Maybe an ROV would be a better alternative . > [Original Message] > From: Alan James <alanjames@xtra.co.nz> > To: <personal_submersibles@psubs.org> > Date: 7/4/2010 6:11:58 PM > Subject: Re: [PSUBS-MAILIST] K250 to K400 modification > > Hi Carsten, > Firstly it looks like it could be a Germany - Netherlands final. > NewZealand could be the only unbeaten team in the world cup! > Re the buoyancy issue-- You would have to go down heavy & > use your thrusters as you could always add air to become more > buoyant, but if you emptied 10 x 90 cubic ft tanks to equalize your > hull this would make you about 100 lb lighter by the time you > expelled the air coming to the surface. > ( a scuba tank is about 10lb lighter when empty ). > > >>>By the way what shall a K250 do in 400ft on a stricken sub? > > Maybe offer moral support. Assess the situation. > Or take a grapnel down & hook it on the sub. > Or locate it for some tech divers. > Alan > > > > ----- Original Message ----- > From: <MerlinSub@t-online.de> > To: <personal_submersibles@psubs.org> > Sent: Sunday, July 04, 2010 11:23 PM > Subject: Re: [PSUBS-MAILIST] K250 to K400 modification > > > > Hi Alan - In General you can go that way. > > A sub designed for 150 ft max dive deepth can double there operation depth > with that way. > > The only real problem is if the boat is in this condition and you pop up > (surface fast). > > There are two possible failtures: > > - Overpressure vale to small and hatch and windows pop out. > > - Over pressure vale has the right huge size and crew gets heavy > decrompression tickness, blown ears etc.. > > - In case of a fire or anything else in the sub - you can not surface in > short time and probably get problems in it. > > We discuss this way some years ago but never go this way. > Its a way only for crew with real expierence with there sub and also real > scuba divers with expierence with decompression dives. > > If you double the cabin pressure just with air this means you double the > amount of o2 atoms per volume. > The fire risk increase.. If you increase the pressure with helium this will > work. The problem starts than when you lower later the pressure - you have > to feed o2 back. > > By the way what shall a K250 do in 400ft on a stricken sub? > > vbr Carsten > > > "Alan James" <alanjames@xtra.co.nz> schrieb: > > Hi Jon, > > The emergency I was thinking of was along the lines of > > a stricken sub entangled at 400ft & the nearest help was > > a sub capable of 250ft depth. > > Alan > > ----- Original Message ----- > > From: Jon Wallace > > To: personal_submersibles@psubs.org > > Sent: Sunday, July 04, 2010 5:41 PM > > Subject: Re: [PSUBS-MAILIST] K250 to K400 modification > > > > > > > > Sorry Alan, I missed the "emergency situation" part. So yes, in an > > emergency where you are > > sinking in water beyond your normal operating depth you could certainly > > counter some amount of > > outside pressure by increasing the pressure within. That may delay > > (possibly prevent depending > > upon depth) hull failure but of course has the potential for some other > > nasty biological side > > effects and I'm guessing in such an emergency you're probably going to be > > at the increased ambient > > depth well beyond no-decompression limits. We had a similar discussion a > > few years ago about > > standardizing on a specific valve so that divers could feed air into the > > cabin of disabled sub that > > did not have life support capability, until that sub could be raised. I > > believe the discussion > > started with "schrader" valves (tire valves) which were determined to be > > too small to be useful. > > Many of the same issues were raised at that time ie...decompression upon > > surfacing, additional > > pressure in the cabin affecting instruments, etc. > > > > Jon > > > > > > On 7/4/2010 12:29 AM, Alan James wrote: > > Thanks Hugh & Jon for the vote of confidance. > > I did qualify this with " In an emergency situation". I think I have > > been misunderstood. > > You take your sub down to its 250ft limit with several extra dive > > tanks on board. > > At this point the outside of your hull is experiencing round 125psi. > > For every 33ft further you go down you add 14.7psi. The hull would > > always be experiencing > > 125psi from the outside as the pressure you're adding would be > > countering the additional > > pressure from additional depth. > > So no pressure as such from the inside would be pushing your view > > ports out. > > The reason I said to increase the O2 flow into the hull is the > > "bellows add" system based on > > sensing a drop in pressure wouldn't work. In that system the O2 flow > > is set below the users > > normal O2 consumption & then topped up from the bellows add system > > because if the O2 > > was set too high there would be a continual pressure build up & 02 % > > increase. > > You could safely bump up the O2 a tad as it would be safer to have too > > much O2 than not > > enough. This, as Jon said wouldn't matter much because your time would > > be constrained by > > decompression tables, & there would be enough air in the hull to > > breath from. > > So in a life or death emergency you could take several air tanks into > > your hull & a set of > > dive timetables, open the tanks by hand at the 250ft mark & go to > > 400ft. > > Alan > > > > > > > > > > > > > ************************************************************************ > ************************************************************************ > ************************************************************************ > The personal submersibles mailing list complies with the US Federal > CAN-SPAM Act of 2003. 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