Re: [PSUBS-MAILIST] Diving Catalina Island

[Trent Mcnelly <trent@ktuu.com>]

The danger in ascending too fast in an ambient sub is the same as  
ascending too fast as a scuba diver.  You need to ascend slowly to  
allow your body to off gas any absorbed nitrogen and avoid DCI  
(decompression illness)  I've been thinking about building an ambient  
sub and have put thought into how to avoid uncontrolled surfacing  
without allowing time for off gassing.  If I spent even 30 minutes at  
100 feet, there would be a required decompression stop and the sub  
driver would have to make sure not to ascend too far and miss a deco  
stop.  As a diver it is pretty easy to control depth, but as Brian  
experienced, even divers have occasional trouble.  In a sub, I would  
expect that depth control could be even more challenging than for a  
diver and extra care needs to be taken not to put your body in a  
position where you could be at serious health risk.  I don't have any  
good answers yet, but do acknowledge that there is a challenge to be  
met and overcome with depth control in ambient subs.

There are also DCI issues to think about with an uncontrolled  
decent.  If all of a sudden your boat gets too negative, you could  
suddenly find yourself in 150 feet of water or more and now you have  
to contend with narcosis as well as deco stops.  I recently had a  
situation where my dive buddy let too much air out of her BC and  
started dropping like a stone.  I swam as hard as I could and caught  
her at 140 feet and she was seriously narcd.  She was having a great  
time and I had to drag her up to 100 feet before she started thinking  
clearly again.

Please let me know if anyone has thought more about this issue and  
has any good suggestions.

Thanks,
Trent McNelly
On Nov 30, 2007, at 7:39 AM, Emile van Essen wrote:

> Brian,
>
> That is a unpleasant expierience.
>
> No danger for fast ascending a abient dry sub.
> -the volume is constant
> -it should have a large vent for the air to get out.
>
> More dangerous is descending too fast, you sinking faster than the  
> regulator
> can give air.........
>
> Regards, Emile
>
> -----Oorspronkelijk bericht-----
> Van: owner-personal_submersibles@psubs.org
> [mailto:owner-personal_submersibles@psubs.org] Namens Brian Cox
> Verzonden: vrijdag 30 november 2007 16:49
> Aan: Personal_Submersibles@Psubs. Org
> Onderwerp: [PSUBS-MAILIST] Diving Catalina Island
>
> Hi All,
>          I had a rather unsettling experience out at Catalina  
> Island this
> weekend.  While diving on the back side of the island, looking for  
> lobster,
> we were towards the end of our dive at about 35'  we decided to  
> drop down a
> bit so I raised my air expel hose from my BC to release some air,  
> but since
> this equipment was still somewhat unfamiliar to me I accidentally  
> hit the
> air inject button instead !  Which sent me to the surface.  I had  
> injected
> enough air so that there was no way I could expel the air in time  
> to make me
> go back down.  I think was rising at about the speed of my bubbles  
> and I
> breathed out the whole time going up.   It really made me think, in  
> that
> situation I really had no way of preventing my accent.  If for   
> some reason
> a valve like that decided to stick on I don't see too many options for
> correcting that situation.  I would think an abient sub would have  
> the same
> issue.  Any thoughts on a solution to a problem like that?
>
> Brian Cox
>
>
>
>
>
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