Steel 72 vs. Aluminum 80?
Stan Springer
Like the iron workers say Allen. Steel is for real. I give my students aluminum ninety's
so they can get some bottom time but seldom will any of them get more bottom time than I
do using-yup a steel 72. I like the fact that when empty they do not go positive bouyant
as much as aluminum. No body wants them so I also get them like real cheap and I never
have had one fall out of hydo and several are over thirty years old.. And for saftey I
dive them as a twin tank rig without the crossover bar, using two first stages. With
this rig I only need 4 lbs of weight using a three mil suit versus 16 lbs if I use a
single 90 aluminum. Also it allows sucking one tank down to zilch as there is a full one
for backup. Works real well for me..If I were to consider a single tank rig for everyday
diving instead of my twins I would go to the steel 100..again for bouyancy reasons..
Regards..Stan
Stan Springer
Rick Dusch
At 500 psi you'll have more air left in a 72 than in an 80
17.5 cuft in 72, 12.8 in an 80 remember usable air is the volume of air
not the pressuse a 72 holds 3.2 cuft per 100 psi an 80 holds (luxfer)
2.5 cuft per 100 psi...RD
> People are always telling me that I shouldn't even consider getting
> steel 72s because they hold "so much" less air than aluminum 80s. When
> I note that ~71 vs. ~77 cf isn't that much difference in my book, they
> counter with something like, "yeah, but you're talking 2250 vs. 3000 psi
> as well," and drop it there. What's the deal? If you suck a tank dry ,
> you're talking about a 6 cf difference. If you take it down to 500 psi,
> I guess you're widening the gap of unused air a bit, but is it really
> that much? I am pretty good with my air consumption, and when I can get
> 2 used 72s for the price of one used 80, I really wonder how much
> "better" 80s really are.
>
> Can someone out there clear this up for me? Thanks.
>
> Allan
> --
>
> To reply, remove the zz's from my address.
Allan Kaplan
Don Porter
Allan Kaplan wrote:
>
> People are always telling me that I shouldn't even consider getting
I like the steel 72's because I dive primarily off boats that fill to
only 2500 psi max. At lower pressures the steel 72 holds more air than
the Al 80. Also for carrying to and from the boat, the steel tank feels
lighter when I throw it on my shoulder, although I haven't weighted
either one. And lastly, a perfectly good, in hydro steel 72 is readily
available used for $50 or so. I see no advantages to aluminum 80's
except that they are cheap to buy new.
Don
Fred Tagge
Allan Kaplan wrote:
>
> People are always telling me that I shouldn't even consider getting
> I note that ~71 vs. ~77 cf isn't that much difference in my book, they
> counter with something like, "yeah, but you're talking 2250 vs. 3000 psi
> as well," and drop it there. What's the deal? If you suck a tank dry ,
> you're talking about a 6 cf difference. If you take it down to 500 psi,
> I guess you're widening the gap of unused air a bit, but is it really
> that much? I am pretty good with my air consumption, and when I can get
> 2 used 72s for the price of one used 80, I really wonder how much
> "better" 80s really are.
>
> Can someone out there clear this up for me? Thanks.
>
> Allan
> --
Steel 72's have about the same internal volume as an AL 100. IOW pump a
72 to 3000 psi and you get a little over 90 ft^3 of air (and a real
nervous tank monkey). There were a couple of manufacturers way back when
that even made tanks with the same internal volume as a 72 but rated at
3000psi WP. BTW Those are my favorite tanks. When diving a 72 I still try
to reach the end of any required deco with 1/6th of my original air, but
that translates to about 300psi, not 500psi. Modify PADI dogma as
required to reflect the real world. Congratulations on noticing that!
IMNSHO Those who use the "but it's only 2250 instead of 3000" argument or
the "AL doesn't rust" argument concerning AL vs Steel need to go buy a
clue. Its a fair bet they'll never develop one on their own. The only
argument that has any real bearing is that the AL tanks are cheaper (in
the US anyway). You'll pay for that economy with more drag per ft^3 of
gas, more lead to stay neutral, and a shorter tank life. The trade off
is yours to make, but all things being equal I'll dive steel over AL in
salt water any day.
Stay Wet
FT
Chuck Hopf
Allan Kaplan wrote:
>
> People are always telling me that I shouldn't even consider getting
> steel 72s because they hold "so much" less air than aluminum 80s. When
> I note that ~71 vs. ~77 cf isn't that much difference in my book, they
> counter with something like, "yeah, but you're talking 2250 vs. 3000 psi
> as well," and drop it there. What's the deal? If you suck a tank dry ,
> you're talking about a 6 cf difference. If you take it down to 500 psi,
> I guess you're widening the gap of unused air a bit, but is it really
> that much? I am pretty good with my air consumption, and when I can get
> 2 used 72s for the price of one used 80, I really wonder how much
> "better" 80s really are.
>
> Can someone out there clear this up for me? Thanks.
>
> Allan
> --
>
is a measure of volume at normal air pressure. Until 72=77, a steel 72
holds about 5-6 cubic feet of air less than an AL80. How much time that
represents is very dependent on you and your breathing rate. If your
firends don't believe you, have them calculate the volume of an AL80
tank at 1ATM. It is not even a particularly large fraction of 80 cubic
feet.
chuck hopf
ForSPBurke
In article <33E21C...@zzmacconnect.com>, Allan Kaplan
<amkap...@zzmacconnect.com> writes:
(snip)
>I guess you're widening the gap of unused air a bit, but is it really
>that much? I am pretty good with my air consumption, and when I can get
>2 used 72s for the price of one used 80, I really wonder how much
>"better" 80s really are.
Where??? I buya bunch of 72's at that price!! PLEASE e-mail location,
seller etc!
Steve Burke
for...@aol.com
A G Dobson
>
>> People are always telling me that I shouldn't even consider getting
>> steel 72s because they hold "so much" less air than aluminum 80s. When
>> I note that ~71 vs. ~77 cf isn't that much difference in my book, they
>> counter with something like, "yeah, but you're talking 2250 vs. 3000 psi
>> as well," and drop it there. What's the deal? If you suck a tank dry ,
>> you're talking about a 6 cf difference. If you take it down to 500 psi,
>> that much? I am pretty good with my air consumption, and when I can get
>> 2 used 72s for the price of one used 80, I really wonder how much
>> "better" 80s really are.
>>
>>
>> Allan
Did anyone mention yet that the steel 72 is only 72 cubic feet when
filled to plus 10 percent, that is 2475psi. After the the tank has
passed a hydro or two and no longer gets the plus rating, it may only
be filled to 2250 psi, and is approximately 65 cubic feet in volume.
That is significantly smaller than the AL80.
I recently switched to using high pressure steel 72 tanks; they are
compact enough to be less cumbersome than the AL80 and the buoyancy
characteristics are better. The lower volume still allows either
reaching no-stop limits on deeper dives, or reaching my thermal limit
on longer shallower dives, so is not considered a big limitation.
But, in answer to your question, which is better?, I think there are
advantages and disadvantages to all tanks, so choose based on the
criteria important to you. It sounds like one of your main concerns is
cost, and you have a line on some inexpensive steel tanks. If so, have
no reluctance in getting them. You'll enjoy your dive just as much
breathing the air in it as you would breathing the air in an aluminum
tank!
Cheers
William Martin
Fred Tagge (fta...@goldinc.com) wrote:
: When diving a 72 I still try
: that translates to about 300psi, not 500psi. Modify PADI dogma as
: required to reflect the real world. Congratulations on noticing that!
Before taking this advice, you should know your first stage regulator,
and where it cuts off effective breathing at depth. For many regulators,
that is around or approaching the 300psi point, not 10 or 50 or 200.
-Will
Art Greenberg
In article <33E77E48...@cisco.com>
"Bruce R'. Miller" <b...@cisco.com> wrote:
> My understanding was that a "steel 72" is really a steel 65 that has
> an overpressurization stamp from it's first hydro. The "+" on the hydro
> stamp means that you can add an extra 10% over the certified pressure
> rating. So at 2250 psi a "steel 72" really only holds 65 cubic feet.
> Now we are talking about a differance 12 cubic feet if the cylinder
> is more than 5 years old since, as I understood it, cylinders rarely
> get the overpressurization stamp after the first hydro.
>
> Am I mistaken?
Yes, but only partly. The "+" rating is available at any time. You must
specifically request the test be done for it, and it may cost more than
the non-"+" hydro.
On the topic of overpressurization, I note that the LP72 holds about 87cf
at 3000 psi. This in a smaller package than the AL80 with only 77.4cf.
Of course, you may be horrified at the prospect.
> The amount of PSI makes no differance when you are talking about how
> long a tank is going to last you. It does, however, indicate a
> differance
> in the size and buoyancy of the cylinder.
>
> -bruce
The buoyancy characteristics of the "standard" low pressure steel 72
are very similar to the "standard" AL80; when empty, they're both
about 3.5 pounds positive. So there is no basis for a selection based
upon weighting.
Art Greenberg
ar...@eclipse.net
David Price
Larry Charlot wrote:
>
> >2 used 72s for the price of one used 80, I really wonder how much
> >"better" 80s really are.
>
> aluminum 80's, not the other way around. Maybe it's something regional?
> In our local dive stores, Luxfer and Catalina AL-80's retail for around $139,
> sometimes less if their having a sale. Steel 72's from Pressed Steel Industries
> or Faber (Italy) retail for around $250, and the larger capacities, like steel
> 100's or 120's are around $350. If someone knows where I can get two steel
> 100's for the same price as an aluminum 100, please let me know ASAP.
>
> Larry Charlot
Larry you missed the key word here *USED* and he's talking steel 72's
not 100's.
Dave
Larry Charlot
Allan Kaplan
> This post is unusual - in my experience, steel 72's cost TWICE AS MUCH as
> aluminum 80's, not the other way around. Maybe it's something regional?
> In our local dive stores, Luxfer and Catalina AL-80's retail for around $139,
> sometimes less if their having a sale. Steel 72's from Pressed Steel Industries
> or Faber (Italy) retail for around $250, and the larger capacities, like steel
> 100's or 120's are around $350. If someone knows where I can get two steel
> 100's for the same price as an aluminum 100, please let me know ASAP.
>
> Larry Charlot
Larry,
As the original poster, I was talking old (~20 yr. old) steel 72's,
which only old timers, it seems, want anymore. Generally come with old
J valves as well. I did indeed buy the 2 for $35 each, with over 4
years left on the hydros. I've seen them for sale for ~$15 out of
hydro, and a friend of mine bought a few once for $5 each at a yard
sale. I'm not sure what you're looking at, but maybe you ought to come
up here to Seattle!
Fred Tagge
David Price wrote:
>
> Larry Charlot wrote:
> >
> > >2 used 72s for the price of one used 80, I really wonder how much
> > >"better" 80s really are.
> >
> > aluminum 80's, not the other way around. Maybe it's something regional?
> > In our local dive stores, Luxfer and Catalina AL-80's retail for around $139,
> > sometimes less if their having a sale. Steel 72's from Pressed Steel Industries
> > or Faber (Italy) retail for around $250, and the larger capacities, like steel
> > 100's or 120's are around $350. If someone knows where I can get two steel
> > 100's for the same price as an aluminum 100, please let me know ASAP.
> >
> > Larry Charlot
>
> not 100's.
> Dave
Data point:
I just bought 4 used steel 72's today, with good valves, for $100 total. Thats
$25/tank. The best price I've been able to find for an out of date used aluminum
Luxfer 80 is $55/tank with valve. All need a tumble and/or hydro so add another
$15/tank on to the base price for useable tanks ready to go. The steels will probably
turn into Nitrox tanks for oil rig bounce diving. The Luxfer may turn into an O2
bottle with a valve change to a GCA 540 configuration, or stay a SCUBA a tank for my
daughter.
Used tanks can be a good deal if you're willing to take the gamble on the hydro. At
these prices the valve alone will cover the cost of the tank.
FT
BTW if you just *have* to carry 100 ft^3 you'll only need to pump them to about 3500
psi. That's still 250 pounds below hydro pressure. Just dive off some other boat,
please.;-) That pressure is a little high even for my strange tastes, especially for
25 year old tanks of unknown past history.
Dave Mabry
Larry,
Sounds like you are confusing the high pressure steel 80 with the low
pressure 72 of old. The 72 are rated at 2250 (+10% for original hydro)
but aren't made anymore that I know of. Pressed Steel makes 3500psi 80
cu ft steel tanks and they are expensive.
I think the discussion is about the old 72 cu ft. They can be found
around for about $50 most of the time. A buddy just picked one up at a
garage sale for $25. However, most of them were not galvanized, some
have epoxy coating inside, some are vinyl coated outside. Most of them
are susceptible to rust much more so than the modern galvanized tanks.
A friend and I are experimenting with a spray on galvanizing for the
older 72 and it seems to work quite well. One spray can costs about $8
and will do one tank. BTW, I use a double setup of 72 for a lot of
shallow diving. I like it better than an aluminum and pony combination.
Take care.
Larry Charlot wrote:
> >2 used 72s for the price of one used 80, I really wonder how much
> >"better" 80s really are.
>
> This post is unusual - in my experience, steel 72's cost TWICE AS MUCH
> as
> aluminum 80's, not the other way around. Maybe it's something
> regional?
> In our local dive stores, Luxfer and Catalina AL-80's retail for
> around $139,
> sometimes less if their having a sale. Steel 72's from Pressed Steel
> Industries
> or Faber (Italy) retail for around $250, and the larger capacities,
> like steel
> 100's or 120's are around $350. If someone knows where I can get two
> steel
> 100's for the same price as an aluminum 100, please let me know ASAP.
>
> Larry Charlot
--
Dave Mabry dma...@mich.com
Great Lakes Maritime Institute Underwater Research Team
NACD #2093 NSS-CDS #42872
Joe Balcius
Allan Kaplan wrote:
> People are always telling me that I shouldn't even consider getting
> steel 72s because they hold "so much" less air than aluminum 80s.
> When
> I note that ~71 vs. ~77 cf isn't that much difference in my book, they
>
> counter with something like, "yeah, but you're talking 2250 vs. 3000
> psi
> as well," and drop it there. What's the deal? If you suck a tank dry
> ,
> you're talking about a 6 cf difference. If you take it down to 500
> psi,
> I guess you're widening the gap of unused air a bit, but is it really
> that much? I am pretty good with my air consumption, and when I can
> get
> 2 used 72s for the price of one used 80, I really wonder how much
> "better" 80s really are.
>
> Can someone out there clear this up for me? Thanks.
>
> Allan
> --
>
> To reply, remove the zz's from my address.
The 80's aren't better. They are just different. I use Steel 72's
filled to 3000psi.
I like them for a few reasons.
1. The smaller size makes it easier to pack all my gear in the trunk of
my car. (damn those small cars!)
2. I use less wieght on my belt while diving.
3. They don't go possitive at the end of my dive.
4. They, typically, last longer than Aluminum.
The down side is that they are more expensive new.
I am VERY happy with my Steel 72's.
-Joe
P Burnhill
I would just like to apologise for my crassness in
(a) sending one message with subject 'Air Supply' but without the intended
text
and then ..
(b) including the right text but ineptly leaving the subject field as
'steel vs aluminium'
I can already feel the weight of the collective sighs, so please don't ...
P
ps I guess I should go and lie down!
David Price
P Burnhill wrote:
>
> I trust that this is an acceptable use of this list.
>
> CLIP
> safety more generally. However, we have recently increased our use of
> pony bottles for safety purposes, and have observed that one or two, who
> regularly dive with a pony bottle, use this to supply the direct feed to
> the stab jacket, keeping the main tank to supply to direct feed for the
> dry suit. Thus, the pony bottle becomes a full back-up system in the
> event of failure with respect to either (or both) of the main systems for
> breathing and buoyancy.
>
>CLIP
I also fill my suit with the main and sling a pony that is attached to
my horse collar for backup,it's nice to know that you have two seperate
systems in you're favor!!!!!!!!!.There is a picture at
"http://www.webspan.net/~dwprice/divelight.html"
Dave
P Burnhill
I trust that this is an acceptable use of this list.
Trained in Scotland as part of ScotSAC, I have recently been reviewing
our training and equipment regime. As a result three of us have
drafted an article to submit to our club mag. But we would appreciate
some critical thought before it goes into print.
Please not that we have well over 1,000 dives and 25 years diving
between us, dive in cold water and regularly wear dry suits. (But
pleased to report that we have just enjoyed the delights of seven days on
a liveaboard in the Red Sea!)
Anyway, critical comments please.
Peter
********** ********* ******** ******* ****** ***** **** *** ** *
Peter Burnhill
Scotland, UK
tel: +44 (0) 131 650 3301 fax: +44 (0) 131 650 3308
Email: p.bur...@ed.ac.uk URL http://datalib.ed.ac.uk
************************************************************************
Twin set and pearls: thoughts on safe equipment for the modern diver
One dive last year, we invited a stranger, found through an Internet
trawl, to make up the numbers on a boat trip. At the time we ScotSAC
divers quizzed him over his BSAC qualification, logbook, and experience
and were pleased to have him join us. As we were kitting up with our 15L
or 12L tanks, with 3L pony tanks and a variety of octopus rig
configurations, and religiously filling our small bottles, we saw that
this stranger was busy fitting two 7L tanks, each with its own first stage
and demand valve.
Our guest had three such 7L bottles in his gear: labelled A, B and C. He
would dive with two at a time, making a total of 14L per dive. At the end
of his first dive he would return to the surface with bottle A 'empty'
(with a small reserve of xx Ats., say), having either merely tested or
consumed part of the contents of bottle B. He would replace bottle A with
bottle C for his second dive. We forget whether the direct feeds for his
dry suit and stab jacket came from separate tanks but suppose that they
did. We have not seen the stranger with no name since but, apres dive (in
the pub), his modern use of the twin set has often intrigued us; that
experience, and a pint or two, have prompted this article.
This article, then, is about the equipment we use for air, for breathing
and for buoyancy. We suggest a re-think of the back-up systems we use for
safety. Our equipment and ScotSAC training reflect what we collectively
view as best practice, and this has evolved over many years. But should
we now consider this practice as best, or even as good when compared to
modern alternatives? In particular, we venture to suggest that the small
'fenzy' bottle has no role to play in modern diving practice, as it adds
cost (expense, weight and complication) and a false sense of security. We
would also welcome comment on the strategy adopted by our mystery
stranger, and would like to hear from suppliers who can help us
economically switch - trade-ins considered?
Let's start with the 'fenzy' bottle, or rather the small bottle we fill
and check before we start a day's diving - even each dive, and then
largely ignore in our diving practice. What is this really for? The
first answer, we are taught, and pass on as trainers, is as an emergency
buoyancy aid: to aid (controlled?) ascent and for inflation on the
surface. We recall that in the past this bottle was regarded as a welcome
and safe substitute for the demands of oral inflation. But now with
almost universal use of a direct feed from the main air tank, perhaps we
should regard oral inflation as the back-up. Is the small bottle any more
reliable? We suggest that very few are practised in the actual use of the
small bottle for controlled emergency ascent, or even for surface
buoyancy, and many would find the experience of trying to use the small
bottle underwater very stressful and potentially very dangerous. If we
really should be practised in its use, why does it not feature in our
ScotSAC tests. And from discussions with dive shops, we suspect that few
have their small bottles tested and serviced as often as they ought.
So, let's look at back-up systems more generally. Most of the divers we
typically encounter in Scottish waters now wear dry suits. We switched
from wet to dry in order to keep warm, but this now means that we have two
excellent buoyancy bags: the suit and the adjustable buoyancy jacket
(ABLJ), or more typically now, a stab jacket. This should be welcomed as
an improvement in safety. We now use the dry suit as the main buoyancy
bag, complete with direct feed - and no call for a supplementary small
bottle, please. The jacket acts as the back-up in case of failure: of the
suit, because it floods, or of the direct feed valve. We acknowledge that
it is not a complete back-up if the diver has only one tank: both dry suit
and jacket share the same source of air and potential failure (tank and
first stage). But, this points to a more fundamental point of failure in
the configuration of our diving equipment, more than a small bottle should
be sought as remedy.
The second reason, it is said, for having a small bottle is as an
emergency source of breathing air, via the ABLJ or stab jacket. We have
tried this in the pool and found it an engaging form of the yogi art, but
we confess that it has not (yet) entered our sub-sea diving practice. Be
serious, if your main air supply failed at depth, do you think that you
would (a) consider this as a answer to your problem, (b) be capable of
making use of this in a timely and successful fashion? We suspect not.
This small bottle is now so much less important as a piece of safety
equipment than two other, more recent additions to our diving practice:
the second demand valve and the second 'pony' tank. Let's be engineers
again, and think about safety through the redundancy of twin systems.
Our impression is that divers are increasingly including a second demand
valve in their diving rig, either as a Air II substitute on the stab
jacket or as an 'octopus' rig addition. (Which you use is itself a matter
of preference, historical accident and continuing debate.) Use of a
second demand valve must be reckoned a good thing, far more significant
than the use of a small bottle. The first and most obvious reason is its
potential use by one's buddy. The focus here, however, is on personal
back-up systems, and the second demand valve clearly does have the
potential to be a back-up in case of failure of one's own main demand
valve. But again, with only one air tank, this potential should be
qualified: both demand valves share the same and air tank and first
stage. Unfortunately, the 'fenzy bottle' is useless in providing remedy.
(In passing we worry that in general, the second demand valve carried by
divers, ourselves included, is generally of much less good quality and
condition than the main demand valve, so it may not work when the better
one fails. We do, however, try to remember to use the second demand valve
on each dive.)
As a further safety measure, many divers now own, and increasingly use a
second source of air, a supplementary 3 litre pony bottle, which
necessarily involves an independent first stage and second demand valve.
If you are like us, you own this because you went to Scapa Flow or do
other forms of repetitive wreck diving not because you wished to improve
safety more generally. However, we have recently increased our use of
pony bottles for safety purposes, and have observed that one or two, who
regularly dive with a pony bottle, use this to supply the direct feed to
the stab jacket, keeping the main tank to supply to direct feed for the
dry suit. Thus, the pony bottle becomes a full back-up system in the
event of failure with respect to either (or both) of the main systems for
breathing and buoyancy.
This takes us back to the mysterious stranger and his twin set. If we did
not already own 15L, 12L and 3L tanks, we would seriously be considering
following his system. So, if anyone fancies specifying an economic and
robust system, please let the authors know, and then we might be selling
some good tanks second hand. And as for the fenzy bottle, we guess, we
shall keep using them together with the webbed rabbit foot, whether we
believe in them or not - at least when on Club dives and in front of the
trainees. What do you think?
Allan Kaplan
> The 80's aren't better. They are just different. I use Steel 72's
> filled to 3000psi.
And what shop will fill them to 3000psi vs. their 2250psi rating?
Allan
Bob Crownfield
Joe Balcius wrote:
---
>
> The 80's aren't better. They are just different. I use Steel 72's
> filled to 3000psi.
> 3. They don't go possitive at the end of my dive.
> 4. They, typically, last longer than Aluminum.
> -Joe
joe:
any tank with ~80 cu feet, is lighter by about 5 lbs when empty, because
the air weighs that much.
Whichever tank you use, you should have the same bouyancy at the end of
the dive, neutral at 15 feet with ~500 psi. if so, you also start the
dive with the same weight regardless of the tank.
the only difference is whether the weight is on the belt or tank.
My AL 80's were bought in 1980, and are in almost perfect condition now,
except for scratches on the outside.
--
Bob_Cro...@QC.edu
Queens College, Computing and Information Technology Services
Photography, Diving, Flying, Delphi RAD addict
Diving Long Island Sound in Fairfield County, CT
ForSPBurke
In article <33F0B3...@zzmacconnect.com>, Allan Kaplan
<amkap...@zzmacconnect.com> writes:
>Subject: Re: Steel 72 vs. Aluminum 80?
>From: Allan Kaplan <amkap...@zzmacconnect.com>
>Date: Tue, 12 Aug 1997 12:02:09 -0700
>
>> The 80's aren't better. They are just different. I use Steel 72's
>> filled to 3000psi.
>
>And what shop will fill them to 3000psi vs. their 2250psi rating?
>
>Allan
>
>
Most!!
Steve Burke
for...@aol.com
John Brett
>I trust that this is an acceptable use of this list.
<snip>
I agree wholeheartedly on the subject of the fenzy bottle. I have one,
and think its wonderful, but then I use it to inflate my blob, not my
jacket. If you come to the conclusion that the fenzy bottle is *not*
an effective safety device, then I believe you have an obligation
*not* to use them in front of novices - there's no excuse for
propagating bad habits & false senses of security.
>This takes us back to the mysterious stranger and his twin set. If we did
>not already own 15L, 12L and 3L tanks, we would seriously be considering
>following his system. So, if anyone fancies specifying an economic and
>robust system, please let the authors know, and then we might be selling
>some good tanks second hand. And as for the fenzy bottle, we guess, we
>shall keep using them together with the webbed rabbit foot, whether we
>believe in them or not - at least when on Club dives and in front of the
>trainees. What do you think?
IHMO - the 'mysterious stranger' just had a larger pony than you guys.
If he didn't do more than take a couple of breaths from the reserve
cylinder, then he didn't plan to use it, and if the reserve had failed
at the worst moment (commencing ascent, turning dive, whatever), then
he would still have enough air to ascend safely.
If you plan to use both cylinders, either alternate useage of both
tanks, or use an isolation manifold.
John Brett BS-AC * PADI * IANTD
Bob Crownfield
Where I dive, the shops seem to be smarter than to do that.
Dave Mabry
Joe Balcius wrote:
> Allan Kaplan wrote:
>
> > People are always telling me that I shouldn't even consider getting
> > steel 72s because they hold "so much" less air than aluminum 80s.
> > When
> > I note that ~71 vs. ~77 cf isn't that much difference in my book,
> they
> >
> > counter with something like, "yeah, but you're talking 2250 vs. 3000
>
> > psi
> > as well," and drop it there. What's the deal? If you suck a tank
> dry
> > ,
> > you're talking about a 6 cf difference. If you take it down to 500
> > psi,
> > I guess you're widening the gap of unused air a bit, but is it
> really
> > that much? I am pretty good with my air consumption, and when I can
>
> > get
> > 2 used 72s for the price of one used 80, I really wonder how much
> > "better" 80s really are.
> >
> > Can someone out there clear this up for me? Thanks.
> >
> > Allan
> > --
> >
> > To reply, remove the zz's from my address.
>
> The 80's aren't better. They are just different. I use Steel 72's
> filled to 3000psi.
> I like them for a few reasons.
> 1. The smaller size makes it easier to pack all my gear in the trunk
> of
> my car. (damn those small cars!)
> 2. I use less wieght on my belt while diving.
> 3. They don't go possitive at the end of my dive.
> 4. They, typically, last longer than Aluminum.
>
> The down side is that they are more expensive new.
>
> I am VERY happy with my Steel 72's.
>
> -Joe
Joe,
You had better check them again. The old steel 72's go about 2 pounds
positive when empty. Their buoyancy characteristics are about the same
as an aluminum 80.
Maybe you are talking about some other tank, though. 3000 is a bit much
for the ones rated at 2250.
John Sowers
I just banded and manifolded two old 72's I bought for $50 ea
(included 95 hydro, fresh vis and a fill).
I just used them a couple of days ago. After getting used to the extra
mass on my back then throwing the wieghtbelt back on the dock, I had
one of the most relaxing dives I've ever had. I got more time than
using 2 80's and felt very at-ease.
If you can find someone who will let you borrow a set, give 'em a try.
You may have to sand and paint occasionally but worth the tradeoffs
IMHO.
Having a great time quarry diving in TN.
John
============================================================
= After diving, everything else is just a surface interval =
============================================================
Fishbre396
In article <5t5ocf$r...@camel2.mindspring.com>, jtso...@mindspring.com
(John Sowers) writes:
>I just banded and manifolded two old 72's I bought for $50 ea
>(included 95 hydro, fresh vis and a fill).
>
>I just used them a couple of days ago. After getting used to the extra
>mass on my back then throwing the wieghtbelt back on the dock, I had
>one of the most relaxing dives I've ever had. I got more time than
>using 2 80's and felt very at-ease.
>
>If you can find someone who will let you borrow a set, give 'em a try.
>You may have to sand and paint occasionally but worth the tradeoffs
>IMHO.
>
>Having a great time quarry diving in TN.
>
>John
>
>
I dived steel 72's in San Salvador (Bahamas) years ago, they were
WONDERFUL!!!! Didn't need a weight belt at all!!! It's a shame that so
many have switched to aluminimum!!!!
Chris London
>
>Joe,
>
>You had better check them again. The old steel 72's go about 2 pounds
>positive when empty. Their buoyancy characteristics are about the same
>as an aluminum 80.
>
>Maybe you are talking about some other tank, though. 3000 is a bit much
>for the ones rated at 2250.
>--
>Dave Mabry dma...@mich.com
Dave,
Steel 72s are popular here all along the East Coast of Canada because many
feel they
are less positive after a dive than AL 80s (by a couple of pounds).
Personally, I use
AL Super 80s, but the steel tank divers I know swear by them. For shallow
dives, I usually
borrow a few as they seem to be less buoyant.
They also last just as long as the AL 80s if filled to 3000. I know they are
rated for 2250,
but they are more often filled to 3000 anyway. Most dive shops will do this
and many of the
employees of dive shops do it for themselves as well. Hydro takes them way
beyond 3000.
They won't over-fill an AL 80 past 3000 though, too hard on the
compressor... drat...
Chris
Lee Bell
Chris London wrote:
> They won't over-fill an AL 80 past 3000 though, too hard on the
> compressor... drat...
Odd. I have compact 80's, rated at a working pressure of 3,300.
Haven't had a problem filling them yet, at least not here in the US>
Lee
Lee Bell
> Allan Kaplan wrote:
> People are always telling me that I shouldn't even consider getting
> steel 72s because they hold "so much" less air than aluminum 80s.
Some people also buy 100's (or larger?) because they can't carry enough
air to do what they want otherwise. Someone also said that steel 72's
are just as buoyant as aluminum 80's.
1. My first tank was a steel 72 and it sank when completely empty.
2. I use steel 72's on most dive vacations and I have been unable
to tell much difference between them and my compact 80's which are
neutral when empty. Both let me take 4 lbs off my weight belt over
a standard 80 and both tend to stay put better.
3. I come up with substantially more than 500 psi on every dive, whether
using a 72 or an 80. I've never noticed a significant difference.
4. As I recall, steel 72's are about the same length and maybe even
longer than standard 80's. They are thiner. My compact 80's are a
bit shorter than the standard. That little bit makes them a lot
easier for me to carry by the valve. I'm 5'8" and the standard 80
is just a smidgen longer than I can lift without bending my arms.
My compact 80's are just enough shorter to make a difference to me.
So, listen to all the advice, then make up your own mind.
Lee
Stan Springer
John Sowers wrote:
>
> I just banded and manifolded two old 72's I bought for $50 ea
> (included 95 hydro, fresh vis and a fill).
use two seperate sets of first and second stages. It is a very, "for real" comfortable
redundant air supply and a very stable rig underwater. Those who would argue for
streamlining: Dolphins are streamlined-divers ain't-- Where are you trying to go in a
hurry?????
As far as the fills. Yes I allow the shop to take them past 2250. Usually pumped to
2700 which cools to about 2500+ and since they are not manifolded together, I can take
one down all the way and this gives me a dive time with one tank as much or more than a
single 80, then I only have to change one tank on top for my next dive, while retaining
underwater a very reliable steel buddy "who don't go wandering off!!"..not to mention
the times I have had to bring someone else up from deep dives (amazing the number of
certified divers who do not moniter their guages) and able to do it with safety and
safety stops included... Stan Springer
> ============================================================
Joe Balcius
They are definately still negative at 500psi. They are also not
old tanks. One was manufactured in 95 the other in 96. Both are
stamped for 3000psi not 2250.
-Joe
--
Joe Balcius
Baker Tom
I have hurt my back and must give up one of my loves - underwater
photograghy. I have been taking photos underwater for just under 20
years, and now must walk away because of a back injury. I would like to
sell the remaining gear that I have.
Nikonis III body - in excellent shape, never been flooded.
Nikonis 35mm lens. Very good shape. Filter threads are slightly dented but
can still be used (Have been using the 16mm lens on it in this condition
for 10 years)
SubSea Mark 150 strobe - 3 power settings (50wt,100wt,150wt), plus slave.
Runs on 510vt dry cell battery. The battery lasts for many, many rolls of
film - great for those dive trips overseas!! The beam angle is 110
degrees, wider than the 15mm lens. Extra o-ring, never been flooded. Have
a half-used up battery with it. E/O connector sync cord (Can be
disconnected and connected underwater!)
Ikelite Photo tray and handle, with attached Sekonic light meter (new
battery).
Ikelite quick release strobe handle and strobe arm
Sea & Sea 16mm lens adapter (this lens screws into the 35mm lens and
expands the lens to 16mm. It really works very well and has excellent
focus across the field of view. Not as good as a 15mm lens but it is
affordable wide angle for people that don't have $1500 for a lens!!! Lens
can be screwed on underwater.
Sunpak Marine 32 strobe and handle/tray. This strobe runs on 6 AA
batteries and is excellent for macro work. Again, with normal batteries,
great for the dive trips. Has sync cord for Nikonis III. Has 2 power
settings and a test setting. Very fast recycle times. Never been
flooded.
Ikelite Photocase. A little beat up but any case will be after 18
years!!! Still closes water tight!
Ikelite 1:1 macro extension tube
Ikelite Viewfinder. This little beauty fits onto the flashsocket on top of
the Nikonis III. It has a viewing field of 17mm, with a bunch of masks
for different lens. It allows you to properly put your subject in the
photo by adjusting for parralex error. Just set the distance, look thru
the finder and shoot. Excellent finder!!
E/O sync cord for the Nikonis III. Lets you use the Mark 150 storbe.
Any other odds and ends I can find that I can't think of at the moment.
Everything but the Sunpak strobe fits into the Ikelite case.
This is a photographer's dream find. This camera set-up will alow you
to take photos as good as anyone, plus not have to worry about finding a
plug for your nicads, flooding your camera (If this happens, simply throw
the film away, rinse the camera body with fresh water, dry, and away you
go!!!). This is a manual system with everything needed to make it work.
It has been used everywhere on the east coast, from the Keys to subs in
150+ water off of New England. I have allows cleaned it after every dive,
lubed every o-ring everytime it has been opened, and love this system.
Only reason I am selling it is because I can't dive anymore. I went with
all of these components because I wanted to keep the system simple but
capable. It is worth - What?
I will part with all of the above, plus anything else I can find as I dig
thru my remaining dive gear, for $700. If that is too much, make me an
offer. I won't give this away but I would like to sell it to someone that
will use it a lot. If you want to take great photos and want to "Take"
great photos (not the camera), then this system is for you.
E-mail me if interested. I can make this sysytem available to be looked
at where there is an airport or if you live near NJ.
Thanks. Tom P.
Jason O'Rourke
Bob Crownfield <Bob_Cro...@QC.edu> wrote:
>any tank with ~80 cu feet, is lighter by about 5 lbs when empty, because
>the air weighs that much.
>Whichever tank you use, you should have the same bouyancy at the end of
>the dive, neutral at 15 feet with ~500 psi. if so, you also start the
>dive with the same weight regardless of the tank.
> the only difference is whether the weight is on the belt or tank.
Err, this is incorrect. A HP 80 weighs less and is less bouyant than an
AL 80. (32 lbs vs 27, +4 bouyancy vs -1). That's a 10 lb difference.
The bouyancy of the tank at the end of the dive is all that really
matters. Most Al 80s are +3.9 at the end, while most steels are between
-1.0 and +0.5. Their actual weight is not the issue.
--
Jason O'Rourke jas...@netcom.com
'96 BMW r850R www.csua.berkeley.edu/~jor
last dive: August 3rd, Whaler's Cove, Pt Lobos.
50 mins at 40 ft max, viz as high as 35'
Bob Crownfield
Sorry. When I posted that, I knew it was not clearly stated. I try
again:
At the end of the dive, with almost all of the 5 lbs / 80 cuft gone, you
want to be neutral at 15 feet no matter which tank you use.
At the beginning of the dive, you should be (not weightbelt) 5 lbs heavy
(the weight of the air you will use).
Because of different bouyancies and tank weights, the lead on the belt
changes. The total weight on the deck will change only by the difference
in bouyancy of the tanks.
I think it is right now ?
--
Bob_Cro...@QC.edu
Queens College, Computing and Information Technology Services
Photography, Diving, Flying, Delphi RAD addict
Diving Long Island Sound in Fairfield County, CT
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Todd
Larry Charlot wrote:
>
> >2 used 72s for the price of one used 80, I really wonder how much
> >"better" 80s really are.
>
> aluminum 80's, not the other way around. Maybe it's something regional?
> In our local dive stores, Luxfer and Catalina AL-80's retail for around $139,
> sometimes less if their having a sale. Steel 72's from Pressed Steel Industries
> or Faber (Italy) retail for around $250, and the larger capacities, like steel
> 100's or 120's are around $350. If someone knows where I can get two steel
> 100's for the same price as an aluminum 100, please let me know ASAP.
>
> Larry Charlot
At my local shop, steel 100's are $225, AL 80's are $165.
Todd