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View Full Version : Noob question: Small doubles or triples?



freediver
11-08-2007, 08:50 PM
Even though I freedive alot, there are times I need to blow bubbles when shooting video so here's my question:

I'm looking for information about getting my first set of tanks. I like the idea of using smaller tanks and wanted to find out recommendations about the ideal first setup. I want to use nitrox with them, and am considering double 40's possible triple 30cu ft tanks. Since I have no idea how this works as compared to a single tank, I wanted to ask the community for some guidance

The reason - they appear to be more balanced and provide a more streamlined profile in the water and this appeals to the freediver in me.

What special considerations need to be taken, etc?

Can anyone give a parts list for what would be needed to put together a setup like this - I understand the tank end of things, but I also dive with Poseidon regs using DIN valves and want to dive that with the dual tanks - how to attach both tanks with a manifold(?) etc is what I'm clueless about.

I was at DEMA and this tech diving stuff is a little overwhelming to this minimalist freediver so any input sure would be appreciated.

My LDS has no clue about this kind of thing so I'm having to find out by asking questions here.

TIA,

The Publisher
11-08-2007, 09:56 PM
Can I vote for none of the above? ;)

How about a high pressure steel 80? They're are full at 3500psi, and are really small. Small doubles are going to weigh a bit more I would think.

The profile of skinny twins may fit slightly closer to your back, but the combined profile drag is actually higher by virtue of more surface area of two tanks. Plus you have the issue of now VIP'ing 2 tanks instead of one, and two hydro's each 5 years.

Not to mention the added expense....BUT, I agree, there is a certain cool factor of running small twins.....U.S. Divers had a slick aluminum triple set we see on E-bay now and then that you could pick up for a couple hundred $.

The US Divers triple al 30's did not use a DIN valve though.

http://www.vintagescubasupply.com/triplemanifoldsm.jpg

acelockco
11-08-2007, 10:07 PM
I agree, you should stay far away from doubles and really far far away from tripples (unless like me you would use them for display and shows).

Doubles are really intended for decompression diving. Of course they don't have to be used that way. The thing is they are very heavy! You are taking about more than double the weight of a single cylinder.

You would be better off with a single aluminum or steel cylinder. They are available in so many sizes you will surely find something that will suit your needs.

I don't know if you are certified yet, but I would think that would be your best first step. There is a lot of things involved with scuba that are not even thought of as a freediver that the classes will cover. They will surely cover the different scuba cylinders out there if not, make sure you ask.

The Publisher
11-08-2007, 10:14 PM
there are times I need to blow bubbles

Leave Michael Jacksons's Chimp alone! (cried to the tune of Leave Brittany Alone!)

http://images.usatoday.com/life/_photos/2003/2003-10/17-bubbles-inside.jpg

The above photo was Bubbles the chimp and Michael Jackson before Michael became caucasian.

acelockco
11-09-2007, 12:46 AM
LOL!

You are nuts!

BamaCaveDiver
11-09-2007, 08:12 PM
Multiple cylinder configurations are setup to provide redundancy, they have nothing to do with the tech crap or deco or whatever else the internet hero's want to class them as. While redundancy is typically a good thing for divers, manifolded systems do introduce new failure points into the equation which must be analyzed to determine if the benefits outweigh the risks for the dives you want to do. There is a bit of a learning curve going from a single to multiple configuration, but it is a relatively short and easy curve and most divers to claim to feel more balanced in doubles as opposed to their singles rig (which I am convinced says more about the inefficiency of their singles rig as they have it configured for their personal use.)

With the cylinder selection available to us today, triple configurations just do not make much sense due to the extra failure points they bring with them; I would much rather dive twinned up lp 45's as opposed to triple 30's. One way to avoid the failure point issues is to dive the setup as independents as opposed to a manifolded system. This setup is typically preferred by solo divers as a failure can never affect more than half the available gas supply without the need for a second set of hands. With manifolded systems you must become proficient with valve shut procedures so that you can arrest any gas loss from a failure; there has been a lot of debate over the efficacy of manifolded doubles these days.

If you do try a multiple setup, I urge you to find a good mentor who can help you establish your trim properly and show you how to best manage your gas supply, to include valve drills should you opt for a manifolded setup. I loved my doubles, but since I mostly dive caves and solo (plus have numerous back, hip, and knee maladies to contend with these days) all I dive any more is side mount (I do still make the occassional single rig dive, but these are rare for me) which is basically independent doubles worn at my sides rather than on my back.

amtrosie
11-11-2007, 10:38 PM
I would echo every thing Bama said. If an open circuit set-up is what you yearn for. Look at HP steel tanks. You may be able to get away with a single tank, depending on your anticipated needs. If doubles are in the future, proceed with care. Try not to get drawn into the hype, and continue to look at the smaller, lower profile cylinders. Triples should not be an option with the myriad of higher volume tanks on the market.

yohanson
11-26-2007, 04:56 AM
Multiple cylinder configurations are setup to provide redundancy, they have nothing to do with the tech crap or deco or whatever else the internet hero's want to class them as.
<snip>
With the cylinder selection available to us today, triple configurations just do not make much sense due to the extra failure points they bring with them; I would much rather dive twinned up lp 45's as opposed to triple 30's.
<snip>

Totally agree with the triple configurations...you're old enough to remember the triple 2 barrel carburetor set ups of the 60s I'm sure (you ought to, you're older than I am):) They became obsolete due to the larger 4 barrel carburetors that became available and the fact that it was damn near impossible to tune all three correctly as well as the more points of failure of the "six pack".



I suggest an HP80 or HP100 with a luxfer 30 stage bottle as a back up.

Papa Bear
01-24-2008, 04:14 PM
Okay, my two cents! Bama is right on! We cave divers are like that, caves seem to bring out the best in divers! I would look at a LOW PRESSURE 98 or 105 single tank! LP is better for Video for one simple reason, you can fill it on a boat or with your portable compressor! If you over fill it you will get a lot more air! They trim well with the right BCD and you just take off an equal amount of wight from your belt. If you fill your HP tank to 90% on say an 80 then you have 72, if you over fill your LP by 10% you have 88Cft. So if you over fill your 105 by 10%, witch most boats can do, then you have 116cft!

One more thing you said you were going to do video on Nitrox with doubles. You have to define your mission better. Deep for a long time? So what do you want to do? Video Freedivers? Define your mission first then choose the tools and training!

hbh2oguard
01-24-2008, 06:59 PM
papa I fully agree you gave me that advice the middle of last year and I got a lp95. It might be a hog but it holds TONS and TONS of air especially filled to 2800-3k

Papa Bear
01-24-2008, 08:13 PM
papa I fully agree you gave me that advice the middle of last year and I got a lp95. It might be a hog but it holds TONS and TONS of air especially filled to 2800-3k

Don't you just love that!???? You can concentrate on diving and stop worrying about your air! And you need less wight on your belt, and safety stops are better!

BamaCaveDiver
01-24-2008, 08:29 PM
I just love my compact 120's (lp 85's filled to 4K) :p

hbh2oguard
01-25-2008, 05:28 PM
I do love it, but I don't know if I'd pump it up to 4k and I think I dropped 9lbs from an Al80.