Would there be anything wrong to dive independant doubles without a manifold?

[metridium]

O-ring wrote...
Banded doubles with iso would be the best choice. I am just thinking what a caribbean dive op would tell me if I walked in and started taking their tanks apart. If you could pull it off, that makes a lot of sense. If not, a little creative staging might be in order.

Okay, that makes sense. I'd been thinking along the lines of having this planned in advance: either clearing it with the dive shop or presenting them with a fait accompli.

O-ring wrote...
I have never staged an 80, but 40s disappear underwater..

Now I'm really tempted to get a 40 and try it out....even though Tech class is at least a year off.

 

[Scubaroo]

metridium once bubbled...
Now I'm really tempted to get a 40 and try it out....even though Tech class is at least a year off.

Just picked up a 40 a couple of weeks ago - it's coming along on 6 dives weekend after next (skiing this weekend - oh the misery). I've used a 40cf of O2 before on a couple of dives - they just ride up out of the way behind your left shoulder. Luxfer is the tank to get - they are more buoyant than Catalinas, and the buoyancy makes them ride up higher out of the way. There's a thread in the tanks section I started discussing which tank to use - someone posted side-by-side pictures of the two tanks underwater, and the catalinas hang like a dead dog (staged of course).

 

[O-ring]

metridium once bubbled...
Okay, that makes sense. I'd been thinking along the lines of having this planned in advance: either clearing it with the dive shop or presenting them with a fait accompli.

Now I'm really tempted to get a 40 and try it out....even though Tech class is at least a year off.

We thought about it briefly in Bonaire, but decided option #1 was the safer choice and we just stuck to the shallow stuff..

 

[metridium]

Scubaroo wrote...
I've used a 40cf of O2 before on a couple of dives - they just ride up out of the way behind your left shoulder. Luxfer is the tank to get - they are more buoyant than Catalinas, and the buoyancy makes them ride up higher out of the way.

Did you have much trouble getting the 02 without a tech or advanced nitrox card?

Thanks for the tip on Luxfers!

 

[Scubaroo]

metridium once bubbled...
Did you have much trouble getting the 02 without a tech or advanced nitrox card?

Thanks for the tip on Luxfers!

Loaner bottle from a dive buddy with his own fill station at home. He took it off me after the second dive - my buoyancy control at the time wasn't good enough to hold the 20' stop while doing a reg change (first dive with doubles ).

I bought mine for a future TDI Advanced Nitrox.

 

[MikeFerrara]

Everyone I know who has a need for doubles dives them more than 10 times per year. I have grown so fond of my doubles that I now prefer them for just about any dive. Depending on the depth of course you might not need more bottom time unless your planning on staged deco. On fairly shallow dives you might run out of gas before bottom time but it will still be a long dive. I treat a decompression obligation similar to an overhead so I want a real set of doubles. If you really prefer independents than dive them but if you think manifolded doubles are best that's what you'll want. IMO, the number of dives per year isn't important. What's important is having what you think is the right equipment for the dive. I know I wouldn't change the way I dive to save the cost of a third or fourth tank to be used as singles. If you own the tanks it isn't hard to break down the doubles when you need a single either. If your traveling by air you usually can't take tanks anyway.

I guess we really should look at the specific dives your planning on doing.

 

[large_diver]

Met,

To follow up on your question about "why sling a stage".....I'll take you through my reasoning. I don't propose this as "the" answer, just my opinion on when a stage can make sense.

To me, diving doubles is something that requires practice -- if you do it a lot, it becomes second nature.

Most of my diving is single tank local shore diving; that being said, I do like to occasionally dive deeper wrecks in the 80-100 foot range. I don't do these dives regularly enough to want to invest in the expense or complexity of doubles, and I certainly don't want to be humping big doubles all over the place on shore dives where slippery boulders and scrambling up/down hills are the norm.

Can I do these dives with a single tank -- yes....but the stage provides a way to further minimize risk without the added complexity, cost and training issues of doubles. I DO NOT use the stage gas in planning my dive...it's just there as a back-up.

To me, the stage provides an option that is easier to manage in many respects -- easier to use, easier to practice with/more manageable at shore diving sites, no breaking down doubles, etc., etc.

My $0.02.

 

[Jackknife]

Scubaroo once bubbled...
Remember the context the question was asked in - Jackknife only wants to dive doubles maybe ten times a year. Using a slung stage, as long as his current BC has another 3 pounds of spare lift capacity he's not using, he can take 160cf of air along instead of 80cf, and only has to fork out for a stage sling kit (~$40), which takes about 2 minutes with a plain screwdriver to assemble on a rental tank, and the $10 or so for a tank rental. No need to upgrade BCs or wings to one that can accommodate doubles bands, which you would still need with independant doubles.

As he said, it's only for "more bottom time", no overhead penetration, so if he did lose a first stage, he can bail out on the remaining tank.

So at $40 for a kit, and maybe $100 in tank rentals, it's cost him a total of $140 for his 10 "doubles" dives for the year, and he doesn't have to buy a new wing or BC, or independant doubles kit, or manifold. He will need another first stage/second stage/SPG though.

Assuming he has shoulder/hip D-rings to sling the bottle from of course

Because I do like to stay down longer on dives, I have been using my 40 cu. as additonal gas, for rock entries or long walks to to the water, that's what I have been doing. It definitely has it's benefits.

 

[Scubaroo]

Assuming non-decompression, non-overhead profiles, and that you and your buddy both have the same additional gas, similar SACs, and you're incorporating using the gas in the 40cf or 80cf stage into your profile, at what point are people doing reg switches?

Breath backgas down to halves minus rockbottom (same as you would if just using a single tank for these types of dives), then switch to the stage? Then, how far do you breath the stage down?

No doubt this sort of stuff is covered in advanced courses like an advanced nitrox, or deco classes, but I don't see any problem in taking along another 40cf of gas if I'm staying under the NDLs for the dives, and it's good practice for future diving where gas switches become necessary...

 

[O-ring]

Scubaroo once bubbled...
Assuming non-decompression, non-overhead profiles, and that you and your buddy both have the same additional gas, similar SACs, and you're incorporating using the gas in the 40cf or 80cf stage into your profile, at what point are people doing reg switches?

Breath backgas down to halves minus rockbottom (same as you would if just using a single tank for these types of dives), then switch to the stage? Then, how far do you breath the stage down?

No doubt this sort of stuff is covered in advanced courses like an advanced nitrox, or deco classes, but I don't see any problem in taking along another 40cf of gas if I'm staying under the NDLs for the dives, and it's good practice for future diving where gas switches become necessary...

Breathe the stage down first and then switch to backgas..