Lifting Bags Shot Lines and Decompression Stations Andy

Lifting Bags, Shot Lines and Decompression Stations Andy Thomson October 25 th, 2003 DUSAC -Advanced Diving Techniques

Introduction n n Lifting Bags Shot Lines n n Types, Construction, Deployment and Retrieval Decompression Stations n October 25 th, 2003 Types DUSAC -Advanced Diving Techniques 2

Lifting Bags n Types n n When to Use n n Open Ended Closed with valve Self-inflating Retrieving items such as shot lines When Not to Use n October 25 th, 2003 Taking items from wrecks that you shouldn’t be! DUSAC -Advanced Diving Techniques 3

Shot Lines n Why use a shot line n n n Marked entry/exit point - aids safe dive marshalling and boat cover Shortest route to/from surface More comfortable/secure Datum point for searches Why not use boat’s anchor? n n Line moves with boat movement Cover boat should be mobile at all times October 25 th, 2003 DUSAC -Advanced Diving Techniques DON’T DO IT 4

Types of Shot Lines - 1 n Simple Shot n n n Bottom-Tensioned Shot n n n Advantages - it’s simple! Disadvantages n Not easily made vertical n Does not adjust for tidal rise/fall Advantages – always vertical Disadvantages n More complicated! n Risk of line tangling Buoy Line Shot weight Bottom Tensioned Shot Line not often used October 25 th, 2003 DUSAC -Advanced Diving Techniques 5

Types of Shot Lines - 2 n Top-tensioned Shot n n Advantages n Adjusts for tidal rise/fall, provides near vertical line n Can give precise position of dive site Disadvantages n More complex, counterweight tangle n Main part of line will move n Not ideal in current or wind October 25 th, 2003 DUSAC -Advanced Diving Techniques Counterweight 6

Shot Line Construction n Line n n Thick enough to grip for recovery, usually about 12 mm Length n n At least as long as it is deep Plus a couple of metres n October 25 th, 2003 n n n Needs to be kept tidy, better at the surface Enough bouyancy to support weight (50% more) Weight – Heavy enough! Counterweight n n n Surplus line Bouy Approx. 5 – 10 kg Depends on conditions Tide Bouy? n DUSAC -Advanced Diving Techniques Small bouy to show current direction 7

Shot Line Connections n Bouy, Line & Weights n n n Attachments n n n Karabiners Knots Karabiners Short loops of cord or other ropes secured by Prusik knots Rolling Hitch Shortening the line n n Karabiners Chain senneting, sheepshank October 25 th, 2003 DUSAC -Advanced Diving Techniques 8

Shot Line Deployment n n n Prepare before arrival at dive site! Deploy on boat cox’n order only! Think about direction of current! Once deployed, re-check! October 25 th, 2003 DUSAC -Advanced Diving Techniques 9

Shot Line Recovery n Controlled Recovery Lift bag bouyancy same or slightly less than weight of shot n Divers fill bag so it is neutrally bouyant or slightly negatively bouyant. n Lift to surface from boat, slowly pulling on line (can become uncontrolled) n n Bouyant Recovery n n n Lift bag bouyancy greater than weight of shot Divers fill bag to send it to the surface Boat AND divers stay well clear October 25 th, 2003 DUSAC -Advanced Diving Techniques 10

Decompression Stations n n n A decompression station is simply a shot line that divers are carrying out stops on! Methods of making this easier and safer are varied. All require divers to return to the shotline for use. Dives should be Planned Accordingly! October 25 th, 2003 DUSAC -Advanced Diving Techniques 11

Deco Stations – Types 1 n n n Can be as simple as a loop tied into a shot line Back-up deco cylinder – perhaps with Nitrox? Lazy Deco Stations n n n Extra line, weight and bouy attached to main shot line Back-up deco cylinder may be attached Can be detached to drift with current - Requires Diver ‘logging’ system October 25 th, 2003 DUSAC -Advanced Diving Techniques 12

Deco Stations – Types 2 n Decompression Trapeze n n Requires two additional bouys, weights, lines and solid bars Bars can be set-up at various or multiple depths. Back-up deco cylinder may be attached if needed Again, it can be detached to drift with current - Requires Diver ‘logging’ system October 25 th, 2003 DUSAC -Advanced Diving Techniques 13

Deco Stations – Types 3 6 / 9 m ------------------- 24 m - - Recommended Stop Peg Board Deco' Stops CFT Extended Range Course 5 Kgs 30 Kgs 48 m October 25 th, 2003 DUSAC -Advanced Diving Techniques 14