Scuba Diving Trip

  • Thread starter Eric Marshall Schoonmaker
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Eric Marshall Schoonmaker

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I've been looking all around the internet for ways to arrange a scuba diving trip out to the Britannic and have found nothing on it either here or any where in regards to the ritannic or simon mills. Does anyone out there know how one would go about planning a trip to scuba dive inside the Brittannic? Please get back to me.
 
May 8, 2001
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Hello Eric. The thought has crossed my mind (recently in fact) to be able to see and touch Britannic, but if I am not mistaken, she is near maximum, if not above, to scuba dive to her. (Meaning a novice like me has no business down there!) Now, as far as dive and go inside and disturb her in any way, I can promise you that is a big "NO". Simon Mills bought her to protect her, and is against disturbing her. Plus I am sure the liability insurance would be exuberant to allow people to dive around her.

I have been informed that Simon Mills does not have a web site at this time, but there is a reputable Britannic web site owned by Michail Michailis and Mark Chirnside (I believe) at [snip] that may be able to answer more in depth questions, although they do stop by here often.

Is your interest to dive only on the Britannic? Have you considered a dive to Bikini Atol? A dive to Uss Saratoga, a 900+ ft. long and 50,000 ton displacement ship would give a good feel for the emense size.

Good luck to you.
Colleen
 
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Jan 5, 2001
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Hi!

As Colleen says, Britannic is deep, 118.5 metres. I also have doubts whether Simon Mills would allow such a dive -- even when the previous expeditions took place, I understand that he helped with the dive plans and tried to ensure the minimum disturbance to the wreck (even from breathing apparatus!).

Michail's website has some more details, as Colleen says, with contributions by Remco Hillen and myself.

Best regards,

Mark.
 

Inger Sheil

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Dec 3, 2000
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I have seen articles on the occasional tech dive to the Britannic appear in dive magazines - obviously she's beyond the limit for rec diving recognised by most dive organisations (40 m), so she's only viable as a tech dive. The articles emphasised how difficult it was to mount these expeditions - organising the necessary permits, etc. Greek authorities also keep a close eye on the site - as soon as one expedition arrived those responsible for policing the site lobbed up and demanded proof of their permission to dive. Its location in busy shipping channels also complicates matters, and even with the required markers designating divers in the water there have been a few hair-raising moments with larger vessels.

All that aside, I'd love to get a place on one of these expeditions. Just need to come up with the cash and the experience to get a place!

Here are a few articles on the subject - hope you've got a tech certification before you even consider trying for a place.


fifthd.co m/divestore/britanni c/brittanic.html

andi.gr/
 
May 8, 2001
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I have been unable to locate information on current allowable dive times to Britannic. In 1976 they could only dive 15 minutes, and decompression was 2-3 hours. Wondering how diving has evolved, what mixture they use now VS then, and what is capable now.
THANKS~!
Colleen
 
May 8, 2001
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In case anyone is interested. I received a reply back from a very kind man named Bob, who is a professional diver, and was on the Britannic expedition. This is what he had to say, in part, in regard to diving now on Her....
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"...Certainly equipment changes have made a difference, but the biggest change is in the commitment to team diving.  The team members were able to do dives in the 20-45 minutes of bottom time, plus decompression.  Look for "Inside the Britannic" on the discovery channel.  A 1 hour documentary on our teams accomplishments, and history of the wreck.........."
 

Inger Sheil

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Cheers for that, Colleen! I hadn't responded to your post because I was hoping to do some research before I answered - I'm still not certified as a technical diver, and didn't want to give you an innacurate answer. Sounds like you got a good answer, though! Did he mention if the actual gas mixes had changed much since the earlier expeditions as well as the equipment? And are the team diving practices he refers to part of the DIR philosophy of diving?
 
May 8, 2001
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Hi Inger. I asked, but he did not specifically respond to the mixtures vs 1976. I understand they use something called "NITROX" in diving, but in watching the Cousteau video, they also mentioned something like Nitrogen mixture (I later heard was his own experimental mixture), so I have no comparison, other than he was a true pioneer. I will keep watching though, and see if I can uncover any other articles.
 

Inger Sheil

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G'day Colleen -

Nitrox has certainly had a huge impact on the diving industry in its recent history - I nearly did a course in it in Palau in 1997 (got too lazy once I got there and decided I didn't need to go longer or deeper than I was on air), and will sign myself up for one once I've gone through another couple of certification I want.

Here's a page with a timeline for the development of Nitrox...while it's been around for a while, it hasn't really made an impact on the recreational dive scene until fairly recently.

 

Inger Sheil

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I should have added - did he actually mention Nitrox? I was under the impression that this was used for depths up to about 130 feet, but I could be wrong on this. A bit of googling seems to indicate that it has been used, or experimented with, at deeper depths.

Here's a study on the mixed gasses that are used in deeper dives:

 

Jeremy Lee

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Jun 12, 2003
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INERT GASES DIVING MIXTURES
Different uptake and elimination speeds suggest optimal means for reducing decompression time using helium and nitrogen mixtures. Following deep dives beyond 300 fsw breathing helium, switching to nitrogen is without risk, while helium elimination is accelerated because the helium tissue-blood gradient is increased when breathing an air mixture. By gradually increasing the oxygen content after substituting nitrogen for helium, the nitrogen uptake can also be kept low. Workable combinations of gas switching depend upon the exposure and the tissue compartment controlling the ascent.

In deep saturation diving, normoxic breathing mixtures of gases are often advantageously employed to address oxygen concerns. A normoxic breathing mixture, helium or nitrogen, reduces the oxygen percentage so that the partial pressure of oxygen at the working depth is the same as at sea level, the obvious concerns, again, hypoxia and toxicity.

Critical tensions can be employed in helium saturation diving in much the same fashion as nitrogen diving. A critical tension, recall, is the maximum permissible value of inert gas tension (M-value) for a hypothetical tissue compartment with specified half-life. An approach to helium exchange in tissue compartments employs the usual nitrogen set with half-lives reduced by 2.7, that is, the helium half-lives are extracted from the nitrogen half-lives following division by 2.7, and the same critical tension is assumed for both gas compartments. Buhlmann extensively tested schedules based on just such an approach. Tissue tensions scale as the relative proportion of inert gas in any mixture. More so than in air diving, computational methods for mixed gas diving and decompression are often proprietary information in the commercial sector.

Helium (normal 80/20 mixture) nonstop time limits are shorter than nitrogen, as reported by Duffner, and follow a t sup 1/2 law similar to nitrogen, that is, depth times the square root of the nonstop time limit is approximately constant. Using standard techniques of extracting critical tensions from the nonstop time limits, fast compartment critical tensions can be assigned for applications, as detailed by Workman. Modern bubble models, such as the varying permeability model, have also been used strategically in helium diving.

Today, the three helium and nitrogen mixtures (nitrox, heliox, trimix) are commonly employed for deep and saturation diving, with a noted tendency towards usage of enriched oxygen mixtures in shallow (recreational) diving. The use of enriched oxygen mixtures by recreational divers is the subject of controversy, aptly a concern over diver safety. Breathing mixture purity, accurate assessment of component gas ratios, oxygen toxicity, and appropriate decompression procedures are valid concerns for the mixed gas diver. Care, in the use of breathing mixtures, is to be underscored. Too little, or too much, oxygen can be disastrous. The fourth hydrogen mixture (hydrox) is much less commonplace.

NITROX
Mixtures of oxygen and nitrogen with less oxygen than 21% (pure air) offer protection from oxygen toxicity in moderately deep and saturation diving. Moderately deep here means no more than a few hundred feet. Hypoxia is a concern with mixtures containing as much as 15% oxygen in this range. Saturation diving on oxygen-scarce nitrox mixtures is a carefully planned exposure. The narcotic effects of nitrogen in the 100 fsw to 200 fsw depth range mitigate against nitrox for deep diving.

Diving on enriched nitrox mixtures must also be carefully planned exposures, but for opposite reason, that is, oxygen toxicity. Mixtures of 30% more of oxygen significantly reduce partial pressures of nitrogen to the point of down loading tissue tensions compared to air diving. If standard air decompression procedures are employed, enriched nitrox affords a diving safety margin. However, because of elevated oxygen partial pressures, a maximum permissible depth (floor) needs be assigned to any enriched oxygen mixture. Taking 1.6 atm (52.8 fsw) as the oxygen partial pressure limit, the floor for any mixture is easily computed. Enriched nitrox with 32% oxygen is floored at a depth of 130 fsw for diving, also called the oxygen limit point. Higher enrichments raise that floor proportionately.

Decompression requirements on enriched nitrox are less stringent than air, simply because the nitrogen content is reduced below 79%. Many equivalent means to schedule enriched nitrox diving exist, based on the standard Haldane critical tension approach. Air critical tensions can be employed with exponential buildup and elimination equations tracking the (reduced) nitrogen tissue gas exchange, or equivalent air depths (always less than the actual depths on enriched nitrox) can be used with air tables. The latter procedure ultimately relates inspired nitrogen pressure on a nitrox mixture to that of air at shallower depth (equivalent air depth). For instance, a 74/26 nitrox mixture at a depth of 140 fsw has an equivalent air depth of 130 fsw for table entry. Closed breathing circuit divers have employed the equivalent air depth approach for many years.

HELIOX
The narcotic effects of nitrogen in the several hundred feet range prompted researchers to find a less reactive breathing gas for deeper diving. Tests, correlating narcotic effects and lipid solubility, affirm helium as the least narcotic of breathing gases, some 4 times less narcotic than nitrogen according to Bennett. Deep saturation and extended habitat diving, conducted at depths of 1000 ft or more on helium/oxygen mixtures by the US Navy, ultimately ushered in the era of heliox diving. For very deep and saturation diving above 700 fsw or so, heliox remains a popular, though increasingly expensive, breathing mixture.

Helium uptake and elimination can also be tracked with the standard Haldane exponential expressions employed for nitrogen, but with a notable exception. Corresponding helium half-lives are some 2.7 times faster than nitrogen for the same hypothetical tissue compartment. Thus, at saturation, a 180 minute helium compartment behaves like a 480 minute nitrogen compartment. All the computational machinery in place for nitrogen diving can be ported over to helium nicely, with the 2.7 scaling of half-lives expedient in fitting most helium data.

When diving on heliox, particularly for deep and long exposures, it is advantageous to switch to nitrox on ascent to optimize decompression time. The higher the helium saturation in the slow tissue compartments, the later the change to a nitrogen breathing environment. Progressive increases of nitrogen partial pressure enhance helium washout, but also minimize nitrogen absorption in those same compartments. Similarly, progressive increases in oxygen partial pressures aid washout of all inert gases, while also addressing concerns of hypoxia.

An amusing problem in helium breathing environments is the high-pitched voice change, often requiring electronic voice encoding to facilitate diver communication. Helium is also very penetrating, often damaging vacuum tubes, gauges, and electronic components not usually affected by nitrogen. Though helium remains a choice for deep diving, some nitrogen facilitates decompression, ameliorates the voice problem, and helps to keep the diver warm.

TRIMIX
Diving much below 1400 fsw on heliox is not only impractical, but also marginally hazardous. High pressure nervous syndrome (HPNS) is a major problem on descent in very deep diving, and is quite complex. The addition of nitrogen to helium breathing mixtures (trimix), is beneficial in ameliorating HPNS. Trimix is a useful breathing mixture at depths ranging from 500 fsw to 2000 fsw, with nitrogen percentages usually below 10% in operational diving, because of narcotic effect.

Decompression concerns on trimix can be addressed, again, with traditional techniques. Uptake and elimination of both helium and nitrogen can be limited by critical tensions. Using a basic set of nitrogen half-lives and critical tensions, and a corresponding set of helium half-lives approximately 3 times faster for the same nitrogen compartment, total inert gas uptake and elimination can be assumed to be the sum of fractional nitrogen and helium in the trimix breathing medium, using the usual exponential expressions for each inert gas component. Such approaches to trimix decompression were tested by Workman and Buhlmann years ago, and many others after them.

HYDROX
Since hydrogen is the lightest of gases, it is reasonably expected to offer the lowest breathing resistance in a smooth flow system, promoting rapid transfer of oxygen and carbon dioxide within the lungs at depth. Considering solubility and diffusivity, nitrogen uptake and elimination rates in blood and tissue should be more rapid than nitrogen, and even helium. In actuality, the performance of hydrogen falls between nitrogen and helium as an inert breathing gas for diving.

Despite any potential advantages of hydrogen/oxygen breathing mixtures, users have been discouraged from experimenting with hydrox because of the explosive and flammable nature of most mixtures. Work in the early 1950s by the Bureau of Mines, however, established that oxygen percentages below the 3%-4% level provide a safety margin against explosive and flammability risks. A 97/3 mixture of hydrogen and oxygen could be utilized at depths as shallow as 200 fsw, where oxygen partial pressure equals sea-level partial pressure. Experiments with mice also indicate that the narcotic potency of hydrogen is less than nitrogen, but greater than helium. Unlike helium, hydrogen is also relatively plentiful, and inexpensive.

With thanks to Abyss Web Library for the above information.
 

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