some pics of my bob head

kevin stone

Hi Mike
Are you using the DIVA with the Hammerhead secondary?
Cool tool
thanks
Kevin

Drmike

I have brought the cables into the head (and potted them off) so I can connect them in the future -but havent connected them up (yet) Just a case of having other priorities - ill likely get around to fitting it after next weeks jolly

Im looking forward to see how the hammerhead performs - Ill give it a fair bash

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Cave diving is a sport
Wreck diving is a sport
Diving in general is a sport

'Rebreather diving' is not a sport
its the delusional obsession with a highly dangerous and often inappropriate piece of equipment

PaulTG2

Hello,

So I'm rather curious... what kind of DSV do you use for a Butt BOB? It seems like a P-Port style would be most comfortable.... although that still seems like a difficult proposition....

What exactly is the WOB like on a Butt BOB? I expect the inhale is a lot harder than the exhale........


=-p

Drmike

DSV is an old one from a MK15 I had laying around that Ive adapted with a p-port fitting. Only temp as I am in the process of putting together a twin dsv.

WOB is superb. Better than my MK15.5 at least as good as my Boris.

The scrubber position doesnt effect breathing - only the CL position does and on the butt bob the CLs are at back mounted at the shoulder so WOB is really good.

Swimming and dragging 4 stages at 80m wob was un noticiable - next week (if we find what we are looking for) I may get the chance to test her at around 135m (again swimming) - but this time no stages at all!!!! yipppeee!!!


[just a small back up 0.5L O2 tank and small 3L tank for wing]

__________________
Cave diving is a sport
Wreck diving is a sport
Diving in general is a sport

'Rebreather diving' is not a sport
its the delusional obsession with a highly dangerous and often inappropriate piece of equipment

DrJM

Who want to swim nowadays isn't it the best way to create CO2

Anyway nice pict Mike, have fun next week, I hope the battery of the hammerhead will last long enough

Jerome

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Deep Cave Exploration

AM

Mike

I would hope that you really are joking when you say no stages any more. There is still the consideration that in a cave profile, going up and down uses a lot of diluent.

Perhaps I have misread you and you do intend to take say 20l drive tank but in my view, it is not possible to dispense with open circuit bailout tanks altogether even with dual CCR. Keeping SCR option at least gives you a chance if you have to do cold bail onto second scrubber below 100m/150m. What if you have to flush the bags or just need much more diluent on a spiky profile?

There is little empirical evidence yet regarding bailing out onto a cold scrubber beyond a certain depth.

You should speak to Rick Stanton (if you haven't already at Oztek) regarding his homebuild, which he has just survived a dive to 177m in the Pearse Resurgence on Dave Apperley's yearly or so Niagara trip.

If you DO intend to take two rebreathers and as little OC as you state, into a cave (even a down and up cave), then in my view, that is downright dangerous. This isn't meant to offend and I might be wrong and you ARE planning big drive tanks.

Regards

AnneMarie

Marc T

l

Did you mean Rick had to bail at that depth? I yes could you give us a link please?
AFAIK its the first time he had to bail out, Im ( we ) are greatly interested with this experience!

Drmike

yes, I have noticed that I have done a couple of reasonably deep cave dives but dil isnt a stage - dil is whats needed, a stage (by definition) can be staged

Next week is a deep wreck salvage trip - not cave. For OW I plan to carry a small back up O2 (loss of O2 is critical with pure twin ccr)
the other tank will be sufficent to provide wing inflation, OC at max depth for a few mins (as sanity check) and semiclosed for a few mins when first going to a cold scrubber at max depth) Likely a 5L will do (max depth 135m)

Bare in mind bob is for deep dives - if I can carry the OC bail gas I cant justify using a bob!!!

I have (unsurprising ) given this some thought. Semiclosed to me (at the moment at least) I believe becomes less and less an attractive/practical option as you get deeper. For eg to do Sra Kew semiclosed I would still need to stage or carry 6 or more tanks in the cave (of various FO2s)in order to get anywhere near a good enough ppo2 to deco out at a reasonable speed. Nowhere rents out small tanks so Id be back to putting/ carrying AL80s in the cave again! On the other hand just a small tank of O2 will get me out on the same schedule with just a drop of dil.

So to me at the moment I do not consider semiclosed a practical solution on a very deep (sub 175m say) cave dive - just need too many tanks and defeats the object (streamline, clean, easier to set up dive, faster to prep cave etc etc)

Why would I need to run semiclosed anyway? 2 scrubbers, four independant ppo2 monitoring devices 2 independant O2 and dil supplies.???

Yes for shallower dives its a viable alternative - but not so on deeper dives (in this case)
Basically I dont plan for full semioclosed bailout for a deep dive - may as well have OC bailout (deep dives)



I know. but I wouldnt go straight to a cold scrubber Id run it semiclosed for a while first to warm it up.

Did that, also talked to JohnV, Paul (and Ringo - only joking ) I dont just wake up one day and decide to do this stuff you know - some thought and research goes into it


I take whatever I need. Next week is OW straight down bit of work (long bottom times) then straight up. I only need a bit of inflation gas and dil - one tank is enough. If I was doing Sra Kew next week Id need at least a 5L just for inflation, probably a 10L offboard dil just for a few mins OC sanity a few mins semiclosed scrubber warm up plus back up O2 tank. It depends on the dive - but the point is 'those arent stages' Those are whats needed. I wont be taking anything as 'bailout'.

Basically my dive plan assumes main CCR to max depth, then bail to OC sanity breaths, bail to bob, semiclosed to warm up, then loss of main O2 and use back up O2 to turn dive and deco.


Pure twin CCR is a mindset change. Min OC gas is needed if you take that mindset change that you will always have a working ppo2 display and a working scrubber - you therefore only need a bit of O2 and a bit of dil to run semiclosed while you warm up the cold scrubber.

There is an interesting alternative;
if you swap from bob to main during the dive to keep them both active you have fast indiaction of one of them failing (so you turn the dive) you have both loops breathable duriung the dive, you have both loops active so no need to run semclosed. This is one alterntive and is something I will experiment with next week

__________________
Cave diving is a sport
Wreck diving is a sport
Diving in general is a sport

'Rebreather diving' is not a sport
its the delusional obsession with a highly dangerous and often inappropriate piece of equipment

AM

No sorry you've got that completely wrong, there was no bailout. The sidemount rebreather survived the dive, I think I made a typo in my original post which has caused confusion!!

Regards

AnneMarie

Drmike

Lets just say Ill have my hands full

__________________
Cave diving is a sport
Wreck diving is a sport
Diving in general is a sport

'Rebreather diving' is not a sport
its the delusional obsession with a highly dangerous and often inappropriate piece of equipment