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Drew M. Mooney <dmooney@cy*.ne*> wrote: >I'd kinda like to put it to the group - is a negatively bouyant hang >deco with liftbag safer? I'm sure there are pros and cons to either >method, and being new to the community, I'd like to get the skinny on >the conventional wisdom. Going suddenly shallower than your stop because of a line up from the bottom breaking would be a Really Bad Thing. If you go down because of your liftbag leaking or the line to it breaking, then you need to maybe pad a minute or two more onto your deco, unless of course you're on your deepest EAN80 or O2 stop, when going deeper could be just as bad or worse than going shallower, but then I hope your gauge never leaves your field of vision during that stop anyway! Regardless of the deco line system you're using, you should never be so positive or negative that you can't quickly arrest an ascent or descent. Since probably a lot of people couldn't see the picture, I'll briefly recap. This "Great Lakes" system involves a reel of heavier line with a short length of "waster" line (50-100 lb test) at the end. You pass that bit around a solid bit of wreck, attach it to itself, make yourself positively bouyant, and unreel upward to the surface. At the surface, you give it a good hard pull and the waster line breaks and you get the whole works back. Competing styles include the "UK" system, in which you send up a lift bag on a line, and then reel upward to the surface, drifting away from the wreck as you go, and the "Jersey" system, where you similarly send up a bag, but then tie off the line to the wreck, cut off the excess and clip the reel back to your belt, and then ascend the line as usual, retrieving the bag while letting the line stay on the wreck. I should note that although I do almost all my diving on the Great Lakes, I've been trained to use the UK system and have never touched this allegedly-local system. Plusses and minuses unique to each system would include: Great Lakes system: - no lift bag needed - no lift bag to mysteriously lose all its air and fall back down - no lift bag to tell the boat where you are - no lift bag shooting upwards jamming your reel and trying to jerk you upwards at frightening speeds - only system that lets you unreel at your own speed - lets you start your ascent sooner than other systems - possibility of damage to the wreck when you heave on it from the surface to break the waster line. UK system: - only system that works when there isn't a wreck to tie off to on the bottom - only system that doesn't keep you onsite (assuming boat is anchored and doesn't want to chase after you, per US practise) - only system that lets you drift with the tide instead of hanging onto a fixed line in a current for dear life (works when boat is drifting with you, per UK practise) Jersey system: - takes longest on the bottom before you can start ascent - leaves line attached to the wreck, necessitating that you use biodegradable line, necessitating that you throw out your line and put on fresh line every few dives even if you didn't use the line. Also note that biodegradation happens much too slowly in cold fresh water; there's much more life in the oceans. - only system that supports line at both ends, so you're just hanging on to it, neither having to be positive or negative. Looking at the reel design itself from the picture, it looks rather large and bulky, its positive bouyancy would be a nuisance during the dive, and I'd worry about it binding or chafing on the arm of my suit while I was deploying it. There are a few changes I could suggest to the design (use nylon line instead of polypropylene, permanently tie a small bowline (or possibly a line thimble or a 1" stainless ring) at the end, then tie the waster from that to a dogclip, wind the whole thing on the reel and clip the clip to side of the reel; to deploy, unclip, pass the clip through the wreck and clip back to the bowline, and up you go; when you break the waster you won't leave any of it on the bottom). BTW, I had to forward that message to work and then reconstruct MIME headers before I could see the picture. A GIF of that drawing is a lot smaller than the JPEG; it helps to use the appropriate format for the type of image. With JimH's permission, I could put it up on my website in case anybody else wants to see and/or critique it. -- Anthony DeBoer http://www.onramp.ca/~adb/ adb@he*.re*.or* (here) adb@ge*.co* (work) #include "std.disclaimer" -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send list subscription requests to `techdiver-request@aquanaut.com'.
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