Tips on starting diving doubles

[old frogman]

Yeah, I understand more than you think.
You know, I will probably end up diving those double 72's with no BC in a 7 mm wetsuit. And I will be using a single second stage and an SPG only.
You probably wouldn't dive them without a wing and a drysuit. In fact you probably wouldn't dive them at all because they have a single center post manifold with a J valve and not two posts with an isolator. And plus its yoke not DIN.

How is it that I dive a single 120 now with no BC, but somehow I'm going to straight to hell if I put on 140 cf air split between two tanks that end up lighter together than the 120?
I'm diving your definition of a "balanced rig" now with a big single. Although "balanced rig" to me means something entirely different from what you think it means. To me I'm just properly weighted for the type of diving I do.
So, how is the twinset different? 10 more cf of air?
Or maybe not if I get a short fill.

I would like a genuine answer, not "you need to do more reading" and "you have a lack of understanding". I've been doing this a while and probably understand more about weighting and minimum weighting than most people these days.

Did you figure it out on your own or did someone feed this to you?

Hi Eric,

I have dived twin tanks with a USD Aquamaster twin hose regulator down to 200 feet on air with no BC, just a wetsuit, on numerous occasions in my younger days. I am still alive and still diving (hence the old frogman). Young men today don't spend enough time in the fresh air, spend too much time with computers and tend to overthink problems. No common sense.

Good luck with your adventure.

 

[John C. Ratliff]

@halocline Good feedback. I do already have the Lp 72's, but I'm not married to the idea of using them for this. Could always use some of my AL 80's (admittedly kinda sucks since I already have Lp 72 bands, but the $70 I spent for two sets of those isn't gonna kill me if I don't use them).

Hadn't thought through the wing profile issue. I do fossil diving, in a river, so generally I dive pretty negative, and sometimes am bring up an additional ten or so pounds of whatever I found down there (which obviously, in an emergency, is ditchable. Sharks teeth and glass bottles aren't worth dying over), so I thought I'd want the extra lift. However, you have a point, the current might make diving the big 60 wing a pain in the tuchas. I'll probably give it a try and if it sucks, see if anybody on here wants to do a 1-1 swap or something.

SM is out due to entanglement risks/me not wanting to faff around with a tank on each side of me. I'll definitely consider the manifold issue. Do you mind sharing why independent doubles would less safe? I understand issues can occur during the switch/you could lose track of which tank had what gas (pressure, both tanks will hold the same gas mix), but presuming I drill the switch a lot (which I intend to) it feels like the safety issue falls out, unless I'm missing something. I'm not super opposed to a manifold; independent doubles just seemed simpler when I was making this plan, but I could definitely pencil a manifold into the scheme.

If I were you, I’d go with the twin 72s. I’ve dived them over the years, and they really perform well in the water. Dry the independent doubles, and know that you can get a manifold if you want to change after trying the other route.

SeaRath

 

[happy-diver]

How do you know it's effing stupid if you never used it?

There are people out there that are quite capable of making a qualified assessment without having used it

Young men today don't spend enough time in the fresh air, spend too much time with computers and tend to overthink problems. No common sense.

Many people of yesterday and today of any age whether they spent time in the fresh air or prefering to read books could also be subject to overthinking issues

Thing about common sense is the people generally lacking don't necessarily need it to the degree others do

 

[happy-diver]

Thing about the cultists and their sooths of doom and their aluminium tanks and drysuits, is that I stay
away from their forum unless it rolls by in What's monthly so if they could just reciprocate the courtesy

I think they're generally okay just a little lonely

 

[SelfDiver]

Your response shows a lack of understanding when it comes to suit compression and the balanced rig. You can talk about reserve pressures and your 15-foot stop until the cows come home, but you're missing a piece of the puzzle.

@eightytwenty
I am very dumb and slow witted. Please help me figure out the missing piece of this puzzle.
Twin LP72 with a wetsuit. What am I missing?

 

[old frogman]

There are people out there that are quite capable of making a qualified assessment without having used it




Many people of yesterday and today of any age whether they spent time in the fresh air or prefering to read books could also be subject to overthinking issues

Thing about common sense is the people generally lacking don't necessarily need it to the degree others do

In general, I agree with all your comments. However, in this instance, this chap has failed to explain why the twin manifold in question is crap. This suggests a lack of capability to assess and then to clearly articulate its deficiencies. In the 1970s and 1980s this particular twin manifold was used by a number of British Commonwealth naval units and special force units successfully and in some very harsh environments.

The selection of these manifolds was based on the following:
Detailed user requirement statement.
Detailed research and development in consultation with scientists and engineers.
Detailed testing by the respective naval experimental diving unit.
Extensive field testing by respective fleet diving units and special force units.
Formal approval by senior commanders.

Sure, there may be superior products on the market today however, the twin manifold at that time worked quite well.

In conclusion, many of the criticisms that have been directed at this particular twin manifold are based on false assumptions. These false assumptions are clearly based on no or limited knowledge of equipment technology over the decades.

I would suggest to these uninformed young chaps to look beyond the doctrine of your particular training agency.

 

[nadwidny]

In general, I agree with all your comments. However, in this instance, this chap has failed to explain why the twin manifold in question is crap. This suggests a lack of capability to assess and then to clearly articulate its deficiencies. In the 1970s and 1980s this particular twin manifold was used by a number of British Commonwealth naval units and special force units successfully and in some very harsh environments.

The selection of these manifolds was based on the following:
Detailed user requirement statement.
Detailed research and development in consultation with scientists and engineers.
Detailed testing by the respective naval experimental diving unit.
Extensive field testing by respective fleet diving units and special force units.
Formal approval by senior commanders.

Sure, there may be superior products on the market today however, the twin manifold at that time worked quite well.

In conclusion, many of the criticisms that have been directed at this particular twin manifold are based on false assumptions. These false assumptions are clearly based on no or limited knowledge of equipment technology over the decades.

I would suggest to these uninformed young chaps to look beyond the doctrine of your particular training agency.

Young?? I wish.

Training agency I can't see beyond. ?? Pick one. PADI. NAUI. SSI. IANTD. GUE. TDI. Which one am I not looking beyond?

When I bought the cheater bar I was new to tech diving. Manifolds were newer, maybe even not around yet. I can't remember. It was a long time ago. I bought it thinking it was pretty good alternative to the independent doubles I was already diving. I looked at it and realized that it was a piece of ship compared to independent doubles. Cheater bar had multiple failure points and so I never used it. If you can't see the failure points then that is due to your lack of knowledge. Not mine. The fact that they were used by various gov't agencies just shows that endorsement by a naval unit is more indicative that there was nothing better available at the time. By the mid-90s there was. The manifold.

I can't see any reason that someone would suggest a cheater bar now when there are much better options available. Unless one is so old and stuck in the 70s that they can't accept that newer stuff is better. In which case maybe it's time to hang them up.

 

[old frogman]

Young?? I wish.

Training agency I can't see beyond. ?? Pick one. PADI. NAUI. SSI. IANTD. GUE. TDI. Which one am I not looking beyond?

When I bought the cheater bar I was new to tech diving. Manifolds were newer, maybe even not around yet. I can't remember. It was a long time ago. I bought it thinking it was pretty good alternative to the independent doubles I was already diving. I looked at it and realized that it was a piece of ship compared to independent doubles. Cheater bar had multiple failure points and so I never used it. If you can't see the failure points then that is due to your lack of knowledge. Not mine. The fact that they were used by various gov't agencies just shows that endorsement by a naval unit is more indicative that there was nothing better available at the time. By the mid-90s there was. The manifold.

I can't see any reason that someone would suggest a cheater bar now when there are much better options available. Unless one is so old and stuck in the 70s that they can't accept that newer stuff is better. In which case maybe it's time to hang them up.

Good on you mate. It is good to see that you can string together a few more words. I agree with you that the current manifolds are superior (in particular for technical/cave diving).

For the benefit of others who may be tuning in. The other chap that is using the cheater bar is not intending to do cave diving or deep diving. He just wants to do shallow recreational level dives. He also wants the flexibility of easily splitting cylinders when required. Granted that the cheater bar has additional "potential" failure points.

When you look at the collective user requirements, it's essentially a question of balancing the "opportunity" presented by the cheater bar with the "potential" risk presented by its inherent failure points.

Consequently, if you do a comparative analysis of opportunity versus risk, based on the user requirements, the conclusion should be the cheater bar.

However, the problem is dogma from some training agencies that are still operating on the concept of safety management which results in stiff and inflexible rules. The result is that the slightest risk is viewed as a fatality waiting to happen. The consequence is a lot of people end up spending a lot of time, money and energy on diving gear and courses they do not necessarily require for their specific diving activity. I would argue that these agencies are the ones stuck in the 1970s mentality.

A strategy that is emerging slowly since about 1995 is risk management. Few people have caught onto it. Essentially, risk management is a structured decision process which enables you to decide what gear and rules/procedures are the most appropriate for a specific diving activity. It does not replace rules. It enables you to apply rules in the most efficient manner, balancing risk with opportunity.

The US Navy has converted to risk management for dive planning. Have a look at the latest edition of their dive manual.

 

[Nick_Radov]

The US Navy has converted to risk management for dive planning. Have a look at the latest edition of their dive manual.

Yes, I've read it. US Navy personnel (and military divers in general) sometimes have to take on certain levels of risk in order accomplish the mission. I have great respect for Navy divers but it's a different type of diving altogether. Sport divers are under no such constraints. We don't really need to "manage" risk: we have ways to cut the risk to virtually zero, even for fairly complex and challenging dives. The stiff and inflexible safety rules are part of what enables this. And we always have Option #1 available.

In 2025 there are no good reasons to ever dive with convoluted junk like a "cheater bar" or back-mounted independent doubles. Proper isolation manifolds are cheap and readily available (along with the training on how to use them safely). If someone wants to dive with obsolete gear due to nostalgia or poverty or whatever then go ahead, do whatever you want. You probably won't die. But you're not going to convince the rest of us that it makes sense or is even remotely a smart idea.

 

[SouthernSharktoothDiver]

@Nick_Radov Why do you say independent doubles are "convoluted junk?" Because I'm been mulling it over and thinking about them, and while I'm not sure they're the best course (still making up my mind on that), they do offer several advantages over a manifold. Ignoring the full redundancy (as many have said, an isolation manifold is reliable enough that I'm not so worried about it failing), you get a few things I like.

First, I have a rig that easy to put up and take down. So, rather than needing a designated set of tanks that are manifolded together (and have to be drained/need new valves to use as singles) I have a pair of tanks that I can turn from doubles to singles simply by removing two sets of bands (<10 minutes of effort, no need to go get new fills). Allows me to run multiple sets of doubles in a day without needing to bring them in as a unit (so I can bring a half dozen individual tanks and pair them off when I'm about to use them, easier to move and store in transit), and cuts down on me having more tanks than I need (which, even ignoring money as a consideration, because I could certainly afford more tanks, I only have so much space to store them). I hear people on here talking about having many sets of manifolded doubles, for different gas mixes and so on, and while I would love to be in a place to able to do that, I can't keep three sets of doubles and eight single tanks in my closet, but I can keep eight single tanks and two sets of bands much more easily.

Secondly, it's a setup I can travel with fairly easily. Much as sidemount divers commonly tout the benefit of being able to use any AL 80 at any destination, I can do the same just by packing a set of al 80 bands in my carry on and renting the tanks at destination. While I might could rent manifolded doubles, or pack in the manifold and valves as well as the bands, both of those are considerably more limiting. I don't currently travel to dive, but this is definitely a consideration.

Now, on the flipside, you do get several advantages versus independent doubles. Draining the gas uniformly removes the need to switch regs periodically, but frankly periodically switching regs is likely good practice for emergencies anyway, builds muscle memory so that if your reg fails for some reason, you can smoothly swap to the other because you've done it a thousand times before. Similarly, a manifold does offer you all the gas in both tanks in failure, whereas independent doubles you'd lose one tank if it failed, but I'm diving neither cave nor deco. I don't have any kind of overhead, and my TTS is usually under 30 seconds, as I'm often in shallow enough water to need even so much as a safety stop.

For my use case, I truly do not see why independent doubles represent any functional concern. I understand that a manifold is "better," but many things in life are "better." My concern is not with whether a thing is optimized, but rather if it's equally safe and functional. For what I'm doing, I genuinely don't see why independant doubles are a huge issue, so I'm planning to give them a try. Maybe I hate them and buy a manifold the next week. Maybe not. In the meantime, I'd love to hear why, for the diving I'm doing independant doubles are more dangerous/truly a problem compared to manifolded ones. Because saying "everybody dives manifolds for a reason" and calling independant doubles "obsolete junk" is not compelling to me.

Not trying to start a fight. Not rejecting anybody's advice. I've just been thinking this over for a little while, and these are my questions/thoughts in the result. I do think I'm going to pass on the "straight pipe" manifold, as I don't want to lose the rendundancy and easy disassembly without gaining the reliability and easy of use you'd get from an isolation unit, but that's a personal choice. No shade to those who dive it.