dive to 300 ft

[Slamfire]

Quickly looking at it I would change the GF to a 30/90 or a 30/95.

I actually meant to change the GF to 30/85 not 35/80. I guess I could chuck that to dislexia... In case any I can see your change as rational.

I would not use a "travel gas".

So you'd be hypoxic until you reached 2 ATAs (a minute or less) thereby doing one less gas switch. Is this correct?

I would lengthen the 70' stop and shorten the 40.

I can see the O2 window logic on lenghtening the 70' but I'm not following you on the shortening of the 40'. Is it to get quicker to the higher ppO2 of the 20' gas switch?

Combine the 20' and 10' stops into one 20' stop with back gas breaks.

I get the combining, but rather than going to hypoxic back gas breaks, wouldn't you rather go to 35/25 breaks?

 

[Slamfire]

Gas load. D18s 10/70...

Did you mean double LP108s?

 

[johnkendall]

Did you mean double LP108s?

Nope. Double 18L cylinders. I'm afraid I don't know a US equivalent.

Thanks
John

 

[JeffG]

So you'd be hypoxic until you reached 2 ATAs (a minute or less) thereby doing one less gas switch. Is this correct?

He is correct and you are not. You might want to check your numbers.

 

[nadwidny]

I actually meant to change the GF to 30/85 not 35/80. I guess I could chuck that to dislexia... In case any I can see your change as rational. So you'd be hypoxic until you reached 2 ATAs (a minute or less)

You don't need to get to 2 ATAs for a 10/70 to not be hypoxic. More like 1.5 which takes about 10 seconds or less.

Now then if it was really snotty out and we thought that we needed to have a reg in our mouth for the surface part we would splash in breathing off our 70 bottle or our 120. But this was rarely the case.

I can see the O2 window logic on lenghtening the 70' but I'm not following you on the shortening of the 40'. Is it to get quicker to the higher ppO2 of the 20' gas switch?

No. It's because it was the time added to the 70' stop.

We used to shorten the 30' but we thought that it was better to spend more time there while on back gas getting ready for the switch to O2.

I get the combining, but rather than going to hypoxic back gas breaks, wouldn't you rather go to 35/25 breaks?

Whatever floats your boat. We went to back gas because it had the lowest O2. Since the purpose of a back gas break is to take a break from high O2 it made sense to us to go to the mixture with the lowest PO2.

 

[gsk3]

Nope. Double 18L cylinders. I'm afraid I don't know a US equivalent.

I believe the closest US equivalent is the HP130, but I think 18's hold still more?

The rating system is annoying to convert between because UK/euro tanks are measured by internal volume (which you then multiply by the pressure in bar to get capacity at 1ATA), whereas US tanks are measured by capacity at 1ATA.

 

[Kevrumbo]

I believe the closest US equivalent is the HP130, but I think 18's hold still more?

The rating system is annoying to convert between because UK/euro tanks are measured by internal volume (which you then multiply by the pressure in bar to get capacity at 1ATA), whereas US tanks are measured by capacity at 1ATA.

Worthington LP121's have a single tank rating of 18.9 L/bar, with a service pressure of 166bar+ (or 2400psi+). Depends on whether you want to "cave fill" 'em and squeeze more gas in at a higher pressure. . .

HP130's are single tank rated at 16 L/bar, but at a higher service pressure of 230bar (3442psi). . .

 

[Akimbo]

Tough to provide a definitive answer. Bret Gilliam, a founder of TDI and an early pioneer of technical diving, set a world record to 452'/137M in 1990 on air in a single 100 Ft³ cylinder. It is hard to argue that Gilliam isn’t a properly trained DIR diver. Yes there were safety divers, tons of workup dives and extensive planning. He described in his book, Deep Diving, that a single was chosen to lessen the equipment load — understanding the spiraling impact it has on stress, exertion, and complexity.

There are a lot of important variables beyond 10 minutes at 300'. 86°F, 100' of visibility, a down line, and calm seas is far different than live boating in the North Sea on October 15th. Will the diver actually do anything other than look and breath? Is this something they do several times a week or their first time below 180'? Is the dive in an area where you are lucky to get an air fill free of CO or does it have a large Trimix station?

For me, I wouldn’t make the dive without a chamber on deck and a competent diving supervisor. For others, it is just another stroll in the park.

 

[danvolker]

Tough to provide a definitive answer. Bret Gilliam, a founder of TDI and an early pioneer of technical diving, set a world record to 452'/137M in 1990 on air in a single 100 Ft³ cylinder. It is hard to argue that Gilliam isn’t a properly trained DIR diver.

Yikes!!!!!! Giliam was never any where near a DIR diver in philosophy, gear choices, or anything....not to mention that he and George could not stand each other George would certainly say that Rule number one could have Giliam's photo permanently attached to it...

DIR does not allow for deep on air records diving..this is antithetical to DIR....it is as smart as trying to make a record as the guy who could chug the most bottles of Tequilla, before speeding in a car through a school zone.

I am not saying that Giliam is not/was not a talented tech diver....clearly he has skills...If you have read up on DIR at all, you would know Giliam's deep air behaviors helped create the movement of the "other side", which became DIR

 

[boulderjohn]

DIR does not allow for deep on air records diving..this is antithetical to DIR....it is as smart as trying to make a record as they guy who could chug the most bottles of Tequilla, before speeding in a car through a school zone.

I haven't met either of the two gentlemen, but I have both DIR and TDI training. I noted with some amusement quotations in the 9-year old TDI trimix text statements that looked to me to be not only anti-DIR but specifically aimed at George as well. Interestingly enough, the 7-year old Advanced Trimix book comes much closer to DIR in approach and contains none of the confrontational language.