Diving too carefully?

[lizardland]

Wow VPM-0
I don't know anyone who could do that, most of my buddies feel a bit niggly at VPM-2. Personally I have ditched VPM entirely after the NEDU study came out and seeing Kevin's heat map comparisons of intermediate tissue loadings.

I ended up in the pot after a VPM profile with no safety. A few caveats, it was the original unmodified version of VPM, there had been a lot of pre-dive exertion and I'd had a minor suit flood so was cold.

I found VPM with no safety worked well up to about 60m, after that I had niggles. Not the wiped out malaise type feelings I got on GFLo 10% feelings, more minor aches and pains. That said, most things work well up to 60m. Never used VPM since it had the B and BE mods, kind of lost interest in it.

 

[rjack]

Most of my buddies are diving OC and so I end up doing a bunch of time at 21m and 18m which Buhlmann doesn't want and gives me no credit for. (There's an OC gas switch to EAN50 there and they use RD). It really messes with my ability to follow any actual modeled GF profile on my shearwater.

However, if I were in a bailout ascent, I would be doing those longer stops associated with those switches. So paradoxically my bailout profile is probably going to have slightly more time deeper than my 'ideal' CCR profile which would be more like 40/75. I don't see any reason to use a more aggressive GF low since my 21m OC stop is already fairly short (few mins). And I see even less reason to switch to a bailout GF high of 90 or 100 because the difference between GF 75 and GF 90 is overwhelmingly just extra time at 3 and 6m. If I'm running out of bailout sure, I will truncate the 3m stop. But its not that hard to bring 300 or 500L of O2 or a bigger bottle of EAN50 to extend a 3m stop by 15-20mins and drop the GF high. This would be for open water deco with modest bottom times to ~65m and ~30 to 80mins of deco. In a cave, it makes even less sense to me to not just hang out longer shallow and drop the GF highs from an aggressive 90-100 to a conservative 70 to 80. The exception for me would be a massive suit flood. Then an aggressive GF high (100+) and surface O2 deco starts making sense since your so vasoconstricted staying in the water at 3m is counterproductive.

 

[emmbee]

Is this the annual deepstops / GF thread

I dived 50/80 last year (except in Truk I sometimes switched to 75 in the shallows because of the amount of diving). From 40/80 the year before, and 30/80 the year before that. No problem.
The plan for this year is 60/80.
I'm sticking with 80 because I don't think there's much argument that a lower high GF, meaning lower overpressure when I surface, is more conservative, and I'm happy with 80.

Bailing out, if needed, I'd increase it to shift towards longer lower depth stops that I have the gas for. I would stick with whatever low GF I have because I already used the extra conservatism there ascending with the computer on the wrong setting. That's the thinking anyway. Any problem?

75/85 is defo my end game for now

Just wondering, how do you figure what the end game is?

Cheers,

Matthieu

 

[rjack]

I dived 50/80 last year (except in Truk I sometimes switched to 75 in the shallows because of the amount of diving). From 40/80 the year before, and 30/80 the year before that. No problem.
The plan for this year is 60/80.
I'm sticking with 80 because I don't think there's much argument that a lower high GF, meaning lower overpressure when I surface, is more conservative, and I'm happy with 80.

Bailing out, if needed, I'd increase it to shift towards longer lower depth stops that I have the gas for. I would stick with whatever low GF I have because I already used the extra conservatism there ascending with the computer on the wrong setting. That's the thinking anyway. Any problem?

Randy had some threads here about DAN bubble testing in the Grand Caymen's (2yrs ago?) which found sporadic high bubble loads at high GF 85 and no incidences of high bubble loads at GF 70. GF low of 30 for both IIRC. That's data which BSAC didn't have when their more aggressive tables were developed decades ago. Ditto the NEDU deep stops study showing that for a given amount of deco time, VPM and other bubble models trying to keep bubbles small by shifting deco time deeper into the profile is counterproductive.

 

[atedeschi]

Here are some graphs I put together when I was playing with profiles. I noticed some interesting things see what you think.

 

[emmbee]

Randy had some threads here about DAN bubble testing in the Grand Caymen's (2yrs ago?) which found sporadic high bubble loads at high GF 85 and no incidences of high bubble loads at GF 70. GF low of 30 for both IIRC. That's data which BSAC didn't have when their more aggressive tables were developed decades ago. Ditto the NEDU deep stops study showing that for a given amount of deco time, VPM and other bubble models trying to keep bubbles small by shifting deco time deeper into the profile is counterproductive.

Hi,

Thanks. Yeah, I'm aware of that one. Haven't read it, tho. Not available from DAN last I checked. Not to your average "person who paid for it", anyway. I'd love to, tho.

Regardless. Higher high GF <-> higher overpressure on the surface <-> higher bubble load. No surprise (yes, I _am_ aware that the equivalence is not strict, for the obvious reason that _detected_ bubbles are in the blood stream, but bubbles, generally speaking, are not). The DAN study confirms. That's great. So I'm sticking with 80: it hasn't caused me any trouble. So far. But if I wanted to be more conservative, I'd lower it allright. Which is what I did in Truk.

At the moment, I'm more interested in spending less counterproductive (your word ) time at depth. So 30, 40, 50, .. 60. The question is, where do you stop?

Cheers,

Matthieu

 

[rjack]

Simon discussed the GF low on Scubaboard and that other CCR board at length. And Kevin made some heat maps of loadings which we posted in both places (very long threads). The opinions generally coalesced around: 1) GF 30 is too deep yet; 2) "deep stops" have some history of 'working'.

So moving 30 low up to 40 to 60 low is reasonable. Up to 70/70 or something like that is beyond what current science and experience would support.

I have no idea what the BSAC tables look like, could someone post them? (I'm guessing they are like my old US Navy tables which are perhaps 90/110 in Buhlmann terms)

 

[Mark Chase]

Is this the annual deepstops / GF thread

I dived 50/80 last year (except in Truk I sometimes switched to 75 in the shallows because of the amount of diving). From 40/80 the year before, and 30/80 the year before that. No problem.
The plan for this year is 60/80.
I'm sticking with 80 because I don't think there's much argument that a lower high GF, meaning lower overpressure when I surface, is more conservative, and I'm happy with 80.

Bailing out, if needed, I'd increase it to shift towards longer lower depth stops that I have the gas for. I would stick with whatever low GF I have because I already used the extra conservatism there ascending with the computer on the wrong setting. That's the thinking anyway. Any problem?



Just wondering, how do you figure what the end game is?

Cheers,

Matthieu

Personal choice but i have been running 90-95GF for a few years now without issue but my deep stops have been 20-30GF

I ran 90-95 folowing the deco advice (now debunked) of get the deep stops right and the shalow stops dont matter

So I have reduced my deep stops gradualy from 20-30 up to 75GF and this in turn has reduced my overall decompresion time so I can afford to be reducing my agressive shalow deco without penaliseing myself on run times.

So reduce 95 to 85 for softer deco


Why stop at 75? why not run 85/85?


In truth I have no answer for that its just a number I picked which indicates I still carry arround the baggage of beleiveing we need a few deep stops to manage the helium?

My deco practices have changed so much in the last 15-20 years I would not be so daft as to sugest that this is the final final alteration.

All I can say is so far so good and the best bit of 75/85 is in my bailout gas planning as i never got bent running 20/95 either


Just to add I have altred my minimum gas OH S#IT bailout plan from 70/125GF to 100/100GF

ATB

Mark

 

[Mark Chase]

Simon discussed the GF low on Scubaboard and that other CCR board at length. And Kevin made some heat maps of loadings which we posted in both places (very long threads). The opinions generally coalesced around: 1) GF 30 is too deep yet; 2) "deep stops" have some history of 'working'.

So moving 30 low up to 40 to 60 low is reasonable. Up to 70/70 or something like that is beyond what current science and experience would support.

I have no idea what the BSAC tables look like, could someone post them? (I'm guessing they are like my old US Navy tables which are perhaps 90/110 in Buhlmann terms)

Sorry but surley more deco dives have been done on 100/100 Bhulman than any other system? More actual scientific test data exists for Bhulman than any other system

Any one who understands GFs will understand going 75 rather than 100 meens your softening the deco but is it not the case we have discovered theres a line between reducing deco stress and just simply on gassing?

With a purley practical mind looking back I dont know why we felt ding 10-20GF deco deep was a must do and then we happily fixed all that on gassing deep with 80-90GF in the shallows???

If 80-90GF is OK shalow then why not deep?

In my case I would harp back to the 90s and 00s when i was told by the gurus that Bhulman over compensated for the helium so the shallow deco was too soft.

Who remembers inputing low He values (IE I am diveing 14/65 and I tell the VR3 14/40) into their VR3s to reduce the He comitment? I know I did.

Then there was the skin bends thing where we were told the deep stops were required for off gassing helium in the soft tissue

Finaly there was VPM RGBM GUEs Ratio Deco and VPMB which were hailed as the new answer to deco and every one was doing deep deep stops and very agressive shallow stops and getting out looooonnnggg before the numpties on GFs

Soon we were all trying to get GFs to look like VPMs. 10/125GF was not uncommon

NONE of thease systems had scientific testing to back them up

We were the ginny pigs

ATB

Mark

 

[GLOC]

We are the ginny pigs

ATB

Mark

FTFY Mark.

Unless you can isolate all of the other variables which come into play (physiology, water temp, true ascent rates (not assumed) etc) and have accurate and reliable data capture of those suffering from DCI, then we are going to continue to be guinea pigs. From data I have collected and from other sources, I reckon the incidence of DCI compared to that reported to BSAC is in the order of 4-8 times as high, so there are still a significant number of people getting bent, not reporting it, or not even going to a chamber.

My bend in Malta (due to PFO) wasn't reported to BSAC and I never went to a chamber as the symptoms (visual disturbances, nothing else) cleared up within 30mins or so of the onset.

The point made by Richard above, what is the hurry to get out?

Regards

 

[Mark Chase]

FTFY Mark.

Unless you can isolate all of the other variables which come into play (physiology, water temp, true ascent rates (not assumed) etc) and have accurate and reliable data capture of those suffering from DCI, then we are going to continue to be guinea pigs. From data I have collected and from other sources, I reckon the incidence of DCI compared to that reported to BSAC is in the order of 4-8 times as high, so there are still a significant number of people getting bent, not reporting it, or not even going to a chamber.

My bend in Malta (due to PFO) wasn't reported to BSAC and I never went to a chamber as the symptoms (visual disturbances, nothing else) cleared up within 30mins or so of the onset.

The point made by Richard above, what is the hurry to get out?

Regards

Not a fair question.

The fact the latest trend in deco is quicker out of the water than my previous 20/80 type deco is happy coincidance. I stuck with 20-80 and 30/90 when other have been getting out much much quicker on RD and VPMB. I can paste links to posts where i put up deco graphs and divers asked "why so much deco"

So I think that gives me the right and some cred when I say it has noting to do with minimum time in water and every thing to do with my prefered in water time of the next 15-20 years or so un injured

HOWEVER

With so many boat skippers thease days being strict about 120min max run times, doing less deco & staying healthy is very fortuitious

I just got back from a dive trip to Malta with Jack Ingle. He asked me to let him know what bailout tanks i wanted before we went out there. I obviously asked what our max run time allowance was.

90 mins he said????? For 60-70m dives????

When id finished laughing and realised he was serious I considered cancling the trip but as it turned out we got away with 2 hours and had to pay extra for 3

With the 2 hour limit I was glad I could still get a decent bottom time with my new deco.

ATB

Mark

 

[Ben Field]

Is this the annual deepstops / GF thread

No, but it has gone woefully off-topic

My OP was less about extreme dives but more the mundane recreational stuff being done after reading too much online and using GF's and VPM fancy deco computers on no or minimal stop dives and doing hugely excessive (from a point of view of necessity) decompression.

I can think of several instances of divers getting cold or hurting themselves rushing to dekit and get to the heads because they've done or waited with a dubby who deco'd their arse off for no reason- divers should know what the bare safe minimum is... my query was do the computer only divers know that minimum and how much they are overshooting?

For the non BSAC divers, the Dive Conduct Slate as mentioned...

 

[Ben Field]

I just got back from a dive trip to Malta with Jack Ingle. He asked me to let him know what bailout tanks i wanted before we went out there. I obviously asked what our max run time allowance was.

90 mins he said????? For 60-70m dives????

When id finished laughing and realised he was serious I considered cancling the trip but as it turned out we got away with 2 hours and had to pay extra for 3

That doesn't sound like another Jack-pay-double-for-the-same-Ingle trip at all... ;-)

FFS- 90min limit, I would have cancelled out of principle!

 

[Engelen D]

I did the 100m bounce dive as part of the OC Trimix course (10 mins bottom time with about 8 mins descent since the bottom was sloping) with deco on a slate, planned with VPM-0. I felt like I had been run over by a bus afterwards. Everything ached. I fell asleep in the restaurant at dinner. I fell asleep in the pub after dinner. I slept for about 12 hours straight. I was still whacked in the morning.

Afterwards I found I had to move to VPM-2 and then VPM-3 to have reliable "no niggles" and after moving to CCR have moved to ZHL C with GFs and would never go back.

Wich GF settings do you use ? ( sorry for asking , just very interested)


Sent by my rEvo scrubber using a shearwater Nerd

 

[Mark Chase]

That doesn't sound like another Jack-pay-double-for-the-same-Ingle trip at all... ;-)

FFS- 90min limit, I would have cancelled out of principle!

I very nearly did mate and I doubt ill be booking again but I got the trip as a cancilation at half price so never say never if theres another cancilation

Jack blamed the boat skipper but I was thinking if he was taking out recreational divers it would be two X 1 hours with an hours surface interval so still three hours on the dive site, so I wasn't falling for this excuse.

ATB

Mark

 

[Mike Ferguson]

so what happens if some want to pay extra for a three hour dive and others don't? do you get fined if you're a 2 hour diver and stay in the water longer? sounds like utter nonsense.

 

[Ben Field]

so what happens if some want to pay extra for a three hour dive and others don't? do you get fined if you're a 2 hour diver and stay in the water longer? sounds like utter nonsense.

You just swim home

 

[Mark Chase]

so what happens if some want to pay extra for a three hour dive and others don't? do you get fined if you're a 2 hour diver and stay in the water longer? sounds like utter nonsense.

We dropped on the Polineasian (65m) and it was stunning so Richard Ayrton and i punched in 2hours 45mins and got a massive telling off and told wed be fined.

Rich and i dropped on the Southwould next day (65 again) and said "so charge us we are here to dive".

I think we were fined 50 euro

I actualy like Jack hes a bit stressey and overexcitable but he worked hard on the trip. Got to say when 12 blokes are doing sod all but diving I dont like being told its 90mins or 2 hours for the dive.

We were told 90mins max for the Stubben (50-55m) Schnell Boat (Bout 60 I think) and 2 hours for the Polly 65m and as I say we told them 3 for the Southwold but it was just the Bow so we did 2.5 and it was enough

If i do the Poly again it will defo be another 3 hour dive dispite the fine. Great wreck.

ATB

Mark

 

[lizardland]

What happens if you tell him to get fcuked with his "fines"? Doesnt sound the trip for me. Running a mix trip and fining you for blowing a 90 min run?

 

[WFO]

What the fook's the point of that unless you like deliberately alienating your customers?

A few times in Scotland I've felt like fining people for diving longer than about 8 minutes... but that's generally when the hail is coming in sideways and you're sat on a RIB.