I'm curious about sidemount

[DevonDiver]

Well I'm taking a swipe at devon because he made a crack about what I was asking without offering any useful information.

I definitely used a smiley

So clearly SM is better for at least some profiles of caves. SM is generally easier on the back. There's a large overlap of dives where it just doesn't matter. They are both tools,...

Agreed. Where it doesn't matter, then the diver might have a preference. I prefer the feel of sidemount in those cases.

.... I don't hear a lot about where the real limitations are.

I think you've identified a potential one. I also think that sidemount diving needs an amount of evolution and testing, on the path to establishing it's limitations.

So, what is the actual practical limit of what divers are really doing SM?

It's an interesting question... and first-hand accounts/feedback on that level of dive is something that I'd want to hear about also.

 

[cool_hardware52]

So what is the reasonable amount of tanks to be carry sidemount either in cave or technically? What are the limitations where it does become no longer the right tool for the job and BM becomes more appropriate?

Are you assuming that when one maxes out the practical number of bottles in SM that BM automatically becomes more appropriate?

I'd speculate that at that point, i.e. more OC gas than can be reasonably carried, RB's including SM Rebreathers would need serious consideration.

Of course dives with these type of gas requirements are well beyond all but a small number of true explorers.

Tobin

 

[lamont]

I am not sure that reasonable describes that situation.

As far as depth limits go:
http://www.scubaboard.com/forums/technical-diving-specialties/428881-300-sidemount-trimix-dive.html

But with 7 bottles: Either way, the only difference if CFy-ness is that your back two tanks are manifolded in the BM version. Either way, I would not consider that a particularly 'reasonable' dive. The fills alone are what? $600 dollars?

Anyone even thinking about those sorts of dives has to be at least considering a rebreather to be considered reasonable. And once the rebreather is considered, then maybe it's just not 'reasonable' to do a dive that needs 7 tanks, four of which are bottom mix trimix. If for no other reason than helium is a precious enough resource that its worth conserving, and swimming around 7 tanks in current is ineffective.

(Actually if we are busting out the word silly now, then 7 tank dives in current are silly. There is essentially no way a diver can actually do anything with 7 tanks on them in current regardless of configuration.)

Even with CCR, though, you still need bailout, and 3 deco bottles with the same amount of gas as you'd carry for OC, which means you have the CCR unit on your back with O2 and dil along with at least 4 other bottles. It isn't a quantum jump up from the OC config in terms of profile (unless you want to use team bailout, which I wouldn't). And there's no way I'd swim with that config, that's a scooter dive.

And I mentioned explicitly that you're pushing the limits of OC there and, in fact, since helium went up and the economy tanked, the only divers on the 300-foot wrecks around here are the CCR guys. And I always used to look at diving that deep on OC skeptically anyway since you suck Al80s dry in 10 minutes at those depth, which involves a lot of regulator swapping at depth anyway, but it has been done quite a bit around here in the past.

(And technical diving is a microscopic pimple on the ass of the helium industry, we could walk into every technical dive center on the planet and open up all the T cylinders of helium and vent it all into space, and while it'd make me cry, it just wouldn't matter economically...)

 

[JamesK]

I feel this is where you start getting in to support divers.

 

[lamont]

http://www.scubaboard.com/forums/technical-diving-specialties/428881-300-sidemount-trimix-dive.html

Heh, just watched that. Warm water and at 7 minutes of runtime they were back at 220 heading up after seeing the magic '300' on their gauges. Yeah, you can do that with 4 bottles. What was that about wasting helium?

 

[FoxHound]

Heh, just watched that. Warm water and at 7 minutes of runtime they were back at 220 heading up after seeing the magic '300' on their gauges. Yeah, you can do that with 4 bottles. What was that about wasting helium?

you could argue that any OC deep trimix dive is a waste of helium.....CCR is much more practical and cost effective for a deep trimix dive, and for CCR, you are still SMing your bailout.

That being said i don't think you will find anything listed on the limitations of SM because quite frankly they haven't been found yet. You can pretty well do any dive in SM that you can in BM. you can easily carry 6 bottles SM, 2 top and 2 bottom mounted stages. that many bottles in BM is a bit more tricky with having to rotate them on a leash, and if you are carrying that many bottles again CCR becomes more practical.

 

[The Chairman]

Two reasons. First, then we'd have to buddy breathe off the left tank instead of donating a reg. Second, the hose routing would get pretty ugly.

I dive with two five foot hoses and use a swivel on both of my right and left regs so they don't go around my neck. That way, I can donate either tank as I see fit.

 

[CWSWine]

Here is video with 6 sidemount tanks...

[video=youtube;ZbWpzg7u3sM]http://www.youtube.com/watch?v=ZbWpzg7u3sM[/video]

 

[jago]

Steve Bogaerts with 6 tanks : [video=youtube;Ex3u5iYARs4]http://www.youtube.com/watch?v=Ex3u5iYARs4[/video]

 

[DA Aquamaster]

Well I'm taking a swipe at devon because he made a crack about what I was asking without offering any useful information.

So clearly SM is better for at least some profiles of caves. SM is generally easier on the back. There's a large overlap of dives where it just doesn't matter. They are both tools, but I don't hear a lot about where the real limitations are. And I've listened to Boegarts get asked this question and he didn't really have an answer, either, and in the past 2 years since then I haven't seen it answered anywhere. So what is the reasonable amount of tanks to be carry sidemount either in cave or technically? What are the limitations where it does become no longer the right tool for the job and BM becomes more appropriate? I know people do SM with at least 4 bottles, but I'm unsure about aluminum-vs-steel for the bottom mix and if people are commonly using large tanks like hp130s with SM config. I also don't know what people are actually pushing the limits of the config to. 7 bottles mounted SM certainly seems silly, but I don't know if that's just due to my limited exposure. So, what is the actual practical limit of what divers are really doing SM?

It depends on what SM system you've got and how it interacts with the rest of the configuration, but available lift is the major limitation for most SM systems.

The Nomad wing, for example, has gotten bigger (Trek Wing to Rec Wing to the current 60 pound Nomad wing) as the Nomad evolved to cover a wider range of SM situations. The downside is that it's gained some bulk and even when you strip off the shoulder pads, back pad, etc, the larger wing makes it notably bulkier than an Armadillo or a Bogarthian style harness with a small lift bladder. So there's a tradeoff involved - smaller profile versus greater lift and what would be ideal in small passage may not work all that well with multiple stages.

It's important to note that side mount wings are also constricted to some extent by the need to control the air cell. A "60 pound" Nomad won't lift 60 pounds as the wing is constricted by the perimeter control of the wing (bungees underneath and the attachment to the waist strap) as well as tank bungees over the top of the wing if you use a loop bungee running over the wing.

I've noted with my Nomad that in it's current old school/bungees over the top and snugly bungeed wing configuration that if I am diving wet (a 5mm suit that's long since been crushed to about 3mm) the Nomad wing works hard to lift a pair of cave filled LP 95s and a stage along with a can light and a primary reel and a couple jump reels.

However, at the same time, if I loosen the bungees controlling the air cell to let a little more gas in the front of the wing, and allow a little more play on the ends of the wing by adjusting the attachment at the waist band, it will easily lift a pair of LP 95s, a pair of stages and a deco bottle with the same wet suit. If I am diving cold water with a drysuit and thick underwear, the Nomad wing then has adequate lift for LP 95s, a pair of bottom clipped stage, a pair of top clipped stages and a deco bottle, and I think it's a lot easier to manage them in SM than in BM - and it's a LOT cleaner and more streamlined in the water.

But, I also see the advantage of a smaller system over all and before I go to MX again, or anywhere else where AL 80s are all you dive, I see a Razor style harness and wing in my future as it offers more than enough for a pair of AL 80s and an AL 80 stage that is adequate for a 2 1/2 to 3 hour dive in the shallow caves we dive there.

So I don't think any single SM system is optimal across the entire range of what a SM diver can do. Still, I don't see my self going back to back mount - just like I don't see myself going below 240' on OC.