Doc Wong Getting Bent in Monterey!

[Chuck Tribolet]

As an example, when Harry says he did 47 minutes at 75 ft, are we talking about a square profile or is he describing an average depth? I suspect it was an average depth.

I'm quite familiar with the area where Doc was diving. It would be a very square
profile. I just checked some recent dives there, and my max was 78, 80, 84 on
them. There's very little relief there. I'm guessing 75 was an average, but it ranged
from 70-80. (I'd let Doc answer this, but he's off diving Pt. Lobos.)

Typical GUE style ascent from an 80 ft recreational dive only really requires about 6 minutes.

I don't think so. The DIR guys I know do a basic ascent rate of 10' per minute, plus some
stops, so Harry's 12 minutes would be about right. Interestingly, my DIR Fundies book
doesn't seem to mention ascent rates.

 

[mweitz]

AG and JT taught 1 minute to 75% of the max ATA, 1 minute to 50% then 1 minute stops every 10' from there. For the second dive you would double the stops IIRC. Most of the GUE trained folks I dived with would do 1 minute per every 10' for the first dive and 2 min per 10' for the second dive.

For the tables that AG and JT taught, 80' would be 35 minutes on 32%.

I don't know what GUE / Beto currently teaches for this.

Mark

 

[pilot fish]

I was not referring to the dives that just preceeded his hit but the accumulation of 170dives, most of which were deco dives, as a possible cause, along with the cold temps and exertion. It is possible he had tissue load from those dives that were not fully eliminated from his system? it is very possible to do a shallow 40 ft dive for 45 minutes and get an undeserved hit from what was accumulated on previous dives in the last month.

Yes, but the dives he did before his presumed DCS incident were a non-deco profile dives and very far from his more challenging dives. Yes, his risk of DCS is probably greater in general, but only when he engages in more advanced dives. These particular dives were not in that category, and due to the extremely controlled ascents one starts employing after getting proper tech training, I'd argue that his risk of DCS on such dives is lower than for an average rec diver, all other things being equal.
(Although it does seem that his second dive may have been a "deco" dive depending on his profile according to a PADI table. His ascent profile was still very conservative, he seems to have done MUCH more deco than say a software such as Decoplanner wants one to do for such a profile.)

Maybe coldness was a factor, too. Harry, were you cold at all?

 

[RS]

PF:
You get it's 170 dives over the last year, not repetitive, right?

 

[TSandM]

it is very possible to do a shallow 40 ft dive for 45 minutes and get an undeserved hit from what was accumulated on previous dives in the last month.

I'm sorry, but this statement is erroneous. It IS possible to accumulate nitrogen in slow compartments over multiple days of diving, and get into trouble that way, but if you had a compartment or tissue with a five day half life (required to take a month to EMPTY it) it would load so slowly that it would take many, many consecutive days of diving to accumulate significant load there.

Trouble from diving from the previous few days, yes; from a month before, no.

 

[Ben_ca]

Deleted... TBQ's reply is better

 

[paulwlee]

get an undeserved hit from what was accumulated on previous dives in the last month.

I don't think so, 48 hours should be more than enough to clear up any accumulated gas loading. And for his Trimix dives with gas such as 18/45, it would be even more so, since Helium will be eliminated even faster during surface intervals.
Now I guess there is the possibility of latent tissue damage accumulating from silent hits which may tie in to the 170 dives per year...

 

[paulwlee]

For the tables that AG and JT taught, 80' would be 35 minutes on 32%.

This is correct, but for 75ft and using the more exact 68/79 ata air->32% conversion factor instead of the shortcut conversion (that's slightly more conservative) that's taught, 75ft on 32% is equivalent to 60ft on air, which is 50 minutes minimum deco time (a.k.a. NDL) according to their tables.

At any rate, as Mark pointed out, the 10'/min ascent Chuck mentioned starts at about half the maximum depth, not at the bottom. A completely linear ascent would have the effect of lengthening the bottom time and hence the gas loading during the deeper portion of the ascent which wouldn't be desirable.

 

[mweitz]

Apples and oranges. You either have to do the whole thing with the "real" tables or with the GUE tables, you can't mix them.

What letter diver was he after the first dive and what is NDL for that letter diver?

Mark

This is correct, but for 75ft and using the more exact 68/79 ata air->32% conversion factor instead of the shortcut conversion (that's slightly more conservative) that's taught, 75ft on 32% is equivalent to 60ft on air, which is 50 minutes minimum deco time (a.k.a. NDL) according to their tables.

At any rate, as Mark pointed out, the 10'/min ascent Chuck mentioned starts at about half the maximum depth, not at the bottom. A completely linear ascent would have the effect of lengthening the bottom time and hence the gas loading during the deeper portion of the ascent which wouldn't be desirable.

 

[Adobo]

Sadly, I recently took Beto's class but cannot for the life of me recall exactly how he described "proper ascent". I wish the new fundies workbooks were done already...

I think the law of primacy is playing tricks with me as the only ascent profile I can remember is 1 minute stops at 50% of max depth with a pause at 75%. I thought two minute stops were used anytime there was insufficient surface interval between dives.

If it were me, I would have probably rounded that 75 feet to 80. Used 40 minutes as my MDL and then done the ascent described above. But then again, what do I know? Harry dives twice as much as I do and takes twice as many classes. (Probably twice as smart as me too.) Given that Harry's ascent and deco were significantly more conservative than what I described, I suspect my profile would have iffy as well.

Like I said, may have been one of those "any given dive" type of things.