+ Reply to Thread
Page 1 of 2 1 2 LastLast
Results 1 to 10 of 12

Thread: First CCR dive impressions on Poseidon MkVI

  1. #1
    RBW Member alpine44 is on a distinguished road alpine44 is on a distinguished road alpine44's Avatar
    Join Date
    Jun 2010
    Location
    New England / Maryland
    Posts
    87

    First CCR dive impressions on Poseidon MkVI

    Greetings,

    As an introduction, I would like to share my first eCCR dive on a Poseidon MkVI at Dutch Springs, PA.

    First, some background about myself. I had no previous experience with rebreathers and only dive since August of 2010 (48 dives total). I have AOW certification through SSI, took GUE Fundies in February, and currently dive DIR double-tank rigs in New England and Pennsylvania as much as time allows. My long-term goal is full cave certification.

    Professional background is engineering; first mechanical, then firmware for IVD devices, now software for renal care. I hold a commercial pilot license with instrument and seaplane rating and frequently work on airplanes for restoration and/or regular maintenance.

    In summary, I would describe myself as a novice diver with strong technical aptitude and intense focus on safety and grace underwater.

    Random Impressions during the briefing for the MkVI:

    · I like the way the unit is designed and manufactured; clean and compact.
    · Pre-packed scrubber is a good idea and almost a must for the recreational market.
    · Blowing diluent and Oxygen across the two O2 sensors for continuous validation of their health is a smart idea.
    · The display 'paddle' is an ergonomic nightmare despite the nice way it presents important information. This needs to become a compact, fore-arm mounted unit with less wasted surface around the LCD.
    · Chest mounted counter lungs are occupying real estate that some divers need and cherish.
    · Can this thing be mounted on a backplate? (Answer: yes)
    · Much lighter than doubles while having more dive time in it - sweet.

    Pre-dive weighing:

    I was in a DUI cf200 with 400g/m2 undergarments and put 20 pound of lead in the Poseidon weight pockets. 17 pound of negative gear buoyancy is enough when I dive OC in that suit but I was still way too light to descend with the MkVI. In the interest of time, the instructor suggested that I use the old "head down and legs in the air" trick to get down and down we went.

    First dive, Saturday May 28:

    While descending, I immediately realized that my lungs are out of the buoyancy equation and I needed to slow down the descent rather quickly with wing and drysuit inflation. At the 25' platform it became even more apparent that my usual buoyancy control was gone for good. With OC gear, I can hold +-6 inches while 'hanging' still in perfectly horizontal trim. On the CCR, I had to work the wing inflator like a trumpet player to hold even +- 3 feet.

    Another annoyance on the MkVI is that the wing inflator hose is rather long and not captured in the chest area. I forgot how many times I had to frantically 'hunt' for this thing. It should be constrained at mid length similar to what the little bungee on the left HOG harness strap does.

    However, the weight and buoyancy distribution of the unit with the recreational BC was surprisingly good and it took little effort to maintain horizontal trim. When I tried some helicopter turns and back-kicks it became apparent that the unit was way too loose on me and wobbled around. I tried to tighten-up the straps but with dry gloves and encumbered by the counter-lungs that idea did not go anywhere soon and I finally left the unit in wobble mode.

    The sensation of making no bubbles and no noise was great. However, the breathing felt laborious, like out of a really bad regulator. I was also frequently bottoming out the lungs and had to trigger the ADV. The ADV function is served by the bailout regulator that is detuned but connected in the closed circuit position. I think that it is a slick idea to eliminate one additional component but that reg needs to be better tuned in both the OC and CC position (I admit, that I am spoiled by diving SP G250s horizontally; even breathing them on the surface in a vertical position now feels annoying).

    To increase the loop volume, you either suck really hard and trigger the BO reg or you block the mouthpiece with the tongue and hit the purge button on the BO reg. The latter is tricky as the button is hard to press and very touchy; you either get nothing or you 'drink' diluent out of a fire hose. This needs refinement too, IMO.

    Getting tired sucking air into the loop and moving it around, I thumbed the dive, switched the BOV to OC and ascended slowly. On the debrief, the instructor mentioned that he saw gas bubbling from the OPV mounted on the right counterlung. That explained why I needed to constantly add diluent but why the gas escaped out of the OPV was still a mystery.

    My feeling after the first dive was that the 'no bubble factor' is cool but that everything else was harder and/or more tedious on a rebreather. I was not really sold on the whole idea.

    In the evening, I surfed the net and got some clues about loop volume, how to control it, etc. and decided to give it another try the next day.

    Second dive, Sunday May 29:

    Armed with more knowledge and understanding about rebreather diving, the second dive was a blast.

    The fact that the weight pockets would not hold much more lead than I carried on the previous dive was solved with minimizing the loop volume by exhaling through the nose. That allowed me to hover at the entry platform and to descend normally.

    While descending, I increased the loop volume by sucking against the ADV. That required less compensation with the wing/drysuit but I was still descending more rapidly than in OC unless I added gas more frequently. At the 25' platform, I noticed that gas would escape out of the OPV if I would slightly pitch head down from horizontal or ever so slightly roll to the left. I cannot verify this with photos, but I think that due to their buoyancy the lower ends of the counterlung were actually riding up on the sides of my chest. This was possible since the harness was still way too loose. I tightened the OPV slightly and that solved the previously unexplainable diluent loss.

    By breathing consciously more like on land - shallow but constantly - the WOB decreased substantially (On OC, I do somewhat brisk Out/In gas exchanges with pauses in between). Again, 'the sound of silence' was music to my ears.

    I achieved a modicum of buoyancy control by running the loop at the lower third of the volume and exhaling through the nose to get down or triggering the ADV with a deep inhale to get up in the water column. While the safety divers commentend later on how comfortable that looked to them, I am still far away on what I can pull off on OC.

    Nice trim was as easy as on the day before. The drag while frog kicking felt similar to my AL80 doubles; maybe a tiny bit worse.

    Unfortunately, the day came to an end before the gas supply was exhausted and I left the water not only alive but smiling from ear to ear.

    In summary, I am hooked on diving a 'bubble-less box of death' and am thinking about designing my own DIR compatible 'breather. Either a smaller version of the Halcyon PASCR (to be called RB40) or a mCCR with an ADV 'in your face' like on the MkVI BOV. I am envisioning a rather large diluent capacity to allow a gas-sharing ascent on OC and may use off-board Oxygen to facilitate that. This unit would be an alternative for deeper wreck dives where the bottom gas capacity of doubles would require stages. It would also reduce the amount of steel and/or aluminum that needs to be lugged to and stored on a boat for multiple dives.

    (Related to the last subject: Does anyone know the outer diameter of the HH body?)
    Last edited by alpine44; 3rd June 2011 at 21:12.

  2. #2
    LEARNING CONTINUALLY rigdiver is a jewel in the rough rigdiver is a jewel in the rough rigdiver is a jewel in the rough rigdiver is a jewel in the rough rigdiver is a jewel in the rough rigdiver is a jewel in the rough rigdiver is a jewel in the rough rigdiver is a jewel in the rough rigdiver's Avatar
    Join Date
    Mar 2005
    Location
    S.E. TEXAS
    Posts
    771
    Inspo Vision

    Classic YBOD

    Re: First CCR dive impressions on Poseidon MkVI

    Welcome and thanks for sharing. The "buoyancy thing" takes a few dives to master. It really pisses some people off initially. Good luck.

  3. #3
    Richie Burr diverreb has much to be proud of diverreb has much to be proud of diverreb has much to be proud of diverreb has much to be proud of diverreb has much to be proud of diverreb has much to be proud of diverreb has much to be proud of diverreb has much to be proud of diverreb has much to be proud of diverreb has much to be proud of diverreb has much to be proud of diverreb's Avatar
    Join Date
    Mar 2007
    Location
    Dover, DE
    Posts
    1,487
    O2ptima FX

    Re: First CCR dive impressions on Poseidon MkVI

    As a quick FYI, short shallow breathing isn't a good idea on a Breather. It allows for CO2 build up, which can bite you in the ass on a dive.

    Richie

  4. #4
    Reads fine print (mostly) Skipbreather has a brilliant future Skipbreather has a brilliant future Skipbreather has a brilliant future Skipbreather has a brilliant future Skipbreather has a brilliant future Skipbreather has a brilliant future Skipbreather has a brilliant future Skipbreather has a brilliant future Skipbreather has a brilliant future Skipbreather has a brilliant future Skipbreather has a brilliant future Skipbreather's Avatar
    Join Date
    Mar 2005
    Location
    Chicago, Illinois, USA
    Posts
    1,327
    MEGALODON MK15.5

    BMR500 IDA71 IDA64 RGUFM AKA60

    Re: First CCR dive impressions on Poseidon MkVI

    Welcome to the board- you’ll find the ‘good input to flame ratio’ here is far better than most places.

    Glad you enjoyed your try-dives. Some of the difficulties you had (like relearning buoyancy) are broadly CCR applicable and some were unit specific and have been much discussed here- especially the lack of manual gas addition valves on the MK VI. It was good you took a second bite at the apple & improved your overall impression.

    You’ve been diving a lot but still less than a year. Here you'll encounter some folks with literally 1000's of CCR dives- each. If your plan is to eventually do deep dives- cave or otherwise- there are other CCR attributes you’ll eventually come to appreciate as well. Chief among them is gas economy in multiple ways.

    One gas economy: Sane deep diving requires helium in the mix. With a CCR, I can dive all season on probably less helium ($$$) than an OC diver uses on one 100 m dive.

    Another: Operational use. Deep OC the clock & gas use are always ticking. On CCR we use so little gas that we have the luxury of TIME to more thoroughly think thru difficulties encountered at depth.

    Another: On extended trips the gas logistics are ENORMOUSLY simplified.

    On designing your own: Walk before you run. Do try dives on several other units- Hammerhead, KISS, rEvo & Meg demos should be easy enough to come by in your area. Pick a rig- used is fine. Take a course, dive it for a year. You WILL have some major re orientations over what you think is important, and what is not. Your back-of-the-mind design will constantly evolve. Like you I am a hard core homebuilder. I’m both a ME and a professional ATP. I’ve built everything from my own airplane (even designing & carving my own propellers) to dive gear. Right now you simply don’t know what you don’t know. Time & a bit of in-water experience will cure that soon enough.

    Enjoy the bubbleless ride!

    Best,
    Ken

  5. #5
    Mostly cold ChrisBrown has a reputation beyond repute ChrisBrown has a reputation beyond repute ChrisBrown has a reputation beyond repute ChrisBrown has a reputation beyond repute ChrisBrown has a reputation beyond repute ChrisBrown has a reputation beyond repute ChrisBrown has a reputation beyond repute ChrisBrown has a reputation beyond repute ChrisBrown has a reputation beyond repute ChrisBrown has a reputation beyond repute ChrisBrown has a reputation beyond repute ChrisBrown's Avatar
    Join Date
    Jan 2008
    Location
    England
    Posts
    1,742
    Evo+, Pos MKVI, Sentinel

    rEvo II & III Minis & Micros

    Re: First CCR dive impressions on Poseidon MkVI

    Glad you enjoyed it!

    One point though - its not really instantly mountable on a backplate. Unless they just changed it?

    It has a proprietary rail that fits Poseidon BC's. The bolts are not standard backplate distance apart. This means you have to machine one yourself or buy a 3rd party one.

    PITA, hopefully this will get addressed if it hasnt been already.

  6. #6
    plays with fire RedSeaDiver is a glorious beacon of light RedSeaDiver is a glorious beacon of light RedSeaDiver is a glorious beacon of light RedSeaDiver is a glorious beacon of light RedSeaDiver is a glorious beacon of light RedSeaDiver is a glorious beacon of light RedSeaDiver is a glorious beacon of light RedSeaDiver is a glorious beacon of light RedSeaDiver is a glorious beacon of light RedSeaDiver is a glorious beacon of light RedSeaDiver is a glorious beacon of light RedSeaDiver's Avatar
    Join Date
    Sep 2007
    Location
    in the Aussie outback
    Posts
    789
    modified Poseidon Discovery

    Re: First CCR dive impressions on Poseidon MkVI

    Quote Originally Posted by Chris at Silent World  View Original Post
    Glad you enjoyed it!

    One point though - its not really instantly mountable on a backplate. Unless they just changed it?

    It has a proprietary rail that fits Poseidon BC's. The bolts are not standard backplate distance apart. This means you have to machine one yourself or buy a 3rd party one.

    PITA, hopefully this will get addressed if it hasnt been already.
    They have just released an adaptor for it that allows mounting on standard backplates.

  7. #7
    Mostly cold ChrisBrown has a reputation beyond repute ChrisBrown has a reputation beyond repute ChrisBrown has a reputation beyond repute ChrisBrown has a reputation beyond repute ChrisBrown has a reputation beyond repute ChrisBrown has a reputation beyond repute ChrisBrown has a reputation beyond repute ChrisBrown has a reputation beyond repute ChrisBrown has a reputation beyond repute ChrisBrown has a reputation beyond repute ChrisBrown has a reputation beyond repute ChrisBrown's Avatar
    Join Date
    Jan 2008
    Location
    England
    Posts
    1,742
    Evo+, Pos MKVI, Sentinel

    rEvo II & III Minis & Micros

    Re: First CCR dive impressions on Poseidon MkVI

    Quote Originally Posted by RedSeaDiver  View Original Post
    They have just released an adaptor for it that allows mounting on standard backplates.
    Is it shipping with the unit? Havent seen it on any over here in the US

  8. #8
    RBW Member alpine44 is on a distinguished road alpine44 is on a distinguished road alpine44's Avatar
    Join Date
    Jun 2010
    Location
    New England / Maryland
    Posts
    87

    Re: First CCR dive impressions on Poseidon MkVI

    Thanks for all replies and suggestions.

    Someone was asking about the reference I made to the Hogarthian harness and how the wing inflator hose is dealt with there. I posted a short Youtube clip .

    "This shows how the wing inflator hose is captured on a Hogarthian rig by a small bungee threaded through the same triglide that positions the left upper D-ring (Someone on rebreatherworld.com was asking for this).

    By being in a defined position, the inflator/deflator can be found instantly; yet the bungee allows the hose to be held up for dumping gas out of the wing.

    On chest-mounted counterlungs, this loop could be wrapped around the counterlung and held by a triglide on the harness underneath. The bungee will prevent the inflator hose from disappearing behind the shoulder.


    Of course, the length of the bungee needs to be sufficient for full inflation of the counterlung."


    Hope that helps.
    Last edited by alpine44; 6th June 2011 at 00:14.

  9. #9
    plays with fire RedSeaDiver is a glorious beacon of light RedSeaDiver is a glorious beacon of light RedSeaDiver is a glorious beacon of light RedSeaDiver is a glorious beacon of light RedSeaDiver is a glorious beacon of light RedSeaDiver is a glorious beacon of light RedSeaDiver is a glorious beacon of light RedSeaDiver is a glorious beacon of light RedSeaDiver is a glorious beacon of light RedSeaDiver is a glorious beacon of light RedSeaDiver is a glorious beacon of light RedSeaDiver's Avatar
    Join Date
    Sep 2007
    Location
    in the Aussie outback
    Posts
    789
    modified Poseidon Discovery

    Re: First CCR dive impressions on Poseidon MkVI

    Quote Originally Posted by Chris at Silent World  View Original Post
    Is it shipping with the unit? Havent seen it on any over here in the US
    I'm not sure - it's only been available for a few weeks. Might be best to contact Poseidon USA - if they don't know about it then get them to contact Poseidon Sweden because it definitely exists - I've seen photos of it.

  10. #10
    All IMVHO obviously... Ben Field has a reputation beyond repute Ben Field has a reputation beyond repute Ben Field has a reputation beyond repute Ben Field has a reputation beyond repute Ben Field has a reputation beyond repute Ben Field has a reputation beyond repute Ben Field has a reputation beyond repute Ben Field has a reputation beyond repute Ben Field has a reputation beyond repute Ben Field has a reputation beyond repute Ben Field has a reputation beyond repute Ben Field's Avatar
    Join Date
    Aug 2005
    Location
    Weymouth, England
    Posts
    3,023
    NVMCCR Inspiration

    Classic KISS, Sport KISS

    Re: First CCR dive impressions on Poseidon MkVI

    Hiya,

    Thanks for posting your thoughts.

    If you don't mind can I make a couple of observations in reference to the quote below-
    Quote Originally Posted by alpine44  View Original Post
    First, some background about myself. I had no previous experience with rebreathers and only dive since August of 2010 (48 dives total).

    · I like the way the unit is designed and manufactured; clean and compact.
    Please take a look at some other units- the MkVI is a total mess when assembled, hoses and cables all over the place! (Not that dissimilar to many other units) but far worse than some.
    If any unit required a cover to reduce the vast entanglement and damage potential its the MkVI.

    Quote Originally Posted by alpine44  View Original Post
    · Pre-packed scrubber is a good idea and almost a must for the recreational market.
    Sorry, this is simpoly incorrect. Until recently almost no units had pre-packed scrubbers and the total incidence or problems from this area is minimal. Packing a scrubber is very simple and the move to prepacked is purely (IMO) for legal reasons and has little practical benefit to the diver and is putting off customers due to the high cost.


    Lastly- while you found it difficult a nice tight ADV is highly desirable (some divers/units even turn the ADV off!) it is a very solid physical indicator that your loop volume has decreased/you've descended or you have an issue- in your case with training you'd likely have noted and solved the OPV issue yourself. CCR divers are gas-misers, using the ADV when not planning to is something we avoid

+ Reply to Thread
Page 1 of 2 1 2 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts