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+--- Thread: Rebreather questions (/showthread.php?tid=500)
Re:Rebreather questions - freedivernd - 04-03-2003
Here's what a professional freediver would need to get to the Gunilda
About $100 worth of equipment.Re:Rebreather questions - igotoofar - 04-03-2003
I have seen the free diving point brought up many time on these pages. The idea that you have a lot of freedom with things like minimal equipment and the ability to retrieve items dropped by SCUBA divers may well be true, but nobody ever seems to point out that as a free diver you don't have the ability to spend much time on the bottom. The thought of doing a penetration free dive would seem suicidal.
This being said I would love to be able to freedive, even if only to 30-40 ft. It still wouldn't provide me with what I want to get out of diving.
Re:Rebreather questions - freedivernd - 04-04-2003
igotofar,
I think you are wrong in thinking scuba allows you more bottom time. It's my understanding that over the time of a day.. freedivers can have much more bottom time than scuba divers. Plus, on southern trips it gives us one more day of diving because there is no fly rule. I'm certified scuba, just can't bring myself to do much of it..(this year for sure, I AM GOING TO SCUBA MORE, I think
) Something addictive happens while you freedive, I think it has a lot to do with the mammalian dive reflex... The big trouble for me is buddies.. think it's tough lining up scuba buddies... try finding someone willling to breath hold to -30 or -40 feet to be your support while freediving. You say to someone.. "o.k., I'm going to the bottom and after 40 seconds (or whatever) take a breath and dive down to -35' (or more) and meet me there on my way back up".. ya you bet! : That'll get you a lot of takers. You gotta come along with me sometime while I'm freediving.. really see what it's all about. Even come along as a scuba diver. It's a hoot.Fred
Re:Rebreather questions - igotoofar - 04-04-2003
I would love to come with to see the Freediving scene. As I said, I think it would be fun. I only wish I had been exposed to the sport at a younger age when I was in better shape.
I see Freediving and SCUBA as different sports, kind of like NASCAR and Drag racing, Both have 4 wheels, a frame and a driver, but their goals are different.
With Freediving you can make multiple short trips to the bottom, where with SCUBA you can stay at the bottom for a longer amount of time but not as frequently.
I wouldn't say one is better than the other, they just provide the diver with different opportunities, with the bounus that they can help support each other.
Re:Rebreather questions - john j - 04-04-2003
I'm still curious about Jon's post that describes trimix diving with doubles but only using one stage bottle of trimix per dive. Please explain how that works.
Are there a lot free divers doing 260-300ft free dives in 38 degree water where there is no light?
Re:Rebreather questions - DRE - 04-04-2003
You dive the doubles on your back and you carry one AL80 filled with your bottom gas (same as doubles) and usually (let's say for a Kamloops or Gunilda dive) two AL40 deco bottles (one with EAN50, one with O2). All three bottles are sideslung on the left hand side only. For the dive you use the AL 80 with bottom gas, so you don't touch the gas in the backtanks, which is reserved for emergencies only, such as sharing air, a freeflow of the AL80, etc. This means that for a week of diving you have to bring one set of doubles, 5 AL 80's (if you don't have refill capacity on the boat) and your deco bottles.
Also, for a week of diving you usually don't need one set of doubles per day (unless you're a total hoover, which means you're out of shape and you're equipment and technique are - let's say - below par). You can easily get two dives out of a set of doubles on the Gunilda or Kamloops. This means that for six dives I would only need two sets of doubles. How? You mix your first set of doubles with your bottom gas and do two dives on it. Your other set of doubles has been filled with heliox for double the amount you would need in a single set of doubles. Now after you've done the first two dives on the one set you empty the remainder of the gas from that set, then transfill between the empty set and the set filled with the heliox. This will give you the right amount of O2 and He in each set of doubles for the appropriate bottom gas, and now all you have to do is top off with air, which gives you 4 more dives.
Re:Rebreather questions - freedivernd - 04-04-2003
No, John, not a lot. A few finning down and finning up, more riding a weight down and finning up, even more going much deeper riding a sled down and going up with a balloon. Cold water and no light? More than we would imagine, those canadians and some europeans are nuts. I'm sure not that crazy. ;D
Fred
Re:Rebreather questions - Freedive WI - 04-04-2003
Sorry I didn't answer sooner, but I have a newborn who won't let me type.
DRE pretty much summed up my answer anyhow. 80's are cheaper than doubles and allow more flexibilty in the dive plan.
As much as I love freediving, you are right that you can't do any kind of penetration diving, but you are not allowed to penetrate the Gunilda to begin with. :'(
There are freedivers out there doing 300 foot freedives in cold dark water. Eric Fattah set a constant ballast( swimming only, no sled) in 280' of 38 degree cold Canadian water with only 3' of vis at the bottom. "Kiki" is a diver from Europe who was out freediving on the Andrea Doria with just a monofin and no sled. He could spend all day just swimming down and back at a relaxed pace. Frederic Bule( Belgium freediver) used a sled to freedive many shipwrecks in over 200' of water off of England a couple of years ago.
I have only freedove the wrecks in Michigan and Huron down to about 100'. I don't have a regular buddy to spot me, or train with, so I am somewhat limited in my depth. It doesn't much matter in Lake Michigan because the good vis, thanks to the zebra mussels, is all above 100' anyhow right now.
When you do a rebreather trip, how much Sofnolime do you need? I didn't see it pictured at all? Also, what do you do for back-up parts to your rebreather? computers , batteries, hoses, and such must take up some space? I imagine that if your diving in a team of rebreather divers you could spread the spares out inbetween the group members. In DIR we are allowed complete redundancy inbetween team members by our OC set-ups. I can switch out a second stage on the fly with a buddy if need be. I know that you must have the same protocol for your dives.
One other question. What about bailout? If your breather goes down, is 40 cuft enough of a bailout to get up and deco? Once you use it up, say on the first day of a trip, are you sidelined for the rest of the trip?
Just curious, not attacking. Although I choose to dive DIR I am not a "nazi" about it. I am always interested in how other teams plan out their safety protocal. I was afirst attracted to Dir because it was a step up form the deep air cowboys around here who are always running out of air and getting bent. The DIR divers that I know actually put safety above brass and I feel very comfortable diving with them.
Jon
Re:Rebreather questions - Inspirationdiver - 04-04-2003
One aluminum 80 filled with trimix isn't really going to be enough gas to do any extended bottom times. I ran a V-planner profile for a dive to 260 for 20 min. 15/50 bottom mix and 36% and 80% for travel gas and deco gas respectively. Total run time for the dive was 74 min. Consumption rates were .6 RMV for at depth and .5 RMV for deco, these are pretty respectable consumption rates. The diver would use 133 cu ft of bottom gas, 26 cut ft 36%, and 17 cu ft 80%. These values are for actual gas used, a smart diver would also want to follow the rule of thirds.
One other thought, why would you sling all three tanks on your left side? Doesn't that get a little cluttered? Why wouldn't you carry the trimix on one side and the two 40's on the other side?
Re:Rebreather questions - DRE - 04-04-2003
So you might have to use a bit of backgas for ascent and descent - big deal (don't forget you're not using the AL80 for wing inflation either so that will cut down consumption by a quite a bit, especially at those depths). When using a stage as in this case you won't follow the rule of thirds for the stage. Rule of thirds is for emergencies, for which you still would have your backgas (which you run according to rule of thirds - think of the stage as added safety buffer)
Several reasons for slinging 'em all on one side: first it keeps the right hand side totally clutter free, which is also the side you'd be donating the long hose from, so no possibility of getting tangled on any bottles; second, that's the side you'd be holding the scooter when scootering (the bottles would only get in the way); third, if you have bottles on either side the slinging motion of either bottle (they counterbalance) would slow down your movement while swimming; fourth, too many people use which side they carry their bottle as a way to identify which gas they're breathing, which is an invitation to disaster; fifth, if you carry a bottle on that side you would need a d-ring on that side, which menas you can't take the light canister off UW (which is part of the weighting system, and must be able to be taken off when going through a restriction).
It's absolutely no problem to carry multiple tanks on one side - when carrying more than two, you clip the neck of the tank off to the hip d-ring - aluminium tanks will nicely float in the slipstream (steel stages are a big no-no).
Hope this helps...