Horse collar BC

[shackle]

That wouldn't be the NOAA ship Ranier by any chance?

[BLT]

Nope, the Miller Freeman, a 215 ft Stern Trawler doing mainly fisheries research on Pollock.

I was VERY thankful I had a dry suit that day.

[scubadiverbob]

One thing no one has mentioned yet is that if you pull a CO2 cartridge, then later have to add more air to keep the bc inflated, you might breath the CO2 ... if I remember right, I think that's why dive stores started plugging the things in the first place.

I'm currently restoring a SeaTec bc that used the 5/8th inch dia., 24 thread per inch, cartridge. Anyone know where I can get a used cartridge or a bolt that will plug it? I've tried North Valley Fasteners and every hardware store around here. Thought this would be a good thread to ask on.

Robert

[Broxton Carol]

Who needs a vest? After reading all this stuff to worry about, Ill junk my vest, and when I need bouyancy, Ill fart in my suit!

[SeaRat]

luis said:

...Not to get too far out of topic, but since it was brought up (I am sure John is aware of it, but for everyone’s benefit):

All dives are decompression dives…some require stops and some don’t. This may sound as a technicality, but it is more important that just a technicality.

In all dive you need to properly outgas the absorbed inert gas and this will involve slow ascend rates and also a safety stop helps for deeper dives. I like safety stops for dives below 50 ft or 60ft, unless they are very short, but some recommend them on all dives below 30 ft.

At first I was skeptical about safety stops and deep stops, but after reading some of the new research (I do need to do a lot more reading) I am thinking that it is a very good idea. Yes we all lived with the Navy tables for years and we even think that we never got DCS; at least we didn’t get the well published acute symptoms. But, we always knew that we were playing with statistics and we have been very well aware of how little we have known about the actual mechanisms and physiology related to DCS.

Safety stops are still considered optional, but they seem to be a very good idea…in real life, no one really ascends as slow as we should.

IMHO, just like we are using modern technology (computers, the internet, new materials, rebuilding procedures, etc.) to find parts and preserve our vintage gear, we need to use modern technology (new research, dive computers, etc.) to protect our vintage bodies from DCS.

New research has shown that you can actually outgas faster on a deep stop or safety stop than on the surface with a high pressure differential. When we did our basic course, decompression theory was all based on Haldane dissolve gas theory only. Research has shown that micro bubble transport mechanics complicates the process of eliminating the absorbed inert gas.

Luis,

You've said a lot here, and I agree with most of it. I would qualify your statement to say that "all dives below 25 feet are potentially decompression dives." Technically, with a vintage 72 cubic foot tank, it is virtually impossible to get into a decompression problem at less than two atmospheres absolute (33 feet, or ten meters, in depth). Most of my dives over the last few years have been a maximum of 23 feet depth, averaging 15 feet. So in this specific situation, you really do not have to worry much about decompression sickness or the other related injuries. I do worry about barotrauma from too quick an ascent, but not decompression sickness.

Cousteau's Conshelf Two oceanauts saturated at 2 atmospheres absolute (the main colony was at 33 feet), and because of the extremely long duration, they did need to decompress from that depth before surfacing, using a "special gas mixture." Cousteau also reported that the support divers, the "Dark Suits who served the men below incurred minor decompression accidents and have been cooked in the recompression chamber, while none of the floor party was harmed." To his credit, Cousteau insisted on having a recompression chamber available on just about all diving expeditions, and it saved a lot of agony for his divers.

The problem is the emphasis on "acute symptoms," with not much discussion of chronic problems of decompression. One of these is known as dysbarism-related osteonecrosis. I have an old publication on this from a symposium in 1974, which discusses the damage to a divers (and potentially an aviator's) bones from decompression problems. These are:

...lesions in the long bones, such as the femur or humerus. As long as the lesions are confined to the shaft, they appear to be of limited consequence. However, if the esions develop in sites adjacent to the joint surfaces of the hip or shoulder (juxta-articular lesions), the consequences can be very serious. Areas of dead bone and marrow (infarct) in these sites can result in buckling of the cartilage around the area infarcted or loss of the subchondral plate over the area of infarct. In the latter case, fragments of bone grind into the cartilage during movements of the point. Continued fragmentation or crumbling of the bone can grind away large portions of the joint. Eventually, the weight bearing joint fractures and collapses. Disruption of the bearing surface or collapse of the dead bone can lead to secondary conditions of incapacitating arthritis. Other types of bone lesions are also associated with dysbaric osteonecrosis...
Somers, Lee H., PhD., The Depth and Gas Delemma, Conference Proceedings ofr the 1991 NAUI International Conference on Underwater Education

[/B], Edited by H. Viders and F. Wells and published by the National Association of Underwater Instructors[/Quote]

I get very concerned about two aspects of modern, "technical" diving. The first is the lack of recompression facilities immediately available in case of an emergency. Nemrod, maybe you can give impressions about the availability, but I don't know of boats carrying technical divers having this capability. Because of this, I will not do technical dives, period. These are "overhead environment" dives, which need special training and where the surface is not immediately available as an option. Cave diving, deep decompression diving, and wreck diving meet these criterion. The second is the emphasis on diving skills, personal protective equipment (redundant systems), etc., which are not always going to work.

More later...it's supper time.

John

[duckbill]

broxtonchuck said:

Who needs a vest? After reading all this stuff to worry about, Ill junk my vest, and when I need bouyancy, Ill fart in my suit!

That sounds more like something the "Voice of Gomez" would say.

[nemrod]

A little CO2 never hurt anybody,

Amazing story and pictures SeaRat.

I love vintage and minimalist diving Duckbill but in the situation you seem to mention I think I would find me a vintage power inflator. Like Luis said, those things barely worked, were not dependable, corroded to hades and are more hazard than help.

Since I contend a BC is just that and not a life jacket, for shore diving in serious conditions I would carry a surf float, inner tube, paddle board, kayak, or similar redundant bouyancy.

Nem, reporting in from SDV

[Voice of Gomez]

Duckbill, even the inventive pioneer GOMEZ would never resort to the rude technique suggested by that broxton chuck. Back in 57 we were told to dump our gear and go up. Usually floated real good with our el thicko wet suits! All that hi tech stuff we never did back then, especially when filming the SEA HUNT SHOWS. Hated those suits, if there was trouble some grip would drag you back on the boat, and dry you out for the next scene!

[luis]

searat said:

You've said a lot here, and I agree with most of it. I would qualify your statement to say that "all dives below 25 feet are potentially decompression dives." Technically, with a vintage 72 cubic foot tank, it is virtually impossible to get into a decompression problem at less than two atmospheres absolute (33 feet, or ten meters, in depth).

John

Well John, you actually missed the point. What I said is not only what I meant, it is in part a quote from some of the latest researchers.

“All dives are decompression dives…some require stops and some don’t.” This may sound as a technicality, but it is more important that just a technicality.

In any dive just below the surface and of any duration you are uploading nitrogen (in the case of using air or Nitrox) and will require the out-gassing. Therefore there is decompression even if no “Deco stop obligation” is required. Again this may be a technicality, but it seems to me as an important point in understanding the latest in DCS research.

The point as related to the subject of a BC was that a proper ascend rate and possible safety stop is always required.

But, since we are off subject anyway I will expand a bit…from the little that I have been reading, interviews I have listened to, and the conferences that I have attended recently. These statements are also to the best of my understanding.

Can you get in trouble on a dive to 20ft for only 20 minutes…Well it depends…what did you do before that dive and what are you doing after? Is that the only dive of the day, are you flying or going in to the mountains after the dive? The absorbed gas still needs to be expelled via decompression. Surface decompression is still part of the process. It is all about the management of absorbed gases.

I have a very high respect for all the research done by Haldane and many other scientists in the past, but until very recently their research was similar to a micro biologist studying bacteria without the aid of a microscope. Most of the studies involved statistical analysis involving the report of major signs and symptom. It seems that they may have been missing a lot of very minor symptoms, etc.

Of course, the previous research and the physics about dissolved gases (described by Henry’s law, etc.), all still applies. But, with the use of newer instrumentation such as Doppler ultra sound instruments we are learning that the mechanics are more complicated and quite different than it was understood.

That being said, IMHO, we are still in the infancy of understanding much of the physics and physiology involved with DCS. Also the newer instrumentation is great, but we have a long ways before we have portable Tricorders (like in the Starship Enterprise).

Some of the new statistical research is also involving data collection from individual dive computers. In the future I think this will all add a much better understanding of DCS. Even after a deeper understanding of the science, there will always be the need for statistical analysis.

Many newer dive computers will support DAN voluntary data collection program.


In this aspect of vintage diving the new research has not made previous knowledge obsolete, but it is expanding it in big steps. As an example, the standard Navy decompression tables are not obsolete, but there are newer tables that involve deeper deco stop which seem to be safer and requires a lot less deco obligation times. Again the statement of safer always involved some statistics and probability, but the newer tables are backed by a higher understanding of bubble formation and gas elimination mechanics.


In reference to the need of decompression chamber for technical dives…well the numbers don’t seem to support the need. I have some reservation to some of the procedures, but for the most part they seem to be successful. The advance courses on Deco procedures, trimix, etc. seem to be yielding very good results. The biggest danger I think is from some of the tech wannabees types.

The use of oxygen therapy as a treatment for minor DCS is also proven to be extremely effective. It is also very effective during transportation of more severe incidents. I am not surprised about the effectiveness of O2. Also new procedures for in the water treatment (with O2) are being looked at.


IMHO, we as vintage equipment divers (and vintage divers) have a lot of collective knowledge that we should share, but at the same time the learning should never stop…there is a lot of new knowledge we can all benefit from.

[SeaRat]

Luis,

I agree mostly with what you say, but there are some dive profiles in which gas loading is really minimal. Here is one of my dive profiles from April of 2006.


I have consulted my dive tables, and I have a number (2 NAUI versions, one NOAA, a Dacor table from 1971-vintage), and all of them start their loading at 40 feet, or 12 meters. My Suunto Reduced Gradient Bubble Model[/B] publication that came with my Suunto Cobra computer shows a table that shows the "Personal Mode" settings. For the "9 metres," using their PO mode (Ideal Conditions, which is the default), it shows "--" indicating an infinite number of minutes available. In "P1" mode, it is 163 minutes available, and in "P2" mode, it is 130 minutes. This publication also discusses the "decompression floor," and "decompression ceiling."

...During any ascent involving decompression-stops, Suunto dive computers calculate the point at which the leading tissue compartment crosses the ambient pressure line (that is the point at which the tissue's pressue is reater than the ambient pressure), and off-gassing starts. This is referred to as the decompression floor. Above this floor depth and below the ceiling depth is the "decompression zone". The range of the decompression zone, is dependent on the dive profile.

Out-gassing in the leading fast tissues will be slow at or near the floor because the outward gradient is small. Slower tissues may be still on-gassing and given enough time, the decompression obligation may increase, in which case the ceiling may move down and the floor may move up. However, dwelling for a minute or two at the floor before moving up to the decompression ceiling will also help limit microbubble growth, by keeping them compressed. The decompression floor represents the point at which the Suunto RPMB is seeking to maximize bubble compression, while the decompression "ceiling" is maximising off-gassing.

The added advantage of having a decompression ceiling and floor is that it recognizes that in rough water, it might be difficult to maintain the exact depth to optimise decompression. However, by maintaining a depth below the ceiling but above the floor, the diver is still decompressing, although slower than optimal, and provides an additional buffer to minimise the risk that waves will nnot lift the diver above the ceiling. Also, the continuous decompression curve used by Suunto provides a much smoother and a more natural decompression profile than the traditional "step" decompression...

That last paragraph helps me understand how Nemrod's dive (see above) in choppy water can be conducted safely. But my contention is that for some dive profiles, probably like mine above, the "decompression ceiling" and the waters surface are the same. In other words, no decompression is necessary. I realize that this may be just semantics, as Luis may say that in fact by swimming the last 22 or so minutes of this dive at less than ten feet, I was decompressing. But I spent maybe 8 minutes below 20 feet. So uptake of nitrogen would be pretty minimal, and I was not purposely decompressing. I was swimming the river bottom. Note that I was working in heavy current at the time and wearing twin 50s. Usually in this area, when I dive a single 72 under these medium to heavy current conditions, I'll go through it in 30 to 45 minutes. Even using the "personal Mode P2, at 9 meters I have about 130 minutes (and I have several of those factors, age, wet suit, cold, heavy current) to justify the P2 mode.

What does this have to do with wearing a vest or not. Not much, but a poorly-designed vest can add drag in heavy current, which can affect work load (mine adds a little, but not like the vintage vests). This would be one factor to add into the personal profile when using a dive computer.

John

PS--Here's the log of the dive from above. It explains the dive profile.

I dove the Healthways Scuba regulator today. Here's an exerpt from my dive log:

This was a dive to test the Healthways Scuba regulator, and in particular the exhaust system. I bought it minus one part of the exhaust system, a duckbill backup valve. The regulator's exhaust is supposed to be sealed by an exhaust diaphragm which pushes in from air pressure inside the regulator. This unique design has a lot of positive attributes, but apparently it does not work without the duckbill valve. That valve. being absent, allowed water to come into the regulator's exhaust hose, which made the exhalation extremely difficult at times. This was especially a problem when I was on my left side. On my right side, the regulator performed well.

The dive also tested whether the single stage unit worked as well as some others from the same era. I had used it as a kid, and had not remembered any detrimental effects from its breathing characteristics. I used my twin 50s, and it was hooked to a 3000 psi source. This made it more difficult to breath on initially, but it was not bad. In the middle pressures, it breathed quite nicely, and below 1000 psi it was pretty good. I'd say it was not quite where a Mistral would be, but I did not suffer from air deprevation, or from unduely hard inhalation.

This was a pretty intensive dive, as the river was high and the current swift. It was the first time I've had current which actually moved rocks on the bottom in places. It also surged a bit. I started out in a pool where the current hit the rocks, and provided a eddy I could get into for awhile while I evaluated the regulator. After about 15 minutes, I actually almost called off the rest of the dive with this regulator, due to the exhaust problems. But then I determined that it was controllable by my position, and so continued under the intense current toward deeper water (I hand surfaced and thrown a large fishing weight out onto the sand). The currents were confusing, and I wanted to be on the other side of the river as I continued downstream. Vis was 4-5 feet, and I could see the rocks coming, and so simply pushed off them when I came by them. At one point in the deep area, I held onto a metal rod to watch the bottom and determine how the regulator was working. When I held my position on my right side, it performed well, and got better during the dive as the tank pressure went lower. All this time, for the first 25 to 30 minutes, I had my Sherwood octopus in my right hand just in case there was a failure of the regulator. That didn't happen, and I never needed the Sherwood regulator.

I went through the high rocks area, and then the current moderated, and I got to where some fishermen wore working the river. I stayed upcurrent from one, spent more time watching the bottom, and then exited. I gave the fisherman a fishing lure that I had found on the bottom.

This regulator definately needs the auxilary duckbill valve. Without it, there are problems with the exhaust system. But the regulator also breaths pretty well underwater. I used a Hope-Page mouthpiece and Nemrod hoses on it. I also had removed the intake non-return valve in the mouthpiece, as this always helps performance in any regulator. Here's the dive profile from this dive:

I noticed that there were some "slow down" alarms on my Suunto Cobra computer. These occurred during the high current parts of the dive, where I had to go up and over very large rocks (ten to fifteen feet high) in the current. I just looked at the manual, and these alarms occur when my ascent rate exceeds 10 meters per minute, or 33 feet per minute. In a river, going over rocks, that's pretty easy to exceed.

I was diving my twin 50s, which are a 3000 psi system. I looked over the seat, and determined that it is much the same design as the Sportsways HP seat (and I had another one in case this seat couldn't take the pressure during my dry run yesterday). I decided it would take the 3000 psi, and so used it there. This produced no problems other than a bit harder inhalation resistance. Because I had relatively long hoses, I could position the regulator well down on my back, and that worked well too. I will have to figure out a duckbill valve for the regulator though. My LDS has two of these regulators on display, and maybe I can talk the owner out of one from one of her Healthways Scuba regulators.

John

PS--This evening, I found that one of the mushroom valve holders for my Nemrod Snark III regulator will fit sideways inside the Nemord exhalation hose, just above the exhaust outlet. I'm going to try that to "fix" the exhaust program.

[luis]

I am sorry that my explanations are not very clear; I will try this one last time.

Decompression is not the same as decompression stop. Decompression also occurs during the ascend and during the surface interval.

You can do a very shallow and short dive were the nitrogen loading is minimal, but however minimal, you don’t ignore it. What if you are going to do a deeper dive next or you want to go flying. After that first dive while you are doing your surface interval you are still decompressing.

In the past divers used to think of decompression as only the decompression stops and that is dangerous. Even if you can go directly to the surface with no stops, you are still decompressing (decompression doesn’t stop when you arrive at the surface). The rate of ascend has been often ignore and during surface interval divers would go skin/ free diving or even flying and forget that they are still decompressing.

Historically, the reason for the safety stop was to compensate for the fast rate of ascend of most (if not all) divers. Recently it has been determined that a safety stop is a good idea even with a lower rate of ascends.

There is also a reason why dive computers have ascend rate alarms. It is not just to annoy other divers in the water when you exceed the maximum ascend rate.

The original reason I brought this up was because an uncontrolled rate of ascend with any BC (with a CO2 cartridge or not) is not a good thing. Even if you don’t have a deco stop obligation and you avoid any barotraumas to your lungs, you may still be violating the maximum recommended rate of ascend and/or any safety stop (either can get you into trouble). Granted, DCS can be treated…drowning can not. This is just something to keep in mind.


I hope that I explained it better.


Sometimes after a tough day at work I feel like I need to decompress, but that works on a totally different principle. ;D

[SeaRat]

Luis,

We now have no disagreement.

Buoyant ascents were used in earlier years, and now should not be unless life is endangered from other problems (as you stated, like drowning).

Things like asceptic bone necrosis can be prevented by use of prudent measures, and your thoughts of always decompressing are good for prevention of these asymtomatic conditions.

One thing that the Suunto publication above noted for going to a "personal mode" was things done after the dive. You have mentioned flying after diving (I used to be in the USAF, so that was a concern then, and I have chased divers out of the water when they hit 12 hours before flying). Some of those things that people don't recognize are things like sunbathing, or hot showers, which heat the skin. Heated blood cannot carry nitrogen in solution as easily (ask any Chinook salmon trying to go up the South Umpqua river in the summer, at 85 degrees--they die; there hasn't been a Chinook run up that river in the summer since the 1950s).

Also, I know what you mean about decompressing after work--that's what I was doing last evening when I wrote the info above.

John

[Broxton Carol]

I decompress after work with a belt of "OLD HAWK 103" You can drink it before flying too! Those salmon wouldnt have any problems if someone added a barrel of OLD HAWK to the river. they would just glide up there!

[duckbill]

I thought everyone knew you don't pop the CO2 at depth. Goes to show what gets lost with disuse- knowledge. Apparently it's a good thing this was brought up.

By the way, maybe a distinction should be made between "decompression" and "outgassing". I think the term "decompression" has been overused and abused to the point that people think it is one and the same as "outgassing". Though related, they are not the same.

I take "decompression" to be when something goes from a higher state of compression to a lower state. Even when your body and the gasses within it are at a steady pressure (as during a standard SIT), you continue to outgas until equilibrium is reached. You aren't really still "decompressing". I know it's nitpicking, but a clarification of the terms may have resolved the misunderstanding.

[luis]

Duckbill, at this point I am going to suggest that you need to start reading some of the latest research. I am getting above my comfort level of having enough knowledge to clearly explain something, but I will try to point. Again I recommend seeking some of the newer research papers.

Your definition of decompression follows the simple pressure mechanics.
With the old theory of just dissolve gasses mechanics your definition kind of applied, but not really.

There is a reason they are calling the out gassing period during the surface interval decompression. This is the definition used by the researches in the field…I think I will follow their definition.

I believe the reason for the definition is as follows:
Even at the surface after a dive you are not at a state of uniform pressure (actually as long as you are alive you are never at a state of uniform pressure). During decompression, the gas pressure in your system is higher than the partial pressure in the atmosphere…otherwise it would not come out of solution if it was in equilibrium. Add to that bubble mechanics and micro bubble transfer mechanics. Keep in mind that bubbles are basically little spherical pressure vessels.

I recall in the old days we used to say that we wanted to avoid any bubble formation, when in reality it has being found that micro bubbles occurs during all diving decompression process.

I am just starting to read about some of these subjects, therefore if their something I am not explaining correctly please let me know.