Sidemount or Backmount?

[PfcAJ]

Feathering a valve is cute till you need two hands.

Swapping regs is cute till the DIN oring falls out.

I'd rather not rely on cute tricks.

 

[kidsdream]

A couple of thoughts and info/experience.

Like some of the other people, I frequently dive different configurations depending in the conditions, or type of dives being accomplished. For cave I converted to SM a couple of years ago. I find the over all stability and balance significantly improved compared to BM doubles and it's certainly does help out in low passages. Of course some caves/passages (portions of downstream Cow or Little River would be "easier" BM). For wreck/ boat diving I find BM easier to quickly rig up and navigate through the typical narrow confines of a ship. I do of course find the valve drills more challenging as I get older and loose a bit of flexibility.

For single tank OW you can't beat a BP & wing. I have a couple steel for diving close to home and alu with weight pockets for travel. I always use a STA so I can convert a BP from singles to doubled quickly.

This said, I just finished a trip to Mexico where I used my SMS 100 for single tank OW backmount (no back plate) dives. It worked sufficiently well, ignoring the fact it has excessive lift (not required for a sings alu. 80) and inherent bouyancy requiring extra weight. I only dove this way as I was doing a a couple of days of diving in Cozumel before hitting the Cenotes for 3 days.

 

[victorzamora]

Feathering a valve is cute till you need two hands.

Swapping regs is cute till the DIN oring falls out.

I'd rather not rely on cute tricks.

I don't know why you'd ever HAVE to swap regs. Also, feathering the valve is really easy....even when you need two hands. I was taught to switch to the good reg instantly, then turn off the bad post. After I settled myself, I switch back to my bad post and feather along the exit/ascent. I was taught to do this until my tank dried up or the imbalance got unbearable. Whenever I NEED both hands I turn off the bad post and switch to my good one. There's no drama.

This happened on my third post cert cave dive (o ring in first stage blew) near Max penetration. I ran every reel in, pulled every reel out, and still exited with JUST above 1200psi.

I'm not saying there aren't advantages to isolated doubles, but calling it a cute trick and implying it's inherently dangerous is unfair and very biased.

Sent from my Samsung Galaxy S4 using Tapatalk

 

[Doppler]

... ... not practicing James Bond stuff

Can I quote you on that? LOL...

 

[Dive-aholic]

I can get the sms100 for the same amount it would cost me to order in a 75- should I still go with the 75 or get the 100 and have some room to grow into it as I gain experience?

Try several different rigs before you spend money on any one rig. There are some of us that own a variety of sidemount rigs and dive some of them pretty regularly. Personally, I own 7 different sidemount rigs and dive 3 of them on a regular basis. You won't find any single sidemount rig that's perfect for all dives, but you can find some that will work for most dives. There's really no way to tell you which rig to buy though without knowing your diving style, your body type, what type of diving you plan on doing, etc. And any rig you end up buying will need to be personalized to you in order to be put to best use for you.

---------- Post added December 16th, 2013 at 09:05 PM ----------

I haven't tried sidemount yet, just want to keep my options open and get a system that supports single tank, back doubles, as well as SM. Does Hollis have any weight system that can be used with the SMS100, or is a weight belt the only option?

While no single system is great for all three there are systems that can be used for all three. I use the Dive Rite Nomad in sidemount and backmount. Haven't used it in a single tank backmount because I can't remember the last time I did a dive that way but it can also work for that configuration. As for a weight system, Dive Rite has a weight plate they created that can be mounted on the top of the Nomad but it does create a little more bulk. Here's what I use when I need to add a little more weight - Weight Vest - Black [ACC-weightvest] - $37.80 : Chipola Divers, Sidemount, Technical, & Cave Diving Instruction & Mentoring. I wear it under my rig with some weights in the pockets. It keeps the weight over my torso/center of gravity where it should be and it very unobtrusive.

 

[DevonDiver]

calling it a cute trick and implying it's inherently dangerous is unfair and very biased.

I agree with this. A skill/drill is only as good as the learning that developed it. Proper training is (should be) given on both techniques; feather-breathing and reg swapping.

Otherwise, if assuming no skill-set behind a drill, it'd be easy to level the same cynicism at valve or manifold shut-downs etc, ... cute tricks... but what happens when you rely on them? We all know the answer - if properly trained and rehearsed, they are no problem whatsoever.

So, that brings us to 'proper training'. If feathering is to be selected as a contingency skill, then it needs to be trained properly. That means extensive practice - in real situtions. The same way you'd practice any other technical/overhead skill. Gain skill familiarization in controlled circumstances, develop muscle memory from repetition, then apply under realistic conditions. It's quite feasible to ask a student to complete all, or a majority, of a dive using feather breathing on one of their cylinders. That'll prove the skill. Skills should be 'proven' before they are adopted and relied upon by the individual.

The same applies to reg-swapping. It's a formal skill for some agencies sidemount courses. The issue of o-ring displacement/loss is covered (even in the PADI 'Tec Sidemount course). It's not something that's been forgotten.

Anyway, you have two o-rings; one from each reg swapped. A wise diver might have a couple of spare too...just in case.

So, let's consider the reality of reg-swapping;

1) A last ditch drill - only for catastrophic regulator failure, where feather breathing is unsuccessful and gas loss/use from the other cylinder (and team) has exceeded your gas management planning parameters. i.e. very, very rare.

2) First resort is to air-share from team when conducting the swap. No holding breath and rushing.

3) Second resort is to swap from a 3rd cylinder, (stage/deco) if available. Again, no holding breath and rushing.

4) Last resort is to swap directly, one regulator to another, with only 2 cylinders available and no team gas-sharing. This encompasses a very unlikely series of profound diver/team errors and equipment failures. It is very unlikely. Even then, practice and repetition make it achievable. The diver has gas and time prior to the swap (it isn't an immediate and time-critical action), so they can prepare themselves, their equipment and ensure optimal circumstances to conduct the swap.

As mentioned, I teach this on the PADI Tec Sidemount course, it's a performance standard (albeit in controlled circumstances). I get AOW/rescue divers sometimes for that training; and they don't seem to have a problem with it. So, I'm somewhat perplexed why Über-experienced cave divers should find it so demanding???

 

[WhiteSands]

I am not cave certified, but.....I believe using GUE procedures the answer to your question would lie in the calculation of minimum gas and turn pressure based on one tank instead of two that are connected. Since in sidemount they are not manifolded (I'm ignoring UTD here) then the minimum pressure calculated would be higher and need to be maintained in each individual tank causing the turn to happen quicker.

Kinda confusing I know, but since doubles are manifolded and manifold failures are so extremely uncommon it's accepted in planning that you will still have all gas available given a single reg failure. Anything beyond that, such as a manifold failure, you would then be dipping into your 1/3 reserve for the overhead environment and still be ok based on the plan of that particular dive. Beyond that you're in a gas sharing situation.

To be very clear, I'm not bashing sidemount, for sure there is a place for it, I'm just questioning the current trend toward it in all cases when there is really no need and manifolded doubles offer a more simple and sometimes safer option. The more complicated the diving becomes, the more planning needs to be done, and with sidemount it's a little more complicated, I hope the training organizations are teaching that.

I didn't ask further but I assumed BM afforded longer range because it used all available real estate whereas SM wastes the space on the back. I'm just guessing though.

 

[Ragnar]

I didn't ask further but I assumed BM afforded longer range because it used all available real estate whereas SM wastes the space on the back. I'm just guessing though.

I was thinking about this and wondered what it would be like side-mounting twin steel 120's a stage bottle and deco.......question answered

---------- Post added December 19th, 2013 at 07:16 AM ----------

Can I quote you on that? LOL...

Sure!.....but I get to keep the Bond girl

---------- Post added December 19th, 2013 at 07:50 AM ----------

I agree. I've been cave diving for 20 years,and sidemounting for over 10 of that,and I for one like the simplicity of the backmount manifold system. I've had to move most of my diving to sidemount because I am either diving small cave,or off a canoe,but I like manifolded doubles. Backmount systems have lost favor,not because of utility,but because of market forces and peer pressure. I say peer pressure,because the same thing that drives people to sidemounting,is the samething that makes young kids buy Nike,Polo,Hilfiger. There isn't a time anymore that I don't here someone at a dive site being belittled-"when are you going to get those tanks of your back". I personally feel a well equipped, and well rounded cave diver is the one that can use both tools proficiently.

---------- Post added December 16th, 2013 at 10:45 AM ----------

Because of the craze I think sidemount is being looked at by a lot of people as the "next step" in diving as if it's an advancement over the "old" backmount, which of course is totally incorrect! (in most instances, including cave diving)

I'll say it again here, I am not cave certified........ended up in this thread because there was a similar conversation going on elsewhere and this thread is more appropriate.......so here are some of my reasons....

1. I mostly dive wrecks and the hallways and hatches are better navigated with backmount. Sure with sidemount you can swing a tank forward and make it, but I don't have to do anything to access normal places.

2. I believe in a having a back-up reg on a necklace and donating what you're breathing if needed. Sidemount creates all kinds of problems with this to the point it's a pandoras box, especially if having to donate a deco reg......what then do you switch to? Which tank would have a bungied reg? What would you donate when breathing off that one?......etc, etc, etc...

3. General hose routing and gas sharing issues to the point where sidemount is really more easily handled solo diving........no manifold needed no buddy needed

4. If doing any extended range diving, not only is it difficult to mount additional cylinders, it pretty much defeats the purpose of sidemounting in the first place. That and as all the additional gas is added the BC's I'm seeing on the market generally don't have enough lift anyway.

5. We've pretty much all agreed that feathering valves and switching regs is pretty much a "last ditch" effort, so with that in mind, besides the loss of gas created by a simple reg failure there is also the issue of redundant buoyancy control due to the BC and drysuit inflation coming from opposite regs.

Given all this I can't agree with karstdvr more, sidemount is a tool for getting into areas where backmount doesn't fit or possibly for someone who just wants to screw around on non deco open water dives, which is fine. In my opinion, all other diving is better served by the simplicity and redundancy of backmount.

 

[DevonDiver]

1. I mostly dive upright wrecks and the hallways and hatches are better navigated with backmount.

Fixed that for you, otherwise what you were saying was sheer nonsense

Cast your mind back many years to something you learned long ago...

Now consider what you learned then, in a new context...

2. I believe in a having a back-up reg on a necklace and donating what you're breathing if needed. Sidemount creates all kinds of problems with this to the point it's a pandoras box, especially if having to donate a deco reg......what then do you switch to? Which tank would have a bungied reg? What would you donate when breathing off that one?......etc, etc, etc...

Training answers these questions. None of them are difficult, most are the same as per backmount. If donating long-hose, rather than 'from the mouth' gives you a coronary, then you have two options; do a UTD sidemount course or decide sidemount is beyond your capacity.

There's plenty enough rookie technical divers progressing through training levels wearing sidemount nowadays. They do the same drills and skills...experience the same simulated scenarios, failures and pressure as backmounted trainees. There simply seems to be no evidence that they find it any harder whatsoever.

Having a belief in one approach does not constitute a problem with another approach. It's a preference. Believing there is a 'problem' with that other approach, simply because of that preference is dogmatic. Nothing more.

4. If doing any extended range diving, not only is it difficult to mount additional cylinders, it pretty much defeats the purpose of sidemounting in the first place.

Is this 'your' difficulty? Or are you saying everyone has difficulty?

At the very worst, a sidemount technical diver can attach deco/stages as per regular back-mount stage rigging. In which case, they're no worse off than they would have been in back-mount anyway.

Sidemount offers more flexibility to better trim/streamline those deco cylinders - and those potential advantages/improvement is where the current sidemount thinking is at.

... all the additional gas is added the BC's I'm seeing on the market generally don't have enough lift anyway.

As for lift, how much do you need? There's plenty of sidemount rigs on the market with ~40-50lbs. Check: A List of Modern Sidemount Diving Systems

5. We've pretty much all agreed that feathering valves and switching regs is pretty much a "last ditch" effort,...

Let's be clear - it's "last ditch" because proper gas planning and management makes it so.

At any stage in the dive, the diver should be able to lose the contents of one cylinder and return entirely upon the remaining contents of the other.

That principle applies equally to backmount (if the isolation valve needed to be closed) or sidemount.

The only difference is; the sidemount diver can still access that remaining gas in the closed cylinder through relatively simple procedures due to the convenient location of the valves. The backmount diver realistically couldn't.

....so with that in mind, besides the loss of gas created by a simple reg failure there is also the issue of redundant buoyancy control due to the BC and drysuit inflation coming from opposite regs.

How is that different to diving backmount?

If you close down a regulator, you lose the LPI if it's on that side. You can orally inflate; or you can use a drysuit fed from the other cylinder; or you can use a redundant bladder BCD fed from the other cylinder; or you can use an alternative form of redundant buoyancy, for instance, a lift-bag.

There are both backmount and sidemount redundant bladder BCDs on the market, if that's your thing..

Given all this I can't agree with karstdvr more, sidemount is a tool for getting into areas where backmount doesn't fit or possibly for someone who just wants to screw around on non deco open water dives, which is fine. In my opinion, all other diving is better served by the simplicity and redundancy of backmount.

Everyone is entitled to their own opinion. The ones you've expressed above just seem based on quite faulty premises... and that's just my opinion.

 

[nimoh]

I don't dive sidemount, and haven't done a dive yet where sidemount would have been necessary to proceed past a restriction. However, as they say, a picture is worth a thousand words, but this picture is worth 10,000.