BOV when jumping off a boat

sheck

sheck

New Member
I just finished my MOD 1 course and I'm about to flight 'solo' ie., without my instructor, this weekend.

All the hours for MOD 1 were shore dives and so I'm wondering what people do when jumping off a boat and assuming they use a BOV.

when OC, I had no problem jumping off a boat sideways, back roll, step and all geared (one or two S080 stages clipped on, etc).
However, how risky is it to jump off the boat while you are on the loop? What if you accidentally come off it and floods? what if you land in a position that for a few seconds makes WOB unbearable?

I'm aware that none of this may be a real issue in real life and that I may just be concerned due to lack of experience...

My thought was to jump off on OC and once stable at the surface, switch to CC and pump the loop with O2 until I go down and to 20 feet.
My BOV would feed from a s080 bail out cylinder so gas wasted wouldn't be an issue. In any case, it'd just be seconds on OC.

is it necessary?

Thanks a lot

Sheck
 
I make sure my loop has lots of O2 in it. I breathe in so the counter lungs are small. I make sure the bcd has air in it and I hold the BOV or DSV to my face. Giant stride off the boat making sure to clear the vessel.

My biggest issue at or near the surface is to keep on the green button to make sure the loop is life sustaining.

The hot drop crowd will have other methods.

Have a great time! Ccr diving renewed my passion for diving and opened up all sorts of new possibilities.


Peter
 
I'm afraid that pumping the loop with O2 until it's full near the surface will end up causing high PO2 after a quick descent, since there is no need to always have a füll loop at depth. You can end up having your loop go way over what youir sensors can read / computer can display just by descending to 60' without adding any gas.

Michael
 
I go on the loop as soon as I can on the boat so I can confirm the cells are moving and the tempstick is warming up.

Jumping in is just the same as OC, no drama there.

As soon as I am in I check the handset. The surface can be a dangerous place as there are many distractions. Check everything is well and you have proper set point.

Then go diving.

Matt.
 
As stated just stay on the loop, have the proper set point, with minimal loop volume and hold onto the BOV (DSV) and mask on entry. Do not complicate your task by going OC on entry then switching keep it simple. As far as finding it difficult to breathe due to a screwed up position this would only last a few seconds until you reposition yourself and if unable to do so bail and call the dive.

Gabe
 
michael_fisch said:
I'm afraid that pumping the loop with O2 until it's full near the surface will end up causing high PO2 after a quick descent, since there is no need to always have a füll loop at depth. You can end up having your loop go way over what youir sensors can read / computer can display just by descending to 60' without adding any gas.

Michael
Click to expand...
I set mine at 0.7 and keep at 0.7 or above. Descending I let the ppO2 rise to 1.5ish which happens around 30-40ft given that I need to add dil to maintain volume just to get down there. Dil flush as needed lower.

You're playing with fire not having a high fO2 loop on the surface.
 
I roll entry all the time but have done some giant strides too. Minimum loop so you don't pop the mouthpiece out when you hit. ADV on or be prepared to hit the dil MAV if you can't get a breath once you're in. Then jump as you would for OC - heel of your hand on the mouthpiece, fingers on your mask. Same same. I flush O2 before I dive and it's saved my life at least once, no worries with high PPO2 on descent coz I'm throwing dil at the loop via the ADV or MAV the whole way down. And michael_fisch, I challenge anyone to start with minimum loop at the surface and get to 20m without holding their breath, adding gas to the loop or getting down so fast by hanging onto the ship's anchor as it drops or being horribly, horribly overweighted.
 
michael_fisch said:
I'm afraid that pumping the loop with O2 until it's full near the surface will end up causing high PO2 after a quick descent, since there is no need to always have a füll loop at depth. You can end up having your loop go way over what youir sensors can read / computer can display just by descending to 60' without adding any gas.

Michael
Click to expand...
It gets worse. I like to spike my cells at the start of the dive at about 6 meters. This tells me they are not current limited at the start of the dive. As I mentioned, a hot drop is a different thing. I would suggest becoming comfortable with the basics before attempting such a thing.
 
The vast majority of my entries are roll backwards off the boat, never had the loop pop out, diving a rEvo I use a Drager mouth piece head strap (also called a gag strap), maybe worth considering if you are worried about the mouth piece coming out.
 
Um, this *should* have been covered by your instructor on your course. At the very least you should have training on loop contents when you enter the water - whether shore or boat. If you still aren't sure, I'd suggest you call your instructor and ask.
 
sunnyboy said:
Um, this *should* have been covered by your instructor on your course. At the very least you should have training on loop contents when you enter the water - whether shore or boat. If you still aren't sure, I'd suggest you call your instructor and ask.
Click to expand...
I think my question wasn't clear.
I do know and was explained about loop content at every step. The problem was that I never jump off a boat during the course and I wondered if it was better to do it on OC to avoid flooding the loop accidentally.
Thanks
Sheck
 
Thanks everyone.
Everything went well. Little has on the loop with O2 and enjoyed a long shallow dive.
Loved it
Sheck
 
1: Always jump in on loop just hold BOV?DSV and mask when you jump

2 THE ONLY gas to be on on the boat or on the surface is 100%02. Its hard to read displays on the surface and being on pure 02 is the only safe way.

You will NOT spike on decent unintentionaly. Rather you will hopfulley spike over 1.6 INTENTIONALY to check for current limiting and then you will take in a bug lungfull of dill and decend.

KISS reduce the margins for error

ATB

Mark
 
sheck said:
I think my question wasn't clear.
I do know and was explained about loop content at every step. The problem was that I never jump off a boat during the course and I wondered if it was better to do it on OC to avoid flooding the loop accidentally.
Thanks
Sheck
Click to expand...

Just keep a firm hold on the loop and it won't come out of your mouth. TBH, I'm more worried about snagging my handset cable on something and ripping the cables out. It has happened to too many people and it looks tantalisingly simple to do it!!!
 
jturner said:
Just keep a firm hold on the loop and it won't come out of your mouth. TBH, I'm more worried about snagging my handset cable on something and ripping the cables out. It has happened to too many people and it looks tantalisingly simple to do it!!!
Click to expand...
Thanks! It ended up working the way you and other people here suggested :)
 
jturner said:
J TBH, I'm more worried about snagging my handset cable on something and ripping the cables out. It has happened to too many people and it looks tantalisingly simple to do it!!!
Click to expand...

cut the sleeves off an UA / Nike compression shirt and run your cables through there. its another thing to faff about with when gearing up but on dives where i am going somewhere with sharp edges ill run them down there to make sure i dont get snagged.
 
I've been backrolling as newb successfully thus far, additional mini-prebreathe on low setpoint (0.7), check bailout on/works, air in wing, palm to mask. I tried it with the OC entry first, but now am just holding the DSV to mouth, usually closed because I am buoyant/not overweighted and would rather hold my breath for a second than flood the loop.
 
michael_fisch said:
I'm afraid that pumping the loop with O2 until it's full near the surface will end up causing high PO2 after a quick descent, since there is no need to always have a füll loop at depth. You can end up having your loop go way over what youir sensors can read / computer can display just by descending to 60' without adding any gas.

Michael
Click to expand...

I always leave my loop full of O2 after calibration, and have done many hot drops and bombed down to my MOD, but never got above 1.6. A partial dil flush at depth is all you need to bring PO2 down. As with all aspects CCR diving, there are trade offs; I’d rather jump with a loop full of O2 and spike at depth, than have a lean loop at the surface.

It seems the majority of O2 tox events I hear of happen shallow after lengthy exposures during deco, when the loop fraction of O2 is at it’s highest. I have not heard of any O2 tox events at depth after spiking one’s PO2, when the O2 fraction is lowest. Makes me wonder if the O2 fraction itself has any bearing on tox probability. Does the presence of a higher fraction of inert/dil gas in the loop at depth somehow mitigate O2 toxicity from accidental spiking? The body would be absorbing high amounts of inert gas at the same time as it metabolizes the spiked O2. Or is it just that most CCR divers would never knowingly allow their PO2 to stay above 1.4 for a long time at depth, and that is why most O2 toxing happens shallow during deco?
 
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