Steel vs aluminum 40 for redundant: which is better?

[coldwaterglutton]

My son needs to add a redundant air source for his first deep ocean dive next weekend.

I have used for many years an aluminum 40 for that purpose, carried as a sidemount.

My son still dives traditional with a backmount tank but will sidemount his redundant setup. This will be nitrox, including up to 36% for next week's ocean dive at 80 feet.

I am wondering on the pros and cons of a HP steel 40 vs a traditional aluminum 40. Obviously the HP is heavier, but has a bit better buoyancy although it may leave him a little unbalanced until he figures out the right weight for his opposing trim pocket.

Is there any reason to go steel vs aluminum?

 

[grantctobin]

My son needs to add a redundant air source for his first deep ocean dive next weekend.

I have used for many years an aluminum 40 for that purpose, carried as a sidemount.

My son still dives traditional with a backmount tank but will sidemount his redundant setup. This will be nitrox, including up to 36% for next week's ocean dive at 80 feet.

I am wondering on the pros and cons of a HP steel 40 vs a traditional aluminum 40. Obviously the HP is heavier, but has a bit better buoyancy although it may leave him a little unbalanced until he figures out the right weight for his opposing trim pocket.

Is there any reason to go steel vs aluminum?

View attachment 843991

Cons:
Shorter (unlikely to actually sit properly as a sidemount bottle)
~6lb negatively buoyant when full with a stage kit and a regulator setup. An AL40 is ~2lb.
Rides poorly, including when empty
Adding additional weight to his right side to offset the bottle will more than likely make him overweighted
You’re making a bottle part of your core ballast system. In the event you remove it, you cork and it’s unwieldy.

Pros:
None

This is silly. If you want to consider suffering him through it or being masochistic, maybe consider giving him your AL40 for the purposes of the class and trying the HP40 yourself. An AL40 can likely be “side mounted” with the simple addition of a bungee to the backplate. I suspect this will be quite a struggle with such a shorter cylinder, to ignore all of the above.

 

[mr_v]

@coldwaterglutton, why does your son need a redundant air source for a dive that is only 80'?

 

[tursiops]

My son needs to add a redundant air source for his first deep ocean dive next weekend.

I have used for many years an aluminum 40 for that purpose, carried as a sidemount.

My son still dives traditional with a backmount tank but will sidemount his redundant setup. This will be nitrox, including up to 36% for next week's ocean dive at 80 feet.

I am wondering on the pros and cons of a HP steel 40 vs a traditional aluminum 40. Obviously the HP is heavier, but has a bit better buoyancy although it may leave him a little unbalanced until he figures out the right weight for his opposing trim pocket.

Is there any reason to go steel vs aluminum?

View attachment 843991

Do you really mean sidemount, or do you mean slung from a chest and waist D-ring?
There is NO reason to carry a steel 40 rather than an AL 40.
Is this a training dive? What agency requires a redundant gas source for an 80 foot "deep" dive?

 

[broncobowsher]

A slung (sidemount style) AL40 can be handed off to someone else without greatly screwing up your own weighting. Try that with a steel and you won't like it.

 

[rongoodman]

What do you mean by “better buoyancy”?

 

[coldwaterglutton]

What do you mean by “better buoyancy”?

I meant if he ends up using the tank it won't go positive as an aluminum one, but it's all relative.

Pretty clear that aluminum is the only way to go.

 

[coldwaterglutton]

Do you really mean sidemount, or do you mean slung from a chest and waist D-ring?
There is NO reason to carry a steel 40 rather than an AL 40.
Is this a training dive? What agency requires a redundant gas source for an 80 foot "deep" dive?

Yes, slung is a more accurate description.

And it's not an agency requirement but a dive boat requirement. Pretty much standard for the NY/NJ dive boats to require redundant, or isolation manifold for doubles, etc. Plus it's also a very good idea.

Just background, taking my younger son to the Mandy Ray @85' to make sure his salt water buoyancy and trim are optimal. Then we are hitting the Oregon, the San Diego and U-853 over the summer. These are all deep wrecks by recreational standards. He has decent northeast experience but at shallower depths and hasn't yet carried a redundant tank. I myself have an aluminum 40 with my old Titan on it that I've carried for quite a while.

 

[mr_v]

@coldwaterglutton, ok, so their boats - their rules. Although the requirement is silly because you can dive with a redundant air source without any practice switching between gas sources to meet the check mark. A diver who has a reduntant air source but no practice using it may take a bad situtation into a worse one.

For better experience, get yourself and your son into doubles. No need to go huge - 50LPs should do.

 

[Paul Desmarais]

Unless you are diving solo, the added complexity of the pony bottle and harness, especially during a wreck dive where you penetrate and risk entanglement seems less safe, not more so. Personally, I dive solo (and am certified self-reliant do so).

That said, my personal preference for solo is an aluminum 19 on chest and belt D-rings. The weight, relative to the weight I carry, is not enough to unbalance me and for depths of 30 meters or less, provides sufficient gas for a safe ascent, including safety stop, in the event of a primary regulator failure. It is also smaller, less awkward both on the boat and for shore diving, as well as during the dive.

To be honest, a requirement for a redundant air source for a recreational dive of less than 30 meters sounds more scam to sell gear as opposed to any kind of honest concern for safety. It's like some boats in Florida that require a nitrox certification to dive on the boat. The requirement has nothing to do with safety and everything to do with selling the nitrox course and streamlining their own support tasks - having to supply only one gas is easier, logistically, for them and reduced the # of personnel hours needed to support the diving.