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  • An Interview with the XCR Rebreather developer - Mr. Phi Le

    by Andrew Rowley

    I have been lucky enough to sit down with Phi Le (via email) and ask him about his experience and what brought him to his design idea for the XCR rebreather. Phi has a colorful background diving on multiple rebreather platforms; he has designed the “Decoweenie” application for Palm Pilots, and is part of the “test group” for Juergensen Marine. To add to the excitement he dives in some of the more interesting and remote places compared to U.S. divers. Recently, he returned from a trip to the Maldives Islands in the Indian Ocean. I would like to welcome my guest Mr. Phi Le.

    (AR) Phi, when you were taking your first rebreather class did you ever think that you would be so involved with the development of so many different rebreather applications?

    (PL) Hi Andrew, to be honest, I never had any idea that I would even be diving another RB when I took my first RB course 6 years ago.

    (AR) What was the first rebreather that you saw and influenced you the most?

    (PL) The first RB that I knew anything about was the Halcyon PVR-BASC which now I passionately call the “Fridge” for its massive size. At the time, I was very impressed with the DIR concept as well as the ideal of a mechanically-driven SCR instead of an electronic-driven CCR.

    (AR) How long was it before you picked up your second rebreather unit? Any particular reason?

    (PL) It wasn’t long at all before I found the “Fridge” to be impractical for an average diver such as myself. I guess at some points in our life, I think we all get a little blindered and wanted to simulate those who impressed us with their achievements.
    When I bought the “Fridge”, the Wakulla project was in full swing and the lead divers of the WKPP were doing some very impressive dives with the PVR-BASC units. However, there is a big difference between what is required to do their type of diving and what we all as “week-end warriors” do. The “Fridge” was simply an overkill for what I needed to do simple trimix dives in the ocean. As far as I know, the unit overwhelmed the majority of its owners, and most, if not all, have sold off their units for next to nothing within a short time frame.
    For the typical trimix dives that I was doing, I didn’t see the gas saving from the “Fridge” as advertised or expected. After each dive, I still have to re-blend the tanks as even though they were not completely depleted, they were no longer full enough for adequate OC-bail-out, if needed.

    (AR) What rebreathers have you dove in your diving career?

    (PL) These are the rebreathers that I have owned and dove:

    - PVR-BASC (SCR)
    - BMR-500 (CCR)
    - Dolphin (SCR)
    - Dolphin (converted to CCR)
    - LAR-V (O2 CCR)
    - MK-15 (CCR, 2 units)
    - KISS (CCR)
    - XCR (SCR and CCR)

    (AR) You are a HUGE proponent of the KISS rebreather system. What impressed you so much about this system?

    (PL) I first bought a KISS just to have a unit to dive when my MK-15 was being repaired. My KISS unit is serial #7 which means the commercial unit just got developed and barely entered the RB market then.
    I was having a conservation with Gordon Smith, who is the designer and manufacturer of the KISS, about the problem of getting some replacement parts for the MK-15. I was bending his ears about the ripped-off prices when rare parts were finally located.
    As you know, the MK-15 is no longer in production and only a handful of the units are available around the world as Biomarines have since upgraded the design to the MK-16 for the US Navy.
    Anyway, Gordon mentioned about the simplicity of the KISS design and how replacement parts could be found easily and cheaply. Plus any modifications to the unit could be done by the user without having to waste time and money to send back to the manufacturer.
    Diving the KISS, when compared to the other units that I have used, is so simple and straight-forward. The unit is very well built, has all of the features desired on a CCR – except for the automatic set-point control which is not a bad thing, multitude of safety redundancy, light-weight, small profile which the user could change and adapt to suit his own diving environment.

    (AR) Recently, you introduced to the world the XCR rebreather. The unit is similar to a RB-80 with the dump system removed and making the unit a closed circuit rebreather. What lead you to the design idea of using an EDO-04 (RB-80 clone design) to make your own unit? Was it the size, style, or perhaps the ability to mount tanks on either side of the unit?

    (PL) As nice as the KISS unit, it is still not optimum to mount large tanks in the back next to the scrubber unit. This is due to the counter-lung housing being placed between the scrubber and the backplate. Therefore, anything large or heavy mounted to the other side of the counter-lung housing with have a large moment proportional to this distance and its weight.
    Therefore, I am forced to carry the bail-out stages in the normal OC position – which is not a problem since I am use to it, but not as nice as keeping the frontal area clean.
    When the RB-80 was introduced, the first thought popped in my mind was “It would be so nice as a CCR unit with that profile…”.
    Of course, I couldn’t and wouldn’t justify paying almost US$10,000 to buy a RB-80 to turn it into a CCR. So nothing more was done for a few years, until I found that the EDO-04 was available.
    With the EDO converted into a CCR (ala XCR), I was able to carry both bottom and deco gas bail-out stages in the back. This gives a similar profile as if I was diving a normal OC twin set with no deco stages. Yet of course, I was having the capacity of providing adequate bail-out gas for an out-of-air diver (self or buddy) from the bottom thru the deco phase.

    (AR) When the unit was converted to CCR did you remove both sets of bellows or did you just remove the inside bellow?

    (PL) For the first few dives, I just removed the flapper valve that force the unit to discharge gas in the small bellow on the inhalation cycle. This effectively allows the loop volume to recycle the same gas at constant depth.
    The next steps were to add the KISS oxygen addition valve via one of the 2 built-in diluent gas injection ports, and to add the 3 PO2 meters to be able to monitor the loop content.
    At this point, the unit is essentially a manual CCR.
    I test dove the unit on one of the local wrecks, the Innis., that we usually dive almost every week-end. The wreck sits upside down at 72m/240ft. The dive went very well with the unit performed exactly as expected.
    Afterward, I just made some minor changes to fine-tune the ADV portion of the unit since it was designed to be used as a SCR. Also, I then removed the small bellow so I could dump all trapped water out of the loop volume easily.

    (AR) Did you find any support from the rebreather community during the development, or were people uptight about such a deviation from a standard product?

    (PL) The only person I discussed with during the conversion process was Gordon Smith since I needed some help in getting the necessary parts. Of course, Gordon was very helpful and supportive.
    Afterward, I found that most people were either surprised at the easy of the conversion, or skeptical about the work-of-breathing (WOB) of the unit due to its counter-lung location.
    In general, people were supportive.

    (AR) When you were ready to manufacture parts for the system how did you present your design ideas? AutoCAD, solid works, or perhaps the traditional napkin with water rings?

    (PL) As mentioned, Gordon Smith provided all of the necessary parts that I need.
    Since Gordon is working on his new RB unit, the travel-KISS, we have been discussing about its design so I felt that I could use a lot of the PO2 metering components that Gordon is making for the travel-KISS to convert the EDO-04 into a CCR unit.
    When I got the EDO-04, I just ordered the components from Gordon solely based on his descriptions on the phone and email. I couldn’t wish for them to work more perfectly.

    (AR) When you started working on the system did you have a singular vision about the rebreather or was it more of a developmental approach?

    (PL) As mentioned, it was a very simple process so I knew exactly how each step was needed. The only thing that I didn’t plan on was how the ADV was functioning since the EDO-04 was designed as a SCR unit. However, it was only a fine-tuning step and was very simple to detect and implement.

    (AR) I was impressed with the inline use of the K1 sensor and placing it in your inhalation line. You have mentioned wanting to move it inside of the canister in future models, how come?

    (PL) I feel that moving the sensor inside will make the unit more robust and streamline. Also, the breathing hose is one of the moistest location in the loop so not the best location for the sensors. Originally, I want to place the sensors there to test the concept as parts are already available.

    (AR) Have you considered selling the “K1 sensor pod” as a stand-alone unit for homebuilders? This could be incorporated into multiple platforms.

    (PL) Yes, the sensor pod could be obtained directly from Gordon. This will allow anyone to make similar conversion very quickly and effectively.

    (AR) Do you see future electronics coming from Juergensen Marine or do you have other plans for this machine?

    (PL) As much as I love the Juergensen electronics since I have them on my MK-15 and KISS, I realize the huge demand of Kevin’s time from other people, many of whom could offer much better return for his time than making a single conversion for the XCR.
    So I still hope one day I might be able to find an empty slot in Kevin’s schedule to get a Hammerhead system for the XCR. But for right now, I will be working to fit a different electronic package in the XCR first. (AR) Where did the name for the “XCR” come from?

    (PL) Just a simple, short name to designate a unit that could be used in SCR or CCR mode, thus XCR or may be xCR to be more descriptive.

    (AR) The web site refers to a test diving to 72meters (235ft,) was their any shallower dives or was the opening dive? How did you feel during the dive knowing that this was a new rebreather?

    (PL) At that time, there were only 2 dive sites that our dive group goes to each week-end. The first is the Innis (72m/240ft), and the other is the Energy Determination (85m/280ft). Therefore, I am very familiar and comfortable diving either wreck so I was quite confident about making the test dive on one of them. It was just happened to be the week-end for the Innis, but I would have been happy to have tested the XCR on the Energy Determination as well.
    In addition, I always dive RB with adequate OC bail-out thus not an issue if the unit had failed to work properly. Since then, we have found 2 new wrecks: the U533 (115m/380ft) and the Anita (91m/300ft), so soon I will be able to dive the XCR on all of the 4 wrecks.

    (AR) Is there anything about this XCR or this type of diving that you would like to add that perhaps I left out?

    (PL) Diving the XCR is similar to diving any other CCR unit, except having the benefit of a clean frontal area while maintaining the capability of having adequate OC-bail-out gas, if needed. This allows a more streamline profile for scootering and wreck penetration – which are what I was looking for.

    (AR) Rebreathers seem to be making a come back with the development of technical diving, and divers wanting to push further boundaries. Do you see a wider appreciation for rebreathers in the near future?

    (PL) Definitely. Personally, I will never go back to diving OC unless I don’t have any of my units with me. There are many benefits of diving RB, but there exist also many potential problems. Diving a RB will require a different mental attitude and commitment to: proper training, diligent gear maintenance and never complacent about following correct and safe RB diving protocol.

    (AR) Phi in closing, what developments do you see as the future of rebreathers and that for divers?

    (PL) I believe that better diver training will prevent a lot of the past accidents from repeating. If the diver is properly educated, he will have a completely different viewpoint and approach to safe RB diving.
    As far as RB development, I believe the next obstacles are more reliable O2 sensors and safety-enhanced electronic (such as the Hammerhead).

    (AR) I would like to thank my guest for taking time out of his busy schedule to give us a little insight in to the workings of his new rebreather the XCR. Pictures and information can be seen at his website www.decoweenie.com. Andrew Rowley