Repetitive diving on CCR

[The Doctor]

Originally Posted by DecoWarrior

thats just too keen!!, back in the day maybe, but i think doing doubkle dives like that in the uk maximises exposure and increases risk, i think one long exposure is better than two exposures personally...

dive.

[onthetrain]

On my trip to Norway earlier this year I did a couple of 50 - 70M dives a day for several days in a row with no ill effects. That was of course in cold water too.


That said the profiles were still fairly conservative as many of the wrecks were so huge that you could do say 15 mins at 70M and then decompress slowly coming up the wreck so that the average depth over the course of the dive is only 30 - 40M and not square profiles like most UK wrecks

I would be quite happy to dive these sorts of profiles, especially on CCR

[Mark Chase]

Originally Posted by daveb0000

If you did a deep dive on ccr at what depth on the first dive would you then consider a second dive to much of a risk of DCI with an SI of 2-3 hours in between dives and what do you base it on ?

For instance would you dive to say 50m and then dive again later to 20m or would you dive deeper and still dive later. or would you keep the second dive very shallow say 10m on top of a reef.

What have you guys done ?

post's or pm's

CNS clock is more of a concern than getting bent. Repetitive dives on constant high PP02 can really set that clock ticking

Residual nitrogen loading can be avoided by using a lot of helium. You can end up getting out of the water with less nitrogen in your system than when you got in.

Residual helium is being off gassed very efficiently by air as there is no He in the air we breath so a massive gradient to the Helium for off gassing.

Consideration would be for damage done to tissues on the first dive by aggressive deco or fast ascents. This damage will have no time to sort its self so jumping in again will increase the risk in such cases.

To avoid this do soft deco.

I have done a 90m two and a half hour dive in the morning and a 30iss for 90mins in the afternoon. I have also done a 50-60 in the morning and a 30-40 in the afternoon on several occasions.

Biggest consideration is not pissing of the OC divers too much by doing two very long dives

ATB

Mark

[Janos]

I found a link:

Bounce diving

It explains the physiology well I think, in that it's not just tissue loading you have to worry about, but bubbles too.

Janos

[daveb0000]

Originally Posted by Janos

I found a link:

Bounce diving

It explains the physiology well I think, in that it's not just tissue loading you have to worry about, but bubbles too.

Janos

wow 18min from 6m to the surface but then again if it keeps you clean and not bent then its got to be good, i aways have a couple of mins at 3m before i get out on the deeper stuff, looks like that could do with a rethink

[Janos]

Originally Posted by daveb0000

wow 18min from 6m to the surface but then again if it keeps you clean and not bent then its got to be good, i aways have a couple of mins at 3m before i get out on the deeper stuff, looks like that could do with a rethink

Yes but they are effectively doing Saturation dives. I wouldn't take it all as gospel, but I think the risk of compressing a bubble and shunting it is non-trivial. The papers in the reversal profile workshop refer to similar stuff.

Janos

[daveb0000]

Originally Posted by Mark Chase

CNS clock is more of a concern than getting bent. Repetitive dives on constant high PP02 can really set that clock ticking


Residual nitrogen loading can be avoided by using a lot of helium. You can end up getting out of the water with less nitrogen in your system than when you got in.

Residual helium is being off gassed very efficiently by air as there is no He in the air we breath so a massive gradient to the Helium for off gassing.

Consideration would be for damage done to tissues on the first dive by aggressive deco or fast ascents. This damage will have no time to sort its self so jumping in again will increase the risk in such cases.

To avoid this do soft deco.

I have done a 90m two and a half hour dive in the morning and a 30iss for 90mins in the afternoon. I have also done a 50-60 in the morning and a 30-40 in the afternoon on several occasions.

Biggest consideration is not pissing of the OC divers too much by doing two very long dives

ATB

Mark

We have run a fair few plans and looked at the CNS side of it and the % drops a fair bit after a 2 hour SI. also Mark i would agree with the point of if you had any problems on the first dive such as a fast part on the acsent then you potentially could have problems on a second then it would be wise to stay on the boat and not to push your luck.

when you say "soft deco" do you mean pad it out ?

As for pissing off the oc guys they can enjoy the lovely sunshine that will be on offer

Regards

Dave..

[Mark Chase]

Originally Posted by daveb0000

We have run a fair few plans and looked at the CNS side of it and the % drops a fair bit after a 2 hour SI. also Mark i would agree with the point of if you had any problems on the first dive such as a fast part on the acsent then you potentially could have problems on a second then it would be wise to stay on the boat and not to push your luck.

when you say "soft deco" do you mean pad it out ?

As for pissing off the oc guys they can enjoy the lovely sunshine that will be on offer

Regards

Dave..

Soft deco for me is a 20/80GF profile. Agresive deco being something like 10/120GF

On a one dive day Id probably run 10/95. On a big dive (by my standards) or on on multi day I revert to 20/80 I always spend at least 6mins getting from 6m to the surface. Id probably spend a bit more on a multi deep dive gig.


CNS figures for an exposure of avg 1.3 are prety high. Three hours in the water and your at 100%

The recomended max exposure to a PP02 of 1.3 in a 24 hour period is 210mins. Fine if your doing 90min dives but if your doing 120min + then your pushing accepted boundries.

[DecoWarrior]

Originally Posted by The Doctor

But Clares not got the pleasure of a ccr were you can cane a good hour plus on the bottom i just do one long dive.

but this post did specifically refer to ccr diving though

[DannyB]

Originally Posted by Clare Gledhill

Regularly do two deep dives a day (50 - 60 metres) Last year we dived a site out of plymouth where tides were irrelevant and we did a 90 minute surface interval but during the sailing ship project we were forced to wait for second slack with the corresponding LONG surface interval.

I prefer to do my deepest longest dive last - and deco out from it accordingly.

Good luck to you, what dil and set points were you running? Be interested to see the planned deco schedules for this, I wouldn't run it.

Danny