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Hi Anthony, Your questions were good----and I can't say I've put a tremendous amount of time in thinking about how to safely train students----right now its becoming an issue I'm thinking a lot about, as are many others on this list. -----Original Message----- From: Anthony DeBoer <adb@on*.ca*> To: techdiver@aquanaut.com <techdiver@aquanaut.com> Date: Thursday, January 22, 1998 11:45 PM Subject: Re: 2nd Press Release by DS Dan Volker <dlv@ga*.ne*> writes: > >When is the safety diver put into the water? > >> They should go in at the predetermined point that the divers will reach > >their first safety stop. If we say we will do 26 minutes at 260 fsw, then > around 27 minutes later, the safety diver should be making their way down > >the float ball line to the predetermined first stop depth. >In this case, would you have the safety diver mix back gas for 260, with >plans to head down the line if no divers arrive by a certain time, or is >the safety diver strictly limited to the planned first stop depth? I'll answer this as we have done it ----and keep in mind my group dives for fun---we don't teach tech to newbies. To us, the safety diver represents your umbilical to the surface. The divers on the bottom have a "virtual overhead", the safety diver does not. Extra trimix should be on the boat, and "could be carried by the safety diver" but I'd rather keep the safety diver on air so if a sudden communication to the boat needs to be made, he does't have to worry about becoming effervescent from a rapid ascent after a few minutes at 130. The divers on the bottom should have MUCH more bottom gas than they need. It will be easy to give them more nitrox at a 100 ft stop, but giving them more trimix by going down to 250 is not good planning. > >... During the entire dive is not > >usually procedure, though with students in the water, I would consider it >> smart for IANTD or TDI to mandate this on all instructor/student training >> dives below 200 feet. In areas where there is a large current, this may >> require a scooter for the safety diver to maintain position overhead of the >> divers---skin friction drag on the bottom can create significantly less >> current on the bottom, not to mention the occasional shear currents where a >> surface current carries the safety diver south, while the divers on the >> bottom are carried north. I would say a training dive should be aborted in >> this scenario. >If a second instructor or other competent person is going to run with the >group the whole time, wouldn't it make more sense to do so with the group >on the bottom than solo and well overhead, both to be able to help the >students more quickly and to be able to be helped if this safety diver >has a problem? You know, the more I think about this, the more the safety diver in the water during the entire dive, seems a poor idea. Aside from the difficulty this job assignment will impose on the safety diver, if he travels at the 120 ft level stop throughout the dive, he will have his own virtual overhead by the time the divers reach the first deco stop. Your suggestion about having an assistant instructor along "with" the instructor and student is a more functional approach----but the safety diver would still need to be deployed at the moment of the first stop. There has to be a communication line opened to the boat and surface support---this is the safety diver. Right now I am reacting with what is almost "paranoia" , about how to make a student safer. But the safety diver overhead throughout an entire dive will be frequently too hard to implement, and would actually require two safety divers, after the first gains a virtual overhead due to saturation levels. An emergency lift bag would certainly alert the boat and pull the safety diver immediately into the water, at any time within the 20 to 25 minute timeline set up prior to the dive----this proceedure would be easier to implement than having two safety divers, and one challenged by the current throughout the dive. When doing the recovery attempt of the 3 missing divers with WKPP, one of the WKPP members and I ran safety for each dive. I did this by freediving, which does allows me to track the divers an entire dive, and to make as many drops to 90 feet or so as I want throughout the duration of the bottom time. And I don't worry about fizzing like you guys do :) Since vis was over 150 feet on the first dive, and over 100 on the second, this was an effective way to be ready for anything. If they needed anything I'd have grabbed it and had it back to them within about 3 minutes. And the other WKPP diver on scuba would have already been helping. Since I do both freediving and tech diving, this was a good option for us, but even in Florida there are not that many 90 to 100 ft freedivers around to run safety :) >> >I am interested in knowing how one can determine the exact amount of > >>negative buoyancy a wet suit (i.e. uncrushed neoprene) can have at > >>depth. > >> I have a simpler solution. Just assume it will have no buoyancy at all on >> the bottom ... >And then there's the even simpler solution of not using neoprene suits, >especially wetsuits, on deep dives. The amount of bouyancy skew between >the surface and depth is something that could be better handled by >ideally a non-neoprene drysuit (better warmth at depth, better bouyancy >characteristics, and backup bouyancy in case of a wings failure, all in >one package). Agreed. I have sometimes found lycra skin suits about equivalent to wet suits on some 280to 300 ft dives......although the wet suits are nicer durring deco. If the water temp calls for more thermal protection than lycra, and the depth is signififcantly past the "crushed like paper" depth of a wet suit, I think a dry suit is the only option. Regards, Dan Volker http://www.sfdj.com -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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