none"></div><div dir="ltr">had a float style level sensor in the VBT.? The water level in the VBT was<br clear="none"></div><div dir="ltr">always moving around so you never trust the reading.? I eventually abandoned<br clear="none"></div><div dir="ltr">the VBT and now just add ballast at the boat CG where the VBT was located.?<br clear="none"></div><div dir="ltr">I find this works great.? The other issue is the VBT restricted access to<br clear="none"></div><div dir="ltr">equipment aft of the VBT so to work on any of this equipment, I had to<br clear="none"></div><div dir="ltr">remove the VBT.? ?All in all, I found the VBT to be a pain in butt.<br clear="none"></div><div dir="ltr">Cliff<br clear="none"></div><div dir="ltr">Oberdorfer 944 Bronze<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">? ? On Sunday, August 13, 2023 at 04:57:24 PM CDT, via Personal_Submersibles<br clear="none"></div><div dir="ltr"><<a shape="rect" href="mailto:personal_submersibles@psubs.org" rel="nofollow" target="_blank">personal_submersibles@psubs.org</a>> wrote:? <br clear="none"></div><div dir="ltr"> <br clear="none"></div><div dir="ltr"> <br clear="none"></div><div dir="ltr">Hi Guys<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr"> ?<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">What make of pump is best for VBT water transfer in/out for 250 psi 1.5 kw.<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">I am looking at a gear pump 1.5kw Oberdorfer 944 Bronze.? These are only<br clear="none"></div><div dir="ltr">rated for 10 bar.? I tried an hydraulic gear pump 30cc where I had a<br clear="none"></div><div dir="ltr">stainless and bronze gear set made up but the aluminium body corroded form<br clear="none"></div><div dir="ltr">the trials and I just found that they had used steel backed sleeve bearings.<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr"> ?<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">Regards,<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">Hugh<br clear="none"></div><div dir="ltr">_______________________________________________<br clear="none"></div><div dir="ltr">Personal_Submersibles mailing list<br clear="none"></div><div dir="ltr"><a shape="rect" href="mailto:Personal_Submersibles@psubs.org" rel="nofollow" target="_blank">Personal_Submersibles@psubs.org</a><br clear="none"></div><div dir="ltr"><a shape="rect" href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" rel="nofollow" target="_blank">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a><br clear="none"></div><div dir="ltr">? _______________________________________________<br clear="none"></div><div dir="ltr">Personal_Submersibles mailing list<br clear="none"></div><div dir="ltr"><a shape="rect" href="mailto:Personal_Submersibles@psubs.org" rel="nofollow" target="_blank">Personal_Submersibles@psubs.org</a><br clear="none"></div><div dir="ltr"><a shape="rect" href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" rel="nofollow" target="_blank">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a><br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">_______________________________________________<br clear="none"></div><div dir="ltr">Personal_Submersibles mailing list<br clear="none"></div><div dir="ltr"><a shape="rect" href="mailto:Personal_Submersibles@psubs.org" rel="nofollow" target="_blank">Personal_Submersibles@psubs.org</a><br clear="none"></div><div dir="ltr"><a shape="rect" href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" rel="nofollow" target="_blank">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a><br clear="none"></div><div dir="ltr">? <br clear="none"></div><div dir="ltr">-------------- next part --------------<br clear="none"></div><div dir="ltr">An HTML attachment was scrubbed...<br clear="none"></div><div dir="ltr">URL:<br clear="none"></div><div dir="ltr"><<a shape="rect" href="http://www.whoweb.com/pipermail/personal_submersibles/attachments/20230816/" rel="nofollow" target="_blank">http://www.whoweb.com/pipermail/personal_submersibles/attachments/20230816/</a><br clear="none"></div><div dir="ltr">301b6d76/attachment.html><br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">------------------------------<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">Subject: Digest Footer<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">_______________________________________________<br clear="none"></div><div dir="ltr">Personal_Submersibles mailing list<br clear="none"></div><div dir="ltr"><a shape="rect" href="mailto:Personal_Submersibles@psubs.org" rel="nofollow" target="_blank">Personal_Submersibles@psubs.org</a><br clear="none"></div><div dir="ltr"><a shape="rect" href="http://www.whoweb.com/mailman/listinfo.cgi/personal_submersibles" rel="nofollow" target="_blank">http://www.whoweb.com/mailman/listinfo.cgi/personal_submersibles</a><br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">------------------------------<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">End of Personal_Submersibles Digest, Vol 120, Issue 36<br clear="none"></div><div dir="ltr">******************************************************<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">_______________________________________________<br clear="none"></div><div dir="ltr">Personal_Submersibles mailing list<br clear="none"></div><div dir="ltr"><a shape="rect" href="mailto:Personal_Submersibles@psubs.org" rel="nofollow" target="_blank">Personal_Submersibles@psubs.org</a><br clear="none"></div><div dir="ltr"><a shape="rect" href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" rel="nofollow" target="_blank">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a><br clear="none"></div><div dir="ltr"> <br clear="none"></div><div dir="ltr">-------------- next part --------------<br clear="none"></div><div dir="ltr">An HTML attachment was scrubbed...<br clear="none"></div><div dir="ltr">URL:<br clear="none"></div><div dir="ltr"><<a shape="rect" href="http://www.whoweb.com/pipermail/personal_submersibles/attachments/20230817/" rel="nofollow" target="_blank">http://www.whoweb.com/pipermail/personal_submersibles/attachments/20230817/</a><br clear="none"></div><div dir="ltr">b598be5b/attachment.html><br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">------------------------------<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">Subject: Digest Footer<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">_______________________________________________<br clear="none"></div><div dir="ltr">Personal_Submersibles mailing list<br clear="none"></div><div dir="ltr"><a shape="rect" href="mailto:Personal_Submersibles@psubs.org" rel="nofollow" target="_blank">Personal_Submersibles@psubs.org</a><br clear="none"></div><div dir="ltr"><a shape="rect" href="http://www.whoweb.com/mailman/listinfo.cgi/personal_submersibles" rel="nofollow" target="_blank">http://www.whoweb.com/mailman/listinfo.cgi/personal_submersibles</a><br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">------------------------------<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">End of Personal_Submersibles Digest, Vol 120, Issue 40<br clear="none"></div><div dir="ltr">******************************************************<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">_______________________________________________<br clear="none"></div><div dir="ltr">Personal_Submersibles mailing list<br clear="none"></div><div dir="ltr"><a shape="rect" href="mailto:Personal_Submersibles@psubs.org" rel="nofollow" target="_blank">Personal_Submersibles@psubs.org</a><br clear="none"></div><div dir="ltr"><a shape="rect" href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" rel="nofollow" target="_blank">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a><br clear="none"></div></div>
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