Category — BOV – DSV

Taking the CCR Sentinel cross over the opportunity arose in March of 2010 when Nader Quarta from Switzerland came to Mexico to do some fine cave diving in the Riviera Maya. When we were setting up his dive trip he mentioned that he was coming with his Sentinel CCR Rebreather and I asked him if he is an Instructor on the unit. With a positive reply coming back I asked if he could do a cross over course with me while here and he was happy to do one for me while here in Playa del Carmen.

prior diving

The Sentinel CCR Rebreather is made in the U.K. and is the little brother from the larger Ouroboros CCR Rebreather. The Sentinel has a manufacturer depth rating of 100 meters / 330 feet and a very unique Co2 sensor detecting a rise in Co2 in the breathing gas should the scrubber material fail. The Sentinel is designed as a back mounted counterlung Rebreather, meaning you have the front of your body clean and the counterlungs protected within the casing on your back.

manual oxygen and diluent injector blocks

Back mounted counterlung Rebreathers are used to be not breathing so well compared to front mounted counterlungs due to the harder work of breathing effort as the counterlungs are a bit shallower then your real lungs, making inhalation a bit more difficult then exhalation. During the last years a number of new Rebreathers with back mounted counterlungs came onto the market with quite good work of breathing besides being a back mounted counterlung design. Keeping the front clean protects the counterlungs in case you want to penetrate small caves or wrecks. For photography and filming it is quite nice too as it gives space to bring the camera close to your face. Smaller people with not so much real estate might find it very comfortable as they are not so cluttered with the counterlungs in front.

solenoid assembly

The Sentinel is a bit bulky compared to other Rebreathers but is packed within a rugged design package, large bore breathing hoses and meaty construction components. All parts are fitted together in a way they can be individually replaced at a reasonable cost. The unit looks it is made to last a life time. A nice feature of the Sentinel is the location of the manual oxygen and diluent injector buttons located left and right on the chest within switch blocks allowing the plug in of additional offboard gases.

The two day cross over program started off with the unit itself, learning how to pack the scrubber and work the electronics, which are very different from all others I have used so far in terms of going through an electronic checklist that will let you only dive when completed poperly. In the afternoon of the first day we went to cenote Eden to get through a nice and long confined water session where I had ample time to get used to the Sentinel and work my way through emergency scenarios such as the three H’s of Hypercapnia, Hyperoxia and Hyperoxia as well as a boom scenario, SCR bailout and various electronic features.

unit in pieces prior diving

The second day we went to cenote Manati to complete the cross over program with two long dives where all emergency related drills and skills where repeated multiple times. When we started our diving that day the water was flowing quite strong out of the cenote through the tunnel and into the ocean. The current was so strong that we had to swim very hard against the water flow in order to get further into the open water area of the cenote.

BOV

I was very happy to be on a Rebreather as I had all the breathing gas in the world and was able to check out the work of breathing while swimming very hard for a longer period of time. At the beginning of the second dive I took the time to go through the complete handset menu various times. Very comprehensive, very sophisticated, very capable.

sensors inside the head

As Nad had asked me quite a view questions about the Classic KISS CCR Rebreather we have in the store I packed my unit in the morning and took it with me to the dive site in order to give Nad an introduction on the Classic KISS CCR. The water current was still very strong, actually the strongest I have ever seen in 15 years. While I was on an open circuit single tank Nad was happily on the KISS CCR and off we went for another dive, this time me being the instructor and Nad being the student.

pre-breathing the unit

I had a great time with Nad to learn once more something new and meet new people. The cross over program was very thorough with Nad being very knowledgeable about Ouroboros and Sentinel CCR Rebreathers.

What I like and what I don’t like – A personal view

I bought my first Inspiration e-CCR Rebreather back in 1999 and back then there was no choice between Classic, Vision or even the Evolution. It was plain and simple the Inspiration, now known as the classic version of a range of Rebreathers offered by AP, and manufactured in the U.K.

As it was my first Rebreather I ever purchased the choice, and my knowledge about choices, was rather limited back then so I had not much to pick from in terms of other units commercially available to the public … or at least I was not informed enough to know about them. The unit was purchased in Singapore by a friend and then came to Mexico. I did a number of deep cave dives on the unit and sold it about 3 years later to a friend residing in Utilla, Honduras where I believe the unit is still up and running.

Late last year I took the chance and offer to purchase a used Inspo from a friend of mine who was willing to part from his Vision Inspiration e-CCR Rebreather with only about 40 hours on the unit. The unit was living in Canada at that moment. When the unit came to Mexico it was in a still spanky shiny new turtle box with no scratches on it as the unit was housed during its 40 hours in a aluminum travel frame.

The things I like on the Vision & what I left as is

Decompression capability – I am actually an advocate of having the dive computer and Rebreather separated but have to say that it is quite nice to have the decompression computer tied into the actual Po2 from the sensors. My CCR capable dive computer (Liquidvision X1) is the primary dive computer and the inline Vision decompression computer housed within the handset my backup.

Handset – I like to be able to put the handset on the wrist as on the classic they were hanging somewhat below my profile and dragging in cave sediments a view times. To have only one hand set on my wrist instead of two is quite nice as well which leaves space on the other wrist for my CCR capable dive computer.

Sensor changing and placement – They changed the design of the head and now you can actually change the sensors without breaking any water sealing o-rings and need no tools anymore in order to do it. The way the sensors are connected now is better as well as on the Classic Inspiration where corrosion and conductivity issues frequently plagued my diving excursions. They changed as well the metal battery housing screw who is now not located directly opposite the second sensor anymore and does allow the unit being laid on its back without condensation water droplets dripping directly onto the second sensor.

Tempstick – I have to say that I like the temp stick display even if I do not use it as a reference on how long I can still stay and use the absorbent.

Hydrophobic membrane – I like the hydrophobic membrane on top and bottom of the absorbent cartridge which gives a bit of protection to the absorbent in case we have some water in the can.

Calibration – I got used to it how easy calibration is on the unit.

HUD -I like the HUD even if the placement is not entirely right for me … because of my big head. I guess.

The things I do not like on the Vision & what I changed

Softpack – I do not like softpacks with all of them straps and plastic buckles. After all these years of cave, wreck, tec as well as dry suit diving I have to say that I do prefer a stainless steel backplate with all through standard webbing and a sturdy crotch strap. With the use of my standard Dive Rite ss backplate I have all the d-rings exactly where I want to have them, and can use the same backplate for oc and cc diving. This is one of the modifications to make the unit right for me.

Wing – The original box wing I do not like. With the softpack went the original box wing which was replaced by a Dive Rite 55 lbs Rec wing, but can be changed for any brand, any size wing either single, double or sandwiched. This is one of the modifications to make the unit right for me.

The inflator and bailout regulator – With the old box wing went the complex and prone to leak (at least mine) inflator and second stage assembly. Not only did I have some leaks but it was hanging below my profile and is in the way of streamlining myself. It makes deflating and sharing gas with another diver at the same time a bit more challenging too. I am an advocate of having my CCR and my bailout gas separated so I am carrying always a separate bailout tank with me. This is one of the modifications to make the unit right for me.

DSV – I did not ever like the original DSV. Somehow I had a problem to remember which way is open and which way is closed. From my prior CCR diving experience I came to like a BOV quite a lot and it was a much welcomed change on the unit. My BOV is attached to the inboard diluent tank. The BOV access to the diluent tank is only a step in-between in my bailout procedure. It allows me to get off the loop very fast and convenient while I am getting my bailout regulator ready. On deep dives I change to larger onboard diluent tanks. The BOV allows my dive partners intervene externally as well in case I am unconscious or behave erratic. I attached a Golem Gear BOV to the unit. This is one of the modifications to make the unit right for me.

The box – The yellow and black plastic container I do not like. While traveling a lot I found the large plastic box a bit too cumbersome. The other aspect was that I had to drag half of it around to get my countelungs disinfected. The cover in my point of view has the potential disadvantage that it can trap gas bubbles underneath in case of a leak with either O2 or diluent, quite a bit of gas actually. I first changed that while drilling little holes into the cover. In the end I placed the unit into a steel frame which did a couple of things for me. The ability to travel light and disassemble the unit into individual pieces, to change the backplate and wing fast with any brand and size, as well does the frame allow for a wide variety of back plate and wing mounting positions helping with trim. The open design of the frame I use does allow my dive partner to see all components of the rebreather in order should a leak arise, as well the amount of gas that can be trapped below the cover is very minimal. This is one of the modifications to make the unit right for me.

Non-detachable counterlungs – Pain in the butt to keep clean and dry. Keeping the unit sanitized seemed to be a drag literally as I had to drag the plastic shell with me to the water source and then somehow place it in a way so the lungs can dry while on the floor or table. I live in a humid environment and want to hang my lungs up to dry, so I cut them off the attachment point and sewed on a d-ring each on top. The top of the lungs are now attached via a quick link to the frame while the bottom part is attached via bungee and a clip to my crotch strap scooter d-ring. The counterlungs are not attached in any way to my harness to allow me to move them around to get to my backup lights, d-rings for bailout or stage tanks or my dry suit inflator. This is one of the modifications to make the unit right for me.

Tank size restriction – The original plastic box allows only one tank size with one particular valve design to be used. As I travel a lot I may choose to travel with small aluminum tanks or don’t pack tanks at all as I rent tanks at my destination. As my destination provider may not have the tanks I like to have the plastic box is limiting me in my choice of tanks. With the steel frame mounted to my unit I can use Alm 13, 19, 30, 40 and 80 cft tanks mounted to my unit as well as 2, 3, 4, 5, and 7 ltr steel tanks. This option is quite useful when traveling. This is one of the modifications to make the unit right for me with the installation of the steel frame.

Special sensor – I do not like the fact much that I do need special sensors for this particular unit but another sensor for all my other units which puts me into a situation that I need to stock two different sensors. However, with the new connector a lot of my old sensor connectivity and corrosion issues have been addressed, and all I can do it stock special sensors for the Vision.

Plastic buckles – I do not like plastic buckles and fast clips at all. In my experience they break way too many times and always at the wrong time, the time I am ready to go diving. With the change to an ss backplate with standard harness and ss buckle this issue has been addressed. With the counterlungs now detachable and connected with metal quick links and clips got me to get rid of all plastic attachment points. This is one of the modifications to make the unit right for me.

The things that don’t bother me much on the Vision

Plastic bucket – The bucket where the absorbent cartridge is living inside is made out of plastic but has hold up very well so far including the metal threading embedded in the bucket walls. On the Classic Inspo you could actually rip them out while over torqing the screws that hold the lid on the can but with the Vision you have them little black rotary clips with a lesser or no chance to rip out the metal thread rods.

Single o-rings – The unit is been designed and sealed with single o-rings in all locations only while other Rebreather manufacturers are using a double o-ring design with at times large and thick diameter. So far I had no problems and the unit is tight with excellent positive and negative checks.

Mesh webbing over counterlungs – The new counterlungs have a partial mesh webbing over the inner and actual counterlungs. Especially in cave diving sediments can fall in there and with a lot of time and rubbing action can damage the inner counterlungs but I have had no issues so far.

Battery life – The battery life is not too bad, could be better but could be worse too. I run the unit fully electronic and just carry extra batteries with me. Fortunately they are readily available in most photo stores anyways.

All in all I am quite happy with the unit after I have done the changes as outlined above. The unit is streamlined, light, is reliable (at least my electronics are), has a very good horizontal trim now with the changes done and is user friendly … at least for me.

Greetings

Matt