Here are several photos of some of my students in sidemount. These were during classes so while the trim is pretty close to perfect some may be a little off. Also, camera angle can affect how the trim looks. This should give you a general idea of how sidemount cylinders should look, though.
Scroll down to also see some stage cylinder photos and to see how cylinders respond to lower pressures.
Worthington LP85s in proper trim
Faber LP85s in proper trim
Faber LP95s in proper trim
AL80s in proper trim
Properly trimmed stage bottle (you can barely see the stage in the 2nd photo)
Pushing one of the cylinders forward
Pushing both cylinders forward
Some photos of Faber cylinders out of trim
The PST 100 in the left photo is only slightly out of trim. What’s happening is because the cylinder has more weight in a smaller area it trims itself out in a horizontal position. In turn, this pushes the diver out of trim. We dropped the bottom of the cylinder slightly and tightened up the bungees to adjust the cylinder and get the diver back to a horizontal position.
The Faber LP95 in the right photo is down to about a pressure of 1100. When the Faber LP95 gets down to about 1600 it starts to rise up like you see in this photo. This is why it’s important to manage your gas so you end your dive before you reach 1600 psi in these cylinders.
Why Fabers get out of trim at lower pressures
In the left photo is a Faber LP95 at the beginning of the dive. The weight of the gas in the cylinder is heavy enough to keep the cylinder pushed down at the rear attachment point.
In the right photo is the same Faber LP95 later in the dive with 1600 psi. Breathing gas from the cylinder has created a much lighter cylinder. As you can see the cylinder is no longer heavy enough to counteract the bungee and it rotates up so the bottom sticks up above the plane of the diver.
Some other issues you can encounter in sidemount
The photo on the left shows a stage cylinder in a poor position. The rigging in this photo is one that has been used by most sidemount divers for a few years. While the stage cylinder can be trimmed out nicely with this rigging at the beginning of the dive when it’s full, it doesn’t stay that way for long. As the gas in the stage cylinder is breathed down the cylinder gets lighter and causes the bottom to rise up.
The photo on the right shows a stock manufacturer’s wing with air in it. The diver is in a dry suit and using AL80s but still needs a little bit of air in the wing to keep him neutral. All of this air goes to the middle of the wing and pushes it up causing the gap you see. There is a way to fix this but it requires sewing in more tabs on this particular wing.
Cold water D ring
This is something we came up with a few years ago for cold water divers. The 2 inch diameter stainless steel ring you see here is useful for divers who wear dry gloves. The ring’s diameter allows the diver to slip a thumb through the center and use it to pull the bungee forward. The diver can then grab the bungee with the other hand and pull it over the valve. The ring also keeps the glove from getting trapped between the bungee and the valve.