I read "just under the surface..." as "just barely positive". It's physically impossible for something with compressible gas spaces to be neutral without an active system controlling it (not counting drastic thermoclines or haloclines).Kim:
Roak
Rob Davie's accident. (aka. BigJetDiver)
- Thread starter Kim
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Roak
OP
Even like that though, the fact that he'd ditched 'substantial' weight (as he told Tobin he carried) to only manage 'just barely positive', would seem to suggest a very serious buoyancy issue. I don't know about others but if I ditch all my weight (actually even if I don't!) and fully inflate my wing I float like a cork. I don't know exactly how one sets up one's buoyancy with a rebreather but certainly the idea in OC is to have your basic buoyancy available with no air in your wing, or maybe at the start of the dive - just a little. I don't know but I would have to wonder....when working out buoyancy needs/redundancy etc with a rebreather is the scenario of a flooded unit taken into consideration?roakey:
cool_hardware52
Contributor
Kim:
I don't dive a rebreather, but I've been exposed to quite a few, and have been asked to recommend wings for RB's.
A total loop flood is a worst case senario, but it can happen. This can leave the diver very negative. Some combination of ditchable weight and wing lift needs to be available to overcome the ~8-18 liters of volume of the RB loop.
I am assuming a few thing here, and I may well be wrong, but the facts support a near total loop flood, a full wing, and no weights. All this combined to leave the diver near neutral at the surface. If that was Rob's calculated solution he was spot on.
Tobin
H2Andy
Contributor
it seems to me that Rob, being a very experienced diver, recovered from a
failure to his system, got neutral or nearly so, and reached the surface
something happened at the surface that has nothing to do with bouyancy. that's
my gut-feeling.
perhaps a heart attack. rob was 59.
rob did alright. he got himself to the surface. he would have made it but for
something out of his control. what that is, i dont' know. but again, i believe
it was a heart attack. rob did alright in my book.
failure to his system, got neutral or nearly so, and reached the surface
something happened at the surface that has nothing to do with bouyancy. that's
my gut-feeling.
perhaps a heart attack. rob was 59.
rob did alright. he got himself to the surface. he would have made it but for
something out of his control. what that is, i dont' know. but again, i believe
it was a heart attack. rob did alright in my book.
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His wife had said that some weight had been ditched, didn't she?
was the autopsy cause of death drowning? yes, Andy my unsubstantiated feeling also, there must be something on the autopsy that would or would not rule out an MI, ...wouldn't there?
How hard is it to leave the entire system and surface?
What is the customary lift used with that system?
Thank-you Kim for posting, seems to me he would want this. The vacume did not feel right.
was the autopsy cause of death drowning? yes, Andy my unsubstantiated feeling also, there must be something on the autopsy that would or would not rule out an MI, ...wouldn't there?
How hard is it to leave the entire system and surface?
What is the customary lift used with that system?
Thank-you Kim for posting, seems to me he would want this. The vacume did not feel right.
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A reasonable specualtion, but certainly not conclusive.
It may be different over there, but official cause of death statement for dive fatalities often state drowning even tho no water may be found in the lungs, and/or even if another problem is discovered.catherine96821:
Do we know whether he bailed out to an external tank or to the on-board reg? You would have thought that he would have got out of the unit once he was near the surface, if that is he was by then still in control. Given how massively experienced and careful he (normally) was, some health issue does sound plausible. Though I do find it difficult to reconcile the state of assembly of the mouthpiece area with the Rob I knew.
OP
An external 5ltr tank containing air.peterbj7:
PerroneFord
Contributor
As long as we are speculating here, I'd like to toss something out.
For what it's worth, I have no experience with the Inspiration, and VERY limited experience with some other units. I did get a quick lesson on rescuing a diver on a KISS prior to my first mixed OC/CCR dive.
Configuration:
If the diver required significant weight to dive with the unit, it would stand to reason that he was successful in his descent, thus the weight would have been in place.
It is also concievable that the diver would have chosen a wing with enough positive buoyancy to float the unit and the diver, sans ditched weight.
Open Circuit bailout bottle chosen would need to be enough to allow diver to solve immediate issue at depth, and then make a controlled ascent. Since adequate gas was still in the bailout bottle we can probably assume the volume of gas was sufficient.
Possible Malfunction:
With the mentioned problems of the mouthpiece, it is likely that either the loop was compromised or sufficient flow was not making it to support breathing as depth increased. So it is possible the diver bailed to the bottle, and then the loop flooded. What is curious is that his buddy saw him switch to the bail bottle, saw him ascend, then saw him "swim" or perhaps drift to toward the boat. What was NOT mentioned was that his buddy saw him ditch the weight, which would have been a farily memorable occurance.
Speculation:
For this to have gone as wrong as it did, it seems several factors were involved. One, is why he bailed off the RB. If he was not getting good breaths, it would explain it. If the loop flooded immediately, it would also explain it. It is possible that if the loop flooded immediately, it seemingly possible it could have compromised his lungs to the degree that he couldn't metabolize (enough) oxygen especially as he got shallow.
We could also speculate that the wing selected was not of sufficient lift to get him truly onto the surface with a flooded RB. This miscalculation would have left him unable to inspire, and would have caused drowning. His being neutral just below the surface would indicate the wing was CLOSE to getting him there, but not close enough.
The oxygen cells would have become unimportant once he was on the bailout. So it seems unlikely he would have been hypoxic. He had the wherewithall to shut down the RB and begin an ascent.
As for lessons to take from this (poignant for me as I hope to dive a RB one day) it seems he had a known issue with the breathing portion of the apparatus. (Red Flag) It appears that he did not attempt to test the unit in the shallows with assistance close at hand. (Red Flag 2). It is not known whether this was the first or second dive of the day. If it was the first, Murphy was knocking HARD, but it would also indicate that the problem with the unit was pre-exisiting, and ignored. If it was the second, or subsequent, it would appear the problem developed on dive 1.
It would be interesting to know the state of his lungs on autopsy. Whether they were damaged at all or if cause of death was fixed at drowning. Seems hard to imagine a simple drowning when he was still on OC with air in the tank.
Anyway, that's my thoughts. Thanks for posting the information.
For what it's worth, I have no experience with the Inspiration, and VERY limited experience with some other units. I did get a quick lesson on rescuing a diver on a KISS prior to my first mixed OC/CCR dive.
Configuration:
If the diver required significant weight to dive with the unit, it would stand to reason that he was successful in his descent, thus the weight would have been in place.
It is also concievable that the diver would have chosen a wing with enough positive buoyancy to float the unit and the diver, sans ditched weight.
Open Circuit bailout bottle chosen would need to be enough to allow diver to solve immediate issue at depth, and then make a controlled ascent. Since adequate gas was still in the bailout bottle we can probably assume the volume of gas was sufficient.
Possible Malfunction:
With the mentioned problems of the mouthpiece, it is likely that either the loop was compromised or sufficient flow was not making it to support breathing as depth increased. So it is possible the diver bailed to the bottle, and then the loop flooded. What is curious is that his buddy saw him switch to the bail bottle, saw him ascend, then saw him "swim" or perhaps drift to toward the boat. What was NOT mentioned was that his buddy saw him ditch the weight, which would have been a farily memorable occurance.
Speculation:
For this to have gone as wrong as it did, it seems several factors were involved. One, is why he bailed off the RB. If he was not getting good breaths, it would explain it. If the loop flooded immediately, it would also explain it. It is possible that if the loop flooded immediately, it seemingly possible it could have compromised his lungs to the degree that he couldn't metabolize (enough) oxygen especially as he got shallow.
We could also speculate that the wing selected was not of sufficient lift to get him truly onto the surface with a flooded RB. This miscalculation would have left him unable to inspire, and would have caused drowning. His being neutral just below the surface would indicate the wing was CLOSE to getting him there, but not close enough.
The oxygen cells would have become unimportant once he was on the bailout. So it seems unlikely he would have been hypoxic. He had the wherewithall to shut down the RB and begin an ascent.
As for lessons to take from this (poignant for me as I hope to dive a RB one day) it seems he had a known issue with the breathing portion of the apparatus. (Red Flag) It appears that he did not attempt to test the unit in the shallows with assistance close at hand. (Red Flag 2). It is not known whether this was the first or second dive of the day. If it was the first, Murphy was knocking HARD, but it would also indicate that the problem with the unit was pre-exisiting, and ignored. If it was the second, or subsequent, it would appear the problem developed on dive 1.
It would be interesting to know the state of his lungs on autopsy. Whether they were damaged at all or if cause of death was fixed at drowning. Seems hard to imagine a simple drowning when he was still on OC with air in the tank.
Anyway, that's my thoughts. Thanks for posting the information.
Was the actual cause of death disclosed ? Do we know if he possibly asphyxiated from water that entered through the failed mouthpiece (mentioned in drmike's post above) ... or was it complications that arose after a reported rapid ascent (described by Rob's wife in the original post)
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