SM regs: XTX50 vs Dive Rite vs ??

[ams511]

FWIW, Dive Rite XT is a balanced regulator - i.e. delivers consistent gas flow regardless of the pressure of gas left in the cylinder and depth. Apeks XTX50 is an over-balanced one, which progressively increases intermediate pressure as depth and gas density increases.

"There are several manufacturers currently marketing high-performance OB regulators, and a growing number of cave divers are using them as their default choice. " (RAID Cave 1 - Equipment manual.)

"Overbalancing" is a design defect that marketing departments have tried to turn into an attribute. Theoretically, a first stage should provide a stable IP throughout both the ranges of depth and tank pressure. There should not be any change in intermediate pressure at all. If you are diving with an unbalanced second stage the increase in IP could cause it to free flow if it was tuned to the edge. This is not something you want on a deep dive. Apeks can get away with overbalancing because all their second stages are balanced which reduces the probability of free flow.

My gut feeling on this it that it is due to the way Apeks adjusts for depth. Apeks uses a mechanical link (the hydrostatic transmitter), while in the past others used some type of oil. For example, in the Conshelf Supreme, which used unbalanced second stages, Aqualung used oil to transmit depth information to the diaphragm. The oil was messy when it leaked so it was abandoned. Many regulators such as Dive Rite, Hog, Hollis, etc. are based on the Apeks design (if not an outright copy) so they are overbalanced also because they have the same defect.

Also why would overbalancing be needed? Divers who dive close to and beyond traditional recreational depth limits are going to be using some type of helium mixture which is lighter than air and has different flow characteristics.

 

[CptTightPants21]

"Overbalancing" is a design defect that marketing departments have tried to turn into an attribute. Theoretically, a first stage should provide a stable IP throughout both the ranges of depth and tank pressure. There should not be any change in intermediate pressure at all. If you are diving with an unbalanced second stage the increase in IP could cause it to free flow if it was tuned to the edge. This is not something you want on a deep dive. Apeks can get away with overbalancing because all their second stages are balanced which reduces the probability of free flow.

My gut feeling on this it that it is due to the way Apeks adjusts for depth. Apeks uses a mechanical link (the hydrostatic transmitter), while in the past others used some type of oil. For example, in the Conshelf Supreme, which used unbalanced second stages, Aqualung used oil to transmit depth information to the diaphragm. The oil was messy when it leaked so it was abandoned. Many regulators such as Dive Rite, Hog, Hollis, etc. are based on the Apeks design (if not an outright copy) so they are overbalanced also because they have the same defect.

Also why would overbalancing be needed? Divers who dive close to and beyond traditional recreational depth limits are going to be using some type of helium mixture which is lighter than air and has different flow characteristics.

No.

The overbalancing isn't so much a defect as it is a byproduct of a diaphragm design. As tank pressure decreases, a larger amount of air (higher IP) is needed to close the high pressure seat. The reverse is true for piston regulators, as tank pressure drops, less air (lower IP) is needed to close the high pressure seat.

 

[ams511]

No.

The overbalancing isn't so much a defect as it is a byproduct of a diaphragm design. As tank pressure decreases, a larger amount of air (higher IP) is needed to close the high pressure seat. The reverse is true for piston regulators, as tank pressure drops, less air (lower IP) is needed to close the high pressure seat.

First, overbalancing as described in the product literature has nothing to do with tank pressure. All it says is that as depth increases then IP increases.

Second, the balance chamber applies tank pressure to both sides of the valve so tank pressure does not affect the operation of the valve. That is unless tank pressure is less than IP.

Third, balanced diaphragm regulators have been around since the days of the Royal Aquamaster double-hose regulator (maybe even before). I don't remember the term overbalancing coming up until the last 10 years of so. In the past, Aqualung certainly did not mention it, I don't remember other manufacturers mentioning it either.

Fourth, whether overbalancing is a design defect or a byproduct is a matter a semantics. What is not a matter of semantics, is that IP varying with depth is not desirable, no matter what the marketing literature says. I am not sure if other regulators exhibit this same trait, if they don't then it is not a by-product but a defect.

 

[tbone1004]

No.

The overbalancing isn't so much a defect as it is a byproduct of a diaphragm design. As tank pressure decreases, a larger amount of air (higher IP) is needed to close the high pressure seat. The reverse is true for piston regulators, as tank pressure drops, less air (lower IP) is needed to close the high pressure seat.

You are confusing overbalancing with overcompensation. What you are describing is how the balance mechanism works and which way it trends *i.e. IP as a direct or indirect function of tank pressure*.
What the over-balancing that we are discussing now is an overcompensation for depth that is called "overbalancing" by the marketing departments of the reg manufacturers. What we are describing is how the IP increases at a higher rate than ambient pressure. i.e. while it should always be say 135psi over ambient pressure, when you get to 100ft it may be 138psi over ambient pressure, or at 200ft it may be 143psi over ambient.
Someone did an experiment with Apeks and the overcompensation was about 3psi for every 33ft.
This phenomenon occurs because the silicone diaphragm for the environmental seal is larger than the spring carrier. If they were the same diameter, then it wouldn't occur. The phenomenon does not occur with the environmental seal removed

 

[stuartv]

Then you've got folks like Steve Martin diving a Mexico/Razor/Stealth rig using loop bungees with fifth port inflators.
And you've got folks using two 7' hoses, both right handed seconds.

Basically what it boils down to is that sidemount is all about being mission and user specific as necessary.

Rob Neto has a pretty good book on sidemount, and Andy Davis website is a wealth of knowledge. If you want to read up more, those are good places to start, and just keep lurking through old threads.

I have Rob Neto's book and have read it twice. It seems to me to be a book that is perfectly adequate to explain SM to people who already know SM. For people who don't already know SM pretty well, I don't think it's really much help.

Also, I am using a Razor/Stealth-style rig (Apeks WSX-45). My regs are DR XTs, so I have the option to use a 5th port. But, I don't. If I used the 5th port, the hose would be coming straight out and poking me in the side. The left side inflator hose coming out of the swivel turret points down along the cylinder and then loops back up to the power inflator. Thus far, the only real use for a swivel turret at all is the right side, so the long hose can fully deploy to an OOA diver without the potential for a sharp bend in the hose.

FWIW, Dive Rite XT is a balanced regulator - i.e. delivers consistent gas flow regardless of the pressure of gas left in the cylinder and depth. Apeks XTX50 is an over-balanced one, which progressively increases intermediate pressure as depth and gas density increases.

"There are several manufacturers currently marketing high-performance OB regulators, and a growing number of cave divers are using them as their default choice. " (RAID Cave 1 - Equipment manual.)

Why is this good? If my 2nd stage can accept a higher IP at depth without freeflowing, why would I not want it to have that same higher IP at shallower depths? The cracking pressure setting on the 2nd stage is going to crack at the same IP, regardless of gas density, right? If the cracking pressure is set so it doesn't freeflow at depth, with an IP of 143psi, then what's the result at a shallower depth with, say, an 138psi of IP? The 2nd stage is just going to be harder to breathe when shallow, right? It seems like what you would really want is an IP that stays the same at all depths and then you can set the 2nd stage cracking pressure for that, so it will breathe as easily as possible at all depths.

I can compare DR to XTX100, which should be the same as XTX50. Both new from the shop (ts-heinemann for apeks, DGX for my DR set), the DR set breathed noticeably harder, on the surface and underwater.
On the other hand, it's still very much acceptable, even at 180' (55m) on air. It gave too much air to the liking of my brother. I also find that DR


I wouldn't listen too much to some others here about "you absolutely don't need a 5th port". It doesn't cost much to have it, and then it's there when you need it eventually later on. Loop bungees are very much used with a 5th port by the way.

I use loop bungees and haven't yet found a use for the 5th port. My tanks are actually right at my side, so a hose coming out of the 5th port would poke me in the side. How do you configure your tank/valve/hoses so that the 5th port is useful? I have been thinking of moving my tank leashes so that the tanks are rotated a little bit, where the 5th port would be pointing down a little bit, directing the hose to go just in front of my ribs, instead of straight into my side.

All that said, I would still only purchase a 1st stage that has a swivel and a 5th port.

Regarding your comparison of DR to XTX, if you bought a new Porsche and it was no faster than a Honda Civic, and it turned out it happened to come from the factory with half the spark plugs not installed properly, would you discount all Porsches as no better than a Honda Civic?

I bought my DR XTs from DGX. I learned after a while that they had indeed come from the factory/retailer set up with a higher cracking pressure than what I ultimately found myself to prefer. Initially, they did not breathe as well as my Hollis regs. Since I've had them adjusted to my preference, they breathe very well (as do my Hollis regs).

DGX sells a complete SM set of DR XT regs, with hoses, including LP and drysuit inflators, for $840. When you can get that setup for that price (whether from DGX or DRiS), why spend $500 or more on a single reg? The only thing about the DGX setup is that their web page says the LH reg hose is 22". I would definitely have to call them about that. I wonder if that's a copy-and-paste error from their BM doubles setup. 22" is WAY too short to work for me and I don't see how it would be long enough for anyone.

 

[Schwob]

I have Rob Neto's book and have read it twice. It seems to me to be a book that is perfectly adequate to explain SM to people who already know SM. For people who don't already know SM pretty well, I don't think it's really much help.

...
Might you you have a book or information source recommendation that you think might be good for the latter group?
...
I in no way have figured it out, nor do I know any of the aspects too well at all. Trying to get there...
Basically it looks to me like: close to infinite variability in how exactly you get there, but the object being that you get two tanks tucked in close to your sides, the weighting and balancing sorted out right and the plumbing sorted out in a useable organized way so you can breath out of either in that position and can also pivot the tanks forward if you had to for a short period of time, ... some consideration for what you might want to do if they or one of them becomes floaty at the tail and how exactly you do that depends in not insignificant parts on your geometry, the stuff you plan on using (Al80 or LPs or HPs... Drysuit or wetsuit... or all of the above... and maybe who you try to emulate, who you listen to and how much you want to fiddle before you like where you are at with your set-up.
So, if it requires some amount of fiddling no matter what then some good advise along the lines of:
"These are the very few important items to fiddle with because and the rest is minor fine-adjustments and flavorings that are less important to worry about initially..."
The diving itself seems rather straight forward. Which kind of regulator to me does not matter any more than for any other dive - I am not sure I grasp why it should... I'll just use what I have (happen to be Apeks) and only bother with something else if I really find a real reason that would matter to me.
5th port - how to use it and why and why not out the side... Yeah, I'd like to know too...
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The whole fiddle with it until it works for you aspect (my view) ... I don't mind it at all really, although I can see how the different results could be a nightmare for tech dive teams... And yes, if there was a proven good recipe on how to start the fiddle sequence, I'll be all ears... but I have to say... short of having a shot at some sort of instructor guru (@DevonDiver : "Hi Andy, a couple of months of Philippines next (I only wish...)") I rather fiddle for a while and maybe save the SM instructor money for tech instruction. That's my thinking at least right now.
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Is it dramatically flawed? Will I take up bad habits without noticing myself they are bad habits ... habits that my local quarry instructor would really have pointed out and corrected? Don't know... maybe yes... but then, a SM class does not really seem to cover all that much - or? What does it cover that one cannot work up to ?
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What does it cover that although one can work up to it is much more convenient to pick up in class? Why?
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Is a SM certification card required anywhere to be allowed to dive SM? Anywhere?

 

[tbone1004]

@stuartv you're using the swivel on the left side to get the hoses to come up at the optimal angle. It's not a huge deal, and while it is a passive use of it since it shouldn't move under normal diving circumstances. It becomes a bit more active during double bottle off restrictions.

@Schwob unfortunately not for a book. The best place for sidemount is still to find someone that actually dives sidemount and start asking questions. Thankfully there are a bunch of those around.

Fiddling is inevitable if you want your gear to look perfect. Sidemount is a variable system because the tanks are rigidly fixed to your body like in backmount. Pros and cons. For open water, getting "good enough" is real easy, heck for cave diving is pretty easy. Getting it perfectly ironed out is something that every real active sidemount diver is constantly chasing. Sidemount being a dynamic system is going to be very gear and individually dependent. Where is the specific CoB on the diver, what kind of tanks, what kind of exposure protection, etc etc. and that is different from diver to diver. There are certain guidelines as mentioned above that will get you "close enough" but not perfect.

5th port is a personal preference thing. Biggest advantage on the right side is that your long hose can swivel forward during single file air shares independently of a drysuit inflator. If you only dive wet, you won't have that inflator, and if you dive recreationally with a 7' hose, you probably won't be fully deploying that hose so it doesn't really matter. On the left, i think it's just a nitpicky thing but I actually find it really annoying to have those short inflators where I go for a bottle off restriction as it puts rotational torque on my inflator which I find uncomfortable. It is also not really compatible with my bottle position and I haven't messed with it in probably 3 years since I didn't have a 5 port first stage. I have some MK25's now and will be messing with some bottom port configurations on my next dive trip in 2 weeks, so I may change my mind.

Fiddling can pose somewhat problematic in a dive team if you have different philosophies on sidemount. I.e. a Toddy diver with a Florida diver would be problematic. Toddy is AL only, and bottle donation. Florida is long hose with steels. Toddy can take a long hose from Florida, but can't give up that bottle if Florida needed to share air.
UTD poses no real issues in compatibility with Florida because long hose sharing is still feasible in an OOA situation.
@victorzamora have similar but different philosophies with our gear configuration, but have no issues diving together or understanding our gear. Our tanks believe it or not are actually interchangeable if we wanted to and while trim may be a bit weird, it would still be diveable. Deco/stage bottles are somewhat different with him using turrets and shorter hoses vs. my using fixed first stages and longer hoses, but they're still compatible. The key is to go through pre-dive checks and understand any strange nuances to gear configurations that are going to be really different I.e. if someone is using a butt pouch vs. hip pockets for storage of stuff, or line cutter placement. Everything else isn't going to be passed from one diver to the other, so it shouldn't really matter.

A sidemount class is great if you want to skip the gear tinkering process, don't have access to a mirror/camera to self-evaluate, or want to rapidly expedite that process provided that the instructor knows what they're doing. I saw some sidemount divers this weekend in a gear config class that was positively terrifying and it seems that that is what most of the sidemount instruction looks like especially if the instructors aren't active cave or wreck penetration divers. Again, it may work fine for open water and be "good enough", but there is a massive difference between what will get you by in that environment and what will get you through a true sidemount restriction safely. Remember that those of us that have been diving sidemount before the agencies really got into making money on it had to figure it all out on our own.
We all went through evolution and many of us without training because it wasn't available at the time
Early sidemount before I had seen any pix or reflections of myself. Set up out of the box with the bungees similar to the Razor, etc. No loop bungee kits out yet from Edd, no ring bungees yet from Dive Rite, etc etc. Working with what we had.

Slightly later in 2010. This is with ring bungees and pulled up a bit tighter

skip a few to 2016 and the tanks are nice and flat, pulled back behind my arm pits, etc. with loop bungees and slow but sure evolution.

no certifications required to dive locations unless Europe has some training requirements for privately owned sites. May be a few in the US, but none that I'm aware of. There are some caves that are restricted to sidemount only, but if there was a cert requirement there would be a bunch of us certifying each other over the phone to get the card because we needed it.

 

[rick00001967]

i can tell you when i was in playa del carmen the dive shop i was going to use had to see my sm cert. but i have been to two other destinations using sm and neither shop asked.

 

[Marie13]

I'll take the SDI (rec) SM class as I want to get everything as squared away as possible from the beginning. Instructor also dives the SMS75 I just bought. I dislike endless tinkering without feedback if I'm getting it correct.

 

[stuartv]

Might you you have a book or information source recommendation that you think might be good for the latter group?

Sorry, but I do not know of any concise guide. However, probably the closest thing, that I know of, is Steve Martin's site. But, you will have to pay to get anything more than his review of the Apeks WSX-25 rig (which I still found to be pretty informative, with a number of little nuggets). I did not pay, so I have not seen his for-pay SM videos, so I can't say how comprehensive they are. I.e. will they prepare you to choose the right rig based on your plans (wet vs dry, steel vs AL)? The right bungee system? Or does his stuff just teach you how to do it the way he does it? I don't know and I haven't yet been willing to ante up the USD$150+ to find out.

sidemounting.com |

I figured out what I have by reading here, watching videos on YouTube, looking at some other websites, and watching Steve Martin's video on the WSX.

It seems like the people who actually know the stuff mostly either want to be paid, so they don't answer a lot of the questions posted here, or they don't have the time to give it away for free. Don't get me wrong. I don't have any problem with an expert wanting to be paid for sharing their expertise! But, it would be nice if there were a good book that really explained it well for divers who know nothing about SM. From what I can tell so far, it's not black magic. It's not even rocket science. Someone who writes well and has a comprehensive understanding of sidemount could write down how to do it just as well as someone else could explain it in person. I just don't know of any book yet where someone has done it. And once you actually understand it, you ought to be able to work out your own actual configuration with no more help than possibly a buddy to look at your and/or take photos or video.

It seems to me that the real keys are two simple things: One, get a buddy to get in the water with you - ideally someplace shallow enough to stand up - and video you. If not video, then they can simply tell you whether you are flat and your tanks are in the right position. Then adjust to get the tanks where you want them and your trim where you want. Anyone with basic diving competency should be able to identify flat trim. There are pictures even in this thread to give anyone an idea of what the tanks should look like.

And two, look around here and find a video on the basic sidemount skills then go practice them. Being able to switch regs, donate air, etc., are important and having a checklist of the fundamental skills will make sure you practice all the right things.

It seems to me that once you have the tanks positioned right and your trim right (both of which you probably need a buddy to help you with) and you work out what hose routing and hose lengths you want (which you can probably do on your own), and you know what the fundamental skills are and have practiced them, you should be set to go do some SM diving.

But, being not an instructor of anything and only done 2 SM dives (in the pool, no less) myself, I could be totally wrong....