Sidemount VS Backmount

[Gary]

If you were not the only one with a CON opinion the thread would be closed by now. There is only so much back slapping that everyone can do before it gets old.

As was said earlier "To say one is better than the other is just misinformed".

Sidemount vs backmount has been discussed many times before in a similar threads.


There are good reasons for sidemount - or for backmount. I think there is a considerable number of persons get into sidemount for lack of other "continuing education" past full cave. Given a similar expenditure of effort and gear modification anyone would have far superior buoyancy and trim in backmount. Many of the benefits of sidemount are exaggerated. Being wider and flatter is only true when the head is down and legs strait out behind - but definitely much wider and floppier.

also from an earlier thread: http://www.cavediver.net/forum/showt...8242#post38242


An important thing to keep in mind in a "sidemount vs backmount" discussion is that there has hardly ever been a death caused by a gas equipment failure. Most cave diving deaths happen due to diver errors with no equipment failures involved. Even in cases where a diver is on a "single tank & single reg" gear failure is typically not involved in any way. Deaths are more likely to be related to gas mix or medical problems than to gear failures of any kind (especially true of Rebreathers where various gear/diver errors/failures often become gas mix problems).

When talking about the limited number of problems caused by breathing system failures manifolds can be considered to be a device used to propagate a leak to an entire system. In most cases I think manifolds have been an aggravating factor rather than a cause or a benefit. As in Shek-Exley - Atlantida (Caverns Measureless p145+) where a free flowing reg "not properly recognized and isolated" depleted manifolded tanks and nearly killed both divers. The same problem on independent tanks would not have been enough of an issue to be writing about.

On sidemount/independent gives ability to exit without depending on a buddy AND still also have buddy with extra air as well. Regardless of the gear failure you "have the gas to make a safe exit unaided/unencumbered" - which is a big benefit compared to being either "flush with lots of extra gas" or "tied together with probably not enough" depending on the type of gear failure (manifold). A limiting gas failure typical of sidemount/independents is a isolated free flowing reg but there remains the possibility of recovering the gas by alternate methods (swapping regs/fluttering valves/breathing off valves). In a limiting gas failure typical of manifolded tanks (isolable/strait bar) in the unisolated leak the gas is gone.

More significant than their possible benefit in a leak isolable manifolds cause problems with fill errors, shut isolators and a variety of other problems. A strait bar does limit those problems but makes any tank side leak unisolable and guaranteed to deplete both tanks.

[phillip1]

I agree, except the trim part, I think that anyone who spends the time to configure his/her gear correctly and practice will have proper trim in BM or SM, I think that it would make no difference at all which system they used.
I also agree on the gas leak thing although when I am far back in a cave I like to have my bases covered, and independent air sources are the way to go for me.

[Jay]

Given a similar expenditure of effort and gear modification anyone would have far superior buoyancy and trim in backmount. .

Gary,

I agree with everything but this part. That may be your opinion, but I don't think it holds true for everybody.
IMHO backmount will never be "far superior" in trim. Just the concept of having all of your weight above your trim line (your wing) will prevent that.
Having your tanks below your trim line (SM) will always be inherently more stable. Now if you sepnd most of your time on your back, then backmount will be more stable.

[Gary]

Just the concept of having all of your weight above your trim line (your wing) will prevent that.
Having your tanks below your trim line (SM) will always be inherently more stable. Now if you spend most of your time on your back, then backmount will be more stable.

I spend my time upsidedown, rightside up, on my head, sideways, slantways - anyways I want and can hang in just about any position with equal ease.

I dislike sidemount wanting to pull me into "its" prefered position - and as I said - rolling onto one's back or head-down-upside down in sidemount is something you do to test if the rig is up to the challenge: if the tanks remain attached you are doing "well". but it won't be "comfortable" (with steel tanks anyway).

Sidemount 40's I can do any angle with comfortably without the tanks wanting to pull me to "stable". Actually most of the aluminum tanks are pretty nice that way with a little lead at the bottom.

The steels at least hang negative all dive I suppose - but the more "comforatable to dive" aluminums will want to butt-float and bang roof worse than backmount - and don't hold much gas.

Backmount tanks can be depended on to stay in line with the body all dive at any angle and in a firm predictable manner. With "wings" BCs the bouyancy moves to the "top" regardless of the body angle creating stable floatation. I don't need sidemounnt tanks to pull me back into "its" position.

Trimming out backmount tanks well is way easy compared to sidemount - just get some wings that fit the tanks well and have multiple grommet holes (usually 3 pairs) to adjust bouyancy up and down slightly - and remember which holes you use.

I didn't know how good I had it. I started with a pair of wings I liked and dove them until the glue holding in the tube fell apart. It took me a couple of wings until I found new wings I liked again (Larry Green - signature series BTW). But that is nothing compared to the various gymnastics involved in finding/building/trimming out different sidemount rigs (even with the new designs on the market I imagine).

With sidemount trim changes a lot depending on what tanks you are diving with. With backmount it hardly matters what tanks you dive and even then you just move up a grommet hole.


Of course there are dives when nothing but sidemount (or nomount) will do. It's true. Some caves are better suited to sidemount diving. Sidemount can be a lot easier on some people's backs. Lots of times, reasons, and places for sidemount - and personal preferences - and nice to have the valves right handy and easily removable tanks for some dives.

[Jay]

I feel just the opposite. It took me a few dives to get my SM trimmed out, but I can never get my BM as comfortable. Even the best case with BM I still feel like tommy the turtle compared to sm. I dive with a Hogarthian BM harness. There is no way it is as snug as a SM rig. The harness will shift with slight movement head down or side to side. That is inherent in a one piece BM harness as it has to be loose enough to get it on and off. You can only get it so tight with a chest and crotch strap. If you are using a more adjustable harness, one could get better results, but that would be moving away from the hogarthian approach.

I have none of the trim issues you were referring to with SM. Even upsidedown my tanks don't shift enough to be a bother. But I spend 98% of my time horizontal.

[phillip1]

I disagree with the trim being way better BM. If BM is what you are used to and then you try SM a bit obviously you will feel more comfortable in BM. I agree that SM requires a lot more messing around with the gear to get it right, but not because the system is more complicated or does not work as well but because everyone knows BM and training is done in that configuration, so that is what 99.9% of every cave diver is used to since they learned that way and you got all the advice for BM.
I think that if you took two people and started from scratch one in cave class BM the other with a SM instructor, they would be more or less the same trim wise at the end of the class.
If everyone took a SM class or knew someone who SM's, they would get the rig setup perfect in a few dives.
In BM you can take prety much any doubles harness and it will be really easy to trim right right out of the box for anyone, but that is due to training.
It took me a while to get my SM rig right, I learned all the stuff by myself and it took me a while, but I really liked it and even though at first I was not in the best of trim I found it much more comfortable and convenient than BM.
I dove with SM guys in Mex and Sweden and learned a lot from them, I changed many things I was doing and I am always looking to improve my technique and gear setup, SM is a constantly evolving system, is super flexible and can be adapted to dive any cave configuration I have come across so far, I cannot say the same for BM.
Knowing what I know now I can take any SM rig and set it up perfect for me in 20-30mins.
I think that there are many people who view SM as way too different than what they are used to and know, these same people maybe try to SM a bit so it feels awkward at first and they write it off before giving it a chance and seeing what it has to offer.
Obviously there are also people who simply do not like SM and prefer BM, you should always dive what you like.
I remember the first time I put on a set of doubles, I was like what the hell is this? I will never get used to this it felt really bad and awkward at first but then you learn and it all falls into place, I think the same holds true for SM, I think that one needs to become proficient at both to really decide what works best for you.
In my humble opinion after diving both extensively I see absolutely no advantage in BM for me and what I do, I am happy I learned to dive doubles and I think everyone should but I will never dive doubles again unless there is absolutely no other way.
I really do not care who dives what all I care about is using the best system I can, so far the best I have found is SM but should someone come up with something better than SM I will definitely start to use that.

[Gary]

all I care about is using the best system I can, so far the best I have found is SM but should someone come up with something better than SM I will definitely start to use that.

but there is no "best system" they are all systems with different advantages and disadvantages and different areas of weaknesses and strengths - plus a lot of personal preference, experience and expectation to boot.

If you want to spend 98% of your dive horizontal and like it SM may be good for that - it's also good for variable geometries and low passages. No-mount is good for smaller passages yet. Backmount is very easy to learn, maintain and very adaptable to a lot of diving. If you want redundant systems lots of independent tanks are good for that. If you want buddy system air-tracking/sharing simplicity manifolds are good for that. Strait bar manifolds are simple use no-problems with valve alignments or fill mix-ups.

But for all the argument that goes into "proving" (theorizing why) one system superior to another there are almost NO real life death counts to indicate that any of this is a problem. Even when diving a "single-tank, single reg and solo" people aren't being found dead due to equipment failure. Out of air accidents are traced back to bad planning, silt outs, not running lines getting lost or confused. Gas mixtures are far more dangerous than tank configuration.

There are a lot of bad ways to set up equipment but no one way that is inherently superior for all needs. Different set ups have advantages in different areas of endeavor. Different people, different types of diving, different conditions and no way to put 100% money and effort into every method all at once.

There are things that are similar for each but not all experiences cross over. An experienced rebreather diver is not inherently ready for a complex sidemount dive (or vice-versa). A diver used to independents but diving on a manifold may think they are out of air on both tanks when they simply had a roll off on one with the pressure gauge. Trying to learn "all configurations" doesn't prepare one as well as concentrating on one or two that best meet your needs.


Even experience with a particular system may not prepare one for the unexpected enough - nor guarantee that one interpets the symptoms properly. Imagine diving into a deep syphon surprised to find your gas going much more quickly than expected - already below 2/3! Turning the dive and heading back (already nearing half) you discover the problem: the manifold valve is closed - you are breathing from just 1 of the 2 tanks. But cracking the isolator open doesn't fix things - instead the pressure drops from just above 1/2 to just above 1/4 - since the isolator valve was already shut when the tanks were getting filled...

[cavemark]

But that is nothing compared to the various gymnastics involved in finding/building/trimming out different sidemount rigs (even with the new designs on the market I imagine).

I have tried two SM rigs, one borrowed from a friend (configured for his son) for two dives and my new Nomad (out of the bag) for a dive Saturday. Both days the only adjustments that I made were to the crotch strap and belt buckle to get the rig into what I thought was the correct position. Once the tanks were clipped I decended to the bottom (~6ft deep) and with a few quick squirts of gas into the wing I stopped and hovered 1ft-2ft above the bottom. No trim or bouyancy issues I just hovered.

I'm not sure what "various gymnastics" you're talking about because I found it way easier to get an initial adjustment in SM than the hours I spent adjusting bands, wing and basic harness for BM. The only gymnastics I experienced was getting the 13" bungies around the tank necks and clipped back to the harness while bobbing next to the boat, but I think that's just learning curve. I'm going to play around in the pool a little and also try the choker method. I might try slightly longer bungies. Now I still have the same issues getting my hose lengths and routing "perfected", but that took a while BM too.

This past Saturday I did a little dive with my daughter in the Crystal River Cavern and found that I could go head down and turn sideways without feeling like I was going to "turtle". With a wing and drysuit I don't see how not to turtle with dead weight on one side of the body and two air bubbles (even small ones) on the other. I still have some adjustments to make with the rigging of the tanks and I have to learn how to clip the tanks to the harness while bobbing next to the boat, but I'm loving it so far. It's was also a lot easier to get the singles out of the water than doubles.

I still love the simplicity of BM, possibly because I am still new to SM. I love being able to just back up to the stand, fasten the harness and walk to the water. But I'm finding that my back can't tolerate 6 trips back and forth to the water, even with my light LP85s, and I almost fall into the water at Little River and Friedman, two of my favorite spots. Peacock and Catfish have setup stands or benches close to the water so I don't have too much difficulty BM with them. Ginnie is a concern for SM because I have to walk away from my tanks after placing them in the water next to all of the tuber goobers by the steps.

I'm not replacing BM, just adding SM.

Mark

[Sludge]

the pressure drops from just above 1/2 to just above 1/4 - since the isolator valve was already shut when the tanks were getting filled...

Wow, reading that gave me the heeby jeevies. Can you imagine being in that situation? You're hoping your buddy has LOTS of gas!

Anyway, great post, Gary. I think we've reached the point that commercial sidemount systems are so advanced that they're just as easy to don as backmount. I dove a 2004 Dive Rite sidemount system for several years, but it turns out I just happen to like backmount better. Edd is still after me to try the latest Nomad. I say let me pay for a new scooter first, then I'll give it a whirl.

[Jay]

BTW, I don't want anyone to get the impression that I am dissing BM. The cool thing about BM is that it is so ingrained into my mind and the Hogarthian system is so simple that it is easy to switch back to. It just takes a minute of getting use to the tank movement/position. Like putting on an old pair of shoes that are already broken in, wriggle your feet into them and you are good to go.
I think everyone should get their training in BM. It gives every cavediver the same base background for emergency response. You know how every cavediver should respond to an emergency. That is one of the reasons I use a long hose on my right tank and my left reg is on a necklace.You can treat any OOA emergencies just like you would in BM.
It's been a long while since I dove BM, I think it's time for me to do a few that way.