View Full Version : Rebreather Question
Is it possible to change the cylinder on a Draeger Dolphin to say a 7L or possibly a 10L.
Im just wondering whether the above is possible, as a method of prolonging dive time.
As i currently understand it, the divesorb last between 60-120 mins, but the gas may last less. I'm looking at ways to improve dive time (theoretically at present).
:)
Is it possible to change the cylinder on a Draeger Dolphin to say a 7L or possibly a 10L.
Im just wondering whether the above is possible, as a method of prolonging dive time.
As i currently understand it, the divesorb last between 60-120 mins, but the gas may last less. I'm looking at ways to improve dive time (theoretically at present).
:)
I dived one with a 10litre with a H valve (the other other outlet having my baliout)
I think this is quite a standard set up.
The downside is by the time I'd added a suit inflate cylinder, the whole thing was heavier than my twin 10's, cost more to run, more hassle, more expensive and did not give me any more dive time (I'm ready to surface after an hour). That was the end of my drager playing !, but many are very content with this set up.
Have fun with it
Tony
I Dive Solo
09-03-2007, 03:37
Tony
It was the same problems that stopped me using the azimuth. Also it would not let me lay horizontal in the water as the C lungs were far to big so I had to carry more lead than a lead factory. Personally I dont think that a SCC comes into its own until 30+ mts. and I am not sure it even does then.Perhaps one day when we dont have to carry so many comps I will try CC. But at the moment it seems that a great amount of work load is needed to use them. But thats only what Ive seen and heard, Ive never used one. Perhaps a small kiss is the way to go for recreational diving.
IDS
I will try CC. But at the moment it seems that a great amount of work load is needed to use them.
You'll hear exactly the same comment from thousands of people who don't dive CC.
Vic.
You can use a 10l/Y valve set up as a virtual 5l + 5l bailout/suit inflate.
Dragersorb is rated for 240 mins.
You could be naughty and put a 40% through a 60% jet - but ensure you understand what you are doing and how to correctly monitor it!
now I wonder who may have done all of the above....?
Mike Rowley
15-03-2007, 12:09
[QUOTE=Odin (Paul)]You can use a 10l/Y valve set up as a virtual 5l + 5l bailout/suit inflate.
Dragersorb is rated for 240 mins.
You could be naughty and put a 40% through a 60% jet - but ensure you understand what you are doing and how to correctly monitor it!
Then of course you could add a small O2 cylinder with manual inject plus a VR3 and O2 sensor plumbed into the counterlung, all to accelerate the real time deco. Then you think about turning it into a CCR.
Then you see sense, realise you have had a brain fart, sell the damned thing and buy an Inspiration Vision or Evolution. End of problems as long as you have a reliable No 1 computer.:D
Cheers
Mike
[quote=Odin (Paul)]You can use a 10l/Y valve set up as a virtual 5l + 5l bailout/suit inflate.
Dragersorb is rated for 240 mins.
You could be naughty and put a 40% through a 60% jet - but ensure you understand what you are doing and how to correctly monitor it!
Then of course you could add a small O2 cylinder with manual inject plus a VR3 and O2 sensor plumbed into the counterlung, all to accelerate the real time deco. Then you think about turning it into a CCR.
Then you see sense, realise you have had a brain fart, sell the damned thing and buy an Inspiration Vision or Evolution. End of problems as long as you have a reliable No 1 computer.:D
Cheers
Mike
Been there done it now on a YBOD!
Just close the blimming loop and get on with proper RB diving. This semi-closed stuff is just plain old silly. It's like buying a Ferrari and only using 1st gear.
Just close the blimming loop and get on with proper RB diving. This semi-closed stuff is just plain old silly. It's like buying a Ferrari and only using 1st gear.
I've always thought that as well, 80% of the hassle 20% of the advantage
[Quote=Woz}This semi-closed stuff is just plain old sillyI've always thought that as well, 80% of the hassle 20% of the advantage[/QUOTE]
It's worse than that, IMO.
Many people see SCR as "easier" than CCR because CCRs involve checking your PO2 all the time.
But I reckon that just disguises the problem; SCRs still have the potential to go hypoxic (and an unfortunately large number have) - it's just that a fair few people don't bother checking what they're breathing; they rely on their equipment not to fail (silently).
So if you add a PO2 gauge to a SCR, you've got pretty much all the taskloading and potential for problems as a CCR, but with all the added problems of a SCR.
It was shortly after worknig that out that I bought my CCR...
Vic.
Im not really wanting to go fully CCR at present, just playing with options at present.
I want something that uses less gas, will do a dive time that is around the same as my twin 12s, at the same depth, while only using the one cylinder.
Im not after anything like a YBOD, because i'd never use it to its full potential. For me pottering around at 18-23m is brilliant, and the ability to spend 2 hours exploring a wreck, reef, or sea based cavern/cave system would be nice. If i had enough gas for more it would be a bonus. But without the faff of having to mix my gas on the fly, which doesnt appeal to me. It would mean i could stay with my current computer, and i realise i would need a PPO2 monitor or two to monitor the gas in the loop. Im not interested in deep diving beyond the ability to do so if i need to, in fact going past 25m serves little purpose to me at present.
I realise their are a few bad/annoying sides to it, but for what i want to do with it the advantages would easily outweigh those.
Nigel Hewitt
15-03-2007, 18:38
I realise their are a few bad/annoying sides to it, but for what i want to do with it the advantages would easily outweigh those.The noises I hear are that having to get the right mix for the dive on SCR puts back all the problems of running just the right nitrox without the option to say poo to it all and dive air.
This was a big feature to me as I do sea-sickness big time so I was forever getting blown out and being left with an OC mix/stages that was exactly wrong for what was on offer the next weekend. Now on the blendermatic my gas and gas bill is independent of depth so even if I do end up feeding the fish while everybody else dives at least I'm all set for next weekend.
Nick Kay
15-03-2007, 20:40
Im not really wanting to go fully CCR at present, just playing with options at present.
Take a look at the Submatix - probably the only unit you can start with as a stright CCR and then upgrade to mCCR and even take the electronics pack
AFAIK, 2 x 2L cylinders x 200B = 800L, breathing rate of 5l/min = 160mins underwater with (dependent on depth) scrubber life of 3hrs
Regards
Nick
Is their any information available on exactly how long the scrubber will last at various depths before it becomes unusable. The reason i ask is Odin (Paul) states that dragersorb is rated for 240 mins, but doesnt mention at what depth. The likelihood of me spending 4 hrs underwater is highly unlikely, but 2-2.5 is quite within what i'd like to be able to do.
Also carrying 4L of gas is probably to small an amount for that, also if i factor in a necessary bailout requirement on the same cylinder, im looking at around the 8-10L mark (including any deco i would need to do). Not that i wouldn't probably carry something in a pony for that sort of situation. But im after simplicity, and cutting down on the number of things i have to carry.
This is something i'll be looking at a lot more before i make any definite decisions. Also the probable cost of training comes to mind. What is the current average training cost for a CCR (and bear in mind im not wanting to dive this thing deep, including on whatever course i do). The dolphin course is ideal for me in depth (20m depth) and cost £300 or less, depending on who i go with, but if i do it, it will probably be done out in Malta this summer, before i purchase the unit (sometime next christmas).
Anymore thoughts are welcome.
Matt
I want something that uses less gas, will do a dive time that is around the same as my twin 12s, at the same depth, while only using the one cylinder.
Why the necessity to do it all on one cylinder?
Even at the depths you're talking about, you're soon going to build yourself a decompression ceiling. Do you really want to get into that situation with just one cylinder?
Im not after anything like a YBOD, because i'd never use it to its full potential.
Bizarre. Do you always need to use things to their full potential before they're worth buying? You might be surprised to find out how often your kit isn't the limiting factor[1].
But without the faff of having to mix my gas on the fly, which doesnt appeal to me.
Why on earth do you think that's a faff? You turn the unit on, stick the mouthpiece in yer gob, and go diving...
It would mean i could stay with my current computer
I dive an Inspiration. For most of my diving, I use a Suunto Solution Nitrox (which is still my favourite computer). For the deep stuff, I have a Uwatec D-timer and a copy of ddplan (and the Solution, which gets very upset...)
I realise their are a few bad/annoying sides to it, but for what i want to do with it the advantages would easily outweigh those.
I'm still not sure I understand what problem you're trying to solve with a rebreather...
Vic.
[1] I used to think I rode quite well. Then I started riding with an antipodean by the name of Paul Lewis. If I could realise half the potential in my bike that he could, *boy* would I be fast...
David Walker
15-03-2007, 23:25
But im after simplicity, and cutting down on the number of things i have to carry.
Soooo.... you want a rebreather for "simplicity"? Have you ever seen or dived with anyone on a rebreather? Picked one up? :confused:
Something like an Inspo is pretty much on-par with twin-12's for weight and bulk, and even the SCRs i've seen were pretty bulky. You'll never escape the fact that as soon as you're into deco then however long your on-board cylinder might last, you will still need to carry a decent sized separate gas supply for when something fails. A 10l onboard won't be of much use if the failure is a freeflow and all your gas gets blown out into the water.
David
Your points are good Vic, and im not going to go beyond what i really said in my last post.
But on your last comment (ie, not the quote one), the problem im trying to solve is the one that requires me to take a large number of cylinders to do the dive i want to do. I get about 30-40 mins a cylinder, which gives me an hour or so, if i take the 10 as well then add another 15-20 mins, because i have a high consumption rate no matter what i've done to improve it, and even after totally relaxing. So to do an average dive i enjoy which would allow me at least 90 mins underwater i end up carrying a lot of cylinders. I suppose i could just go with the twin 15's or 18's, but my back would be broken if i did. So i need a way to stay underwater for a fairly long amount of time, while carrying less cylinders and kit, that is fairly easy to use and operate. Also it has to be a relatively cheap solution (i cant afford to blow 3-4k on something). This leaves me with two options, a drager ray for around £1000 or a dolphin for £1800 or round abouts, plus a £300 course to use either of them. The ray gives me from what i read 60-90mins, while the dolphin for a few hundred more gives me an extra 30-60 mins. At present i will likely go down one of those routes. It will become my first rebreather, and will allow me to learn a bit more and do the diving i want for a couple of years until i have the money available to buy expensive kit that can do longer dives, but has more electronics and faff factor. At present things i dont want are, computers running things, i dont mind computers monitoring things, but running things is a different ball game for me. The whole 'nozzle supplies gas to the loop at a fairly constant rate' appeals to me.
One day somewhere down the line i will probably get myself a better rebreather, that has more bells and whistles, and can maybe be dived deeper, but for now i dont need something like that. I just want a something that runs on one mix, hopefully works for 2 hours (give or take) at a time, and is easy to maintain, whilst also fitting into my budget constraints. :)
Soooo.... you want a rebreather for "simplicity"? Have you ever seen or dived with anyone on a rebreather? Picked one up? :confused:
Yes, yes, and yes. I've also tried on a dolphin and ray to compare weight to an Inspo, they were both a lot lighter. Dont get me wrong im not going into this without any thought, its been on my mind for a couple of months now.
Something like an Inspo is pretty much on-par with twin-12's for weight and bulk, and even the SCRs i've seen were pretty bulky. You'll never escape the fact that as soon as you're into deco then however long your on-board cylinder might last, you will still need to carry a decent sized separate gas supply for when something fails. A 10l onboard won't be of much use if the failure is a freeflow and all your gas gets blown out into the water.
Carrying a 7L of something for deco and a 3L to bailout on isnt something i would shy away from. But it would depend on the dive as to whether the deco gas came with me. WIth regard that im still trying to find information on gas switching blocks. If i had a FFM would it be easier to plumb into something like that? Their are still many questions that i need to ask and hopefully get answers too, hence why im still at the contemplation phase.
Also on deco (i had a look at a copy of some TDI tables i sourced) if i dived 40% instead of 36% and reduced depth to 19m my no stop time is 150 mins before i incur any major deco. In reality factoring in various things you could call that 2hrs. But this is all theoretical at present.
But on your last comment (ie, not the quote one), the problem im trying to solve is the one that requires me to take a large number of cylinders to do the dive i want to do. I get about 30-40 mins a cylinder, which gives me an hour or so, if i take the 10 as well then add another 15-20 mins, because i have a high consumption rate no matter what i've done to improve it, and even after totally relaxing.
I thought you were trying to fix a high consumption rate. Guess what the thrust of this post is going to be...
So to do an average dive i enjoy which would allow me at least 90 mins underwater i end up carrying a lot of cylinders. I suppose i could just go with the twin 15's or 18's, but my back would be broken if i did. So i need a way to stay underwater for a fairly long amount of time, while carrying less cylinders and kit, that is fairly easy to use and operate.
You're trying to increase your time by carrying more gas, rather than using less gas. The implication is that you've decided you can't reduce your SAC. Given the numbers you've quoted, I think you're wrong; the dives you're talking about shouldn't pose any real difficulty with a modest twinset.
I suspect you're making one of the usual mistakes, so let's start with one simple question: how much lead is there on your weight belt?
Also it has to be a relatively cheap solution (i cant afford to blow 3-4k on something).
If you're going to start RB diving, you're going to blow £4k. Draegers might look cheap initially, but you're going to burn your way through that cash one way or another.
This leaves me with two options, a drager ray for around £1000 or a dolphin for £1800 or round abouts, plus a £300 course to use either of them.
Oxygauge?
At present i will likely go down one of those routes. It will become my first rebreather, and will allow me to learn a bit more and do the diving i want for a couple of years
Well, that's your choice. But I'm certain you can do the diving you're talking about for very much less money and faff.
At present things i dont want are, computers running things
Nor I. That's why I dive an Inspiration.
i dont mind computers monitoring things, but running things is a different ball game for me.
I agree with you. That's why my RB doesn't do that.
The whole 'nozzle supplies gas to the loop at a fairly constant rate' appeals to me.
But there I don't. Take a look at a graph of FiO2 against work rate. Some people find that acceptable - I'm not amongst them.
I just want a something that runs on one mix, hopefully works for 2 hours (give or take) at a time, and is easy to maintain, whilst also fitting into my budget constraints. :)
Well, it sounds to me like SCR is going to be a very disappointing experience for you. I'd love to be wrong there...
I've also tried on a dolphin and ray to compare weight to an Inspo, they were both a lot lighter.
My Inspiration is too light - I need lead in it.
The relevant point to my mind is not its weight in air (I don't often use it to dive in air), but its weight in water.
But it would depend on the dive as to whether the deco gas came with me. WIth regard that im still trying to find information on gas switching blocks.
On CMF-type SCR, your injection orifice is selected according to your feed gas. What effect do you think switching that gas is going to have?
If i had a FFM would it be easier to plumb into something like that?
So now you're talking about an SCR, a gas switching block, and a FFM. I thought you were on a budget?
Also on deco (i had a look at a copy of some TDI tables i sourced) if i dived 40% instead of 36% and reduced depth to 19m my no stop time is 150 mins before i incur any major deco. In reality factoring in various things you could call that 2hrs. But this is all theoretical at present.
Hmmm. I strongly suggest you look at how you achieve a given O2 fraction (feed gas, orifice, and work rate) before you do too many calculations of that nature. You might be in for a surprise or two...
Vic.
I'll do this quick(ish).
Weight on belt depends on whether im wearing the drysuit (12-15kg), or one of the wetsuits (have 3mm, 5mm, 7mm) so 6-12kg, also i use less with the shorty obviously.
The rest i'll answer tomorrow.
I need to look into this all a lot more, but then i have the time. Im still not convinced about going to CCR straightaway, but theres 9 months for me to change my mind.
But on your last comment (ie, not the quote one), the problem im trying to solve is the one that requires me to take a large number of cylinders to do the dive i want to do. I get about 30-40 mins a cylinder, which gives me an hour or so, if i take the 10 as well then add another 15-20 mins, because i have a high consumption rate no matter what i've done to improve it, and even after totally relaxing.
Matt,
CAn I be cheeky and ask how many dives you've done now. I wouldn't normally ask, but last time you were active on the board asking about twinsets I think you were an Ocean Diver.
There are a couple of things that one (ie not you specifically) can do to reduce air consumption. Diving lots, and just being comfortable in the water will do wonders for you. But you can also improve fitness and lose weight (less Janos = less air required).
You sound a bit like me when I first started diving - I enjoyed it so much that I was desperate to make every dive last as long as possible. However, now that I'm diving more (I dive most weekends) it's taken the stress out of it all.
Janos
Dive wise about 100, in as many mixed environments as possible.
As far as BSAC is concerned, still an OD Salt, with 4 OW practical skills to get signed off. As far as other agency stuff goes, PADI AOW with a few specialities. Other stuff, O2 admin course signed off, but i see no point in DL lectures when im not even a SD yet.
As for lowering air consumption, i run a couple of times a week, usually a mile or two, on occasion with a couple of bricks in the rucksack, depending on how high an impact i want. I also hit the gym, but the weight doesnt come off. Also even when i relax into my dives i find i can huff my twin 12s to reserve level quite quickly, and thats with a slow S.A.C rate. :(
I get to dive at the minute about 2-4 times a month, and usually rack up 3 dives per day. Once it gets a bit warmer im after increasing that to a couple of times per week. I'm doing Farnes all being well in May, and Plymouth in June/July. Beyond that im looking to do a weeks worth of diving around the Lizard, down in Cornwall sometime late August, and i'll be heading abroad at least twice through the summer to do courses (PADI Cavern and one of the SCR courses) and just dive for fun (Malta/Gozo and somewhere else that i havent decided yet, but possibly Gibraltar or Cypress). Also wouldnt mind heading to some of the other sites around the country that i havent been to yet.
All in all, im hoping to surpass 200-250 dives by next November.
I've now been around a bit, been diving on and off for around 3 years. Done some nice high vis dives, and some absolutely crap vis dives. Been in the sea and fresh water. Done a few wreck pens and a fair few cave/cavern pens. Inadvertantly done a couple of solo dives. And the best part im not dead yet or injured (well unless you count the suspected dcs from last year, but thats another story with its own catalogue of errors).
I know this thread looks like the same old Matt style of the bad old days, but its not. Its just me asking questions, getting answers and then making some decisions. As its always been.
Have a good day Janos.
Ben Panter
16-03-2007, 09:26
Hi Matt,
Have you spotted this on the wiki? Heavy Breathing (http://www.bsacforum.co.uk/wiki/index.php?title=Heavy_Breathing). Lots of tips and tricks for reducing air consumption.
Cheers,
Ben
Michael Purcell
16-03-2007, 09:28
Speaking of air consumption this thread has had me look for the first time at my SAC as indicated in my D9 logs. (I've looked at individual but never looked at the bigger perspective)
From dive 10-20 it dropped from 18 SLM - 12 SLM.
From dive 20-30 it was in the range of 11 SLM - 14 SLM
Nearing dive 50 I still had numbers in the 10-12 range but a low of 8 SLM
Between 50 -100 I had numbers between 7.6-13 with a couple 14 SLM
So from a high of 18
To a low of 7.6
And a mean (approx) 10-11
I don't know if it is good or bad but it was an interesting exercise.
Weight on belt depends on whether im wearing the drysuit (12-15kg), or one of the wetsuits (have 3mm, 5mm, 7mm) so 6-12kg
I thought you'd say something like that.
Do yourself a favour - do a weight check.
Whilst doing it, it's important not to fin. This might sound obvious, but I've had several people swear blind they weren't - and I could see them doing it!
Get your weighting right, and your buoyancy control will become *dramatically* easier. All of a sudden - and without you doing anything - your trim will improve, and your SAC will come right down.
So instead of shelling out on a RB, spend half an hour on a beach stripping lead off your belt. It's a lot cheaper, and will do much more for your diving enjoyment - whether OC, SCR, or CCR.
Vic.
Thanks Vic, will try that.
Is their any formula for working out the difference in weight you need between diving fresh or salt water, or is it just a trial and error process?
Also thanks Ben for the wiki link, it has some good ideas for me to try.
So from a high of 18
To a low of 7.6
And a mean (approx) 10-11
I don't know if it is good or bad but it was an interesting exercise.
It's a useful set of real-world numbers.
Taking your mean of 10l/min, 180 bar out of a *single 12* is going to last you nearly an hour and a quarter at 20m[1]. With your low of 7.6l/min, that goes up to over an hour and a half.
Now yes - this is a very simplistic calculation, assuming everything happens at 20m (which, obviously, it won't) - but is useful to illustrate that the sort of dive times and depths that Matt is looking for are completely achievable without resorting to rebreathing.
Vic.
[1] That being the sort of depth that Matt wanted to do...
Is their any formula for working out the difference in weight you need between diving fresh or salt water
There is, but it's not worth doing.
If you know the weight of yourself *in full kit*, you can work out your total displacement (Archimedes' Principle).
Salt water is roughly 3.5% denser than fresh water, so you can work out the change in upthrust between the two fluids. That change is the amount to remove from your belt when diving in fresh water.
Ot you can just take off a couple of pounds, like everyone else does...
Vic.
Thanks Vic, will try that.
Is their any formula for working out the difference in weight you need between diving fresh or salt water, or is it just a trial and error process?
Also thanks Ben for the wiki link, it has some good ideas for me to try.
Going from salt to fresh water you need to increase your total weight by 2.7%, so jump on the scales with all your kit and work it out.
Or alternatively do what everyone else does and bung on a couple of K
Nigel Hewitt
16-03-2007, 10:27
Going from salt to fresh water you need to increase your total weight by 2.7%, so jump on the scales with all your kit and work it out.AWWWWWW.........
I wanted to say that.
It's not often we catch Vic out on numbers.
It's not often we catch Vic out on numbers.
Ahh, knickers to the lot of you.
It's early morning[1], and I'm busy planning things for your enjoyment. So I'm allowed. Right?
Vic.
[1] For me. It's well-known I'm a vampire really, so I'm allowed to be off my best during daylight hours...
AWWWWWW.........
I wanted to say that.
It's not often we catch Vic out on numbers.
So infrequent I actually went and checked after I saw his post :D
Chris Cherrington
16-03-2007, 11:04
... do a weight check.
Whilst doing it, it's important not to fin. This might sound obvious, but I've had several people swear blind they weren't - and I could see them doing it!
..
I think many people who are overweighted (and have been for a while) fin sub-conciously as it is and always has been their method of bouyancy control. Its a very healthy and useful thing to do a proper bouyancy check now and again, if a little boring.
Chris
I think many people who are overweighted (and have been for a while) fin sub-conciously as it is and always has been their method of bouyancy control. Its a very healthy and useful thing to do a proper bouyancy check now and again, if a little boring.
Chris
I always get students to cross their ankles when doing a buoyancy check as it is virtually impossible to fin then
Chris Cherrington
16-03-2007, 11:38
I always get students to cross their ankles when doing a buoyancy check as it is virtually impossible to fin then
Sounds like a plan. Then a quick zip tie and away you go :D
Chris
Sounds like a plan. Then a quick zip tie and away you go :D
Chris
Evil! I like your style :D :D :D
Going from salt to fresh water you need to increase your total weight by 2.7%, so jump on the scales with all your kit and work it out.
Or alternatively do what everyone else does and bung on a couple of KYou sure about that Pete? I am no physics guru but I would think you need to decrease weight:eek:
I think many people who are overweighted (and have been for a while) fin sub-conciously as it is and always has been their method of bouyancy control. Its a very healthy and useful thing to do a proper bouyancy check now and again, if a little boring.
Chris
Time to wind a few people up.
Air consumption can be reduced by not being "over weighted"
How do you know if you are "over weighted" ? Stand naked in front of the mirror and look at yourself.
Ask a good friend "am I over weighted"
propelling less mass is easier to move around than more mass.
We are not suprised when we teach thin girls and discover they have low consumption but people say things like "small lungs" - which I think is poppycock. It is just an excuse why we have a high rate.
Do you need to reduce your weight ? Go see a specialist and see how much body fat you have (or hijack this thread to say how bad BMI is a calculation)
If you weigh more than you did when you are 21 , ask why ?
We can be fattist is our 'sport'. Being fat as a diver is not big and clever, it is often an indication of lack of fitness and can make rescues harder - for the overweight rescuer OR rescuing the overweight.
(or in the old BSAC days, look in the mirror and say "am I an NI")
Back to the thread, I'm not convinced one should move to a RB until air consumption has been mastered (as it means something else has not been mastered .....) as once on a RB the diver does not have to worry about consumption, so it is likely to go up and they may not be carrying enough bailout ?
Tony
You sure about that Pete? I am no physics guru but I would think you need to decrease weight:eek:
Not sure about the % increase, nor am I a physics guru either, but as I understand it he's right, you do need to increase weight for fresh water dives. Think of the dead sea, it's salt content is much higher than normal, everyone floats.
edit:
My 1st answer is wrong....ish, I meant the other way round. You need to add weight in salt water. So MattS is right.
I know, I'll get my coat now....... :o
Nigel Hewitt
17-03-2007, 10:48
Back to the thread, I'm not convinced one should move to a RB until air consumption has been mastered (as it means something else has not been mastered .....) as once on a RB the diver does not have to worry about consumption, so it is likely to go up and they may not be carrying enough bailout ?No. You move to a rebreather when the sort of diving you do calls for a rebreather.
And you are right. Rebreathers teach me always to breathe steadily and don't penalise me for it so, when I switch back to OC, I use a lot to start with. I just have to factor this into my bailout sums.
I tend to always dive overweight. So what? I can control it. You just need to adjust well in advance so you don't overcorrect and draw zig-zags on the computer plot. The overweight comes from two steel stages that I want to be able to hand off without any danger of a Polaris ascent.
Nigel Hewitt
17-03-2007, 10:50
Not sure about the % increase, nor am I a physics guru either, but as I understand it he's right, you do need to increase weight for fresh water dives. Think of the dead sea, it's salt content is much higher than normal, everyone floats.So, by that argument, you need more weight in salt water to go diving.
Which is correct.
So, by that argument, you need more weight in salt water to go diving.
Which is correct.
oh, erm, yes, should have read it better before posting :o
I'll wake up in a minute :D
You sure about that Pete? I am no physics guru but I would think you need to decrease weight:eek:
Yes you are right, worrying more about the numbers than the direction
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