Hi Vance, allright :-) I prefer for a small psub say for 2-3 people with a diver exit hatch that the sub is at anchor or on legs. I decide for my boat that anchor will be better because legs catch a lot of drag and if the tide switch - the boat is maybe in the wrong direction - and get the currents from the side for example. I think a good (!) anchor system will be better in currents. The boat swings in the right direction like a airship on a mast. But you are absolut right: The system is better if the anchor is heavier and the hard tank bigger. So a psub designed for look out mission at anchor should have two drop weights - one in the bow (the anchor and chain) and the other in the stern area to release. Say 20 % of this psubs weight is ballast weight - that means in Kraka 7 tons size that 1,4 ts ballast or a 700 kg (abt.1500 pound) for the maximum anchor size. If this boat has filled his anchor-compensating-tank (in general the forward hard tank) with 350 KG additional water it needs 350 Kg force in one or the other direction - a lot for a tiny small 7ts boat. Ps.: Euronauts anchor and the chain is designed to be drop in emergency also. best regards Carsten <vbra676539@aol.com> schrieb: > Carsten, > > Yes, of course it works. Most diving bells and ARMS bells operate this way. They have a clump weight on a wire/winch arangement, which can be set on the bottom. Then a winch can run the bell up or down from underneath for fine adjustment. The bell is strongly positive above the clump, so that divers and equipment leaving the bell do not affect its position. Or, they ballast heavy and hang on their tether at a predetermined depth. Your drawing is a version of the former, except bells don't use VBT systems. In addition, the clump weight on bells runs about ten to twenty per cent of displacement (ie., approaching a ton) which would be quite a load for a free swimming, psub style submersible. > > The comment about X-boats is invalidated by history. Modern lockout boats were 8 to 20+ tons all up, depending on the vehicle. Deep Diver, the originator of modern lockout diving (with proper credos to Simon Lake) weighed 8.25 tons originally and Taurus, the largest, weighs 24 tons. The X-craft weighed 27-tons, and were a testament to their designers, builders and operators. When you get that heavy, the vessel is substantially less prone to abrupt vertical transients due to what must be considered minor trim changes compared to overall displacement. Plus, the X-craft flooded the dive chamber, transferring trim water to do so and keeping the whole thing internal, an important consideration for their mission profile. There was no much of a safe haven there for the divers, who drowned with alarming regularity both in training and on the job, or surfaced and had their heads shot off. The real issue was stealth, and they went to great lengths to achieve it. > > Luckily, we don't have the Tirpitz to worry about anymore. And, our preferences these days is for a dry chamber. The Brits couldn't use that because to do so would require the release of large volumes of air while venting to atmospheric pressure. Stealthy mid-water submersibles would raise the Navy and Republican ire in this country, too, as they are likely to take a dim view of anyone sneaking under their battleships. > > Vance > > > > > > > > -----Original Message----- > From: MerlinSub@t-online.de > To: personal_submersibles@psubs.org > Sent: Sat, 26 May 2007 11:59 am > Subject: Re: [PSUBS-MAILIST] Diver lockout VBT > > > > I made a drawing to explain my words.. > www.euronaut.org/content/upload/notes/AnchorandExit001.jpg > Note - I study the x-craft > X-craft have many troubles - mostly electric. > ut the diver exit in mid water works. > :-) best regards Carsten > > MerlinSub@t-online.de> schrieb: > I forgot something. The trunk is below the hatch. I can close the hatch with a > ry chamber any time. Dosen't matter how the waterlevel in the trunk is. > > Anchor underwater is simple - just make the boats forward hard tank heavy with > he weight of the anchor. Euronauts anchor is a simple lead bell with 488 pound. > > Boat is than still neutral but anchor is than with 488 pounds in the mud.. > Realy havy currents are may a problem. > > best regards Carsten > > > <MerlinSub@t-online.de> schrieb: > > Gentlemens.. > > > > The diver exit on Euronaut is on the bottom of the diver chamber. > > And has a exit trunk below it. > > > > If a diver has ready to dive a density of say 1 - there is no compensating > ystem required except this trunk. > > > > Say volume of the diver is 1 something and remaining air volume of the > hamber is 10 something. Air pressure is equal to outside pressure and hatch is > pen. > > > > If the Diver leave the chamber the free air volume in the chamber increase > o 11 - right ? - But that means that the air or gas pressure goes down - and > he water from outside climb a little into the trunk until the chamber volume > ithout the diver is back to 10 - right ? > > > > The water which climbs into the short trunk has also a density of 1 - > ecause the diver is neutral in the water - so boat is allways compensate. > > > > Euronaut trunk is such high that three divers can leave the chamber before > ater climb into the chamber.. > > > > Keep it simple.. :-) > > > > The chain is only there to compensate small differences in water density and > emperature and other small items to compensate - not to compensate a diver exit > > > > > The boat is on anchor during diver exit about one divers high over the > eabottom - The anchor is 400 pounds heavy.. and the hardtank on top of the > nchor system is flooded to this 400 pound to make the anchor 400 pound heavy. > > > > best regards Carsten > > > > > > "irox" <irox@ix.netcom.com> schrieb: > > > > > > I don't think 170-200lbs object leaving the sub would be > > > negligible, the sub would float off with out it. Carsten > > > suggested a neat way of dealing with that, having a heavy > > > chain resting on the sea floor attached to the sub, when I > > > diver gets out, the sub gets lighter and lifts a link or two > > > off the sea bed. Search the archives for Carsten's original > > > email about this system. > > > > > > Cheers, > > > Ian. > > > > > > -----Original Message----- > > > >From: Rob Bryan <Sundiver2000@earthlink.net> > > > >Sent: May 25, 2007 12:46 PM > > > >To: personal_submersibles@psubs.org, underseacolonies@yahoogroups.com > > > >Subject: [PSUBS-MAILIST] Diver lockout VBT > > > > > > > >I've no experience with sub lockouts. I would think lockouts while > > > >hovering would be very difficult and dangerous, so assuming sitting on > > > >the bottom... > > > > > > > >Getting in and out of a vertical hatch with gear on is quite a task, > > > >whether scuba or line (with a bailout). In dive bell lockouts, the bell > > > >is flooded a little to make it easier. Wouldn't you do that in a sub > > > >lock out? So if the lock was 48" in diameter and you only flooded it up > > > >a foot, that would be 800 lbs. The diver leaving would be negligible, > > > >no? (this doesn't even include any trunk volume). Is this actually a > > > >problem? > > > >Rob B > > > > > > > >ShellyDalg@aol.com wrote: > > > >> Hi. This is in response to the diver weight compensation question. > > > >> Every dive trip in your sub requires careful measurement of what you > > > >> bring on-board. > > > >> If the dive plan calls for a diver to exit the sub while at depth, I > > > >> would think that it would be better to add buoyancy to cover the > > > >> divers extra weight while on-board, and then dump that buoyancy ( air > > > >> bubble ) when the diver exits the sub, there-by maintaining neutral > > > >> buoyancy while the diver is outside. > > > >> When the diver is back on-board, blow the required amount of air back > > > >> into the trim tank ( a measured amount of water to compensate for > > > >> exactly how much the diver weighs ) and again maintaining neutral > > > >> buoyancy. > > > >> A sub with a diver lock-out function would need a bigger trim tank > > > >> than a sub without that capability. > > > >> Don't forget to calculate how much air the diver displaces with his > > > >> body, as this will figure into the required additional buoyancy too. > > > >> You don't need a separate pump system, nor would that be desirable, to > > > >> let a diver exit and re-enter the sub. The lock-out chamber is > > > >> controlled by air pressure, and any small amount of water that > > > >> remained within would be easily compensated for by the additional trim > > > >> tank volume. > > > >> You WILL need some means of dumping the air from the lock-out chamber > > > >> once the water is blown out and the hatch is closed so the diver is > > > >> once again at one atmosphere. This needs to be monitored closely so a > > > >> diver has time to dump the excess nitrogen absorbed by his body > > > >> tissues and blood. A diver lock-out chamber is really much like a > > > >> de-compression chamber, but is located inside another chamber ( the > > > >> sub's pressure hull ) so a compressor to drive out the additional air > > > >> is required. > > > >> Frank D. > > > >> > > > >> > > > >> > > > >> ------------------------------------------------------------------------ > > > >> See what's free at AOL.com > > > >> <http://www.aol.com?ncid=AOLAOF00020000000503>. > > > > > > > > > > > > > > > >************************************************************************ > > > >************************************************************************ > > > >************************************************************************ > > > >The personal submersibles mailing list complies with the US Federal > > > >CAN-SPAM Act of 2003. 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