300 bar, 7 liter doubles

mstroeck · December 6th, 2005, 01:10 AM

Hi,

Does anybody have experience with 300 bar 7 liter doubles? Are they a good choice for my first set of doubles? They sure look nice, and I find them more comfortable to lug around than 232 bar 12l doubles. Opinions?

*Clare Gledhill* · December 6th, 2005, 01:13 AM

Hiya - I did my DIR - F in twin 300 bar 7s. I thought I wouldn't be able to cope with 12s. I got rid of them a short time later and now happily dive 12s.

Pros - they are smaller.

Cons, they are not much lighter.
It is hard to get a 300 bar fill.
They do not hold the gas you need for your team.

Up to you of course - but I wouldn't.

mstroeck · December 6th, 2005, 11:33 AM

Hmm, I'm hearing that a lot, Gledders... Thanks for the info! I'll probably go for double 12s....

Rob Dobson · December 6th, 2005, 12:32 PM

Another vote for twin 12's. Def the best way to go. As Gledders said you need to be able to spare some gas for your team.

If for whatever reason you do cling to the idea of 300 bar 7's then I would suggest you also look at 232 10's. Weight the same 300 bar 7's, hold the same gas and everywhere does 230 bar fills whilst a 300 bar fill isn't technically possible (equates to something like 292 bar even if the pressure was @ 300 bar) should you ever find somewhere that would actually attempt it.

The energy required to take a fill from 200 bar to 230 bar is about the same as the enery required to take it from 0 to 200 bar. So the energy required to take a fill from 230 bar to 300 bar is.... loads - enough to do several 230 bar fills and therefore uneconomical for the gas station. Expect most places that claim to offer 300 bar fills to actually give you 240 - 250 bar - in the same way that most 232 fills are more like 220 bar.

So:
2 X 7L 300's = 14L X 250 = 3500L
2 X 10L 232's = 20L X 220 = 4400L
2 X 12L 232's = 24L X 220 = 5280L

I used to dive twin 10's and they are nice but a little short if you're a tall (ish) person. The difference between twin 7's 300 / twin 10's 232 and twin 12's 232 is not really noticable TBH.

Go with the 12's.

*Brian Allen* · December 6th, 2005, 02:16 PM

Quote: (Originally Posted by Rob Dobson)

If for whatever reason you do cling to the idea of 300 bar 7's then I would suggest you also look at 232 10's. Weight the same 300 bar 7's, hold the same gas and everywhere does 230 bar fills whilst a 300 bar fill isn't technically possible (equates to something like 292 bar even if the pressure was @ 300 bar) should you ever find somewhere that would actually attempt it.

I keep reading everywhere that you can't get a decent 300bar fill, and don't quite understand. If someone has to stand around and wait at my fill station for 300 bar they get a warm 300, and once in the water they normally end up with about 275. If they can leave their set overnight they'll get a cold 300 everytime. Understand that this isn't actually 300 and more like 290 in real terms because of gas laws.

Maybe we're just conscientious, but am sure there's got to more centres like mine out there.

Re which to go for - i'd go for the 12s as i'd have enough gas for me and my buddy if I have a problem at depth near the end of the dive. Plus on a 2 dive UK boat trip, i'll often have enough for both if i plan my dives correctly and the 2nd is a bit shallower. If they're a bit heavy, then use a trolley for carting them around.

Just mho

lizardland · December 6th, 2005, 02:52 PM

I used to have a 7/300 twinset and loved it. It is great for a dive that you would normally use a single. At lot of shore diving along the Scottish coast means lugging kit across rocks and down small cliffs, it is miserable work in 12's but easier in 7's. Ok, there isn't too much weight difference but you also have to remember the proportions are different, the centre of gravity is different, the whole balance is different, far easier to walk/scramble in. Underwater, I need no weight at all with the 7's and the centre of buoyancy is perfect, all the weight is in the right place for staying horizontal.

I've flogged them but I keep a set for sidemount diving where they are excellent.

300bar fills shouldn't be a problem with air. However, I find it is, there aren't many places that will do it properly and underfilled 7's really aren't good. It really gets to be a problem with mixes. Forget ever getting a 300bar trimix fill. Even nitrox isn't always that easy as you need higher supply pressures so your supply gas doesn't go as far. With low pressure cylinders you can get more fills from a j bottle.

Tricky · December 6th, 2005, 03:01 PM

Quote: (Originally Posted by Brian A)

I keep reading everywhere that you can't get a decent 300bar fill, and don't quite understand. If someone has to stand around and wait at my fill station for 300 bar they get a warm 300, and once in the water they normally end up with about 275. If they can leave their set overnight they'll get a cold 300 everytime. Understand that this isn't actually 300 and more like 290 in real terms because of gas laws.

Maybe we're just conscientious, but am sure there's got to more centres like mine out there.

I dived with 300bar 12s for a couple of years (as singles

) and only had a problem with them once - when the guy at the dive centre wasn't warned and had to fart around with his filling rig to accommodate them. I still got good fills from him. I always managed to get pretty close to 300bar fills.

mstroeck · December 6th, 2005, 04:46 PM

As others have said, getting air at 300 bar is not an issue, there are enough dive shops here that will do it. However, I'll order the 12s. You convinced me. Now you'll have to convince me that I shouldn't pay 70 Euros extra for these shiny, shiny tanks: http://www.deepstop.de/catalog/images/doppel3.JPG

:D

December 6th, 2005, 01:10 AM	#1 (permalink)
mstroeck(Offline) New Member Join Date: Nov 2005 Location: Vienna, Austria Posts: 156	300 bar, 7 liter doubles Hi, Does anybody have experience with 300 bar 7 liter doubles? Are they a good choice for my first set of doubles? They sure look nice, and I find them more comfortable to lug around than 232 bar 12l doubles. Opinions?

December 6th, 2005, 01:13 AM	#2 (permalink)
Clare Gledhill (Online) GUE Instructor Site Admin Pacman Champion! Join Date: Nov 2005 Location: UK Posts: 1,540	Hiya - I did my DIR - F in twin 300 bar 7s. I thought I wouldn't be able to cope with 12s. I got rid of them a short time later and now happily dive 12s. Pros - they are smaller. Cons, they are not much lighter. It is hard to get a 300 bar fill. They do not hold the gas you need for your team. Up to you of course - but I wouldn't. __________________ Clare . "Keep away from people who try to belittle your ambitions....Small people always do that, but the really great make you feel that you too can become great." Interested in DIR dive training? Always happy to chat/answer questions so get in touch via PM or visit www.dirdiver.co.uk

December 6th, 2005, 03:01 PM	#7 (permalink)
Tricky(Offline) New Member Join Date: Nov 2005 Location: Reading, Berkshire Posts: 555	Quote: (Originally Posted by Brian A) I keep reading everywhere that you can't get a decent 300bar fill, and don't quite understand. If someone has to stand around and wait at my fill station for 300 bar they get a warm 300, and once in the water they normally end up with about 275. If they can leave their set overnight they'll get a cold 300 everytime. Understand that this isn't actually 300 and more like 290 in real terms because of gas laws. Maybe we're just conscientious, but am sure there's got to more centres like mine out there. I dived with 300bar 12s for a couple of years (as singles ) and only had a problem with them once - when the guy at the dive centre wasn't warned and had to fart around with his filling rig to accommodate them. I still got good fills from him. I always managed to get pretty close to 300bar fills. __________________ "I know that you believe that you understand what you think I said, but I am not sure you realise that what you heard is not what I meant." "Make me one with everything" said the Mystic to the Hamburger vendor. UK Diving Forum Sryth: A Free Online Text RPG Join the Adventure! Fallen Sword: Free online RPG Last edited by Tricky; December 6th, 2005 at 03:02 PM. Reason: More info added

December 6th, 2005, 04:46 PM	#8 (permalink)
mstroeck(Offline) New Member Join Date: Nov 2005 Location: Vienna, Austria Posts: 156	As others have said, getting air at 300 bar is not an issue, there are enough dive shops here that will do it. However, I'll order the 12s. You convinced me. Now you'll have to convince me that I shouldn't pay 70 Euros extra for these shiny, shiny tanks: http://www.deepstop.de/catalog/images/doppel3.JPG :D Last edited by mstroeck; December 6th, 2005 at 04:49 PM. Reason: Typos and general shitty wording

December 6th, 2005, 11:33 AM	#3 (permalink)
mstroeck(Offline) New Member Join Date: Nov 2005 Location: Vienna, Austria Posts: 156	Hmm, I'm hearing that a lot, Gledders... Thanks for the info! I'll probably go for double 12s....

December 6th, 2005, 12:32 PM	#4 (permalink)
Rob Dobson(Offline) Chillin' with the ninjas Join Date: Nov 2005 Location: Oxford Posts: 536	Another vote for twin 12's. Def the best way to go. As Gledders said you need to be able to spare some gas for your team. If for whatever reason you do cling to the idea of 300 bar 7's then I would suggest you also look at 232 10's. Weight the same 300 bar 7's, hold the same gas and everywhere does 230 bar fills whilst a 300 bar fill isn't technically possible (equates to something like 292 bar even if the pressure was @ 300 bar) should you ever find somewhere that would actually attempt it. The energy required to take a fill from 200 bar to 230 bar is about the same as the enery required to take it from 0 to 200 bar. So the energy required to take a fill from 230 bar to 300 bar is.... loads - enough to do several 230 bar fills and therefore uneconomical for the gas station. Expect most places that claim to offer 300 bar fills to actually give you 240 - 250 bar - in the same way that most 232 fills are more like 220 bar. So: 2 X 7L 300's = 14L X 250 = 3500L 2 X 10L 232's = 20L X 220 = 4400L 2 X 12L 232's = 24L X 220 = 5280L I used to dive twin 10's and they are nice but a little short if you're a tall (ish) person. The difference between twin 7's 300 / twin 10's 232 and twin 12's 232 is not really noticable TBH. Go with the 12's.

December 6th, 2005, 02:16 PM	#5 (permalink)
Brian Allen(Offline) GUE Instructor Join Date: Nov 2005 Location: London & Plymouth Posts: 593	Quote: (Originally Posted by Rob Dobson) If for whatever reason you do cling to the idea of 300 bar 7's then I would suggest you also look at 232 10's. Weight the same 300 bar 7's, hold the same gas and everywhere does 230 bar fills whilst a 300 bar fill isn't technically possible (equates to something like 292 bar even if the pressure was @ 300 bar) should you ever find somewhere that would actually attempt it. I keep reading everywhere that you can't get a decent 300bar fill, and don't quite understand. If someone has to stand around and wait at my fill station for 300 bar they get a warm 300, and once in the water they normally end up with about 275. If they can leave their set overnight they'll get a cold 300 everytime. Understand that this isn't actually 300 and more like 290 in real terms because of gas laws. Maybe we're just conscientious, but am sure there's got to more centres like mine out there. Re which to go for - i'd go for the 12s as i'd have enough gas for me and my buddy if I have a problem at depth near the end of the dive. Plus on a 2 dive UK boat trip, i'll often have enough for both if i plan my dives correctly and the 2nd is a bit shallower. If they're a bit heavy, then use a trolley for carting them around. Just mho

December 6th, 2005, 02:52 PM	#6 (permalink)
lizardland(Offline) LCS Join Date: Nov 2005 Location: Evidently Chickentown Posts: 591	I used to have a 7/300 twinset and loved it. It is great for a dive that you would normally use a single. At lot of shore diving along the Scottish coast means lugging kit across rocks and down small cliffs, it is miserable work in 12's but easier in 7's. Ok, there isn't too much weight difference but you also have to remember the proportions are different, the centre of gravity is different, the whole balance is different, far easier to walk/scramble in. Underwater, I need no weight at all with the 7's and the centre of buoyancy is perfect, all the weight is in the right place for staying horizontal. I've flogged them but I keep a set for sidemount diving where they are excellent. 300bar fills shouldn't be a problem with air. However, I find it is, there aren't many places that will do it properly and underfilled 7's really aren't good. It really gets to be a problem with mixes. Forget ever getting a 300bar trimix fill. Even nitrox isn't always that easy as you need higher supply pressures so your supply gas doesn't go as far. With low pressure cylinders you can get more fills from a j bottle.