Doubles etc.

[NJScubaDoc]

I have been happily diving a single 95 with a 30cuft pony. Most of the time it is filled with 28%, and most of the time I don't get to reap the benefits of the oxygen rich (and expensive) gas, as I run low on air before getting close to my NDLs.

The next logical step then, would be to move on to doubles. With the right Nitrox Mix and an inshore location I could easily streatch my NDLs to my little hearts desire and spend a greater amount of time on the whatever it is I'm diving. This is all well and good for a site less than 100 ft, but then arises the question of the deeper wrecks. At 130 feet, with 28% you get 13 minutes of NDL....that isn't very long. So what's next....decompression diving.

I'm a little apprehensive to venture into this type of diving, particularly because I only have a neophytes understanding of the techniques and equipment involved in its application.

I understand there are a few schools of thought in diving doubles period. The manifold setup is one I see most often, but some also dive independent doubles. What are your thoughts on this?

When applying double tanks to decompression diving what is really involved? Sling bottles of greater O2 mixes for decreased hangs? Advanced computers for gas switching? More advanced dive planning? A fat wallet?

Bottom line is I'm trying to extend the time I get to spend underwater.

Gills would obviously be the best solution, and I've got a few geneticist friends trying to figure that one out Wink. Until then though I'll just have to stick to current technologies.

Would appreciate any feedback

 

[fire_diver]

Definately make sure you wallet is the correct size (XXL) before venturing into the wonder world of doubles and deco!

 

[NJScubaDoc]

Well that much I figured....as with anything involved in diving its uber expensive.

 

[gafftape42]

I feel the biggest change between rec and tech diving is attitude. The surface is no longer a solution once you move into deco. You and your team must be prepared to handle all problems underwater. I would suggest finding a good local mentor and progressing slowly. Also if you see someone with a particular rig ask them why they use it. There should be a reason behind pretty much every piece of gear they are carrying.

 

[nereas]

I have been happily diving a single 95 with a 30cuft pony. Most of the time it is filled with 28%, and most of the time I don't get to reap the benefits of the oxygen rich (and expensive) gas, as I run low on air before getting close to my NDLs.

The next logical step then, would be to move on to doubles. With the right Nitrox Mix and an inshore location I could easily streatch my NDLs to my little hearts desire and spend a greater amount of time on the whatever it is I'm diving. This is all well and good for a site less than 100 ft, but then arises the question of the deeper wrecks. At 130 feet, with 28% you get 13 minutes of NDL....that isn't very long. So what's next....decompression diving.

I'm a little apprehensive to venture into this type of diving, particularly because I only have a neophytes understanding of the techniques and equipment involved in its application.

I understand there are a few schools of thought in diving doubles period. The manifold setup is one I see most often, but some also dive independent doubles. What are your thoughts on this?

When applying double tanks to decompression diving what is really involved? Sling bottles of greater O2 mixes for decreased hangs? Advanced computers for gas switching? More advanced dive planning? A fat wallet?

Bottom line is I'm trying to extend the time I get to spend underwater.

Gills would obviously be the best solution, and I've got a few geneticist friends trying to figure that one out Wink. Until then though I'll just have to stick to current technologies.

Would appreciate any feedback

I believe that your "next logical step" would rather be a larger single tank.

Single tanks in the USA get as large as 140 cu ft. That should be plenty for you for NDL diving.

There is still a huge weight advantage in a large single tank compared with doubles.

There is no need for you to venture into the doubles realm, unless you are contemplating (1) decompression diving, in which case doubles are critical for redundancy, or (2) extremely deep diving as in the case of deep-shipwreck or cave diving, which involves decompression diving as well.

 

[xwhitesmokex]

just my .0001 cents...
You cannot venture into passing NDL's unless you are ready to take on decompression procedures.

A larger tank as stated, doesn't increase your NDL's which is what you want, unless at lower depths!!

still taking on doubles is cheaper and relatively "safer" than going rebreather at least the first few years..

(no beat ups on the "Safer" for rebreathers please!)

 

[NJScubaDoc]

the problem with a larger single tank is that its going to be High Pressure. Getting a complete fill on a high pressure tank in the middle of the busy summer is next to impossible. It will cool down and eventually offer no benefit over my LP 95 that is juiced up to 3000 PSI.

The problem with a larger single tank is the length....they get rediculously tall and that doesn't do much for my near perfect trim.

Thanks for the insight though.

 

[LIVES4SHARKS]

I am just now moving into a BP/W setup with a single tank. But I will be in Doubles by next year since I want to take the GUE 'fundies" course. Definitely do your research. Talk to the Tech, DIR, GUE guys and ask questions. Educate yourself and really look at what you want to do with your diving. Also, start diving with those who have the experience with the type of diving you want to do. I have been reading and educating myself on my own and also meeting and going to other forums and asking questions. You will get alot of opinions here and I think it's easier to talk in person and be shown the what and why of things. That is why the advice of getting a mentor is good. Mine has opened a whole new way and world of diving to me!

Good luck and Happy Diving!
Carolyn

"Doing It Right: The Fundamentals of Better Diving"
by: Jarrod Jablonski

This is a good read and explains alot!

 

[Data]

I believe that your "next logical step" would rather be a larger single tank.

Single tanks in the USA get as large as 140 cu ft. That should be plenty for you for NDL diving.

There is still a huge weight advantage in a large single tank compared with doubles.

first off, don't listen to something like this.
diving a balanced rig has nothing to do with how many tanks you use. let's just stay with that and not go any deeper into it.

I think NJScubaDoc is taking this approach from the wrong side.
once you go into doubles, there is a lot more to it then only giving you more gas.
maybe you should work on extending your bottom time with what you have.
let's do a little SCUBA math.
depending on what gas you use and which tables, let's just say you have a NDL of 30min at 100'
if your setup is dragging, your weighted wrong and your trim and buoyancy is crap, you might have a SAC rate of 1.0.
this means at 100' (4ATA) you suck through 4cf of gas per min.
to get to your NDL you would need 120cf of gas.
now you change your setup, you become perfectly balanced, your trim and buoyancy is spot on and you dive a lot more.
your SAC rate is now 0.5 and all of a sudden you only need 60cf for the same dive (easily done on a AL80).
first things first, check your dive profiles, find out what your SAC rate is and if it is excessively high, find out why, talk to experienced divers and ask what changes should be made on your current setup and see how it goes.
only when you're sure you have done everything possible to get the best out of what you have, look into taking a different route in your diving adventures.
simply taking more air with you might cause more problems (and even lead to your death) then it solves.
and before you take on doubles etc. get certified in deco procedures, it will save your life.
just my 200psi

 

[Jimmer]

before you take on doubles etc. get certified in deco procedures, it will save your life.
just my 200psi

I agree with everything in your post, aside from this. There is no reason you need to be deco certified to dive doubles. Infact it's my feeling that being experienced and comfortable in doubles BEFORE taking your deco cert is the logical step. Obviously being deco trained before doing deco diving is necessary tho.

Jim