What is the difference between a SMB and shooting Lift Bags in Scuba Diving? |
I had a protege that I have been practicing with that asked me the difference in bag shooting at depth, what can be substituted for what? Many SMBs will have different features. The biggest feature that a SMB can have is an over-pressure relief valve (OPV). The primary difference between a SMB and safety sausage is that a SMB will be deployed from depth. Whereas the safety sausage is deployed at the surface for signaling. Now we need to precise SMB and DSMB construction. SMB are sealed whereas DSMB suaully are not. Most of them are open bottomed, some are semi-sealed. As the DSMB rises from depth, the gas trapped inside will expand. As the gas expands it will stress the stitching that holds the SMB together. If there isn't some sort of mechanism to release this gas, then the expanding gas will rip apart the stitching of the DSMB and releasing all of the gas. Thus rendering the DSMB useless. So this cannot be possible for SMB. 2) The diver will signal to the team to watch them deploy the SMB 3) The diver shooting the SMB will pull the SMB and finger spool from their storage locations, generally in a diver's dry suit pocket. 4) If the spool isn't already attached to the SMB, the diver must attach it. Generally, most SMBs will have a small d-ring located on the bottom of them. Using the double ender of the finger spool as a weight, the diver will feed the double ender snap (with line attached) through the d-ring. Once through, the diver can pass the entire spool through loop of line at the end of the spool. Remove the double ender from the line and keep it on the right chest d-ring. 5) The diver should signal to a member of the team to look up to make sure that the SMB will not come into contact with another diver, boat, or other obstruction. 6) Once cleared to deploy, the diver should wrap up the spool, line and any access SMB material into one hand. Making sure that no materials, line, etc. are wrapped around fingers, dive gear, etc. 7) The diver should move into a slightly head down position. This makes recovering from a runaway SMB much easier as the diver will need to swim down to control the SMB. 8.) Holding the SMB and spool with the left hand, inflate the SMB till about half full. If you are orally inflating the SMB, take a normal breath, remove the regulator from your mouth with the right hand, blow a half breath into the SMB, repeat until the SMB is half full. You will want to avoid taking to deep of a breath or exhaling to much as it will change your buoyancy. If you are using a LP inflator, use the right hand to hold the LP hose and connect the SMB to the inflator hose. Pay careful attention to how fast the SMB is filling up so that you can remove the inflation hose to prevent the SMB from getting too full. I tend to avoid holding anything with the right had just in case I need to deploy the long hose in an emergency. 9) Once gas is in the SMB, hold the SMB in the left hand and the finger spool in the right hand. Verify that the knot/line attachment to the SMB (from the spool) is in place. 10) Let go of the SMB. As it rises, be careful as to not squeeze the finger spool to tightly. This could lead to a possible runaway ascent. The finger spool should gently unwind between the grasp of your fingers. 11) Once the SMB reaches the surface, extra tension should be put on the line in order to make the SMB stand straight up. To do this, wrap up the line on the finger spool 3 or 4 times. 12) You can lock the spool in place by removing the double ender snap from your right d-ring and clipping the line inside the double ender snap and through a hole in the spool. This will stop the line from unwinding from the spool. |