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We also used a similar deco system to this which has worked well over the years, although we have recently changed over to utilising a trapeze attached to the shot where ALL the team accumulate for the deco before casting the trapeze adrift, as the primary means of drift deco after diving a wreck, using a red DSMB as reserve. This has the added bonus of keeping the team together & the skipper only has one buoy to concentrate on, plus spare gas can be hung on the trapeze. We found that the DSMB work very well & insist that all on the boat have one (plus a flag) which combined, has elimanated all boat/diver seperation on the surface. However if used incorectly they have a few drawbacks... > The reason the DSMB is deployed from the wreck is to ensure that the > current does not drift us a significant distance away from the wreck to > an area where the skipper may not be focusing his attention. If not deployed from the bottom this is a real problem, which we found out to our cost - from 50/60m the divers can drift a fair way before they deploy mid water. Add to this a few foot chop - once we missed the buoy & the divers sat on the surface for an hour before their flag was spotted some half a mile away. We learnt from this stupid mistake & all deployment is done ON the wreck. I prefer to be in solid contact with the bottom before deployment, incase of reel jam & double reel (using buddies reel - not taking down 2 reels) to avoid losing line incase of a jam. If, as is normal, the current is flowing by now, you need more line to account for the fact that the buoy don't go straight up but at an angle. > In the event of a failure of the primary DSMB or reel we discard it and > switch to a secondary. This is a small red DSMB which is self inflating > using a CO2 cartridge and sealed to stop gas escape. Again sold by > Advanced Diving Products. These are really small and easy to deploy but > require an additional reel. My secondary DSMB only has 10m of line & is also my 'yellow' signalling buoy, as I don't wish to carry two reels. Instead I have a little film cannister inwhich I stuff the 10m of line and all rolls up together quite compact. To deploy - pop the canister, drop the weight & the line unravels, then send up DSMB. However, to have needed to rely on the reserve as my main DSMB, I'd have missed the trapeze, had failure of my primary and then failure of my buddies, or become seperated from him! If a signal is needed the 'yellow' is either sent up form the trapeze, or sent up my primary DSMB, where the boat has spare gas all rigged & ready to go. If necessary a slate can be attached to the top to supply further info to the boat. > The main problem with the primary is that it is bulky - I carry mine in a > pouch on my waist section of my harness, pushed to the rear to ensure > minimal drag. The other SMBs are not a problem due to their small size. > AP Valves sell a nice inexpensive DSMB that is manually inflated and > seals itself when inflated. This is a cheap alternative but does not > have the advantage of simple deployment that does not affect the > buoyancy. Another problem with the sealed DSMB - one guy (yes a friend of mine - I've not done it 'yet'!) is forgetting to charge the cyl. In this case the primary has failed. I've attached a cyl to a large self sealing DSMB so that when I do forget, I can resort to the good old dv up the spout! These DSMB are VERY buoyant - in the region of 20kg/40lbs depending and two divers can easily suspend themselves if necessary without pulling it down. One other problem, however, is I know one guy to have been hit by a DSMB being sent up from the bottom, while he was on his stops!! Had no time to do jack & found himself on the surface, popped back down to complete his stops & then ended up down the chamber the following morning with slight problems! All in all though they are a fantastic ways of deco'ing on the drift & keeping both boat & divers in contact. Lifting bags are for lifting bits of wreck and should stay that way - this was a hard leason for one guy, who was hanging under a lift bag, which got almost hauled onboard before they saw the line coming off it! His stops were a bit seesaw!! This side of the pond DSMB are a basic bit of kit to do a specific job - likewise the lift bag has it's job and the two are kept seperate to avoid complications! Just felt like saying something Alex -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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