What would you do?
- Thread starter geoff w
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ermaclob
Contributor
i think the individual u quoted mentions jumping on another tank at 70 ft which i would assume is perhaps the depth one of these stages is at. Your plan is what i would go with tho. What ever gas is on me is what i would rely on.
---------- Post added January 30th, 2014 at 01:07 AM ----------
so tell me if im getting this strait. The dive op. takes people to do a dive to 150 ft with a 10 min bottom time and 100 min of total underwater time before coming back up?
taking a quick look at deco planner, i get about 8 min of deco time and at a sac of .7 about 60 cuft of gas for the total dive. so ideally the dive is doable on one tank if you breath good. You just have to be ok with dieing if something goes wrong because the're no contingencies or back ups :/ not even gas sharing.
how much releaf does this ship have 100 min bottom time is defiantly a multi tank dive.
SmacA
Registered
In direct answer to you question, would I do it:
No. The thought of NEEDING to find a WORKING stage tank on the way back up, puts me off immediately.
Secondary Question, would I drop down have a quick peek, and come back up.
Quite Possibly. If I understand correctly, there is a shot line which you drop down and ascend, this is attached to the wreck. I'd plan my dive to not leave the line, keep a good eye on my SPG and computer, and take a buddy who's willing to stick with this plan.
Back on the boat you can look at the photos and discuss the dive with the more qualified (or less risk adverse / foolhardy) divers. They won't think any worse of you. Then you can reflect if you'd like to do similar dives in the future, and get training / gear more appropriate to the situation and risks you are willing to take on.
You don't climb Everest without spending some time at base camp first
No. The thought of NEEDING to find a WORKING stage tank on the way back up, puts me off immediately.
Secondary Question, would I drop down have a quick peek, and come back up.
Quite Possibly. If I understand correctly, there is a shot line which you drop down and ascend, this is attached to the wreck. I'd plan my dive to not leave the line, keep a good eye on my SPG and computer, and take a buddy who's willing to stick with this plan.
Back on the boat you can look at the photos and discuss the dive with the more qualified (or less risk adverse / foolhardy) divers. They won't think any worse of you. Then you can reflect if you'd like to do similar dives in the future, and get training / gear more appropriate to the situation and risks you are willing to take on.
You don't climb Everest without spending some time at base camp first
I don't do metric . . . Here's what I got: 2 people, stressed SAC rate of 1.0 cfm (and it may well be higher in people without a lot of stress training):
1 minute at 150 to solve the problem = 11 cf of gas
Ascent from 150 to 90 at 60 fpm = 9 cf
Ascent from 90 to 70 at 10 fpm = 13.7 cf
That's 33 cf to your 70 foot bottle, if you have a 70 foot bottle. (This is one of the reasons for using 50% as a deco gas, because you can get on your deco bottle sooner, if you have a gas problem with your main supply.)
If you have to continue to the surface:
70 to 0 at 10 fpm = 28 cf; total is 61, which is doable on a FULL Al80.
Now, you do not have to make the assumptions I did. You are ostensibly within no-deco limits, so there may well be no reason to slow your ascent as deep as I did. (I believe it is probably advisable to slow it in the shallows, though!) You are counting on making it to hang tanks, which are probably at 20 feet, which would shave a little more off the amount needed. But the bottom line is that, if you have spent any time at depth at all, you do not have enough gas to get someone else to the hang tanks.
Most people, when they think about deep dives, worry about DCS. As my wonderful instructor, Joe Talavera, once said: You are asking the wrong question; you should be asking about whether you have enough GAS. You can generally fix bent, but it's awfully hard to fix drowned.
1 minute at 150 to solve the problem = 11 cf of gas
Ascent from 150 to 90 at 60 fpm = 9 cf
Ascent from 90 to 70 at 10 fpm = 13.7 cf
That's 33 cf to your 70 foot bottle, if you have a 70 foot bottle. (This is one of the reasons for using 50% as a deco gas, because you can get on your deco bottle sooner, if you have a gas problem with your main supply.)
If you have to continue to the surface:
70 to 0 at 10 fpm = 28 cf; total is 61, which is doable on a FULL Al80.
Now, you do not have to make the assumptions I did. You are ostensibly within no-deco limits, so there may well be no reason to slow your ascent as deep as I did. (I believe it is probably advisable to slow it in the shallows, though!) You are counting on making it to hang tanks, which are probably at 20 feet, which would shave a little more off the amount needed. But the bottom line is that, if you have spent any time at depth at all, you do not have enough gas to get someone else to the hang tanks.
Most people, when they think about deep dives, worry about DCS. As my wonderful instructor, Joe Talavera, once said: You are asking the wrong question; you should be asking about whether you have enough GAS. You can generally fix bent, but it's awfully hard to fix drowned.
Foxfish
Contributor
The emergency air consumption rate I've used seems widely accepted. I've assumed the diver is in decompression and needs to make decompression stops. I'd want to extend the safety stop even further if possible to further reduce saturation levels prior to ascent.
Ideally I'd want to carry the reserve air with me so I'd be carrying at least a couple of tanks. Diving with less reserve air means a lot higher risk than is normally recommended for recreational diving.
Ideally I'd want to carry the reserve air with me so I'd be carrying at least a couple of tanks. Diving with less reserve air means a lot higher risk than is normally recommended for recreational diving.
Oh, I totally agree that doing this dive on a single tank is not at all advisable! I'd do it on doubles, with a deco bottle; but then again, I want more than 10 minutes of bottom time, and I don't like cutting anything very fine with respect to gas.
The emergency consumption rate I was taught was 1 cf/min, doubled for two divers. As I said, I don't do metric. The OP made it clear that he would not be going into much, if any, mandatory deco.
The emergency consumption rate I was taught was 1 cf/min, doubled for two divers. As I said, I don't do metric. The OP made it clear that he would not be going into much, if any, mandatory deco.
Foxfish
Contributor
Eric Sedletzky
Contributor
Yes, but shaving time that close combined with depths beyond recreational limits means that only one thing going wrong like extending bottom time or a bit deeper than planned and it pushes the dive into a different level.
A lot of people who haven't had any tech training might see this dive as no big deal as long as everything goes right. I found that once I got some tech training I learned things that changed my thinking about dives like this and I realized all the stuff that can go wrong and why tech training exists and why people use the proper tools and techniques for dives like this. It's a classic example of "you don't know what you don't know".
There has to be a line somewhere between tech and rec. I see this dive as stepping into the tech realm. For me I would go into it with that mindset and I wouldn't put myself in this situation unless everyone else around me was of the same mindset.
Foxfish
Contributor
This has been an interesting thread. A number of times I've stood in a circle of divers listening to the retell their tales of diving to depths beyond recreational limits in overseas countries and then walked away wondering what I'd do. Was this the accepted norm and was it safe? Obviously a lot of people do it and survive, but the risks are high.
Post #53 in this thread http://www.scubaboard.com/forums/accidents-incidents/453884-us-expat-fatality-vanuatu-6.html is telling. The context is a woman recounting her experiences diving a wreck with a dive operation in Vanuatu. Plenty of lessons to learn from her experiences. The broader context is that someone had previously died while diving with the same dive operation. Several people on the thread chimed in with their own bad past experiences diving with the operation.
Post #53 in this thread http://www.scubaboard.com/forums/accidents-incidents/453884-us-expat-fatality-vanuatu-6.html is telling. The context is a woman recounting her experiences diving a wreck with a dive operation in Vanuatu. Plenty of lessons to learn from her experiences. The broader context is that someone had previously died while diving with the same dive operation. Several people on the thread chimed in with their own bad past experiences diving with the operation.
Adventure-Ocean
Contributor
I would make the shallower dives because I think that's where there is more living action. Since you are asking this question I'd say you are not prepared to do a deco dive. Deep diving and decompression stops should be learned slowly with experienced divers until you feel confident to plan your own deep dive. Adventure-Ocean
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