DIR repetitive diving

[Woz]

So. In t'Egypt I did 22 dives in 6 days. Each dive normally about an hour (even for bi-focals or vari-focals). Each day was normally the deepie first (40m ish) with a couple of 20m dives later on and a 15m night dive- so up to 4 dives a day (in fact we did 5 dives in one day but that was due to some slightly shoddy navigation where we managed to miss the reef the boat was tied to. Ahem.)

Did the whole lot on the computers on nitrox.

So. I have a question. How does the whole ratio deco / DOTF cope with multi-day repetitive diving? Downloading the Suunto shows the slower tissues building up a fair bit of residual nitrogen over the course of the week. If you believe what it says.

[Clare Gledhill]

Sounds like a typical week in Florida

Come out clean - ascending slowly, decoing properly and diving the correct gases. If your surface interval is less than 90 minutes double the shallow stops on next dive, if more carry on as normal.

Keep an eye on CNS and more importantly perhaps for this sort of diving, OTUs. 4 hours in water a day - especially if pushing PPO2s - can easily start to hit the notional limits we and all the technical agencies teach.

If in doubt whack a load of dives in your PC and have a look.

[Howard Payne]

From a personal perspective - even with 2 hour plus sensible surface intervals - I tend to increase the shallow stops by about a third (usually adding 5 min 6-0m to the profile at / from 6m rather than including it as part of the time at 6m) I also tend to use O2 for about 6min 6-0m (3min at 6m then 3min to the surface) on shallower min deco Nitrox second dives of the day to clean me up a bit. We found this strategy worked very well last week at Scapa.

Diving rich Helium mixes makes a hell of a difference - it was really obvious in the way I felt after a 40m dive on 26% Nitrox on the last day (boat had run out of Helium) Did a conservative sensible profile with a good ascent and still felt way more tired afterwards than I had doing similar dives on 25/25 or 21/35 on previous days. Bloody expensive - but I can't argue that it works

HTH mate

[SoggyFox]

that was a question i was going to ask after reading Garfs Scapa report.

[Woz]

Well I dived on 32% all week and set the computer a bit weaker than that plus on the deeper dive took a stage in (it was 42% but ho hum that's what you get from topping off a random 10 of O2 with air). Felt absolutely fine all week even though I was the loon lugging a twinset about. CNS loading increased a teeny bit but not too much and only the bottom OTU blob was flashing on the Suunto.

Here's an interesting aside: in the spirit of experimentation I ran a simulated dive on the Suunto last night 45m 20 mins on air. On the way up I did some deep stops and what the Suunto did was stop increasing the TTS figure- it stayed at 31 mins for the whole of the deepstop bit. That's on an old Vyper. However the Suunto minutes were noticable as I did the shallow stops at 6 rather than 3 and a bit. Mind you, decreasing the shallow stop to 5m like on the PADI RDP made less impact on the Suunto minutes.

So here's a thought for you non-DIR Suunto divers with non-DS computers. Rack up the deco on your Suunto, then calculate the deepstops a la DIR bgased on the TTS figure-3 and eventually sit it out at 6. You'll do about 10 mins more than you would calculating it on a single backgas deco profile. I reckon. Probably. Although, not for the first time, I may be talking utter bollocks. Sort of a Suunto-Deepstops-RatioDeco-OnTheFly method.

[Howard Payne]

Fair comment mate - I just really noticed it because I'm so used to diving Helium in this range. 32% takes a fair bit of the Nitrogen out of the equation?

[Garf]

We had 2 to 3 hour surface intervals so we mostly just did the bog standard ratio deco and then padded out the shallow stops for a bit of extra comfort, or in case GLOC had run his deco-in-the-pot ascents for us again.

[wilbo]

Originally Posted by Garf

We had 2 to 3 hour surface intervals so we mostly just did the bog standard ratio deco and then padded out the shallow stops for a bit of extra comfort, or in case GLOC had run his deco-in-the-pot ascents for us again.

[divingniknaks]

Originally Posted by Garf

GLOC had run his deco-in-the-pot

Keyboard owed !


.

[neilh]

Originally Posted by Clare Gledhill

If your surface interval is less than 90 minutes double the shallow stops on next dive, if more carry on as normal.

Is there a simple definition of a shallow stop?