- Messages
- 99,927
- Reaction score
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- Location
- On the Fun Side of Trump's Wall
- # of dives
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What size is most appropriate depends entirely on what you're using it for. The most popular size local to me is the 3-4 foot version. That works well in most places in Puget Sound, since it's an inland sea and fairly protected. Around here the biggest waves we might encounter on a given day is when the ferry goes by. Small DSMBs are easy to deploy and generally work well in fairly protected conditions.
When we move out to the Straits, or out into open water in places along the coast, the smaller bag is fairly useless because conditions are choppier and it's more difficult to see, particularly if it's laying down in the water. A bigger bag is a more practical choice in those conditions. But larger bags are more difficult to deploy, and introduce potential risks for the less experienced diver, who may struggle with buoyancy while deploying it or risk getting pulled up if the line's mishandled. As with all gear there's a trade-off that needs to be weighed against your application and experience, in terms of risk-mitigation.
As for how much line you need, depends entirely on how deep you plan to deploy. Give it about a 2-to-1 margin (depth-to-distance) to account for currents. Anything below about 75 feet means (for me) that I bring a 400-foot reel rather than a finger spool. Reels are harder to manage during deployment because there's a higher risk of rats-nesting if you mishandle the line. So you need to practice how to deploy while keeping a slight bit of tension in the line at all time while the bag's ascending. I use my index finger to maintain just a slight pressure on the side of the reel while it's deploying. Spools are easier because you can usually just let go and allow the weight of the spool to maintain tension while it's deploying ... you just have to remember to grab the spool once it stops spinning, or it'll sink.
Smaller bags are generally closed-cell. Larger ones can be open or semi-closed. I like the semi-closed ... it allows me to use a second-stage for inflation without too much extra effort, and I don't have to worry about keeping pressure on the line to prevent the bag from going sideways on the surface and letting all the air out. Seems like a nice compromise.
Like most equipment choices, which works best depends a lot on where you're using it. As to the comments about boat distances, I'd prefer to get my bag on the surface before the current pulls me too far from where I expect the boat to be. There have been times I shot a bag while quite deep, managed an ascent that took me far from the intended dive site, and came up with the boat right next to me ... they just followed my bag as the current took me for a ride. Visibility is important, but it's even more important if you suspect the current's taking you to get that bag on the surface ASAP ... the closer it surfaces to the boat, the better ... especially if you anticipate a lengthy ascent.
... Bob (Grateful Diver)
When we move out to the Straits, or out into open water in places along the coast, the smaller bag is fairly useless because conditions are choppier and it's more difficult to see, particularly if it's laying down in the water. A bigger bag is a more practical choice in those conditions. But larger bags are more difficult to deploy, and introduce potential risks for the less experienced diver, who may struggle with buoyancy while deploying it or risk getting pulled up if the line's mishandled. As with all gear there's a trade-off that needs to be weighed against your application and experience, in terms of risk-mitigation.
As for how much line you need, depends entirely on how deep you plan to deploy. Give it about a 2-to-1 margin (depth-to-distance) to account for currents. Anything below about 75 feet means (for me) that I bring a 400-foot reel rather than a finger spool. Reels are harder to manage during deployment because there's a higher risk of rats-nesting if you mishandle the line. So you need to practice how to deploy while keeping a slight bit of tension in the line at all time while the bag's ascending. I use my index finger to maintain just a slight pressure on the side of the reel while it's deploying. Spools are easier because you can usually just let go and allow the weight of the spool to maintain tension while it's deploying ... you just have to remember to grab the spool once it stops spinning, or it'll sink.
Smaller bags are generally closed-cell. Larger ones can be open or semi-closed. I like the semi-closed ... it allows me to use a second-stage for inflation without too much extra effort, and I don't have to worry about keeping pressure on the line to prevent the bag from going sideways on the surface and letting all the air out. Seems like a nice compromise.
Like most equipment choices, which works best depends a lot on where you're using it. As to the comments about boat distances, I'd prefer to get my bag on the surface before the current pulls me too far from where I expect the boat to be. There have been times I shot a bag while quite deep, managed an ascent that took me far from the intended dive site, and came up with the boat right next to me ... they just followed my bag as the current took me for a ride. Visibility is important, but it's even more important if you suspect the current's taking you to get that bag on the surface ASAP ... the closer it surfaces to the boat, the better ... especially if you anticipate a lengthy ascent.
... Bob (Grateful Diver)
