Weighting Going From Single To Double Steels

[cool_hardware52]

If that's what you really meant, I'd probably limit my statements a bit from the beginning if I were you.

Initially, you said "Doubles implies staged deco", i.e. a vast generalization which I challenged. Now you're more or less saying "Double 100s implies staged deco", which is a slightly different kettle of fish. And I don't disagree with that, since a twin 100 cuf rig holds pretty much the same amount of gas as the D12x232 set I was talking about. A double 100cf rig is way to big and heavy to be a good alternative for no-stop diving. Unless the diver is a masochist...

I speak with 1-2 divers a week that are making the transition from singles to doubles. I've lost track, many hundreds of divers.

Not a single one, as in zero (0), are doing so just to have more gas for recreational dives. *Every* *Single* *One* is doing so in preparation for learning deco diving. All of them.

Based on that I'm going to run the risk of making the horribly sweeping statement that doubles implies deco......

Tobin

 

[Storker]

I speak with 1-2 divers a week that are making the transition from singles to doubles. I've lost track, many hundreds of divers.

Not a single one, as in zero (0), are doing so just to have more gas for recreational dives. *Every* *Single* *One* is doing so in preparation for learning deco diving. All of them.

Based on that I'm going to run the risk of making the horribly sweeping statement that doubles implies deco......

Try visiting the East side of the pond once, it might broaden your perspective a bit.

FYI, rec doubles are rather common in Northern Europe. You're welcome.

 

[Colliam7]

I speak with 1-2 divers a week that are making the transition from singles to doubles. I've lost track, many hundreds of divers. Not a single one, as in zero (0), are doing so just to have more gas for recreational dives. *Every* *Single* *One* is doing so in preparation for learning deco diving. All of them. Based on that I'm going to run the risk of making the horribly sweeping statement that doubles implies deco......

And, I certainly won't challenge your experience, which is obviously considerable, and your statement - it is your experience, and you are simply explaining how your experience leads to your view of the relationship between doubles and deco, and forms the basis for your 'horribly sweeping' statement. Rather, I will add that, in my experience (different than yours) with East Coast, Mid-Atlantic region diving, I know of a number of divers who use doubles for recreational diving, and who do no technical / decompression diving at all. A 'two tank' charter off the NC coast is well-served with a set of double 80s, or (even better) double 100s, Many divers use the same set of doubles for both dives, obviating the need to carry two individual cylinders and change them out between dives. And, those divers stay with recreational NDL limits throughout both dives. Maybe, that is just something unique to this area. My favorite recreational rig for coastal charters, from the perspective of buoyancy and trim is a set of double 80s. In fact, in the shop where I previously worked, we advocated recreational double 80s for that reason, and even had a very handsome set of polished AL80s on display, labelled as a 'Carolina Coastal Rig'. I have taught Open Water (Recreational) Sidemount courses (involving 'doubles') for a number of years, to recreational (only) divers who wanted the advantages of a) additional gas, b) gas supply redundancy, and c) a very stable rig.

I don't know the OP, and have no insider knowledge of the OP's future plans. But, like Storker - who I understand sees a number of recreational divers, new and more experienced, in doubles rigs in Europe - I couldn't make a sweeping statement that doubles always imply deco, simply because that has not been my experience. I agree, that such is a reasonable possibility, but by no means an inevitability.

 

[cool_hardware52]

Try visiting the East side of the pond once, it might broaden your perspective a bit.

FYI, rec doubles are rather common in Northern Europe. You're welcome.

Welcome for what, continued condescension?

DSS sells worldwide, as in *everywhere* I can point you to a recent thread where a diver in the UAE elected to rely on my advice.

I've had contact with literally 100's and 100's of divers making the jump to doubles. Just how much more perspective do you think I need to understand that the vast majority of divers considering doubles are doing so specifically because they want to explore diving beyond rec limits?

Not one wanted to buy two tanks just to dive within rec limits.

Not one wanted two tanks to maintain , VIP / Hydro / just to dive within rec limits.

Not one wanted two valves and a manifold to maintain just to dive within rec limits.

Not one wanted to invest in a new wing just to dive within rec limits.

Not one wanted to pay for two fills just to dive within rec limits.

Not one wanted to buy two first stage regs or maintain them just to dive within rec limits.

Not one looked forward to the extra weight of two cylinders.

Every single one of these many hundreds of divers were equipping themselves with doubles so they could dive beyond rec limits, or atleast believed that they would eventually.


As I have said many times doubles are a two edge sword, more gas (even in modest sized tanks) which is often enough to get people into deco, but may not be enough to get them out.
I'd (gasp) recommend those considering big singles understand the implications of larger gas supplies too.

Are there divers that use doubles recreationally? Sure. Does that somehow mean that it is wrong to include and plan for these same divers getting into deco? Please explain specifically why.

Tobin

 

[cool_hardware52]

I don't know the OP, and have no insider knowledge of the OP's future plans. But, like Storker - who I understand sees a number of recreational divers, new and more experienced in doubles rigs, I couldn't make a sweeping statement that doubles always imply deco, simply because that has not been my experience. I agree, that such is a reasonable possibility, but not an inevitability.

Humm, when did I say doubles makes deco a certainty? It's only prudent to include the possibility of needing to "deco out on back gas" when calculating required ballast. This thread was after all started by a diver asking about weighting.

Where is the harm in 1) Understanding the implications 2) Preparing for them?


Tobin

 

[Storker]

I have taught Open Water (Recreational) Sidemount courses for a number of years, to divers who wanted the advantages of a) additional gas, b) gas supply redundancy, and c) a very stable rig.

This is also the most common reason I hear for preferring a small twinset over a single: They sit better on your back, and your rig's COG is closer to said back leading to less tendency to turn turtle.

 

[cool_hardware52]

I don't include the actual webbing as it is near neutral, the stainless bits yes the webbing no for purposes of ballast calcs.

A basic hogarthian harness kit does not include a 2nd buckle either. Some use them some do not, and many like myself that dive with very little additional ballast use a plastic buckle to constrain the can light.

Tobin

I weighted a DSS medium plate with the harness kit, but without the harness webbing, 5.9 lbs. The 12 ft of webbing that we furnish, which is far longer than most need, is about .85 lbs.

Tobin

 

[Colliam7]

Humm, when did I say doubles makes deco a certainty?

Uh, maybe it was the '. . . horribly sweeping statement that doubles implies deco . . . '? Of course, I was using what may be a somehow archaic, albeit still common, definition of 'implies' - i.e. 'to express or state indirectly'. Or, maybe, we are like the Brits and Americans (to paraphrase what was probably a misquotation to begin with), 'two countries separated by a common language'.

I do confess, that reading your 'horribly sweeping statement', immediately after reading your vigorous assertion that:

Not a single one, as in zero (0), are doing so just to have more gas for recreational dives. *Every* *Single* *One* is doing so in preparation for learning deco diving. All of them.

caused me to perhaps naively leap to an interpretation that is not entirely accurate. But, I am glad you have clarified your meaning. And, I find that we are probably not entirely at odds, even if our experiences have been different:

Where is the harm in 1) Understanding the implications 2) Preparing for them?

No harm at all. I fully agree with both points.

 

[kelemvor]

All,
Just trying to get a rough idea of what to expect going from single steel to double (yes I know the whole story of doing a weight check...etc. just looking for a place to start). Currently in fresh water cold diving with drysuit I wear 15lbs lead, steel backplate (6lbs) with steel cambands(not plastic...add probably 1lb negative), and a STA (2lbs) along with a Faber FX 100 (which is about -.5lbs empty). I will be going to double tank Worthington x7-100 which are a bit more negative compared to the Faber FX100s. How negative are a typical manifold and tank bands? I know I will add another reg set so that may be another say 2-4lbs negative as well. Any thoughts and considerations to get me a ballpark. I will be doing the proper weight check when I get to the water, just want an idea of where I might end up. Thanks!

I switched to sidemount double worthington x8-108 and I don't need any lead with a drysuit. There's no plate in that setup, either. Diverite sells a plastic (kydex maybe?) backplate, but it's not really much less negative than my aluminum apeks plate.

The buoyancy loss exit simulation in cave class with this rig was probably the most fun part of cave class for me. It wasn't particularly difficult, except to try and keep from laughing about how absurd it must have looked. I might have to rethink the configuration if it was some other scenerio than cave where I could just bounce on out in the event of total buoyancy loss.. on the other hand, there's both BCD and bladder that would have to go for that to be an issue. Only other option is carry less gas, afaik.

 

[cool_hardware52]

Colliam,

I noted my direct experience communicating many hundreds of divers from all over the world to counter Storker's repeated efforts to paint me as an ignorant "provincial" who doesn't really understand who is diving what or how. Apparently the recreational use of small doubles is some sort of hot button for him. I have no idea why. We went to the mat previously when I had the unmitigated gall to suggest that divers using doubles should be trained on how doubles and manifolds actually work.

This thread was started by a guy living in New York inquiring about weighting for 2 x hp 100's

I quoted his post and replied directly to him.

I do believe that any diver stepping off the boat with enough gas to get themselves into deco should 1) Have some working knowledge of the risks, and 2) Be equipped to use the gas they have to solve the problem if they happen to wander in to the land of virtual overheads.

It's pretty hard to get into much deco with typical single cylinders. Not impossible, but most won't be going the chamber to get unbent if they are diving 80-100's They might incur a bit of an obligation, particularly if they do back to back dives with insufficient surface interval, but they will still for the most part be on the low end of the risk range.

Not true for the guy diving even 2 x 72's Lose track of time, get distracted, get lost and can't find the up line and now things have changed. They may have planned only to use their doubles as a convenience, i.e. two rec dives without changing tanks, or prefer the stability, or want to gain some experience before they take "Intro to Tech" but they have enough gas to get into more trouble than they would with a lp 95.

I'm pleased to learn that you agree that being weighted so they can finish their deco as they pull a vacuum on their back gas is a prudent choice.

Tobin