Minimalist sidemount setup in cold saltwater?

[Plummet]

Hi! I've never dived sidemount before, and have some questions. I haven't dived much at all actually, so bear with me here.

The idea of a minimalist sidemount setup appeals to me, such as this: New System - The Deco Sidemount

From what I have read (The Two Schools of Sidemount Diving Heritage), that type of setup is considered "British" style (rather than "American"), and is typically used with aluminum cylinders (rather than steel).

However, out here in northern California, backmount divers seem to often use steel back plates and steel cylinders to compensate for the drysuit or 7mm wetsuit + 7mm vest.

So does anyone have thoughts on using a minimalist sidemount harness/wing with a drysuit or thick wetsuit in cold saltwater? It seems like one would have to use either steel cylinders, or aluminum cylinders with more weight, neither of which seems generally done.

And isn't the UK cold? Also, the 2008 CDG manual says that steel cylinders are common for UK cave diving (and it has a different, probably older, definition of "British" vs "American" harness styles).

 

[Patoux01]

Stealth (among others) works perfectly in cold water.

 

[AJ]

I'am not a sidemount diver, but I am a cold water diver. It's all about weight. Heavier tanks compensate the amount of lead needed. For the rest: tanks are tanks, not much difference. If you can dive, you can dive alu and steel.

 

[bamafan]

Check out Sump UK on Facebook. Andrew Goring does exactly what you are suggesting. He has some great products too but sadly he lost his wing production capability in a fire so they are not available at this time but the rest of his products are.

 

[Plummet]

Check out Sump UK on Facebook. Andrew Goring does exactly what you are suggesting. He has some great products too but sadly he lost his wing production capability in a fire so they are not available at this time but the rest of his products are.

Funny you should say that - I have already messaged him!

 

[Subcooled]

So does anyone have thoughts on using a minimalist sidemount harness/wing with a drysuit or thick wetsuit in cold saltwater? It seems like one would have to use either steel cylinders, or aluminum cylinders with more weight, neither of which seems generally done.

If you dive in very cold water then you will want a drysuit and you will want a lot of insulating air inside. This translates to a lot of lead. Steel cylinders really lessen the burden on your belt. A typical solution is to use 12/232 steel Eurocylinder + 12lbs or 7/232 steel Eurocylinder + 18lbs with a drysuit and some fluffy undergarments. If you dive in salt water, please do add at least 4lbs.

If your drysuit fails, you will need a wing that can carry your tanks and the lead.

 

[runsongas]

steel tanks and the xdeep work just fine, but why do you want to switch to sidemount? sm isn't really required for anything locally. we have no wrecks or caves. do you have a health concern that you can't walk into the water with a tank on your back and you want to be able to clip on in the water instead? that will restrict where and when you can dive in norcal.

the vast majority of local divers here dive backmount because it works better for shore diving with sometimes less than ideal entries/exits. take a look at a drysuit and bpw before you make a decision.

 

[jerrwhy01]

I have that same DECO rig. It's very much a minimalist rig. It works great in warm water, with a 3 mil wet suit and AL-80's. The problem that I encountered is that if I dove my preferred minimalist side mount tanks-LP-50's(cave filled) that I would have to run the wing fully inflated just to stay off the bottom-at least in fresh water anyway.

My solution was to switch out the bladder to the X-Deep 35 pound side mount bladder. This affords me the same minimalist rig that I can use for recreational/lite technical/cave diving that travels well.

If you're a recreational diver, diving from the shore, or a kayak then LP-50's work really well in this regard. They're about as much of a pain in the butt in terms of handling, and weight as a BP/W and AL-80 set up.

Cold water diving is going to necessitate the need for more weight. You can drop some lead off your rig if you switch to steel tanks.

Personally, if you're looking at diving cold water with steel tanks that DECO rig probably isn't the ideal choice. You could probably make it work if you're wearing a drysuit as it would share some of the lifting burdens with the wing. However, I'm not convinced.

A better rig in my opinion for what you're describing would be something like the Xdeep. By the time you've bought the DECO harness and the Xdeep bladder you've spent just about as much. The Xdeep rig should be able to handle up to LP-85's/HP-100's. Add the butt plate kit and a larger wing and you should be able to handle heavier tanks.

 

[Peter.]

As mentioned lift is the issue.

For you to (wearing enough weight to) hold a safety stop or mandatory stop with near empty tanks in shallow water you'd be struggling to stay off the bottom with full tanks at depth.

This problem is further magnified with a 7mm wetsuit versus a dry suit as the wetsuit compresses at depth.

I dive 12L steel tanks with 7mm wetsuit, 6lb of weight and 45lb lift wing in freshwater.

 

[DevonDiver]

The deco sidemount has 10kg (22lbs) of buoyancy. This is ample for warm water diving, even for 3 cylinders (AL80) doing basic tech.

A Faber 100 is just shy of 15lbs (~7kg) negative when full. You'd carry 2.

An OMS 85 is just shy of 7lbs (~3.2kg) negative when full. You'd carry 2.

Obviously, tanks alone take a significant amount of buoyancy requirement. Larger capacity steel tanks are beyond the capacity of the bladder.

Next to consider is your exposure protection. The buoyancy of the bladder must be able to lift you when:

1) Your wetsuit compresses at depth and loses buoyancy. It must offset, in addition to carrying the cylinders, the amount of buoyancy lost from the wetsuit. This depends on the thickness and size of the wetsuit (the volume of neoprene total).

2) Your drysuit leaked/flooded at depth and lost its buoyancy. You shouldn't plan drysuit dives in the assumption that your suit wouldn't fail. Although you could jettison weight if this occurred...as you'd probably be aborting anyway. You wouldn't put yourself in a deco obligation in this instance.

You could probably get away with a Deco Sidemount if diving goes drysuit, but you wouldn't have sufficient buoyancy if the suit catastrophically failed. With larger capacity steel cylinders you'd be very negative in this instance...and might be unable to kick up.

It might *just* be possible to dive lower capacity steel tanks in a wetsuit, but your weighting would have to be absolutely accurate...

"Wetsuits are made from neoprene, impregnated with tiny air bubbles. When divers descend, these air bubbles are compressed and lose buoyancy. Wetsuits that provide 11 pounds/5 kilograms of buoyancy at the surface will only provide about 2.5 kg of buoyancy at 33 feet/10 meters where the ambient pressure is two atmospheres (ata). At an ambient pressure of five ata, which occurs at 130 feet/40 meters, its buoyancy will be reduced to about one kilogram"
The Ups and Downs of Buoyancy Control — DAN | Divers Alert Network — Medical Dive Article