Doubles

[jonnythan]

Also, if you're 10 minutes into the dive and your isolator is closed... keep it closed and abort the dive.

Who knows what is in the other tank. You don't want to hear the woosh and then realize you're diving an unknown mix.

 

[wedivebc]

Also, if you're 10 minutes into the dive and your isolator is closed... keep it closed and abort the dive.

Who knows what is in the other tank. You don't want to hear the woosh and then realize you're diving an unknown mix.

Wouldn't it likely contain whatever gas you used last dive? I usually check things like valves open and isolator position befoe the dive so it's never been an issue

 

[Tom Winters]

Having big tanks doesn't magically turn people into idiots.

Nope - I didn't need big tanks at all...

 

[pickens_46929]

Rent (or borrow) the tanks and BC... practice in the pool before open water... go with some other experienced people who dive doubles... go through a DIR/Fundamentals class.

Started out purchasing the duals and trial and error... learned many lessons the hard and expensive way... still had fun but would do things differently now.

How you might ask?

1) BP/W

Got a very good deal on a Dacor RIG/2 which is a nice BP/W but not quite what I'd call a "pure" BP/W like Halcyon, etc. Too many little danglies, wing is connected to the plate... I like it but it isn't exactly streamlined.

I'd go for a more streamlined setup the next time (or will be soon myself anyways) like a Halycon or ... (insert board favorite here)

2) DIN

Went yoke initially since all my regulators were yoke and the tanks had inserts to do either yoke or DIN. Now converting everything over to DIN or buying new DIN regulators. Just delayed things a bit rather than avoided the cost.

Would have kept my original yoke regulators for warm water and purchased a set of decent (insert Apex, Scubapro... here) DIN regulators for my doubles.

3) HP tanks

Ok, maybe this is still under debate... I'm now overfilling my LP tanks and am very satisfied but have been diving with buddies now that have double HP tanks... dual HP 108's are about the same size as my LP 85's... and they aren't doing anything "bad" by filling to 3500 psi...

4) DIR

Now that I know what I know and as important, know what I still have to learn, DIR really looks like the way to go in many ways... simple pressure gauge, bp/w, etc. all make for a more streamlined diver and also a self-reliant diver (as opposed to relying upon technology like computers)... doesn't preclude the use of computers... just relying 100% on them.

Well that's my $0.02...

 

[pickens_46929]

Wouldn't it likely contain whatever gas you used last dive? I usually check things like valves open and isolator position befoe the dive so it's never been an issue

I don't use anything but air in my doubles right now, so unless you're doing trimix or nitrox, you shouldn't have an issue opening up the isolator valve underwater.

This also brings up the issue of manifold shutdown / isolation drills and practicing them both above water, in shallow or confined water and finally at depth. Good bouyancy control is required but this is an essential skill for anyone diving doubles.

Dave

 

[pickens_46929]

I'll toss in that it's also much easier to use doubles on a boat than singles. No tank switching or anything.. easy easy. And you also get to use more of your gas.. no leaving 1200 psi in one tank and 1000 psi in another, which you then have to get filled. You've got enough for one more dive after that in dubs.

I do strictly rec diving, and while tech diving is in my future, I find the doubles much more convenient for what I do now.

Gotta agree here with Jonnythan... being able to do two dives without switching tanks... the added safety of all that gas on your back... plus all the weight coming off your belt and getting balanced in the BP/W + tanks... it'll feel weird to start with but once you get used to doubles, you'll find diving a single strange.

 

[JS1scuba]

Ok i have a question for you all. I would like to get into using doubles. What would be the best way to start.SHould i just go out and get a Rig and learn as i go or is there any classses that deal with doubles...Not soo much Techincal class but just diving doubled at a rec. level. Anyways let me know how you all got into it. Thanks

Doubles ......... if a single tank is not working for you because you want to do longer dives or to take advantage of the extended times available on recreational depths with oxygen enriched air ....... doubles is the way to go.

You do not need to be a "Tech diver" to use doubles.

What do you need ?

two tanks
manifold
tank bands
BC that will mount to it
two regulators,

go diving.

A quality professional dive center should be able to set you up without much of a hassle. You dont need long discussions of style or methods or religion etc.

What you need to know is this. When you have a lot of gas you can get into trouble really fast. Especially if you extend into decompression and do not plan for it.

To practice with doubles adopt the rule of thirds.

1/3 out
1/3 back
1/3 left in the tank when back on the boat.

Or if no-stop diving .......

1/4 out -- 1/4 back --- half on the boat

then you can use the set for a 2nd short dive.

Best tanks to start out with .......

warm water --- twin alum 80s
cold water heavy wet suit or dry suit twin LP-85s ........

I dive with doubles on 90% of my dives. The balance is perfect, the fit is great, dual regulators are safer, its just a better way to be.

Regards,

 

[WaterDawg]

Wouldn't it likely contain whatever gas you used last dive?

Not really. At the shop I work for we do PP EAN fills and its not uncommon to get called away mid way thru. If the Tech filled from the left post and the Iso was closed you guage would read full and you RIGHT tank, the one your breathing from off the primary reg has the mix you last used. So yeah its a good idea to switch IMO.

 

[jonnythan]

Wouldn't it likely contain whatever gas you used last dive? I usually check things like valves open and isolator position befoe the dive so it's never been an issue

Maybe, maybe not. How do you know when the isolator got closed?

How do you know what went on at the fill station, who closed it, and at what point in the gas mixing it got closed?

Are you really going to chance it?

 

[wedivebc]

Maybe, maybe not. How do you know when the isolator got closed?

How do you know what went on at the fill station, who closed it, and at what point in the gas mixing it got closed?

Are you really going to chance it?

Good point, I have my own compressor so no one fills my tanks but me but I guess most people wouldn't have the same advantage. Just seems if you trust the tank monkey to fill 1 tank with good breathable gas, why not 2?