SM vs. BM

[jdobbertien]

I dive at Jackson Blue frequently and side mount is the norm there. When I talk to people they general say the big advantage to SM is redundancy. My question is if you dive BM and isolate then switch regs every 200 or so psi how is this any less redundant that SM(besides the slim chance of isolator failure)? Don't mean to stir the SM BM pot on this one just looking for objective reasons.

[bent]

And while we're at it: What's the better party, democrates or republicans? Should you get a Dodge truck or go for Ford? And finally, are you a boob-man or butt-man.

Go with what you find is the coolest, that's what everyone does. Both works just fine unless you really want squeeze into a tiny hole.

[v101]

Few general things,
Can fit through small restrictions
Easy access to valves vs reaching around behind your head
Can visually see if something is leaking, bubbling, etc.
I find my trim is much better in SM vs BM

[Kelly Jessop]

My question is if you dive BM and isolate then switch regs every 200 or so psi how is this any less redundant that SM(besides the slim chance of isolator failure)? Don't mean to stir the SM BM pot on this one just looking for objective reasons.

Good question and if you do an archive search you will find more answers from previous discussions, plus on other forums too.

BM has an excellent history,and isolater failure is probably as rare as being struck by lightening. Your scenario of isolating and alternating regulators is what you'd experience with independent doubles,and has basically the same gas management as sidemount. As far as redundancy, the open isolator,and using standard Hogarthian type configuration has a stellar history.

SM and BM are both tools that have advantages and disadvantages of each,with really no system prevailing over the other and dominating completely.

[phillip1]

Well in BM you are limiting yourself to caves where you can fit, well over 60% of the caves I explore including Malazamanga in Madagascar which is massive I mean 300 foot wide tunnels, theses caves all have sections/entrances that you could not pass in BM,
So if you BM you are in essence crossing off your list a massive amount of insane cave.
I can dive 100% anything anywhere efficiently in SM, I pretty much can't dive anything or explore efficiently in BM.

You can say what you want but BM is an antiquated tool whose time has passed with the rise of modern SM.

What is almost considered a restriction in SM is considered the end of the cave in BM.

[Kelly Jessop]

I think the OP poster was asking about redundancy and gas switches. FWIW,I think the discussions about configurations advantages and personal preferences has been beat to death,and it could be beneficial doing an archive search.

[Red Hat Jef]

Hard to see tanks and leaks behind you. I use the cover of my predator as a mirror on a bright day near the surface to check for leaks but that's still tough.

If I'm going to do anything where I'm either solo or effectively solo I'm doing it in sidemount. I can get to bottles and hoses if I have problems. I can adjust or swap regs if I really need to.

Regarding getting stuck - I've been stuck plenty in both BM and SM. The kind of stuck that a little bit of effort won't dislodge and you have to stop and think. If it came to it, I'm happy with the solution of removing my doubles in that case, then putting them back on - yes I would be floaty but it's a small passage and I can use the restriction to help and I've done this in a pool for practice. (It will be different in real life I know but I have the rest of my life to figure it out right?). The thing I'll say about this with regards to redundancy is that when this stuck situation occurs it tends to be abusive on gear - I've torn up tank valve knobs, almost always have roll off, and generally put everything on my back and neck area through the rock grinder. Don't know if you'd call this a redundancy thing, but the valves and other life support equipment don't get the same type/vector of abuse in sidemount. Sure, stuff is small, and I plug regulators with sand and gunk all the time, but it's not rock crunchy typically.

[nakatomi]

SM provides inherent redundancy, visual and convenient access to all vital components and the ability to easily switch to no-mount.
Just the fact that all failure points can be identified and accessed, makes it a very safe way to dive.

Another point worth mentioning is the possibility to get stuck. As Jef, I have gotten stuck both in BM and SM. The latter is a lot easier to wiggle out of, since most of what is on our backs in SM is very flexible.
Getting stuck in BM can be a real difficult situation to get out of, having the valves and first stages out of reach at this point, with an added risk of getting them rolled off, makes it downright dangerous.

As a result of all this, plus the fact that SM opens up some of the prettiest caves (or cave passage) out there, I tend to agree to what Phillip says, backmount has no future in cave diving.

[jvalve]

Like most guys my age, I started cave diving in back mount and was mentored for several years by a cave instructor that only dove BM. When health issues prevented my original mentor from diving, I was fortunate to be mentored by an accomplished sidemounter. In short, I AINT going back! Better trim, easier ingress and egress,easier to access valve and hose issues.What Phillip said!!
And if you still love BM, I've got a nice Faber 95 twinset for sale!

[tbone1004]

I'll beg to differ on the better trim and easier ingress and egress, as both of those are still better for me in twinsets and still use them, just not in caves.....

Regarding the original question, if you close the isolator you still have the potential failure of the valve, so unlikely it isn't worth worrying about, but it is there, especially since it can be turned and banged around if it isn't locked all the way down. With true independent doubles, gas management and redundancy is the same, and some people do dive independent doubles, Paul Clarke is one of the more well known for doing it and if you hang around Cathy's for any length of time you'll run into him. I still dive ID's off of boats pretty regularly as I'm far too lazy to keep multiple sets of doubles around. So there's redundancy and gas management, it's the same for truly independent doubles as it is on sidemount, the real benefit for me is being able to see everything if something goes wrong and it is more comfortable.