Forget Wilder versus Fury, the big showdown when it comes to technical diving is sidemount versus backmount. Recreational diver Gavin Jones took the plunge with tech instructor trainer Garry Dallas to try out both forms of twin-tank diving.
Back in the day, when it came to open-circuit technical diving, the default ‘base’ from which to develop your skill set were trusty doubles, either manifolded or two independent tanks. Having two 80- or 100-cubic-foot tanks on your back gave you ample gas and redundancy over a solitary tank to venture a little beyond so-called recreational diving depths, and then by adding one or more side-slung cylinders as your training in the world of technical diving progressed, you could really start to explore those alluring depths.
Then sidemount burst on to the scene. Now diving with two tanks, one on either side of your body, with a streamlined wing on your back for buoyancy, was nothing radically new – cave divers had been utilising this set-up for many years – but several years ago it became very en vogue, and suddenly diving sidemount on reefs and wrecks became the ‘in’ thing. It also provided a stable base from which to add more tanks as tech training developed.
So you are a recreational diver, with a few years of diving under your belt and a couple of hundred dives in your logbook, and you are looking to enter the work of technical diving. Now you have a choice – sidemount or backmounted doubles? We recruited Gavin Jones, a keen single-tank Master Scuba Diver and RAID 40 diver from Shropshire, UK, who was showing an inclination to ‘go technical’ in the future, to be our ‘guinea pig’ and try out both forms of twin-tank diving. He has trained with Shrewsburybased RAID centre Severntec Diving, and already uses a backplate-andwing and long-hose set-up, so was well on his way to the technical ‘dark side’.
Gavin said: “As I progressed through various courses and my depth limits, one thing that was always at the forefront of my mind was redundant gas supply. While I acknowledged the buddy system, I didn’t want to rely on the ability and skills of an unknown diver while diving on holiday.
“As I reached the limits of recreational diving, I opted to always carry a stage tank with the same gas for non-deco dives deeper than 65ft for my own peace of mind and to be self-reliant. This reduced my anxiety, gave me comfort and allowed me to enjoy the dive.
“My first experience with doubles was unloading our club’s van – I enquired how they managed to even stand up with that on! The reply was ‘you get used to it’, and ‘you don’t notice in the water’. Sidemount seemed easier to manage at the dive site, but the set-up looked nothing like my backplate-and-wing, so I was sceptical if I’d be able to understand a different way of doing things.”
DID YOU KNOW
Sidemount divers often dive with two smaller tanks that are attached in the water. This makes carrying them and kitting up easier, especially for those who have difficulty lifting or walking with a traditional backmounted doubles set-up.
We then roped in technical instructor trainer Garry Dallas as our mentor to take Gavin on extended trydives both in backmounted doubles and sidemount so that he could see the pros and cons of both forms of technical diving.
To the Delph
A bright, sunny morning greeted us as we rolled into the car park at the Delph. Garry maintains a classroom here, so it made sense to conduct the trydives at this location.
After introductions and the obligatory coffees, we went into the classroom and Garry immediately went into ‘instructor mode’, explaining the differences between doubles and sidemount, and getting Gavin sized up with the right wings and harnesses. Although he is well known in sidemount circles, Garry also teaches and dives in doubles (as well as with rebreathers), so he was the perfect guide to show Gavin the ropes with both systems. First up was sidemount.
Sidemount
This was a totally new concept to Gavin. He commented: “I carried both tanks to the water, placed them in the shallows and returned to get into my harness. I noted how easy it was to get set up and at no point was I carrying anything heavy. Once the sliding D-rings were correctly positioned and the tanks were bungeed up, the whole system was very neat and streamlined – nothing protruded wider than my shoulders or deeper than my body.”
It took a little while for him to get properly rigged up with the tanks sitting in the correct position, but at least he was used to the long-hose set-up, and this meant that that aspect of sidemount didn’t feel completely alien to him. I know from back when I did my sidemount course with Garry, it does feel very odd to be in the water with nothing on your back, and to have the valves on two tanks sitting either side of your chest. On the other hand, this positioning also helps you achieve a nice horizontal trim very quickly.
One thing that Gavin did have to get used to was swapping between his regulator second stages to evenly deplete the gas out of his two tanks. One sits round the neck on a bungee, as per normal long-hose recreational or doubles diving, while the long hose is equipped with a P-clip so that when that regulator is not in your mouth, it can be securely clipped off onto a D-ring on your right shoulder strap. He said: “Keeping the gas in the cylinders balanced was straightforward and the regulator switching was not as often as I thought. I was told to keep them about 300 psi apart, which meant when you’d switched you could breathe the next one down 600 psi, and so forth.”
Under Garry’s watchful eye and tutelage, Gavin soon got to grips with sidemount diving. His trim and position in the water was nicely horizontal within a matter of minutes, and I could see he was enjoying the ease of access to both pillar valves for shutdown drills, etc. Garry doesn’t do anything by halves, and really worked with Gavin to ensure he got the best possible introduction to this form of diving. He also put him through several skills and drills, including backfinning, turning, and so on. Gavin concluded: “The whole system felt very balanced, streamlined and stable and I was able to turn and manoeuvre with minimum effort. I liked the fact that everything was right there and accessible, I could easily see and manipulate valves, check SPG and hose routing. Entering and exiting the water was easy, and rigging up was much easier and quicker than I envisaged.”
A quick spot of lunch in the on-site café at the Delph and then it was time to go diving doubles.
Backmounted doubles
Gavin immediately looked more comfortable out of the blocks with traditional doubles on his back. As he was used to diving with a backplate-and-wing and a long-hose set-up, other than the fact he now had two tanks on his back instead of one, everything else was very familiar and fell easily to hand.
However, there was that weight to get used to. Gavin said: “I’ve suffered with a bad back on and off for many years from a motorcycle accident, so I wasn’t particularly looking forward to hoisting all that weight up and walking to the water.
However, I was pleasantly surprised that once I’d got it up and everything secure, it wasn’t too bad – I managed the walk and the entry to the water without a problem.”
One of the key skills when using backmounted doubles is the S-drill, or shutdown drill, and Gavin found there was a definite knack to reaching up and over your shoulders to turn the knobs on the tank pillar valves and the central manifold knob. Garry said the skill does become easier over time, as a result of muscle memory and increased flexibility, but this was the only aspect of doubles diving that Gavin appeared to find a bit awkward. He commented: “I instantly felt comfortable with how everything was set up and worked – until we discussed and went through shutdown procedures. In my drysuit I struggled to reach the valves to turn them. Maybe with some physio and practice this wouldn’t become an issue.”
Once under the water, Gavin’s trim and buoyancy in the water was very good, and he didn’t seem to have any major issues, even through all of the skill-and-drill circuits directed his way by Garry. He said: “I liked the instant familiarity with the set up and rig, and once on my back it wasn’t as heavy and bulky as I thought it would be. However, I wouldn’t of liked trying to get out on slippy rocks or up a boat ladder.”
Conclusion
So, which is best? Well, it isn’t quite as straightforward as that. As with many things in diving, it is a bit ‘horses for courses’. What works well for one person doesn’t necessarily tick all the right boxes for someone else. Either set-up makes a sound starting point for technical diving. Sidemount allows a lot of flexibility – for example, it is a simple matter to just rig up one tank and go diving if that is a better option for a particular dive than needlessly lugging two tanks, whereas with doubles, you are stuck in that layout. Likewise, you can carry your sidemount tanks down to the water’s edge and entry point one at a time, reducing the weight you are having to carry in one go. Many sidemount devotees note the reduced strain on your lower back, and the enhanced freedom of movement from having the tanks on your side rather than mounted on your back. On the flipside, you get those who see rigging sidemount as a real faff, and prefer just being able to sling doubles on their back and go diving.
Technical divers do tend to be tinkerers and are always fettling their kit anyway, but sidemount divers can take this to a whole new level of ‘tweaking’, so I understand this viewpoint to an extent.
Which one came out on top for Gavin? Well, he was undoubtedly more comfortable in doubles from the outset, however he liked the flexibility of the sidemount system and towards the end of his trydive in this rig, was looking very streamlined and trim in the water. A few weeks later, he bit the bullet and did his first course using two tanks – in sidemount, in case you were wondering…
The Gospel of Garry
There’s so much subjectivity regarding the pros and cons of backmounted doubles and sidemount, that it’s hard to see the wood for the trees – and egos. From an unbiased POV, given my earlier technical diving path on doubles, from diver training through to trimix instructor, seeing the differences was obvious, hence I’m still diving religiously today. For the last 60/70 years, innovation has improved on all scuba systems, so now RAID have released, alongside doubles, the most up-to-date sidemount training manual – the primary author being me.
Fundamentally, every unit should keep you safe, redundancy being your safe, accessible back-up. For this main reason, sidemount cave divers found this configuration the safest choice. If anyone can’t – or really struggles to – reach their valves easily every time, without losing buoyancy, then they need to change configuration. Period! Other reasons you’ll learn on a RAID course are minor in comparison, for instance… carrying double the weight on land as opposed to singles, while L4 and L5 vertebrae screams on the way back to your vehicle. Can sidemount be a faff? Of course, when someone hasn’t trained on it. Everything is hard work when you don’t know what you should be doing. Train ‘hard’, dive easy!
Photographs by Mark Evans
This article was originally published in Scuba Diver North America #11. Subscribe digitally and read more great stories like this from anywhere in the world in a mobile-friendly format. Link to the article
Cave divers do not prefer sidemount because of redundancy. They do so because it’s easier to get into thin passageways than with twin tanks. Also it’s easier to detach tanks to get through even smaller passageways.
Also to make this article thorough you would need to consider boat diving and not just shore, in which case it’s much easier to gear up twin tanks. Consider as well that a longer hose means higher fault risk, which you do not require with twin tanks.
This article claims it gives an “unbiased POV”, but it is quite sidemount biased in reality.