Appeared in DIVER August 2007

Cam-band savvy

They wont get your pulses racing in the dive shop, but certain basic products can make or break a diving experience. John Liddiard shares his observations on a humble piece of webbing

I ALWAYS TRAVEL WITH A SPARE CYLINDER CAM-BAND, the band of webbing that attaches a cylinder to a BC. Not because the main band is ever likely to fail, but because a spare is incredibly useful for other things.
Firstly, I hate the floaty feeling of aluminium cylinders. Threading a couple of 2kg weights onto the spare cam-band and attaching them right at the top of the cylinder makes it heavier against my back and more comfortable in the water.
Moving weight to the top of the cylinder also adjusts trim, tipping me forward in the water and making it easier to keep my fins clear of the reef.
Even with steel cylinders, I sometimes like to add a couple of weights on a cam-band, especially when diving with a wetsuit. It gets rid of weight from my belt, and helps to keep my feet up and clear of the reef.
Some BCs have trim-weight pouches behind the shoulders to facilitate this, but using such pouches does not get rid of that floaty cylinder feeling.

width=100% Improvised triple set of bottom, bail-out and deco gas. The long purple cam-band wraps the lot. Above it, two standard bands are joined together.
A second use for a spare cam-band is to improvise a twin-set, although of course this would also require a second regulator, or at least a first stage and gauge that can be fitted with the octopus from the first regulator.
Just join a pair of cam-bands end to end and wrap them round both cylinders.
Its not as secure or rigid as an AP twinning kit with four bands and blocks, but it is a convenient way of rigging a bit more gas for the occasions when this is wanted.
I found I was using this trick so often that I made an extra-long cam-band. With a single cylinder, I just tie the loose end off to stop it flapping about. It will even stretch round a bundle of three cylinders to improvise a rig for a shallow trimix dive.

Obvious Perhaps, but even experienced divers sometimes get flummoxed with this, especially if they are rarely called upon to do it from scratch, or are in a rush.
Cam-bands typically have two slots in the plastic cam. With the cam folded back on itself, thread the webbing beneath it and out through the second slot from the hinge.
Then it goes back through the slot closest to the hinge, so that the webbing is flat against itself. With the cam-band over the cylinder, pull the webbing tight with one hand while using the other hand to wiggle the cam until its just past halfway over.
Now thread the loose end of the webbing through the second slot from the hinge again. Keep pulling it tight as the cam is wiggled all the way over to lock.
To tidy the loose end, some cam-bands come with a webbing loop or Velcro positioned to hold it flat.
Another variation is a third slot in the plastic cam through which the webbing can be threaded again. If in doubt, many cam-bands come with instructions stitched inside!

hspace=5 While on the subject of twin-sets, a set of cam-bands and blocks for independent twins can come in very useful for making the most of an average two-tank boat dive, as the Americans like to call it.
A two-tank boat dive is the pattern of diving where each diver gets to use one cylinder on a moderately deep first dive, followed by a short surface interval and a second dive so shallow that residual nitrogen loading from the first dive is not an issue.
The first dive usually ends up being limited by the gas available in a single cylinder, especially when using nitrox. Later on, people on the second dive often return with plenty left over.
The solution to a better spread of gas between the two dives is to configure the two cylinders as a twin-set. That way, I can use one-and-a bit-cylinders for the first dive and keep enough for a shallow second dive and reserve.
The minus side is an additional 2-3kg of buoyancy variation, as towards the end of the second dive there are now two empty cylinders strapped to my back.
So while a twin-set is a good way to make the most of a two-tank dive, I still prefer to use just a single cylinder if I can get away with it.
With a longer surface interval, a non-trivial second dive and three cylinders available, a twinning kit can also be used to share the gas out at one and a half cylinders for each dive, by breathing one cylinder most of the way down, and swapping it for the second dive.

hspace=5 Another creative use for a twinning kit is for multi-level air/nitrox dives, to carry one cylinder of air for the deeper part and one cylinder of nitrox for better time and decompression on the shallower part.
This configuration is known as the Bantin Rig after DIVERs John Bantin, who is fond of this combination.
It is a convenient way to make use of the facilities available on the average Red Sea boat with a nitrox machine and plenty of 12-litre cylinders, but no dedicated technical gear such as side-mount cylinders.
For a dive that goes a little beyond the limit of the nitrox available, perhaps even a little way into decompression, but follows a multi-level profile, an independent twin-set with one cylinder of air and one cylinder of nitrox is a very practical solution.
Of course, you have to remember which regulator supplies which gas, but that is a problem any technical training will have covered.
The thing to remember about this configuration is that it is a compromise. It is not a substitute for a more conventional twin-set and separate decompression stage cylinder for heavy-duty decompression diving.