Drawbacks of Sidemount, compared to backmount diving

[DA Aquamaster]

I have issues carrying AL 80s long distances as well as I have to lift them a bit to clear the ground rather than letting them hang on fully extended arms. *But* I have no issues carrying them suspended by the shoulder D-rings and towel bars on a Nomad.

One downside is that some tank changes make a big difference and can require some tweaking For example, AL 80s trim much differently and may require some bungee adjustment, stage kit adjustment and weight/trim adjustment, so the first few dives may involve some futzing that would slow down the gearing up process, but a dive boat is not a great place to work out those bugs.

 

[ajduplessis]

I don't SM ...yet. I have no knowledge on the subject but have vast experience with BM so please don't :gun: if I make some wrong assumptions. What I believe to be possible drawbacks to SM for me are the amount of gas carried. I dive with twin faber hp120/15litre cylinders giving me 7200 litre backgas (I think that is 240cft of gas??). I am not sure if you can do this with SM. I was told AL80's or steel 12litres (think hp100???). Is this correct. The only other drawback is that of workload switching between the cylinders every now and then. These are assumption and how I perceive SM are being done.

 

[CaveMD]

I don't SM ...yet. I have no knowledge on the subject but have vast experience with BM so please don't :gun: if I make some wrong assumptions. What I believe to be possible drawbacks to SM for me are the amount of gas carried. I dive with twin faber hp120/15litre cylinders giving me 7200 litre backgas. I am not sure if you can do this with SM. I was told AL80's or steel 12litres (think hp100???). Is this correct. The only other drawback is that of workload switching between the cylinders every now and then. These are assumption and how I perceive SM are being done.

Incorrect, "Someone I know" dove sidemount with galvanized low pressure 108's(equiv to HP140) filled to 4000(approx 160cuft gas each, just over 9000L total) with 14/60 trimix, 4 al80's of bottom gas/deco mixes and an al40 of oxygen.

"Someone I know" has done more dives than "Someone I know" can count off the top of "their" head with those lp108's filled to 4000 of nitrox and I know quite a few people who have used low pressure 121's in sidemount, which, when filled to 4000, hold 10300 liters.

I of course would never over fill a cylinder...

 

[shoredivr]

A buddy of mine uses two 130 cu ft which he was finding a bit big. I'm using steel 100s. You can stage mount other tanks, others have mentioned this either on this thread or the "Curious about sidemount" thread, I forget which.

 

[ajduplessis]

@CaveMD: Any cylinder can be overfilled, should they is another story. Let's stick to manufactures specs for this purpose . I don't think anyone teach/recommend filling LP's to 4000psi, do they?? BM divers can also 4 or 5 stages to further extend range/deco obligations, nothing new here.

I am here to learn more about SM because I have my own perceived views of it. I might even give it a go at some point in time, maybe not with overfilled LP's but something else. I first however need to understand its limitation if any.

PS: I don't see less gas as a limitation.

 

[Mike2Fst]

I don't SM ...yet. I have no knowledge on the subject but have vast experience with BM so please don't :gun: if I make some wrong assumptions. What I believe to be possible drawbacks to SM for me are the amount of gas carried. I dive with twin faber hp120/15litre cylinders giving me 7200 litre backgas (I think that is 240cft of gas??). I am not sure if you can do this with SM. I was told AL80's or steel 12litres (think hp100???). Is this correct. The only other drawback is that of workload switching between the cylinders every now and then. These are assumption and how I perceive SM are being done.

My usual sidemount setup is 2 steel HP 120s, going deeper than 200 I add 2 aluminum 80c and 1 53 aluminum for deco/stage, less than 200 I have 1 53 and 1 40 for deco/stage.

 

[Paul S]

I don't SM ...yet. I have no knowledge on the subject but have vast experience with BM so please don't :gun: if I make some wrong assumptions. What I believe to be possible drawbacks to SM for me are the amount of gas carried. I dive with twin faber hp120/15litre cylinders giving me 7200 litre backgas (I think that is 240cft of gas??). I am not sure if you can do this with SM. I was told AL80's or steel 12litres (think hp100???). Is this correct. The only other drawback is that of workload switching between the cylinders every now and then. These are assumption and how I perceive SM are being done.

I'm sidemounting with steel 12s at the moment, but there's nothing stopping me doing 15s. It's just I don't fancy carrying the weight of them on dry land. I'll give it a go sometime though.

I guess I could do 18s or 20s too, but I think I'd rather take a couple of stages.

 

[CaveMD]

PS: I don't see less gas as a limitation.

I was referring to this

What I believe to be possible drawbacks to SM for me are the amount of gas carried. I dive with twin faber hp120/15litre cylinders giving me 7200 litre backgas (I think that is 240cft of gas??). I am not sure if you can do this with SM. I was told AL80's or steel 12litres (think hp100???). Is this correct.

Which I was showing not to be accurate. An lp104 is roughly equivalent to an HP130, you can easily carry HP130's in sidemount, a friend of mine, Forrest, pretty much only dives with 104/130's unless it's small passage requiring smaller tanks.

 

[DaleC]

I think, when looking for drawbacks, one must first define the type of diving one is doing; otherwise the whole exercise gets hijacked by the exceptions.

From a rec perspective:

I can say that, having carried my two 72's BM and SM, SM is easier. Clipped off, the tanks transmit the load lower, directly along the center of gravity instead of higher up and out back from the center of gravity.

Initial hose routing does take a bit longer but the rig is easier to get into solo compared to BM where there is a lot of shrugging and heavy lifting from awkward angles or where a lost or trapped hose to the rear can cause one to have to remove the rig to resolve.

As for being a hazard on a boat, I don't get it. In my low profile harness I can suit up before the others, stand facing my two tanks that are already set up with regs, clip in the tops, route hoses and clip in the bottoms (still facing the tanks). Now I'm wider but I can wrap my arms around the tanks and guide them and see/feel if I'm going to bump someone or something (unlike BM where one cannot see what one is going to hit). Walk to the edge and jump in. I can see a narrow gate being a pain but how much more so than when BM with a stage or two clipped off.

Single SM, I could literally pick up my tank, clip the top off, hold it in my hands, put the reg in my mouth and jump off the boat, connecting everything once I was in the water.

As one who BM's ID's the gas issue is the same, a non issue.

So, for rec diving I see no drawbacks other than the initial futzing. Did I mention how much futzing I did with my basic BM single rig when I first started diving... everything is relative.

But really, if you're not harming others who cares. My buddy and I did a dive yesterday Him BM and me SM. We entered at the same time, dove the same profiles, saw the same things and enjoyed the same dive. Not once did his gear choice or my gear choice effect the quality of our dive.

 

[Dive-aholic]

If you mean double BM, then that is leaving out the bolting the backplate to the bands. If you mean single BM, then you are leaving out fastening the cam strap.

I am not sure anything but inexperience makes SM any more involved in terms of suiting up. And add in the fact that a SM divers can kit up without a bench or buddy, and its much easier.

I mean double BM, and how much time does it take to screw a couple of wing nuts?

And kudos to you if you can gear up in SM on land without a bench. Personally, I need a bench or a table if I'm putting my tanks on while on the boat.

---------- Post Merged at 10:49 PM ---------- Previous Post was at 10:47 PM ----------

Stage bottles are easier with sidemount.

Really? I see it the other way. Most BM divers have no issues with clipping on a stage. Most SM divers have to go through a learning curve to figure out how to top mount a stage. And most of them are still top mounting stage bottles that sit too high at the bottom.

I'm not sure I think the open water sidemount class is a wonderful idea, but that's just my opinion.

So how do you propose people learn how to sidemount?