View Full Version : Twin 12's for Nitrox. 232 or 300 bar?
Hello.
I was wondering what was more popular for twin 12s, 232 or 300bar?
I'm looking to invest in a set of 12s for when I go Nitrox and keep the 7s for air.
Looking at the Beaver website they quote the weights as:
7L 300 bar 9.5kg (x2 19kg)
12L 232 bar 13kg (x2 26kg, diff of 7kg from 7s)
12L 300 bar 17kg (x2 34kg, diff of 15kg from 7s)
Assuming the difference in the weight of the manifolds and bands is minimal.
With 8kg on my belt does it equate that I would only need 1kg for 232s and be 7kg overweight for 300's or do the larger tanks have increased buoyancy?
A guy I dive with is using twin 12L 300 bar and they feel like they weight a ton. I won't want to fall on the rocks with those bad boys on. Or have to lift them on to a boat for that matter.
I would deffinately need to try his before I went for 300s but wondered what the norm is.
The other option is twin 15L 232 which are quoted at the same weight as 12L 300bar but weight for weight you get a bit more air in 12L 300bar.
BUT... If I wanted to mix my own Nitrox I believe it gets more complicated above 232 bar due to some strange gas law. Is this true? Therefore the 12L 300 bars stumbles at the first hurdle and it's a two horse race...
300 12s!! Heavy duty kit there mate! I have 232 12s and Buddy band them up when needed. Heavy but liftable...
Do you know of a dive shop that you can get a proper full 300 bar fill? That is something I would look at if getting 300 bar tanks.
300 12s!! Heavy duty kit there mate! I have 232 12s and Buddy band them up when needed. Heavy but liftable...
Yes, very heavy. Really wanting to know if anybody sees the need for 300bar twin 12's
Do you know of a dive shop that you can get a proper full 300 bar fill? That is something I would look at if getting 300 bar tanks.
Yep. My local shop, Shore SCUBA supplies in Gourock, do a full 300 bar.
Lizardland
17-07-07, 12:10
Don't just look at weight, you need to look at buoyancy as well. Try the calculator at www.subaqua.co.uk
Twin 12 300's aren't just heavy on the surface, they are very negative underwater. Don't underestimate just how heavy a 34kg set is once fully rigged, getting off a kitting up bench, getting up a ladder, climbing over rocks, etc., is not easy. I know someone who snapped his thigh going over in a set of twin 18's (which aren't much heavier than these). I dived in twin 20's for a while and suffered a lot of back problems and pulled muscles all the time. I've also found 300bar fills take a lot more effort to do.
I'd go for Faber 12's, they are nice and light on the surface and fairly neutral underwater.
Cheers,
Stuart
Don't just look at weight, you need to look at buoyancy as well. Try the calculator at www.subaqua.co.uk
Twin 12 300's aren't just heavy on the surface, they are very negative underwater. Don't underestimate just how heavy a 34kg set is once fully rigged, getting off a kitting up bench, getting up a ladder, climbing over rocks, etc., is not easy. I know someone who snapped his thigh going over in a set of twin 18's (which aren't much heavier than these). I dived in twin 20's for a while and suffered a lot of back problems and pulled muscles all the time. I've also found 300bar fills take a lot more effort to do.
I'd go for Faber 12's, they are nice and light on the surface and fairly neutral underwater.
Cheers,
Stuart
Cheers Stuart. Is there much difference between faber and beaver cylinders?
dont forget if you are buying for Nitrox purposes to get M26 threads or you may end up having to replace them!!
As for the weight of 300bar 12's, I use one 300 bar 12l and I can assure you the weight difference between that and my 232 is big!
The fill on a 300bar takes a lot longer too. There is also a debate as to whether you can actually get a decent fil at all given the sceintifics of compressing air to 300bar!
I havent voted as I dont know and dont have an opinion on your personal set-up.
Lizardland
17-07-07, 14:00
Cheers Stuart. Is there much difference between faber and beaver cylinders?
Not sure. When I'm buying steel I tend to always buy Faber as I've never had any problem with corrosion or failing neck threads (which I've had on others).
Cheers,
Stuart
If it's for nitrox then unless you have a huge air consumption then I can't see the need for 12/300's or god forbid 15 litre twins (unless you are looking at OC trimix.)
I have a friend with twin 10/300s and they are obscenely heavy, plus I am told a 300 bar fill only equates to (approximately) 270bar ish due to the gas laws going non-linear at high pressures.
imho anything bigger than twin 12/232's are boat diving equipment only, and even then they're (12/232's) on the nasty side for carrying on anything but the easiest of shores.
Remember you only have one back! :eek:
(and if you need *that* much gas, have you considered a rebreather?)
I agree with the others: 12L 232 bar would be my choice (and in fact was :eek:).
I've never been short of air even when doing 2 deepish dives (30-40m) from a boat. I've had 3-5 dives from two cylinders when we've been away places and doing shallower diving.
2 x 12L 300 bar cylinders would be abhorrently heavy IMHO. :o
I've a spare set of twin 12 232 bar fabers which dependent on when you need them you can borrow them for a dive or two. If your interested pm me.
Can't believe nobody has said this yet - You want to blend your own Nitrox !! Whats wrong, do you have a death wish ? Really dangerous thing to try and do at home in you garage, there was some photo's on YD last year of a garage or what was left of it after home blending went wrong. Anyway the cost of buying and maintaining your own oxygen supply would outway any financial saving you would make. On the tanks Twin 12's 232 but are you really needing twins ?, depends how deep and for how long (ie deco planned). I did dive twin Indie 12's 232 on a Tekwing for a while but as most of my diving is in the 40m Max range i've ditched them and plan on going back to my 15l with 3l Pony. I would only rig up my twins again if I was planning a dive which was deep enough/long enough/interesting enough to justify them. Chill out, do your nitrox course and get yerself up to Powmill on Thursday Night for 7.30pm.
BUT... If I wanted to mix my own Nitrox I believe it gets more complicated above 232 bar due to some strange gas law. Is this true? Therefore the 12L 300 bars stumbles at the first hurdle and it's a two horse race...
this jumped out at me, i would say, if your even considering blending o2 you should at least know basic gas laws.
the 'strange gas law' is very true, you might want to swat up on it for any gas management dive planning on air.
Can't believe nobody has said this yet - You want to blend your own Nitrox !! Whats wrong, do you have a death wish ? Really dangerous thing to try and do at home in you garage, there was some photo's on YD last year of a garage or what was left of it after home blending went wrong. Anyway the cost of buying and maintaining your own oxygen supply would outway any financial saving you would make.
its no more dangerous doing it in a garage than in a dive shop, only the operator of the equipment is different, which is where most problems lie.
a blending course is the way to go.
i did see the pics your on about, don't think his mortgage insurance covered that one!
cost effectiveness, well £32 for a 50'J of O2 & £12 a month rental of their cylinder is far better than paying £5 a cylinder, per fill IMHO.
4 twinset fills a month is £40 right away!
& its even more cost effective if you have a booster pump.
twin 12's x 232 is the way i'd go.
Good good, plenty of reactions :D
I'll lay some of your minds to rest.
I wouldn't be doing any blending before I had nothing short of a full understanding of what is going on. As for the safety aspects I'm with Stewart, it's the operator you need to worry about. The only thing I would add is the upkeep of the equipment. Neither of these will be an issue.
From a weight point of view I had suspected 232s would be more popular. Really wanted some feedback along the lines of these give plenty of air and got it. Cheers.
From a volume point of view I dive twin 7s 300 normally so there is no point seperating 12L 232s for a shallower dive. I'd just use the 7s.
I'm a great believer in buying once with the future in mind. So these will eventually be used in planned deco. Not for a while yet but it won't cost me another £400 odd when I do.
In the mean time they will give me plenty of air for multiple dives off a boat or weekend away.
My 7s will still be the most heavily used.
I've got a redundancy cheque waiting for me in 5 weeks. Just making sure I have my shopping list at the ready :D
I'm a great believer in buying once with the future in mind. So these will eventually be used in planned deco. Not for a while yet but it won't cost me another £400 odd when I do.
In the mean time they will give me plenty of air for multiple dives off a boat or weekend away.
My 7s will still be the most heavily used.
I've got a redundancy cheque waiting for me in 5 weeks. Just making sure I have my shopping list at the ready :D
Then... with future proofing in mind... Used Inspirations are around 2.5k, used KISS possibly even less, a Drager or similar semi closed around the £800 mark used, all will give you masses of duration down to 40m on Nitrox (eg as much or more than a twinset), if and when you decide to use devil gas the closed circuit ones will do 80 metres for when you decide to do *serious* deco ;)
Keep in mind that if you want to do trimix diving later on then open circuit can cost over £100 a dive and helium is not going to get any cheaper I'm told :(
Oh and the ones I've lifted weren't as bad on the back as twin 12's!!
Personally I'm skint so I have my Drager Dolphin for up to 40m (pretty much 2 hours worth of gas at any depth up to the 40) and beyond that I use my twin 10/232's. Add a sideslung bailout to either of these and there's plenty gas.
But all that is only my own opinion and I reserve the right to change my mind ;) :rolleyes:
Right now if I were to replace my diving gear with one set (if I had the cash!) with future proofing in mind, I would buy a Classic KISS and do the Nitrox course on it. But meantime I'm enjoying what I'm using and hope never to have to lift twin 12's ever again :eek: ;)
Then... with future proofing in mind... Used Inspirations are around 2.5k, used KISS possibly even less, a Drager or similar semi closed around the £800 mark used, all will give you masses of duration down to 40m on Nitrox (eg as much or more than a twinset), if and when you decide to use devil gas the closed circuit ones will do 80 metres for when you decide to do *serious* deco ;)
Keep in mind that if you want to do trimix diving later on then open circuit can cost over £100 a dive and helium is not going to get any cheaper I'm told :(
Oh and the ones I've lifted weren't as bad on the back as twin 12's!!
Personally I'm skint so I have my Drager Dolphin for up to 40m (pretty much 2 hours worth of gas at any depth up to the 40) and beyond that I use my twin 10/232's. Add a sideslung bailout to either of these and there's plenty gas.
But all that is only my own opinion and I reserve the right to change my mind ;) :rolleyes:
Right now if I were to replace my diving gear with one set (if I had the cash!) with future proofing in mind, I would buy a Classic KISS and do the Nitrox course on it. But meantime I'm enjoying what I'm using and hope never to have to lift twin 12's ever again :eek: ;)
I hear ya man :cool:
It is very tempting but when I started diving I promised myself I wouldn't rush through to advanced stuff too quickly. I always said I would do at least 100 dives (or there about) before looking at Nitrox and planned deco. And now that I've had the taste for a RB then I've set that bar at 200 or at least 50 planned deco dives. I'm at 45 dives at the moment, hoping to be at 100 by the end of the year.
Nowt but the upmost respect for what our playground can do to us. And courses alone won't make a good diver.
But I'll spent a couple of hours with you underwater one day :D
Lizardland
18-07-07, 21:18
used KISS possibly even less
You'll be lucky. There are thousands of YBOD's in service but at the latest count there are only about 180 CK's. They don't come up that often and they sell very quick, usually at the asking price. It's a seller's market. Especially in Europe because it avoids getting hit with import duties.
I hear ya man :cool:
It is very tempting but when I started diving I promised myself I wouldn't rush through to advanced stuff too quickly.
I'd definitely agree with that. Get as much time OC as you can. When things go wrong on a RB you are back on OC and that is not the time to find out you're not comfortable where you are! And when OC goes wrong it is less likely to be as bad as when CCR goes wrong.
Cheers,
Stuart
Good points as always Stuart, a bit of wishful thinking on the KISS values I guess :o ;)
I also agree build time on OC before making the leap to the dark side (should you decide to). It's just that (unless the gentleman is particularly heavy on air) I can't see the need for twin 12's for the sort of diving we're talking about.
If you are looking at future proofing for deep mix dives, then fair enough, but for EANx with a realistic max depth around 42m I can't help but think that perhaps a 7l 232 stage/bailout used with the existing 7/300 twinset would be reasonable and a lot cheaper/easier on the back (even use two if need be). Also good practice for deeper longer dives if you do decide to go down the monster twinset route:eek: Oh and *if* at some point in future you went to a rb they'd *still* be useful to you.
I feel like I'm harping on about it but I work in a job where I'm used to some pretty horrible lifting and I only use twin 10's, even then I sometimes feel they are so heavy to be a real pain, and that's not good when I dive for fun!
Twin 12/232's imho are on the outside lmits of useable for general diving and anything larger is too specialist.
But all the above is only opinion so I'll shut up now and stop boring you all ;)
Regards,
Smudge
ps a good friend, ex Commando who is built like a brick outhouse just sold twin 10/300's because they were simply too heavy... I'd strongly recommend trying a few sets before deciding! :)
I did notice the twin 12s 300bars for Nitrox, you may want to brush up of those pesky gas laws...
First Mr. Van de Waal
http://www.nigelhewitt.co.uk/diving/maths/vdw.html
and some partial pressure stuff too.
http://www.nigelhewitt.co.uk/diving/maths/pp.html
Good points as always Stuart, a bit of wishful thinking on the KISS values I guess :o ;)
I also agree build time on OC before making the leap to the dark side (should you decide to). It's just that (unless the gentleman is particularly heavy on air) I can't see the need for twin 12's for the sort of diving we're talking about.
If you are looking at future proofing for deep mix dives, then fair enough, but for EANx with a realistic max depth around 42m I can't help but think that perhaps a 7l 232 stage/bailout used with the existing 7/300 twinset would be reasonable and a lot cheaper/easier on the back (even use two if need be). Also good practice for deeper longer dives if you do decide to go down the monster twinset route:eek: Oh and *if* at some point in future you went to a rb they'd *still* be useful to you.
I feel like I'm harping on about it but I work in a job where I'm used to some pretty horrible lifting and I only use twin 10's, even then I sometimes feel they are so heavy to be a real pain, and that's not good when I dive for fun!
Twin 12/232's imho are on the outside lmits of useable for general diving and anything larger is too specialist.
But all the above is only opinion so I'll shut up now and stop boring you all ;)
Regards,
Smudge
ps a good friend, ex Commando who is built like a brick outhouse just sold twin 10/300's because they were simply too heavy... I'd strongly recommend trying a few sets before deciding! :)
All opinions are welcome and it is a valid option. Food for thought.
I'm just thinking for a long day with multiple dives and no top ups. But then a 2nd set of 7/300s and a 7/232 would cover multiple dives and cover me for deep as well....
Thanks for the links t2t.
Just a thought what about twin 10,s 232bar not too heavy for shore diving good for boat diving and can fit most stab jackets:)
Any thought,s on this would be helpful:D
Lizardland
19-07-07, 13:00
Just a thought what about twin 10,s 232bar not too heavy for shore diving good for boat diving and can fit most stab jackets:)
Any thought,s on this would be helpful:D
I'm not a massive fan of 10's mainly because it's hard to get decent shaped 10's in the UK. It's not easy finding tall 10's, they're usually too short (European 10's are much better). I find they give me a lot of back pain, they're difficult to get in and out of and horrible for sitting about in waiting to get in the water. They're not much lighter than 12's, not much cheaper than 12's and you're getting 900 litres less wind as well.
You may have guessed I don't like them :D
this is a very interesting debate and I am taking note.
I currently have 2 cylinders for trips away, 1 300bar 12l and 1 232bar 12l. I can either squeeze 2 dives out of the 300bar or one long dive then a shorter one with the 232bar. I have no intentions of twinning just yet as I have never ended a dive because of lack of air, it has either been NDL reached or buddy running low. I dont dive beyond 30m and I have recently added a pony to my kit and would only consider twins if/when I venture beyond 30m on a regular basis. I did at one point consider twin 7's but it would have meant purchases more kit, i.e. regs/wing/etc. and I would rather spend my money diving.
Whereas I'm a shorta**e and find tall 10's too long, "normal" short ones don't hurt my back, are easy to get in/out of and are fine for sitting around in waiting to get into the water...;) and I don't notice the lack of 900 litres of air as I carry a pony for deco if it's *that* deep and my sac allows the 10's to be pretty useable.
Just goes to show you *need* to try before you buy!
Just to add complication.. mine are inverted which I think is *far* superior to the "normal" orientation... :D
Confused yet!! :D
I'm not a massive fan of 10's mainly because it's hard to get decent shaped 10's in the UK. It's not easy finding tall 10's, they're usually too short (European 10's are much better). I find they give me a lot of back pain, they're difficult to get in and out of and horrible for sitting about in waiting to get in the water. They're not much lighter than 12's, not much cheaper than 12's and you're getting 900 litres less wind as well.
You may have guessed I don't like them :D