How much bailout would you take?

[ucfdiver]

Curious here...how much bailout would you take if you're diving CCR to apprx 10,000ft back in Manatee Springs when the flow is down during a flood. How do you calculate it? How many scooters would you use?

I think I've seen every ccr diver on here state that they take more gas than needed...I'm curious how they determine that.

Feel free to use Morgan Springs or something else similarly long if you wish.

 

[w ripley]

Wish I could chime in - as this is one of my favorite topics - but just haven't been in Manatee enough to give you an intelligent response. Generally, I base my solo BOs on swimming out, and my buddy DPV BOs on one of the divers being towed out.

For the caves I know better I run the dive on V-Planner first, figuring full penetration on CC. Obviously if you plan your BO on full penetration but have a problem getting there you will necessarily have enough BO to get out. Assuming that the purpose of the penetration is to get to point "B" and then work there, I figure my dive plan on completing my scheduled work time and then having to bail.

When solo I don't plan on DPV exits with my BO, but rather determine where I will plant my stage BOs based on using 2/3 of their contents, based on swiming my normal distance/CF given the anticipated flow. (I have taken the time to measure this in different upstream and downstream flow conditions, as I believe most deeper cave divers have.) The other 1/3 is not for a buddy, when I dive with one, but for me if I'm really spooked and breathing hard.

If I have a buddy and we have multiple DPVs, then our BO will be calculated on leaving the work area after the scheduled time, and our exit & BO will be calculated at the rate of one diver being towed out (again flow dependent). Sure, the odds of all of one of the diver's DPVs dying is remote, but figuring our exits that way EVERY TIME has become second nature + builds in a huge safety margin, especially if only one DPV actually dies. And with both divers carrying 100% of their own BO, there should be some extra air between the two if some additional unforseen event occurs.

Deco is obviously based on V-Planner, and usually involves 100% O2 at the entry/20-ft level, and other gases depending on the length and depth of the penetration. It's always nice when some of the stage BOs can have have a higher O2 percentage as the exit gets shallower, like when coming out of the Well at Madison.

I would think that a 10,000 foot penetration in FL would require some setup work (BO stage planting, for example), as it's hard for me to imagine that you could carry all of your BO with you. Still, you hit the flooding right, as you stated, and lots of cave penetrations look a whole lot different.

So, did you buy that RB or is this just speculation.

 

[bletso]

Having never dove Manatee I couldn't hazard a guess except that;

For that distance OC bailout would probably consist of some dropped bottles along the route on set up dives. The gas needed would have to be planned for the DPV/'s dead and whether you would leave them and come back for them later.

Further I would add enough extra gas for no current, I know it isn't so at Manatee, but extra won't hurt. To that I would probably add another 50% .

Dale

 

[ucfdiver]

So, did you buy that RB or is this just speculation.

Just trying to pick a dive where people have to give calculations. I hear lots of CCR divers say they bring tons of bailout, and they do, because they're SM'ing LP108s, but I have always wondered is that calculated, or just a wild ass guess based off convenience of carrying that much bailout.

I was pushing for things like what SAC rate? What exit speed? Are you rotating scooters to avoid heat buildup, or riding one for 75min on exit? Are you maintaining gas to do all deeper stops from backgas, or do you take a 70ft bottle to ease up some of that rock bottom?

 

[Cave Diver]

I'm unfamiliar with Manatee and don't use DPV's so I didn't bother replying before. My normal buddy and I tend to prefer slower dives where we take our time and look around, going in and coming out.

Off the top of my head planning a dive like this I'd look at depth/distance/sac to get an idea what the swimming bailout gas requirements are. 10k is a pretty good swim, so I'd also look at deco gas requirements if I had to come off the loop. In addition, I'd want to give some thought to scrubber duration.

Under the conditions you set forth, I'd probably plan for one failure, either CCR or DPV. Complete failures of both means I probably had bigger issues going on anyway and likely would never make it that far.

Failure of the DPV means I'm swimming out, or being towed by my buddy. Things I'd look at is how long is that going to take, what's our depth, is there any additional workload? That will give me an idea if the dive is within my comfort level for scrubber duration.

For CCR failure and subsequent OC bailout I'd look at our typical exit speed, distance, and sac and plan to drop bailout and deco gasses based on those figures. I'd probably also throw at least an extra 40 and most likely an extra 80 on (in addition to the one I always carry) past the last drop point as a precaution if I did have multiple failures at max pen. and was delayed getting back to my first cache.

I don't really like making guesses on new dives though. If it's a cave I haven't been in before I'm going to do some progressive penetration dives and familiarize myself with it some before attempting to plan a long dive.

 

[w ripley]

... I have always wondered is that calculated, or just a wild ass guess based off convenience of carrying that much bailout.

I was pushing for things like what SAC rate? What exit speed? Are you rotating scooters to avoid heat buildup, or riding one for 75min on exit? Are you maintaining gas to do all deeper stops from backgas, or do you take a 70ft bottle to ease up some of that rock bottom?

James,

I don't think too many people would do a 10,000-foot push without calculating their BO, vs taking a guess.

SAC rates will vary with each diver so other people's rule-of-thumbs wouldn't do me much good + they are different for each depth and each flow rate.

I would say that when on OC, and hence breathing each bottle brought in, there was a sense of urgency for getting to where I was going (so as to have some gas to work with when I got there) so we always tended to push the DPVs harder on the way in. With a RB that sense of urgency isn't there (as much) so unless we are really working against a hard flow we would run the DPVs in with the prop setting much farther back. On exits I always get into more trouble than it's worth if I try to exit with the flow on a higher prop setting. So, every DPV exit for me is with the prop setting just a little higher than the speed of the flow.

You've been using a DPV for some time now, and the same guidelines you are following on your current dives will apply to the longer pushes, RB or OC.

I would say that if I were doing your proposed dive, I would tend to set up my staged BOs once, and then do several dives to the 10,000-foot mark while just leaving the BOs where they are (I wouldn't bring them in and out for each dive). That's one of the beauties of diving a RB vs. diving OC: You don't use the staged bottles unless you need them.

Personally, I prefer dropping larger BO bottles and sidemounting Al 40s. As you know, my RB has two steel 45 Dil bottles on the canister, so I have a large amount of gas always with me. It's just that I can swim easier and clear restrictions better with the two smaller SM bottles than carrying two larger ones.

Hope all of this is somewhat helpful but, after all, it's just how one person dives. I'm sure you will have your own configuration when you go to your RB.

 

[ucfdiver]

I don't think too many people would do a 10,000-foot push without calculating their BO, vs taking a guess.

I would agree with that. I suppose I could have worded it "what's the least about of BO you'd take for a dive to the Heinkle in Ginnie, Courtyard at Madison, etc". The main reason I didn't ask it that way was I was afraid I would get the "I take way more gas than needed" answer. I think most ccr divers do indeed take more BO than needed, but because SM'ing two large steel tanks allows for that without much thought. I was trying to pick a dive where taking BO would require some thought.

While I don't have plans of getting a CCR at this time, I did post this here because I thought CCR divers would have more thoughts on the topic. I think I could get a similar discussion going if I asked about siphon diving on OC. I got the idea from another forum, where a dive plan was discussed and no one wanted to give numbers, but rather vague "it depends" answers.

I would think everyone has a method of planning these things, but I can't seem to pry it out

 

[Dsix36]

I plan all of my dives in basically the same way, I use my own personal SAC rate and a somewhat average depth of the cave (for instance, in Ginnie, I use 99') in order to figure the amount of gas that I need for that particular cave. I use my swim rate of 50' per minute to figure distances. whatever my gas requirements are will then be mutliplied by 1.5 to get the amount that I will carry.

I will plan for a failure at the max penetration to calculate the needed BO gas. I do not calulate using the flow or current (these things might change during the dive). If i am scootering solo, then I plan for a swimming exit. If I am scootering with a buddy we will plan for 1 CCR failure and 1 scooter failure at the same time.

Depending on the dive and restrictions involved, BO gas may increased to allow for extra time during exit or for the initial oh-crap moment.

 

[ucfdiver]

Curious...why would you plan for exiting without the flow's assistance which really doesn't change during the duration of a dive, but count on a scooters assistance which is less reliable?

I ask because I always rely on flow to get me out if I'm calculating swim speed for scooter failure, but never break 1/3rds, if that's the more conservative option.

 

[Cave Diver]

I would think everyone has a method of planning these things, but I can't seem to pry it out

Ok James, since you're looking for a methodology, I'll throw some stuff up.


Since 1) I don't scooter dive and B) I'm not familiar with Manatee at all, I'm going to make the following assumptions/parameters here:

Flow is negligible, so it will neither impede penetration, or assist with exit speed.
My estimated avg depth for Manatee is ~80'
DPV speed = 200 fpm
CCR setpoint = 1.0
Diluent + Bailout gas = 32%

Deco gas 100%

OC Swimming SAC rate - .7 (this is estimated a little high)

To reach 10k on a DPV @ 200 fpm is going to take 50 minutes. Just for grins, I’ll round this to a solid hour to account for any slow downs, etc that I may encounter along the way.

At max penetration, there is a complete CCR failure necessitating switching to OC bailout. SCR is not an option.
I now have 1 hour on CCR at 1.0 set point.
I’m facing an hour on 32% to exit with an average depth of 80’.
V-planner shows 33 minutes of deco and 176 cft (approx 2 1/4 AL80's) of OC gas without using O2 for this profile.

I’m gonna carry AL80’s, (77 cft actual).
If you want to take potential gauge error into account and discount the last 500 psi, that takes an additional ~13 cft from each tank, giving you 64 cft per tank.
176 cft needed / 64 cft per = 2.75 bottles needed, so that rounds up to 3 AL80's for bailout.

Adding an AL40 of O2 in drops my deco time to around 15 minutes, reduces my Nitrox need to 147 cft.

I need 3 bottles to complete this dive, but I'll add a 4th.
That gives me 256 (64 x 4) cft of 32% which is ~ 100 cft more than I need. This extra gas will take into account the possibility of a "lost gas" scenario.
My personal dive planning would probably actually mean a 5th bottle, just to reduce distance between drops and the chance of lost gas. I would also want to do a setup and cleanup dive to drop and retrieve two of the bottles + O2. The other 2 I'd carry and drop during the dive and the last bottle (5) would stay with me at all times as bailout.

Estimating a DPV failure at max penetration I came up with close to 6.5 hours for exit and deco. Personally, that's cutting my comfort level with scrubber duration wayyy too close. IMO, this dive is not something I'd attempt without carrying two DPV's, but DPV failure procedure is beyond my experience.

Similarly, assuming a LHOTP scenario, a failure of both CCR and DPV at max penetration requires a stupid amount of OC gas required to make a swimming exit, so I'd really have to give some consideration to a backup CCR at that point.

Like I said, this is purely a mental exercise for me because I tend to do shorter penetrations, but just spend more time poking around than trying to do EOL stuff.

Other possibilities I might consider is swapping out my 19cf onboard tanks to larger tanks (30 or 40) and equipping them with regs or adding quick connects to second stages. Doing that could reduce some of my off board bailout needs.

Anyone with more experience planning a dive like James described, feel free to critique my plan.