Sidemount Heresy!

Text by David McLean. Images courtesy of D. Mclean.

🎶 Pre-dive Clicklist: Dr. John – Right Place Wrong Time 🎶

So what if heresy was part of your dive mission? Heresy has been part of my personal mission in diving since I went to work for my first dive gear manufacturer in 1982. So what do I mean by heresy? Well, it is the creative push to examine and improve upon institutional normalization and the hygienic policing of commonly held understandings that prevents innovation. WTF does that mean? Clearly, in our world today, many divers are alive because understandings were developed and then normalized, often after tragedy and accident analysis, and many understandings have been revised because of heretics like me and good science. Sidemount diving has hit a mature phase in its product life cycle (so have I) and it has fractioned into different flavors and toppings that are now staunchly defended. Never having liked Kool-aid as a kid, I tend to look at all the goodness offered and then go from that baseline to pursue heresy.

Me the Heretic

My personal jones has always sat in the subaquatic human – equipment experience. I have a few thousand hours doing this from the 80s and 90s (yes, I went to TEK ‘93, yes I was at the first AAUS meeting). In 1998, I commenced to earn a living outside the dive industry. Popping out from the end of that specific personal mission, here I am at 64, blessed to be living in Seattle with a bunch of early retirement available dive time, mostly physically active, and I still have my jones for gear. I have XX active diving years left, and I just ordered my last drysuit. Let’s look at a new mission for me, the aging active coldwater diver, with some heresy.

Proposed Aging Diver Mission

I now have a primary mission of “mostly” cold water (42 – 52 degree) recreational-level non-hard overhead fun diving 30 – 40 times a year. Mild deco diving is OK. I own a Blacktip Tech scooter (older diver mobility device). I deal with much higher personal air consumption, so to get an hour underwater I dive with at least 130 and preferably 160 cubic feet of gas to meet reserves. Doubles now kill my back, so no more double 120s and even the single 130 is heavy. I have about 290 hours on the Ocean Technology Systems (OTS) Guardian Full Face Mask with Comms. I am one of those sick puppies that loves to talk when scootering, and I suck more gas with a full face mask (FFM) talking.

Mission Solution – Sidemount Heresy!

The Seattle area/Puget Sound doesn’t have a lot of surf entries per se, unless a container ship goes by. It’s a perfect venue for carrying tanks into the water and staging them and my scooter. This is PERFECT for my back. Here’s a look at the sidemount adventure into heresy that I’ve gone down:

Bladder Heresy: I repurposed a discontinued SEAC KS01 bladder because it is built really tough. It has 27 lbs of lift, which is fine for the tanks chosen. It serves as a test bed until the next system iteration. I disliked the shoulder attachments to the bag top, the dangly shoulder buckle adjustments and the lack of adjustment for back length, so I frankengrafted the bag onto a Y harness (316 SS bolts). Heresy, perhaps, that I am not diving a current name brand sidemount BC like a cool kid. Remember that inner tubes and MSR bladders were the go-to early on. 

Harness Heresy: I built a standard Y harness with soft weights on the waist strap and spine. Stainless parts were off the shelf. This is not a prebuilt harness, and it wasn’t cheap as many advertise. My comms electronic package mounts to the Y plate. This is the least controversial part of this whole rig so I won’t bore you with details. I would say I subscribe to the UK sump diving perspectives, Texo-Florid-Ucatan, and some coldwater viewpoints, and equally offending all with my choices. I am a Facebook outcast in some groups.

Tank Heresy: Knowing a bit about tanks and harnessing, I chose two magical tanks for my sidemount rig – 30 year old Catalina HP 80s @ 3300 psi. These shorter tanks are neutral when empty, negating the waist D-ring change that you would do on a standard Luxfer floaty 80.  But wait, here’s the heresy! The Catalinas are rigged like stage bottles! Looking at the top bolt snap you’ll see a 1” web bolt leash holds the snap snugly against the tank valve back! I’ll explain this next. 

Bungee Heresy: The second most controversial part of the harness. Diving a Hogarthianish harness with a loose web “eye” around the shoulder has to be mitigated and tightened with a bungee attachment point high in the diver’s armpit to a high point on the divers back into the “Y” plate (or a slider with bungee holes). This creates a tight retracted loop that suspends the full negatively buoyant tank snugly under/behind the arm in its drag shadow while allowing the tank to be pulled forward to see a pressure gauge. Did I mention 64 year old eyeballs and near field focus aids? This web/bungee loop has been coached by some instructors as just right when “uncomfortably tight.” My bungees attach to the upper plate at the Y (no heresy yet), importantly are 100% stretch and not 50% stretch bungee material, so they are instead comfortable and tight, and they attach to a set of “expedition side mount” rings. These rings are a large SS loop ring, SS oval and bolt snap on the bungee, that is then clipped to the front shoulder harness D-ring. I snap my tank-neck bolt snap onto the SS ring. The lower tank bolt snap attaches to a fixed waist plate/ring just below my kidney because I have big, long bolt snaps for cold water dry gloved hands. The tanks hang textbook in location and angle both full and empty. 

Nods to Lamar Hires [Dive Rite founder] for the ring bungee and stage cylinder configuration that is now 12 years old. I can walk out of the water with the tanks on the harness with this. Properly configured it works very well, and improperly configured it is horrible to dive with and so apparently never caught on. Your mileage may vary. Added bonus: I can rappel down into a sinkhole with tanks with this rig, but I ain’t trying it. 

Manifold Heresy: Here we go with the big one. To be able to sidemount dive the OTS Guardian FFM, I use the 2021 Ben Bos’ LP combiner manifold configuration over the back neck. It needs a catchier name than that. This is not the older “Z system” with the isolation valve and block on the back neck.  This newer system uses QC6 couplings on two LP manifolds and two first stages and an inline isolation valve at the right chest manifold on the crossover hose. All parts are non-specialized “off the shelf,” with many parts common to CCRs. All valves and couplings are on my chest or viewable, and that’s huge with a FFM. It’s really comfortable to wear too. The system allows me to drill almost as if with doubles, which is a strong argument for this configuration. The manifold weight on the upper chest does wonders for in-water trim. I am easily flat in the water, and could be a sidemount poster boy if you ignored everything else going on. I have nothing but good things to say so far with regard to this manifold after tuning the configuration over ten dives. I should also mention I can gas switch or hand off a tank with the QC6 connectors, as my buddy dives a similar configuration. I believe we have yet to understand the value of QC6 connectors in air sharing, connecting gas supplies in a team without cylinder removal, and switching to deco gas with FFM. I’ll get back to you on that.  

So that’s about it. I am successfully diving a mission-specific sidemount rig that may carry me forward for those XX years and my last drysuit. I do get stares in the parking lot with it. I can hear you laughing, so I won’t summarize anything more here, but I appreciate the opportunity to entertain. 

I am open to critique, feedback, or questions and you can try to change my opinion, too! 

Dave explains the integration of the OTS Guardian full face mask and crossover manifold with his sidemount rig in this video: Sidemount Diving with the OTS Guardian FFM

DIVE DEEPER 

UDT Scuba Diving: DEMA 2021 Presentation on SIDE MOUNT by Ben Bos

David McLean has been SCUBA diving since 1972. He holds Instructor, Master Diver and a few other important forgotten certifications. He is a past Design Engineer for Underwater Kinetics and SeaQuest, first Product Manager for Mares USA, past Florida Sales Representative, past Director of Sales and Engineering for Soniform, and past Product Manager for Scubapro. He is known for designing the “Advanced Design Vest” style recreational BC, and contributing to ‘90s technical BC development. He now dives primarily in Puget Sound and the Seattle Aquarium, inspiring children to conserve and protect our oceans.