BSAC ocean diver test

[Jon H]

OK I'm doing it this Friday and i think some of the questions of the BSAC websites to me ain't that very helpful could some one give me a few questions or a link to a norther website with more questions.

thank you

[Rick]

just go over the lectures and the Sports Diver book

Try the worked examples in the BSAC tables and you will be fine

[Jon H]

just go over the lectures and the Sports Diver book

Try the worked examples in the BSAC tables and you will be fine


I don't have a BSAC 88 tables which is a problem and by sports diver do you mean ocean diver student workbook?

[Rick]

ok i will humour you here - i think from looking around you should have done OT4 lecture which explains the use of the BSAC tables

It isnt important at this stage of your diving to think if this is the best way to go about it given your limited experience but it is very important to understand the principles involved

I am very suprised that you might be going for an exam without knowledge of these (or any at your level) tables and I would suggest that maybe you should hold off taking the exam until you have either done the theory or talked to someone in the club about the theory especially at Ocean Diver/Open Water level

Maybe some of the greybreards will explain it better than me but I have noted a couple of threads recently where this has come up

[David Walker]

I don't have a BSAC 88 tables which is a problem and by sports diver do you mean ocean diver student workbook?

Borrow some then - if you can't do tables then there's little point in taking the exam. For other questions, there's some at the end of each chapter in the student notes, they cover everything you need. If you can't do them, then re-read the chapter or ask your instructor for help.

David

[Matt-75]

You can buy a set from the BSAC shop, hal752.

I got mine a couple of weeks back.

They are a worthy investment and knowledge on how to use them is an essential piece of knowledge if you want to dive safely.

[TerryH]

I don't have a BSAC 88 tables which is a problem and by sports diver do you mean ocean diver student workbook?

Have a look at the appendices on page 144 & 145 of the Diving Manual.
You should also have done lecture OT4 and matched that with your Ocean
Diver workbook.

All the awnsers to the exam questions are in the Manual and workbook, so if
you you think there are gaps, then maybe you should discuss this with your
Instructor.

TerryH

[amy-ward]

When you sit your test, the tables that you get given should have examples and instructions on how to use them in the front of the tables. So if you get stuck, just look at that.

correct me if Im wrong guys....

Amy

[Dave (Simmo)]

Hi Amy/Jon

Jon don't hold your breath on that i was provided with a copy of the table pages so i HAD to know how to use them

but i'm sure you'll be fine as long as you've revised and studied them

dave

[amy-ward]

dave,

very very true, i think its best to know how to do them generally and you feel better about doing them then (confidence and all that jazz). i need to do some swatting up on the old tables and nitrox tables etc.

Aimz x


Hi Amy/Jon

Jon don't hold your breath on that i was provided with a copy of the table pages so i HAD to know how to use them

but i'm sure you'll be fine as long as you've revised and studied them

dave

[David Walker]

Jon don't hold your breath on that i was provided with a copy of the table pages so i HAD to know how to use them

If they bring their own tables it would be very mean to not allow them to use them, and give them photocopies or whatever instead. They'll have the instructions there when they're diving, so if they can work the answer out from the exam in that way, then they can do the same when they're diving.

Its kinda like giving someone working in a supermarket a mental arithmatic test when it works exclusively with barcodes and computers and has no ability to take money if the till isn't working.

David

[Taff Griffiths]

Yep you're right

In the front there are examples of how to use the tables, but I am still amazed how many people still get the questions wrong. :(

Why?

IMHO it is because they have not fully understood the lesson and have not practiced using the tables.

As an instructor I give my students tables exercises to complete as homework and make sure as far as possible that they understand them. Also as Ocean and Sports diver students when they dive with me I get them to use tables to plan all dives regardless if they have a computer or not.

This may seem harsh in this day of computers but I have had several instances where people have forgotten their computers or they have gone U/S and no replacement available. They then fall back on to tables, if they have a copy! Then they attempt to use them to some alarming results. :eek:

So get your instructor to give you some tables exercises and be honest and admit if you do not fully understand, because IMHO if you do not understand the basics now it will only become more confusing later. :confused:

[Jester]

Don't forget that BSAC now have two versions of the '88 tables book @ £17.00 to members, and the THE BSAC DECOMPRESSION SOLUTION CALCULATOR @ £9.95 to members, sliding card one (I find the new ones very handy).

I usually talk novices into purchasing a set of tables when I order the BSAC OD pack for them, it saves a lot of hassle later and gives them the opportunity to familiarise themselves with the tables.

Why don't BSAC include '88 Tables in the OD pack? It would seem to me to be a logical thing to do.

[amy-ward]

i couldnt work that one out either.....it woulud make total sense.....guess they want to make money out of us?

aimz


Don't forget that BSAC now have two versions of the '88 tables book @ £17.00 to members, and the THE BSAC DECOMPRESSION SOLUTION CALCULATOR @ £9.95 to members, sliding card one (I find the new ones very handy).

I usually talk novices into purchasing a set of tables when I order the BSAC OD pack for them, it saves a lot of hassle later and gives them the opportunity to familiarise themselves with the tables.

Why don't BSAC include '88 Tables in the OD pack? It would seem to me to be a logical thing to do.

[Ben Panter]

Well, the cost of the tables has to be incorporated somehow. Either you put them in the OD pack and increase the cost of the pack or you make purchase optional and seperate. I prefer this way - it allows you to purchase a second hand set of tables, or use a set belonging to club.

Ben

[Andy Botten]

...the cost of the tables has to be incorporated somehow. Either you put them in the OD pack and increase the cost of the pack...

This is what we do in our branch. The students need the tables for the lessons & the exam. I also get them to plan each dive before they go in the water.
Let's face it, questions on BSAC 88 tables are in exams for all BSAC grades.

I have asked this before but...
Given that BSAC now issue Safety & Rescue in PRM & the Seamanship book in boat handling; why have they not done the same with Tables :confused:

[Tony Dwyer]

Don't forget that BSAC now have two versions of the '88 tables book @ £17.00 to members, and the THE BSAC DECOMPRESSION SOLUTION CALCULATOR @ £9.95 to members, sliding card one (I find the new ones very handy).

I usually talk novices into purchasing a set of tables when I order the BSAC OD pack for them, it saves a lot of hassle later and gives them the opportunity to familiarise themselves with the tables.

Why don't BSAC include '88 Tables in the OD pack? It would seem to me to be a logical thing to do.

At our branch we do include the tables in our new member pack. Our treasurer has a stock and shoves one in every pack.

[Steve in Sharm]

Given the "Health and Safety" and "Insurance" encroachments into our sport I think it only wise that each new diver gets his/her own copy when they join up.

This way there is less chance of anything bouncing back to the club/instructor if they later go out on their own and get hurt doing dives outside of the scope of tables and blame it on the fact they did not have tables cos they were loaned a copy for their course.

Steve

[Ben Panter]

Surely by that logic we must also give them regs, tanks, gauges, drysuits....

Ben

[Terry]

Don't forget that BSAC now have two versions of the '88 tables book @ £17.00 to members, and the THE BSAC DECOMPRESSION SOLUTION CALCULATOR @ £9.95 to members, sliding card one (I find the new ones very handy).

I usually talk novices into purchasing a set of tables when I order the BSAC OD pack for them, it saves a lot of hassle later and gives them the opportunity to familiarise themselves with the tables.

Why don't BSAC include '88 Tables in the OD pack? It would seem to me to be a logical thing to do.


Including tables in the pack is the way to go. We were discussing including them and I think that we will do just that if BSAC themselves dont.
Terry

[Ben Panter]

I would far rather it remained optional for the club to do it. For uni clubs in particular we have to make every effort to reduce the cost of diving. Five sets of tables living in the lock up as well as instructors' personal copies is enough to cover our requirements without putting another tenner on the cost of learning to dive. Yes... diving is an expensive sport, and eventually I would hope that all divers would purchase a copy, but ten pounds on the headline cost would knock a substantial fraction of our annual intake.

Ben

[Steve in Sharm]

I would far rather it remained optional for the club to do it. For uni clubs in particular we have to make every effort to reduce the cost of diving. Five sets of tables living in the lock up as well as instructors' personal copies is enough to cover our requirements without putting another tenner on the cost of learning to dive. Yes... diving is an expensive sport, and eventually I would hope that all divers would purchase a copy, but ten pounds on the headline cost would knock a substantial fraction of our annual intake.

Ben

Cant you add 1 pound a monthly to subscriptions and give it to them for free, or is that me trying to be overly simplistic? :rolleyes: Even better, 2 quid a month and get a little extra income for the club. :D

We did it when I ran the Watisham club, no hassles, no one moaning about costs etc etc

Steve

[Steve in Sharm]

Surely by that logic we must also give them regs, tanks, gauges, drysuits....

Ben

We do!, dont we?, surely that is what club kit is? Then of course they go out and buy their own when they know enough to be trusted to get it :rolleyes:

[Ben Panter]

Get money monthly? I'm afraid everything is based annually Steve, and although once they've caught the bug properlly they'll spend half their loan on kit, it's key to keep the initial costs down.

Ben

[Ben Panter]

Yes... we lend them tanks, we lend them regs, we lend them BCDs, what is the problem with lending them tables?

Ben

[Steve in Sharm]

Get money monthly? I'm afraid everything is based annually Steve, and although once they've caught the bug properlly they'll spend half their loan on kit, it's key to keep the initial costs down.

Ben

But isn't that what monthly membership fees do? Like yours I ran a club where most members were on a tight budget, getting them to pay a few quid monthly was a lot easier than asking them to cough it all up in one fell swoop

We also had a link with the local dive shop, who gave very good discounts to club members if they brought stuff through the club (more money in your bank account = more interest).

Just an idea :)

[Ben Panter]

But isn't that what monthly membership fees do?
When virtually all costs are annual (lockup hire, equipment servicing, BSAC membership, Boat insurance...) then no, I don't think it makes sense to charge monthly when in all likelihood for six months of the year you won't see the majority of your membership. And yes, of course we have agreements with the LDS for discounts on kit and fills.

This is rapidly losing the point. Non-essential increases in headline costs will turn off members. Uni branches, well, one member of one in this case, say "No thanks".

Ben

[David Walker]

Given the "Health and Safety" and "Insurance" encroachments into our sport I think it only wise that each new diver gets his/her own copy when they join up.

There are thousands of things that we could force people to buy that might make them a bit safer... it doesn't mean its a good idea. First aid kits? DSMBs maybe? Why don't we make all Ocean Divers do the O2 course before we let them near the water? Or first aid courses? And maybe buy their own O2 kit?

People can share tables - I don't see the problem. Not having their own shouldn't matter while they're an OD, because they should be diving with some suitable surface cover, who should be able to provide club tables maybe?

Virtually no one in our club (or any club i've ever been a member of) uses tables outside of their OD lessons at Stoney... so whats the point in having them?

David

[Gareth]

I don't want to sound like an old fart - but......

One of the problems I seem to see more & more of, is a lack of dive planning.

I still use tables prior to diving, even though I dive on a computer.

For general recreational diving the 88's give me a rule of thumb if the computer dies (,OK I've been doing it so long I have a fair idea without looking at the tables).

If it's a more adventureous dive I'll always cut a series of back up tables (from one of the many software packages available) - even if the complete dive is to be run on the computer. This is irrespective of equipment used, OC or CCR.

I always carry a set of tables on me when using the CCR, these are worst case tables. One side defines max no-stop time, then some fairly agressive dive times with the required deco. The other, bailout tables to 27% (the bailout gas I am most likely to carry). I should never need these, the computer gives me a more accurate deco profile. But....

I worry when the general attitude is that we don't need tables, we don't need to plan, we don't need to question what the dive computers are telling us, we don't need to have some idea what to do when the computer packs up.
No wonder we see real problems on advanced Nitrox coarses where its evident that people can't plan air consumption, use the tables, & supply sensible backup plans. - These people are doing dives with potentially significant decompression & have no idea what the risks are or what to do when it all goes wrong!

I'm not having a poke at any one in particular, I see the same problems in my own club.

Understanding tables, means having some understanding of decompression. Planing decompression means planning the dive.
Planing alternate decompression protocals means that you are planning for what could go wrong.
These are fundimental to long term safe diving, the time to ingrain these disciplines is when people start, not when they turn up on Advanced Nitrox or ERD courses! Having Ocean divers throw their tables away does not bode well for their future!

Gareth

[David Walker]

I still use tables prior to diving, even though I dive on a computer.

[...]

While I understand the point, I don't see the BSAC tables as useful in planning bailout or backup plans, etc. They are good to understand how deco works - how a short amount of time or a little extra depth can make a big difference, and helps us make the point about being careful with planning. In themselves though, using them day to day, I just don't find them helpful.

If my computer dies and I switch to tables, in most cases I'd find anything beyond the first dive would fall off the end of the tables. That doesn't mean dives shouldn't be planned (although there are many very safe ways of ensuring safety without pre-planning a dive to certain depths / times) - you say yourself you don't use BSAC tables, but instead use software. But there are other backups available, and not planning everything pre-dive is not necessarily a bad thing. For most dives we simply do not know enough about the profile to plan it in advance. While I could plan all my dives as square profile, it is so far from realistic times is becomes pointless. If tables give you 30mins of deco, while even a conservative computer doesn't give any deco, then the tables are inadequate bailout. That will change for very long bottom times or very long deco, but that isn't what most people do. Reality is, if my computer fails I will know to within a minute or two how much deco / remaining no stop time I have, because I keep an eye on it. Worst case, I know that I have enough air left to complete all deco, and stay at 6m until I get down to 50bar. Chances are, i'd probably still be up before the tables would have let me! This all of course ignores the fact that my buddy would have a totally independent way of monitoring this, and its unusual to dive with a different buddy on the same day (except during training, when people usually are using tables), and our profiles would never be that different.

So what is the value of tables? Well they're really good to help understand how deco works, very clear, very obvious to see how the times change with depth etc. But even doing Ocean Diver in Stoney we seriously struggle with them because, while we might touch 20m, most of the time is 6-8m, which technically isn't quite shallow enough to count it as the end of the dive (but is close enough, so I usually do otherwise we can only do one dive a day). While I agree that understanding the approximate length of deco etc you will end up with on a certain dive, since most people dive on computers I encourage them to plan that on their computer rather than tables - at least it gives them an idea of the bottom time they can expect, without being a factor of 2 or more out!

David

[Gareth]

My main point is it is a state of mind.

Ocean Divers, & to a reasonable extent new Sports Divers, can do a lot of diving using tables before they become a significant limiting factor. Especially if you are limited to single day diving or weekend diving.

I get the feeling that the reduction in dive planning has followed the drop in price of dive computers. To the extent that you do see ocean divers with computers before they have a full set of kit!

I am not knocking dive computers, great toys, really useful, great aid to diving safety. But they do breed lazy divers, jump in, swim about a bit surface when you are low on air - or bored, cold etc.

In the old days (makes me sound like an old git), dive computers where reletively expensive, one of the last gadgets you bought. This ensured that a large number of dives where inititially done on tables. This breed discipline - you had to preplan - you had to know how long the dive would be so that you knew that you could safely surface. It also instilled basic dive discipline, diving to the time PLANNED, within the depth PLANNED. Both of these seem quite alien to a new generation of divers!

Gareth

[David Walker]

In the old days (makes me sound like an old git), dive computers where reletively expensive, one of the last gadgets you bought. This ensured that a large number of dives where inititially done on tables. This breed discipline - you had to preplan - you had to know how long the dive would be so that you knew that you could safely surface. It also instilled basic dive discipline, diving to the time PLANNED, within the depth PLANNED. Both of these seem quite alien to a new generation of divers!

But in the end, planning depth and time in advance isn't necessary anymore - computers give us the flexibility to change plans as we see whats actually down there. Point is, for the typical recreational diving done in the UK, there isn't a big necessity to have carefully laid out plans for depth and time - just an idea of what kind of time you can expect to get at a certain depth. As long as you know your air will be ok (you don't need very precise depth plans to calculate your air requirement) then where's the problem? There are plenty of backups in case the computer fails, as I mentioned above, so can't see why detailed planning is necessary for the majority of dives. Indeed, so so few people do it, yet we all come back every time.

A bit of an analogy - i'm sending this reply through the forums. I can sit in my living room, eating my breakfast, and just click "send" and its gone. While I could have asked you for your address and hand-wrote a nice letter, there's no point - technology has moved on and this is a more suitable way of doing it than the old hand-written postal method. Yes it might be considered lazy too, but it doesn't make it worse.

David

[MattS]

Hi Gareth

I agree with both yourself and David!

You are right, dive computers are being purchased earlier than ever, planning seems to be an optional extra for many people these days and that is not a good thing. David is absolutely right that trying to do two useful dives in a day on 88s is not that easy these days.

I think what we have to consider is that general dive depths have got deeper (even in training) and bottom time expectations have increased. A glance at the 88s shows that any useful first dive deeper than 15m is going to result in a surface code of D or above. A look at the SI table shows that it takes 3 hours to get back to a B. The vast majority of table planned dive days turn out as A then C. Table C is all but useless for dives deeper than 12m. So unless the branch has a lot of 10m to 15m dives going on it stands a very good chance that an OD is going to need a computer sooner rather than later.

As soon as the computer is on a diver's wrist the 88s are an irelevance pretty much. Hennessey 88s deco algorithm is sufficiently different from the Buhlmann ZHL algorithm, implemented in the vast majority of computers, as to be virtually useless. Hence I don't support making the purchase of 88s compulsory. The situation for BSAC Nitrox divers is somewhat worse, they are compelled to buy the Nitrox 88s and they definitely can not be integrated with a dive computer. Dive computers use the EAD priniciple which Hennessey has never accepted.

I guess it is an example of BSAC doggedly trying to stick to the BSAC way while mainstream diving shrugs it's shoulders and moves on regardless. It leaves me, as an instructor, out on a limb integrating tables and software cut profiles into my dive computer use, but unable to pass those techniques onto the branch members I dive alongside.

For those interested my black magic involves nothing more than carrying a single submersible version of the Buhlmann table and noting the EAD of whatever I happen to be breathing. On the surface I can quickly check no deco/deco times far more easily than tapping computer buttons. Provided I know max depth and time I can get a deco solution should my computer fail underwater. It's not perfect but it is very useful and removes any need to guess decompression. Of course, no one should ever do this without proper training ;)

The 88s have backed the training courses up against a wall. We (instructors) are teaching one thing and doing something completely differently with absolutely no guidance from the central body toward good and bad practise :(

So let's look at what we do teach. How many hours spent on tables (lets just say lots)? As you say we know full well that more and more people are using computers earlier and earlier. Yet the old ND/SD course had more lesson minutes on dive computers than the courses we have now. Surely we should be spending more time teaching about computers and their sensible use, not less. I assisted on a BSAC Advanced Nitrox course for the first time over the weekend. I was pleased to be assigned the lecture which includes computers - I have a fetish about such things. I wasn't so pleased to find a single paragraph basically listing a feature set :(

The practises we do teach are rather dated and somewhat problematic in conjunction with computer use. We have David guessing his bailout decompression at 6m, although a 5m, 4m, or 3m stop would see his gas last longer and Nitrogen exit his body faster. BSAC still teach (by suggestion) that breaking 6m is going to cause an immediate bend :eek: So all the BSAC divers do their last deco stops at 6m (usually deeper) and we end up with so called 'Suunto minutes' - only because the Suunto algorithm considers 6m too deep for the last stop and basically doubles the predicted 3m stop time. It's a while since I checked but I seem to recall that the Suunto stop prediction is fairly accurate when the stop is completed between 3m and 5m. BSAC have conditioned divers to think that stops shallower than 6m are not possible. As a result BSAC divers are using there instruments a little incorrectly.

Where I disagree with you Gareth is in where the fault lies. The new generation of divers is no more more lazy than we were - well maybe when it comes to climbing ladders :) They are no less concerned about their safety. They are not planning dives because we are not teaching them or those that lead them, how to do so sensibly alongside the computers we all know everyone uses.

[MattS]

Point is, for the typical recreational diving done in the UK, there isn't a big necessity to have carefully laid out plans for depth and timeDavid I sort of get where you are going. I can't agree with it though. We are teaching people to survive in a non-life supporting environment. Do you not think that planning how long you will be in that environment is a very basic safety point?

As I put it to my trainees - NASA would not send an atronaught into space without working out how much air they need. Ok I know that's extreme but it tends to focus them on the gas calculations ;)

Indeed, so so few people do it, yet we all come back every time.Except some people do not come back. OOA incidents happen far too regularly. The vast majority are most likely completely avoidable.

[Gareth]

David

I think you've just agreed with me???

What I see more of is that divers plan the dive on the fly in the water - my air lasted longer, I've still got no stop time etc.

This doesn't matter so much in the 20m zone in sheltered water.

But is does start of have an impact when you go deeper or off shore.

I've been on charter boats where we've been about to, or have called in lost divers, just because the dive plan changed under water! "We had more air than we thought so we stayed a bit longer!" Although the Coastguard have been understanding its very poor practice.

I've also seen people come out with 0 bar, or miss stops because they run out of air. The answer being "well its normally alright, at 20m, I hadn't realised that we would use some much air that deep!"

If the discipline to PLAN the dive is not instilled in people as trainee's & Ocean Divers, its harder to develop it when they graduate to Sports Divers! Checking decompression obligations (tables) is step one of planing a dive, if they stop doing this, they are likely to stop planning altogether.
In 20m of water the risks of running out of air/ having a serious decompression obligation is minimal (you should be able to safely make a swimming ascent (if using a single12) from 20m).Life gets more complicated at 30/40m.

We teach buddy checks, they become an instinctive part of kitting up (because they are always done - in one form or another).
If we don't DO planning, they fail to become an instinctive part of the predive procedure! - Thats my concern!

Gareth

[Steve in Sharm]

Just playing devils advocate - so dont jump down my throat :rolleyes:


But in the end, planning depth and time in advance isn't necessary anymore - computers give us the flexibility to change plans as we see whats actually down there.

I noticed your an OWI - dont you teach "Plan the dive - dive the plan" anymore - or has that somehow dissapeared from the DTP since I looked yesterday :confused:


Point is, for the typical recreational diving done in the UK, there isn't a big necessity to have carefully laid out plans for depth and time - just an idea of what kind of time you can expect to get at a certain depth. As long as you know your air will be ok (you don't need very precise depth plans to calculate your air requirement) then where's the problem?

Now air planning calculations have dissapeared from the OD DTP - now your starting to worry me - you sound like a PADI Instructor :o


There are plenty of backups in case the computer fails, as I mentioned above, so can't see why detailed planning is necessary for the majority of dives. Indeed, so so few people do it, yet we all come back every time.
David

Such as? The only backup I know of is pre planning with tables! If your computer goes Pete Tong how do you know what your depth and time was?

Do you borrow someone elses computer and go back in to finish your deco?

And if we all do come back better tell Keith at HQ that his statistics are all ficticious and Dive and Diver, plus the BBC etc are making up those diver deaths they report :eek:

Steve

[Steve in Sharm]

Excellent answer, but you've got so much green Im not sending you any new - sorry. :o

When teaching OD I always give tables the respect they deserve (dont forget, air consumption for these fellas makes tables very very relevant) and then take time out to show them the difference between ultra conservative BSAC 88 and PADI tables as well, also have a very good Suunto Viper demo video that shows exactly what a computer does underwater and how it credits us for coming shallower during the dive.

I tried a thread last year (may have been on handbagnet) where I asked that if we compared how 88 tables was so restrictive compared to the rest maybe it was time for 88 tables to be re-evaluated. Got shot at big time, but I still think that the over conservative 88's need to be revalued.

Going back to my earlier post. I know I prattle on about PADI (and most of their standards are US law based) but they have now been advised by some legal eagles that all students should have their own copies of manuals and tables etc etc to prevent any legal comebacks if former students then go off and do some sort of diving outside of the scope of their training and get hurt and subsequently try to sue their instructors - the simple fact that they had a copy of tables in their possession etc would make their claim very hard to pursue - I could go on but I wont bore you. :rolleyes:

With this in mind, its why I think we should ensure every student gets a copy, it also saves em having to buy one later on in their diving career for SD/DL/AD OWI etc etc

Steve

[Janos]

I tried a thread last year (may have been on handbagnet) where I asked that if we compared how 88 tables was so restrictive compared to the rest maybe it was time for 88 tables to be re-evaluated. Got shot at big time, but I still think that the over conservative 88's need to be revalued.

88' s give similar no-stop times to PADI tables. 88's may be 'restrictive' but no more so than other recreational dive tables.

Janos

[Steve in Sharm]

88' s give similar no-stop times to PADI tables. 88's may be 'restrictive' but no more so than other recreational dive tables.

Janos

True on the no stop times, but you try planning a 2 dive day to 20m with 2:45 surface interval...... and as for a 3 dive day, forget it (didn't we have this chat on handbag net?)

Steve

[Gareth]

Hi Gareth

section removed

Where I disagree with you Gareth is in where the fault lies. The new generation of divers is no more more lazy than we were - well maybe when it comes to climbing ladders :) They are no less concerned about their safety. They are not planning dives because we are not teaching them or those that lead them, how to do so sensibly alongside the computers we all know everyone uses.

Matt

From my other post

We teach buddy checks, they become an instinctive part of kitting up (because they are always done - in one form or another).
If we don't DO planning, they fail to become an instinctive part of the predive procedure! - Thats my concern!

This is what really concerns me, failing to plan using tables - tends to lead to failure to plan altogether.

Gareth

[Jon H]

ok this is weird because i only posted one dive test and there is two. Went to devil bridge and people in that area are mad they go jumping of bridge. Plus the kids are barbarians they throw rocks at bubbles of dv weird people. luckily know one was hit.

[David Walker]

David I sort of get where you are going. I can't agree with it though. We are teaching people to survive in a non-life supporting environment. Do you not think that planning how long you will be in that environment is a very basic safety point?

I noticed your an OWI - dont you teach "Plan the dive - dive the plan" anymore - or has that somehow dissapeared from the DTP since I looked yesterday

Now air planning calculations have dissapeared from the OD DTP - now your starting to worry me - you sound like a PADI Instructor

Ahhh, knew I shouldn't reply to things quickly on a morning before work. When I say "planning depth and time in advance isn't necessary anymore", what I really mean is the detailed, minute by minute "i will spend 13 minutes at 22m, and then another 24mins at 18m before starting my ascent which will take 2.5mins to reach 6m where I will stay for 5.5mins" type of planning. Its just not necessary. The point i'm trying to make is that technology has allowed us to move on from that. I don't usually know what exactly i'm going to find before I jump in, and so its unreasonable to plan the dive precisely before it happens. While in some cases that might be relevant, for the average diving in the UK i just don't think it is. If i'm going to have worthwhile backup plans from the BSAC tables, that will mean that the second dive I must stick to table limits - if I go beyond the limits of the tables, then there's absolutely no point in having the backup - as far as they're concerned i'm already dead!


Ok, a practical example of using tables as a backup:
I was going to do a UK example, but all the diving i've done here recently has been with me on nitrox and a buddy on air, so i've been well within no-deco limits and so doesn't really work as an example.
Take some diving I did last year. First dive was 40m, second was 28m. A decent 3.5 hour surface interval. Both on air. First dive I reached 6m after 26mins, which would give me 1@9 and 6@6... if something failed on the first dive, I could happily have done those stops. But I didn't. So what happens when I come to the second dive? Do I decide not to dive again, knowing that my backup plan is now wrong? Should I have done those stops, in which case why not just dive on the BSAC tables all the time? In any case, if I do the second dive i'm going in on a C, and returned to 6m after 40mins, and did a 3minute safety stop.

Problem is, what happens on the second dive if my computer failed after 35mins, when I was at about 15m? According to the tables, at that point i'm already way off the end of the tables - for 26mins they give 2@9 and 18@6... but i'm already 9mins beyond that time, and tables simply don't go that far. Yet my computer wasn't even into deco.

So, what do you do with your backup tables in that case? Either you're diving to your tables, or they're completely useless to you. You couldn't possibly do all the stops they wanted, and again this dive was not even close to going into deco on the computer.

While its all well and good to teach people how to plan dives on the tables, and I do during training as in the syllabus, it simply isn't practical for most real diving people do - you'll have blown the table on the first dive, and so you have no backup (essentially) on the second dive, because you're out of the tables' range.

Now what I encourage people to do post-qualification is to check their computer planning functions for an expectation of the time they can spend at their planned depth. I don't think detailed planning is necessary - I teach it, but don't actively encourage it post-qualification, because I simply do not believe it is useful. If my computer fails during a dive, then I know what it said no more than a couple of minutes ago. I therefore know, to within a couple of minutes, what my deco obligation would be. I also know the ceiling I have in which to complete that deco. If the computer fails, I therefore ascend to the depth I know the deco should be (usually 6m on my computer), and stay there for longer than I know I need to be there, "just to be safe". And yes, I have alternative means of knowing the depth, depending on the site that could be shotlines, sloping shorelines, markers on my DSMB line (including my spare), guessing from looking up to the surface (surprisingly accurate), my buddy, or I used to carry a backup depth gauge too. That would not be a problem. For timing, I can either use my watch, my buddy, count in my head, or simply stay until my air starts to get low. I know that at any point in te dive I had more than enough air to surface safely, so worst case is I stay there til my air runs out. In practice, that wouldn't be necessary. A slow (1m/min) ascent to the surface completes the dive, perfectly safely despite computer failure. And that would be assuming i'd lost my buddy too - if they were still with me (very likely), then it would be even easier.


So is planning absolutely necessary? For trainees, definitely. They don't have any idea of how long air lasts, how long they can stay at certain depths, etc, and so its very important for them to plan and stick to it. Beyond OD/SD? I know how long my cylinders will last on various types of dive, and don't feel the need to sit down, map out my expected profile and calculate exact air requirements. I also know roughly how long I can expect at a certain depth before hitting the no-deco limit, and can match that up with air limits. Underwater, if air runs down quicker than expected, I ascend earlier. If I hit deco unexpectedly early for some reason (eg deeper than expected), then I will monitor air more closely, and if we hadn't agreed to do deco then start to ascend earlier.

Is what I do very carefully planned, absolutely not. Do I think the way I dive is unusual, absolutely not. Do I think the way I dive is unsafe, most certainly not. Fact is, I can see absolutely nothing which pre-planning a dive in detail gives me. If someone can point out a risk which I might face which I can't cover without carefully planning every dive, then please do tell me, and I might be able to make my diving safer. But as far as i'm aware, I could deal with absolutely any failure of my kit (or brain) without any hassle whatsoever.

And well done for reaching the end :D

David

[MattS]

Hi David

I think you just provided a very good example of what I was talking about when I said BSAC are not teaching you how to use tables in conjunction with a dive computer.

After your first dive the 88s are useless because you should not be switching deco tables (algorithms) mid series. It is really important as the residual gas calculations are completely different.

Your first dive looks to be 26mins@42m, on 88s. Your computer is most likely a Buhlmann derivative. The closest profile on my Buhlmann table is 20mins@42m which gives 2@9m , 2@6m, 12@4.5m (the 4.5m stop will be around 15mins or so if carried out at 6m). The difference in stop times compared to 88s provides an indication of just how different the algorithms are. One problem with the 88s is that they are not very granular when it comes to calculating residual gas (as Steve indicates). This makes them very safe, but quite restrictive for subsequent dives (and perhaps unsuitable for computer implementation).

We are talking about planning so both profiles should be decided in advance. Personally I would sit down and plan two Buhlmann table profiles, with deco stops I was prepared to do and have the gas to do. I can then use the computer to dive inside those profiles but still be able to bale to a slate should the computer fail. It's not completely risk free, but neither is using a mult-level computer in the first place. The benefit of being able to complete the series without having to guess is worth the small additional risk - and a healthy dose of HI-FO2 during deco to mitigate.

The table profiles are worse case and I dive inside both those worse cases. The important part is that the table I am using was produced with a derivative of the same algorithm that is in my computer. So I don't fall off the table after the first dive.

The alternative method of providing redundancy is to carry a second computer. Apart from it being an expensive option it adds complication which I don't think is desirable personally.

While its all well and good to teach people how to plan dives on the tables, and I do during training as in the syllabus, it simply isn't practical for most real diving people doIt is not practical to try to mix BSAC 88s with modern dive computers for decompression diving, that I will agree with. You can sensibly mix tables with computers but BSACs allegiance to 88s prevents it being covered in lessons. I am not against the 88s by any means. I am not against the use of them for teaching no-decompression diving (where the times are not disimilar to most computers).

I teach it, but don't actively encourage it post-qualification, because I simply do not believe it is useful.Because no one has taught you a way to do it that is useful, perhaps. The problem comes when someone you have taught moves outside the relative safety of no-decompression dives. There is an amount of uncertainty. Decompression diving is all about certainty; certainty that you can hold the stops, certainty you have gas to breathe, certainty of when it is safe to surface. Of course you can fudge around these things, but the risks will go up and accordingly the incident figures.

I therefore know, to within a couple of minutes, what my deco obligation would be. I also know the ceiling I have in which to complete that deco. If the computer fails, I therefore ascend to the depth I know the deco should be (usually 6m on my computer), and stay there for longer than I know I need to be there, "just to be safe".It is a bit of an advanced topic. The ceiling is not at 6m at all. It is constantly ascending throughout the stop (look at the earlier Buhlmann example which shows the bulk of the last stop above 6m). In an emergency situation you might consider halfing your stay at 6m and carrying out the remainder at 3m. Ambient is halfed, offgassing is increased and breathing rate decreased accordingly. You could use 5m or 4m instead of 3m, they all better options than 6m provided you are not already bent.

Beyond OD/SD? I know how long my cylinders will last on various types of dive, and don't feel the need to sit down, map out my expected profile and calculate exact air requirements. I also know roughly how long I can expect at a certain depth before hitting the no-deco limit, and can match that up with air limits.Decompression algorithms involve some logarithmic calculations across a number of time based compartments. As is the nature of simultaneous logarithms, a very small change to the inputs can produce very large changes to the outputs.

So unless you happen to have run the exact profile (or series) you could get a nasty surprise. Compare the difference in no-deco time at 21m compared to 25m, and how deco piles on at 40m+. A particularly common mistake caused by multi-level computers is when divers, used to seeing a couple minutes deco disappear during ascent from a 30m dive, assume the same will happen, but find the stops times increasing when they stay a little longer or go a little deeper. Each one of these surprises is a potential incident.

Is what I do very carefully planned, absolutely not. Do I think the way I dive is unusual, absolutely not. Do I think the way I dive is unsafe, most certainly not.Personally I would say this comes down to knowing when you have stepped into unknown territory. Which you can't really judge without planning the profile. Should you fail to spot that you have made the step, and neglect to plan because of that, I would venture that you are at much greater risk. More to the point, are those people you have trained able to spot it.

Diving isn't safe and decompression diving definitely isn't safe ;)

[Jon H]

They dont evan really tell us how to use a computer. Only tables only learnt to use dive computer of my instructer and i really didnt use. Its was used to find my dive profile. But i know how to use my tables. when would you sugest when to buy a dive computer. in ocean diver,trainee,or sport?

[Dave Sydenham]

The use of computers is covered in lesson OT4 although as there are so many different models it is unlikely that you will be taught exactly how your specific computer works, more a generic computer overview. I would expect that your instructor would go through this more specifically and show you how yours works on a practical lesson/dive as you have said.

I would buy a computer when you feel you need one/ can afford one. You don't need a computer to go diving as long as you have some means of measuring your depth and time. You do need regulators, masks, fins, diving suit and so on...So computer would not be top of my shopping list when starting out. Also before you buy one speak to others in your club with different computers and see what you/they like dislike about their computers to help you decide.

Cheers!

Dave
:)

[David Walker]

It is not practical to try to mix BSAC 88s with modern dive computers for decompression diving, that I will agree with. You can sensibly mix tables with computers but BSACs allegiance to 88s prevents it being covered in lessons. I am not against the 88s by any means. I am not against the use of them for teaching no-decompression diving (where the times are not disimilar to most computers).

I like the BSAC tables! They're very good for getting people to understand decompression, understand the effect depth and time has on things, essentially to give them some understanding of decompression - you just cannot get that from a computer, and of the other tables i've seen its not as obvious as with the BSAC tables. I just think, as I think you agree, that they're not useful *unless* you're ONLY diving with them. Using them as a backup to a computer is just pointless and potentially dangerous... dangerous because people think "oh i'm fine, i've got my tables as backup", who when it comes down to it may find that they've already fallen off the end of the tables!


The ceiling is not at 6m at all. It is constantly ascending throughout the stop (look at the earlier Buhlmann example which shows the bulk of the last stop above 6m). In an emergency situation you might consider halfing your stay at 6m and carrying out the remainder at 3m. Ambient is halfed, offgassing is increased and breathing rate decreased accordingly. You could use 5m or 4m instead of 3m, they all better options than 6m provided you are not already bent.

Ah yes, I understand that in practice its not as simply as a 6m ceiling. However, in most cases, given a slow ascent rate (which I always do anyway, with a deep stop if i'm diving fairly deep / not in any hurry to get out) I can ascend to 6m without any long intermediate stops below that. I'm not exactly sure of the algorithms used by Buhlmann and similar, but there's always compromise when trying to deco shallower - you could of course say that you'd offgas quickest on the surface, but chances are that'll bend you. In reality, the exact stop depth often depends on circumstances - if its very rough weather, it'll be a little bit deeper. If i'm on a gently sloping shot / anchor line i'd probably work my way up slowly. With a DSMB I often start reeling in very slowly (1m over a few minutes) after a while. If its a crowded shotline i'm coming up I might go above or below everyone else. There are a lot of variables that go beyond the point I was trying to make.


A particularly common mistake caused by multi-level computers is when divers, used to seeing a couple minutes deco disappear during ascent from a 30m dive, assume the same will happen, but find the stops times increasing when they stay a little longer or go a little deeper. Each one of these surprises is a potential incident.

Ah see, that kind of problem can be solved with a quick look at tables / computer planning tools, it doesn't require a detailed plan of the dive with every minute accounted for - i'm not advocating removing all planning altogether, just saying that you don't need to plan minute-by-minute to dive safely. I have no objection if others do, but I don't believe it is necessary.

David

[Young Diver 101]

Hello Everyone,

Me and my Dad have just started diving and are soon to finish the lectures, just in time for the theory test! :D does anybody know the questions so I can get a head start on it please?

[Gareth]

Hello Everyone,

Me and my Dad have just started diving and are soon to finish the lectures, just in time for the theory test! :D does anybody know the questions so I can get a head start on it please?

This is an old thread. It is normal practice to start a new thread when a thread is so old.

However, the answer to your question is have a look here (http://www.bsac.com/page.asp?section=1548&sectionTitle=Interactive+Learning) ,these are now a bit dated, but should give you an idea.

You will need to log into this area seperately (it is the main bsac forum).


Gareth