YD Scuba Diving Forums banner

1 - 5 of 5 Posts

·
Banned
Joined
·
1,217 Posts
Discussion Starter · #1 ·
Imported post

Nicked from somewhere else.  I'll bet a couple of you can get an argument out of this.  No names mentioned of course.

If anyone is interested in a deep dive story...heres a condensed version of
a reasonably deep one

Plan was 320m at an open ocean divesite in Phuket Thailand...charted depth
under the dive boat 414m-484m (keeps the anchor from dragging nicely :)

back gas was 5/76 gave a high END but this kept the HPNS undercontrol
nicely and made the next gas choice easier.

the drop down was smoothish, the dry suit gas was bottom mix (forget what
you may have read...argon...helium bad insulator etc  blah blah blah).
This flows nicley and kept me nice an warm when the the water was 3-4'c.

The descent was stopped at 313m for a couple of reasons,

ascending at 15m per minute dropping to 10m per minute from 250m. The
subsequent gases all contained 30% N2 or less   and the N2 values were
always dropping.  many reasons for this.

the stops went well largely due to the support team and having lots of
spare gas.

Breathing high helium to the surface culminating in a 3 hour session from
9m to 3m on heliox was a very difficult experience. Helium cooled me from
the inside out when on open circuit, body has huge problem heating the
inspired gas , long hoses to the surface did a reasonable job raising gas
temps. vast quantities of warmed water consumed.

The Po2's were low so as to eliminate air breaks with their often
disastrous affects. Air breaks may work in a chamber but not too well
during a trimix dive (depending on size of dive)

Obviously back gas switches were out of the question , I had 8 other
trimixes to choose from, but all contained some N2.

Some unpleasantness occured when a long hose was swapped at the surface. My
tongue was sucked into the partial vacuum, but luckily the hose wall
yielded and i pulled my tongue free (now 6'' longer)

The deco plan was created on propietary software, but apart from the deep
stops placing and times looks similar to a traditional buhlman model with
the helium values changed. Deco ran 6 hours 40 mins...I surfaced exhausted
and suffered pulmonary toxicity for  3-4 days.

I have a deco plan analyser which can check plans created from even the
most comical dive software. When the interface is more user friendly (to
me!) I will send some details...you need to see it !  Any dive plan will
have its weakneses revealed both DCI/ICD related and oxtox and body work
load

Most planners generate deeper stops from the top down...this is just crap.
The free gas "miracle" dive planners need leaving well alone.


I am not claiming this as anything other than the deepest solo dive on
scuba, which happened to be (more importantly) the first without
significant DCI.

I appreciate this is a very brief message, if anyone is interested I can
send a detailed account.

cheers...Mark E

Sorry for nicking Brens job
 

·
Registered
Joined
·
12,240 Posts
Imported post

[b said:
Quote[/b] (DougParker @ Dec. 28 2003,16:01)]Sorry for nicking Bren's job
Doug mate,

Please feel free to submit that which you choose!! I'm only here to contribute to the games!  


A very good precise on a worthwhile debate squire! More of the same please! Not that you need my permission!!
 

·
Snap Happy
Joined
·
2,802 Posts
Imported post

I'm amazed he managed to do this so quickly - Less than 7 hours deco on such a dive is, I think, incredible.  

The burning question has to be tho, did he rig all his deco tanks on the left?
 

·
Banned
Joined
·
1,389 Posts
Imported post

Some more info on the dive from another source..

Hi again, thanks for all the personal replies asking for info, heres a blanket response, I hope you don't mind. Rather than a full account of the deep dive, which I hope to put into a magazine, heres some text on how I planned it.

I mentioned last Feb that I got very busted up on a similar dive and it took me 3 months to start walking OK and another 3 months to get diving again and another 3 months to start thinking about tech diving. Over those 9 months I had plenty of time to reflect on the weaknesses of the last dive. The majority of the problems came from following a plan from crap (expensive) software, this led to too long down deep with too little deco in the 150-40m range, causing ICD Anyways now I can build my own plans and its not really rocket science with all the information freely available and man tested long before most of us were born.

If its new (as I found out to my cost) it has not been tested outside of a PC or Petri dish. (I think) A dive below 300m needs a rapid descent. This causes HPNS and this can be minimised by using a high END. I used an END of 72m. The Po2 was high 1.6+. The reasons for this. The exposure was short, so not problematic (for me). Keeping the helium as low as possible means easier to pick the next deco gas. There will always be a step up in nitrogen on open circuit, unless you have yet another bottle. My N2 "spike" was down deep when critical tensions were not yet high.

The 140m deco gas went up 10% N2 with a raise of 6% o2, this meant that the rest of the ascent gases could keep the same or more helium starting with 60% from 140m. all the subsequent ascent gases kept the same helium content from 140m to 9m, the only changes were to increase o2 and decrease n2.At 9m Heliox was used, it has no n2 to complicate matters and is fast to deco. because the PO2 was low at 6m no air breaks were needed (call them what you want)
Air breaks work OK in a o2/n2 (chamber) environmentbbut are possibly suicidal on a trimix/heliox dive. Trimix "air breaks" or Heliox "air breaks" are just as bad, (depending on many factors) No "p02 breaks" (better term for air breaks) is hard from a pulmonary toxicity point, also breathing heliox on open circuit for multiple hours is horrendous. It might be "easy" to breath but the body struggles to heat it and therefore overall work load can reach unsustainable levels. (He has high leading values) I chose the heliox route, to avoid counter diffusion only and knew that its use was troublesome but less life threatening. To counter the enormous dehydration I had to drink 2-3 litres every hour and this was difficult.

A CCR would be the better alternative on the heliox deco (warm and moist) A dropping set point would be my choice also. The longer times on deco that this would have caused would be worth enduring. The OTU and CNS count on this dive was high and managed by not chasing a 1.6 Po2, If I had then who knows. Pulmonary Toxcity was a problem for 5days + afterwards. But this may have been in fact, lung fatigue from breathing un heated un hydrated gases for long periods (my own view). A sort of HPRS This text is not a recipe for deep dives, but simply how I did it and (possibly) how it turned out so favourably.

You will note that I did not mention ascent rates (critical), where the deep stops were (critical), why my suit gas was bottom mix. Also I didn't mention any mix values or the stop depths/ times themselves. I dived in Phuket Thailand 35 miles offshore. The dive site on the edge of the continental shelf at 450m+ depth. The drop line was weighted and marked every 1m. The tides were right the day of the dive as was the weather. The dive had been aborted previously due to weather (and other less predictable factors). The dive boat and rescue boat were courtesy of ScubaCat.com (where Ive been working). The support divers were great again as they were in february when they held me on the line while I convulsed vomiting for 3 hours due to ICD induced DCI (a painful almost palindrome!)

Medical support is great in Phuket with plenty of state run (good inexpensive) chambers and a selection of the "usual suspect" private chambers. Phuket treats its divers seriously and you need be never more than 1 hour from a chamber (our rescue boat had 900 petrol horsepower bolted out back and made the jump to light speed with ease) The MARES regulators were chosen for there heavyweight construction (heat sink theory). The DFC system is great at manging high gas flows with its smooth operation as opposed to venturi flow support, Finally no environmental seal means regulators as warm as possible.

The water temp was 3-4 c (M1 and stinger) the gas flows were enormous but all resulted in zero free flow or stutter. Drysuit was Otter  Wing from OMS, Reels from Kent Engineering. Ive kept this short, in the magazine story will be slower written and mention the 8' jelly fish (?) encounter near the bottom and the earthquake tremors that day in the area. I hope this answers some questions you may have
regards...Mark Ellyatt
 
1 - 5 of 5 Posts
Top