Negative entry vs Using a downline

[PfcAJ]

I do this dive with dual 80's and a 30 cu ft bottle of pure O2. The 80's are "jacked". Still, I am not very heavy....there have been occasions when I jumped in and someone had a scooter issue or something, and I had to stay at the surface--and swimming was an easy way to do this...although by this time, you know you have blown the drop, and you resign yourself to adding gas to the wing, and the likelihood of getting back on the boat for a re-drop.. This is an issue that either gets resolved in about 5 seconds, or it is back on the boat we go....

Double 80s and a 30 of o2? A little thin on the reserves, aren't ya...

 

[danvolker]

Double 80s and a 30 of o2? A little thin on the reserves, aren't ya...

Bottom time was always limited to 25 minutes or less. We did too many of these to count....Being slick was more of a big deal than carrying huge reserves....and there was always 3 to 5 of us. None of us ever were in a low on air issue of concern.....though one of our standard safety precautions, was always having our own safety diver that would drop on the torpedo float line at 26 minutes into the dive--see us at 50 to 80 feet, and then make sure everyone was good for gas...We never needed this, but it was nice to have.....we would have one of us taking turns for the safety diver job each week.

 

[Greenjuice]

This is another one of those "minor changes" that turns a mistake into a close brush with death.

A negative entry gives no second chances for anybody who discovers that their air is off.

Yes, I know this isn't supposed to happen, but it does.

I reported in post #14 that I witnessed this just last week. To an experienced UK diver, BSAC trained, hundreds of dives in the UK. We had been doing negative entries 3 - 4 times a day for several days in a row on this liveaboard, and it happened on the 16th or 17th dive of the trip.

One event, of taking your eye off the ball, in 25 x 18 = 450 man-dives conducted on this one boat trip.

Odds are very low but not zero. In risk management scenarios it would considered a 'near miss'. One or two other near miss events occurring at the same time and you have a reportable incident.

In addition to a lost fin and mask slippage on negative entries, I've witnessed a jammed locking mechanism on a reel attached to a torpedo buoy (he wasn't going anywhere!). As mentioned, $hit happens and none of these are serious enough to be reportable.

There is not one single place I could imagine wanting to dive at, where the use of a line for ascents and descents is not defective

We have plenty of days with zero current--and when this happens, the dives are still far superior without the nonsense of the lines.... If you had to do a wreck in 10 foot vis or less... I suppose that is an argument FOR the lines....but not a good one....

The Castor...
[video=youtube_share;PIaXVw61qJI]http://youtu.be/PIaXVw61qJI[/video]
Whether we have 100 foot vis, or if it was after a storm and the vis was only 10 feet, this is ideally a negative entry, drift drop....whether there is current or not !

Once you experienced how easy this style of drift dropping is, you would DEMAND this of any boat you chartered....

At about 4:00 minutes into your Castor video, isn't that your buddies/wife using a line?

How does she manage the negative entries with her camera rig? Does just jump in negative holding it above her head?


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[LiteHedded]

i dont wanna be a party pooper but i'm not sure how you did 25 mins at 240ish with two 80s to get you all the way to 20 feet
even getting super creative with the minimum gas calculations...

 

[PfcAJ]

Interesting.

25mins at 250 uses about 107cuft of gas with a .5 sac rate. What's min gas for a dive to 250 all the way to 20', Dan?

 

[MXGratefulDiver]

Double 80s and a 30 of o2? A little thin on the reserves, aren't ya...

... depends on your contingencies, I suppose. For team diving, that doesn't leave a lot of gas to share.

Last year in the Great Lakes I did a dive to nearly 250 using double 100's and two AL40's for deco (EAN50 and O2), and I thought that was cutting it a bit thin. With a team of three I figured we had adequate gas for one major failure.

... Bob (Grateful Diver)

 

[danvolker]

Interesting.

25mins at 250 uses about 107cuft of gas with a .5 sac rate. What's min gas for a dive to 250 all the way to 20', Dan?

AJ, We are talking about the dives I did with George and Bill in 90's a decade before the GUE concept of min gas.....and it worked better for us, than for other dive teams we would see carrying the extra stage bottles with all the drag this entailed. Even today, Bill and I prefer this form of diving for the deep Palm Beach wrecks. Remember, I don't speak for GUE....I only speak for DIR.

 

[PfcAJ]

... depends on your contingencies, I suppose. For team diving, that doesn't leave a lot of gas to share.

Last year in the Great Lakes I did a dive to nearly 250 using double 100's and two AL40's for deco (EAN50 and O2), and I thought that was cutting it a bit thin. With a team of three I figured we had adequate gas for one major failure.

... Bob (Grateful Diver)

Just a quick glance and that seems legit to me, depending on the bottom time. But for a "DIR" guy to dive to 240 with double 80s and a 30 of oxygen seems way out of line. Especially if you want to do a 25min BT and all the associated decompression.

---------- Post added April 2nd, 2014 at 05:51 PM ----------

AJ, We are talking about the dives I did with George and Bill in 90's a decade before the GUE concept of min gas.....and it worked better for us, than for other dive teams we would see carrying the extra stage bottles with all the drag this entailed. Even today, Bill and I prefer this form of diving for the deep Palm Beach wrecks. Remember, I don't speak for GUE....I only speak for DIR.

There's nothing DIR about a cowboy dive without enough gas to even do the deco, let alone some kind of delay or issue.

 

[MXGratefulDiver]

There's nothing DIR about a cowboy dive without enough gas to even do the deco, let alone some kind of delay or issue.

To be fair to Dan, I don't think they were DIR back then ... I know some old-timers who did dives like that on air, steel 72's, and no oxygen. But they were diving under the "my gas is my gas" principle.

... Bob (Grateful Diver)

 

[danvolker]

i dont wanna be a party pooper but i'm not sure how you did 25 mins at 240ish with two 80s to get you all the way to 20 feet
even getting super creative with the minimum gas calculations...

A. We did not use the Min Gas concept the GUE's do...
B. We always had plenty for team members to reach 20 feet with --never had any close calls
C. Our descent and ascent rates on trimix are not remotely similar to what GUE does today..this was George Tables..Different Shape deco.
D. When these guys started me on this deep stuff, I was using dual independent steel 72's filled to about 3000....when I switched to manifolded 80's, these were always over 3500psi...sometimes well over Slick was and is a big deal to me on these dives. If I want to follow a Jewfish around, I am not going to lug 100's with stages..I might as well not dive....In the 90's, it was just for good spearfishing--but that also meant I needed to be slick.
You can check with Bill or George, or even Jim Mimms about those dives in the old days with the dual 72's