Why Double Small Tanks?

[Michael Kazma]

Redundancy all the way!

 

[ajduplessis]

Sometimes you can explore all of it with double 50s... Not all of them have miles upon miles of passage. Sometimes a bigger tank is just too big to get in, and small tanks must be utilized. Even if not the case, I'd hate to push into some cave, only to have the regulators fail on my single tank... and be screwed. All your eggs in one basket?



First off, you can get into deco on 1/3rds of smaller tanks(I've done it). I'm not talking about safety stops. Second, this isn't only about deco, this is about redundancy for technical applications, which can go beyond just a soft overhead(deco). It could mean an actual overhead. Either way, diving thirds with added conservatism if necessary should be enough to get you out, if you lose a tank.

Thats the entire point of diving thirds.

You should go ahead and agree with everything in my posts, cause its all fact

No one said you can't dive into a deco obligation with small tanks. I know idiots that do that on a regular basis!! The fact that you state ..."diving thirds with added conservatism if necessary should be enough to get you out, if you lose a tank." illustrates the small safety margins diving like this.

There is always one thing you take in abundance and that is gas!!!! Not seeing with what the absolute minimum you can get away with.

You should go ahead and agree with everything in my posts, cause its all fact!!

 

[garyd54220]

Redundancy


In a technical situation, you often have an overhead, literally, or by means of manditory decompression stops. If you lose one tank, you want another at your disposal to get you to the surface.

Wouldn't you get the same from one larger tank and an H-valve? Don't know since I dove doubles but the OP was talking about weight advantage of a single and in that respect wouldn't a large single with an H do it? I imagine small doubles would have a lower profile and balance better though.

 

[Jimmer]

Wouldn't you get the same from one larger tank and an H-valve? Don't know since I dove doubles but the OP was talking about weight advantage of a single and in that respect wouldn't a large single with an H do it? I imagine small doubles would have a lower profile and balance better though.

That's my reason precisely. I could dive my single lp 104, but my double 45's with a bit of an overfill gets me similar gas volume, but much lower profile and very stable and comfortable.

 

[bletso]

One thing would be for a short person, double 40's would trim easier than a single 80. A more stable platform and the ability to custom a backplate makes a lot of sense. Plus the advantage of redundancy shouldn't be ignored.

I had a customer who put his 4'10" wife in a similar set up. It worked great.

Dale

 

[lowviz]

Wouldn't you get the same from one larger tank and an H-valve? ...................

No, if your manifold has an isolation valve. Yes, if it doesn't.

 

[Elvistheking]

I've tried twin 300bar 7's and they are lovely in the water, if I started doing a lot of RIB/shore diving I'd definitely get a set, much nicer balanced than a single 15, and I could use exactly the same regs that I use with my twin 12's. As to the point about them weighting more, so what just means less lead. And whilst I wouldn't be doing any serious deco with only twin 7's, you do still have a little more redundancy over a single.

 

[SuPrBuGmAn]

Wouldn't you get the same from one larger tank and an H-valve? Don't know since I dove doubles but the OP was talking about weight advantage of a single and in that respect wouldn't a large single with an H do it? I imagine small doubles would have a lower profile and balance better though.

Sometimes the physical dimensions are enough to discount a single large tank.

Then there's the redundancy, **** happens.

If that reg was free flowing, or rolled off... You'd be in a world of crap with a single tank eh?

No one said you can't dive into a deco obligation with small tanks. I know idiots that do that on a regular basis!! The fact that you state ..."diving thirds with added conservatism if necessary should be enough to get you out, if you lose a tank." illustrates the small safety margins diving like this.

There is always one thing you take in abundance and that is gas!!!! Not seeing with what the absolute minimum you can get away with.

Every major tech agency out there teaches 1/3rds, with added conservancy for outside factors - still called 1/3rds. Why is it OK to do it with larger tanks, and not smaller tanks?

How do you plan your gas for a dive? You can dive 1/16ths if you want, but its prohibitively ridiculous.

I agree to some extent. The tank sizes mentioned I believe is to small especially for deco (I assume you are talking deco and not safety stops), as half the gas (in the event of "losing" one tank) will not be enough to get you out. I think these size doubles in general is to small if used with rules of 1/3 in any case.

All things being equal, why would losing a tank at 1/3rds, not get you out?


Why are 40s, 45s, 63s and other smaller tanks too small to be dived at 1/3rds and larger tanks are fine(again)? Wheres the logic in that? Your an idiot.

 

[lowviz]

..............All things being equal, why would losing a tank at 1/3rds, not get you out?


Why are 40s, 45s, 63s and other smaller tanks too small to be dived at 1/3rds and larger tanks are fine(again)? Wheres the logic in that? ................

First, nice image. Says it all.

Thirds will get you out, emphasis on YOU. Diving 1/3's on stupidly small tanks will allow you to violate "halves plus rockbottom". For anything of reasonable size, thirds is just a really simple way to exceed that which really matters, "halves plus rockbottom". -unless you are diving solo (of course).

 

[Superlyte27]

Wouldn't you get the same from one larger tank and an H-valve? Don't know since I dove doubles but the OP was talking about weight advantage of a single and in that respect wouldn't a large single with an H do it? I imagine small doubles would have a lower profile and balance better though.

Until a burst disk goes or tank oring.