Totally incorrect. Today's manifolded doubles have two completely independent first stages, each can access either or both tanks.
Twin-set manifold vs Sidemount vs Independent Twins
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Manifolds have two regs in case of a failure.
I'm new to this doubles thing and for that matter sidemount thing too.
Side mount benefits seem to be easily rent tanks, not having 70# on your back. It seems a bit of a challenge to learn, I've heard complaints about doing it from boats (entering, exiting, crews) but doing shore entries is much easier as you can float tanks out verses carrying them.
Manifold doubles it seems to me would be hard to rent, getting the same tanks every time etc.... Real easy to learn. Single doubles would add the task of balancing your gas volume in each tank, same thing you do in side mount though.
It most depends on how you're diving and where you're diving. I rarely get to dive how I want - you have to do what everyone else is doing. If you're doing solo or diving with like minded friends - I'd think it'd be a toss up between the two with side mount maybe winning out with easier to rent and not having to own.
I'm new to this doubles thing and for that matter sidemount thing too.
Side mount benefits seem to be easily rent tanks, not having 70# on your back. It seems a bit of a challenge to learn, I've heard complaints about doing it from boats (entering, exiting, crews) but doing shore entries is much easier as you can float tanks out verses carrying them.
Manifold doubles it seems to me would be hard to rent, getting the same tanks every time etc.... Real easy to learn. Single doubles would add the task of balancing your gas volume in each tank, same thing you do in side mount though.
It most depends on how you're diving and where you're diving. I rarely get to dive how I want - you have to do what everyone else is doing. If you're doing solo or diving with like minded friends - I'd think it'd be a toss up between the two with side mount maybe winning out with easier to rent and not having to own.
The easy answers are: BM for boats, SM for shores, caves. Independent doubles backmounted is a last choice, if at all.
recreational openwater sidemount is often chosen because of back pain. Only few advanced divers go into so narrow caves that they need sidemount for technical reasons.
When you're 30 and fit then twin 12l tanks mounted to a steel backplate with installed p-weight lead seems to be acceptable to lift out of your trunk, carry to the water and back, carry it up and down the stairs to your basement, filling station and so on. Add a few more kg of lead for the drysuit for cold saltwater diving. (You don't have to carry the backplate and p-weight for filling of course). But when you're 45 and start having lower back pain or already had spinal disc surgery, then you'll look for alternatives. I have a handful of buddies, former twin tank technical divers, who eventually had to give it up and go to either single tank sports diving or sidemount because of severe back pain.
When you're 30 and fit then twin 12l tanks mounted to a steel backplate with installed p-weight lead seems to be acceptable to lift out of your trunk, carry to the water and back, carry it up and down the stairs to your basement, filling station and so on. Add a few more kg of lead for the drysuit for cold saltwater diving. (You don't have to carry the backplate and p-weight for filling of course). But when you're 45 and start having lower back pain or already had spinal disc surgery, then you'll look for alternatives. I have a handful of buddies, former twin tank technical divers, who eventually had to give it up and go to either single tank sports diving or sidemount because of severe back pain.
broncobowsher
Contributor
Sidemount giant stride off a boat gets interesting. Most gate openings are not wide enough. You end up with a new technique of the sideways giant stride.
Or you can have a tank (or more) meet you in the water after you get in. I know people who will tie off sidemount tanks and climb the ladder without tanks. Fish them up after on deck. That can really help if you have issues climbing a ladder loaded. Fishing a single tank isn't that bad, try that with a set of doubles and you understand why some boats will have cranes on them. But there are dangers to taking tanks on and off in the water. I know about where there is a complete tank and reg sitting on the bottom of a lake. So far I have not heard of anyone recovering it.
Or you can have a tank (or more) meet you in the water after you get in. I know people who will tie off sidemount tanks and climb the ladder without tanks. Fish them up after on deck. That can really help if you have issues climbing a ladder loaded. Fishing a single tank isn't that bad, try that with a set of doubles and you understand why some boats will have cranes on them. But there are dangers to taking tanks on and off in the water. I know about where there is a complete tank and reg sitting on the bottom of a lake. So far I have not heard of anyone recovering it.
I am interested in this discussion. Particularly the information on side mount diving.
I started on single, then single + pony.
When the dive durations and depths meant that a pony was no longer a viable redundancy, I switched to twins.
I dived independent twins for a prolonged period.
I always used independents the same way.
Enter on reg A, reach the bottom of the shot, switch to reg B. Breath cylinder B to 150 bar, switch to reg A, breath to 100 bar, switch to reg B, breath to around 100 switchback and look to ascend. (The ascend pressures are really dive dependent).
To be fair it worked great, until I damaged a damage a second stage (filled it with grit, shell, rust etc), it got under the diaphragm (an old cave diving problem), it didn't breath so good - only water. The problem could have as easily been a free flow.
I couldn't get at the remaining gas. Which in itself wouldn't have been an issue other than I had to retrace my steps to exit via the shot. Which was no longer practical with my available gas. So it compromised my safety, and more importantly that of my buddy.
I was well aware of the risks with independent twins, but had been happy to ignore them until this point.
After that I switched to manifolded twins. So all gas was available, even if I lost a regulator.
Since then I made the switch to CCR. (Which I find much more relaxing).
Most of my twinsets are out on loan. I seldom see the point in diving them. If I'm teaching, a single and pony are normally sufficient. although there are some courses that a twinset is a requirement.
I like the idea of side mount for the occasions when I do dive a twinset, or on holiday. Especially since I now have reduced shoulder mobility making shutdowns less comfortable.
My big issue with side mount is it is a return to the compromise of independent twins. Which, after I put my buddy (and myself) at risk, I swore I would never do again. I don't see a way around that problem.
How do those regularly diving side mount mitigate the issue.
I don't dive caves, so the benefits of side mount for access are not really a requirement.
I started on single, then single + pony.
When the dive durations and depths meant that a pony was no longer a viable redundancy, I switched to twins.
I dived independent twins for a prolonged period.
I always used independents the same way.
Enter on reg A, reach the bottom of the shot, switch to reg B. Breath cylinder B to 150 bar, switch to reg A, breath to 100 bar, switch to reg B, breath to around 100 switchback and look to ascend. (The ascend pressures are really dive dependent).
To be fair it worked great, until I damaged a damage a second stage (filled it with grit, shell, rust etc), it got under the diaphragm (an old cave diving problem), it didn't breath so good - only water. The problem could have as easily been a free flow.
I couldn't get at the remaining gas. Which in itself wouldn't have been an issue other than I had to retrace my steps to exit via the shot. Which was no longer practical with my available gas. So it compromised my safety, and more importantly that of my buddy.
I was well aware of the risks with independent twins, but had been happy to ignore them until this point.
After that I switched to manifolded twins. So all gas was available, even if I lost a regulator.
Since then I made the switch to CCR. (Which I find much more relaxing).
Most of my twinsets are out on loan. I seldom see the point in diving them. If I'm teaching, a single and pony are normally sufficient. although there are some courses that a twinset is a requirement.
I like the idea of side mount for the occasions when I do dive a twinset, or on holiday. Especially since I now have reduced shoulder mobility making shutdowns less comfortable.
My big issue with side mount is it is a return to the compromise of independent twins. Which, after I put my buddy (and myself) at risk, I swore I would never do again. I don't see a way around that problem.
How do those regularly diving side mount mitigate the issue.
I don't dive caves, so the benefits of side mount for access are not really a requirement.
I am surprised you see that as an issue. I used to dive twinset and twin stages. I now dive CCR and stages. My 'width' must be similar, if not the same as a side mount diver, and I have never had an issue stepping off the boat.
The biggest issue I have is on the converted trawlers where you have a minimum of a 6 foot drop into the water.
Where are you based?
One of the benefits in the UK these days is we don't generally have to climb a ladder to exit. The majority of the dive boats have lifts. Which is significantly more comfortable than a ladder
.
noj3333
Contributor
OP
It may sound silly but the only thing I really find scary so far is when a boat has a high platform. I have a bit of vertigo so it scares me to giant stride and even more so when the platform is high ...I am surprised you see that as an issue. I used to dive twinset and twin stages. I now dive CCR and stages. My 'width' must be similar, if not the same as a side mount diver, and I have never had an issue stepping off the boat.
The biggest issue I have is on the converted trawlers where you have a minimum of a 6 foot drop into the water.
Where are you based?
One of the benefits in the UK these days is we don't generally have to climb a ladder to exit. The majority of the dive boats have lifts. Which is significantly more comfortable than a ladder
My first dive after my OW was in Plymouth from of these trawlers and I can remember the height of the platform and everybody shouting at me to hurry up as there was some current at the surface
It may sound silly but the only thing I really find scary so far is when a boat has a high platform. I have a bit of vertigo so it scares me to giant stride and even more so when the platform is high ...
My first dive after my OW was in Plymouth from of these trawlers and I can remember the height of the platform and everybody shouting at me to hurry up as there was some current at the surface
These days I carry a camera, so a hot drop into current from a high freeboard is not something I look forward too. I worry about the risk to the camera, the strobe, or the lenses.
Plus if you don't have your arms pushing down on the stages, you are likely to get one in the face as you hit the water.
I used to have a video clip of someone tripping as they dropped in at Scapa, and doing a faceplant from a 6ft drop off the deck, complete with stage cylinder giving them a thump. Lucky no one was hurt .... other than their pride.
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