Sidemount Diver Ballast and Weighting

[CGE925]

New diver here, very seriously considering transitioning from BM to SM. I currently dive up north here in Canada in a drysuit, Halcyon BP/W and single AL80. I require about 30lbs of ballast split between the BP/W and a weight belt. When I add up all the weight I have to carry to and from the water it easily exceeds 90 lbs, and I have trouble carrying that much on my tired old legs, especially when water entry is dodgy. Even donning the fully loaded rig is murder, hence my interest in sidemount. I was on the Conestoga wreck in the St Lawrence this past weekend and two of the others were in SMSs; they looked SO much more relaxed than I was.

I've started doing a lot of reading and research, and one area that I can't find much detail on concerns weight configurations. I'm leaning towards a basic system, for simple non-overhead diving, that can be used with everything from my drysuit configuration to a dive skin down south on a vacation. I like the looks of the SMS75 (the SMS100 seems overkill for what I'd do with it) and am leaning towards buying while DGEx has them on sale.

How does one determine their weight requirements in an SM configuration? In the BM world, a simple "float at eye level" weight check works pretty well, but does that apply to SM? Would I require about the same amount of lead were I to SM in a drysuit? If I need less (and I'm hoping so), what are the technical reasons behind the decision.

Thanks in advance...

Jeff

 

[00wabbit]

Look up balanced rig to learn about weighting.

Basically you you want to be neutral at 15ft with no air in the bc or drysuit. Then you should be able to swim up your rig.

With doubles lyou will enter the water very negative due to the double capacity of air you are carrying. You need to have enough lift to support this and your drysuit if it should flood.

You out also want redundant lift. For instance your drysuit and your bc. Or a dual bladder bc etc etc.

to to get some of that lead off your body you should look at steel tanks that are more negative.

Im in a big floaty guy but with my double steel tanks in saltwater I only need 10pounds additional lead. This is easily carried on my back.

Once you get into these systems you will most likely be diving without ditchable weight.


I dialed in my sidemount weight by going to a pool with my tanks at 700psi and sitting my lead on the bottom and picking up lead as needed to sink.

 

[decompression]

Weighting for SM is similar to BM, but do not factor in the neg (if neg) weight of the tanks as they can be removed/shared unlike BM. The balanced rig calculation works in SM as well, add up all positive and negative then determine lead requirement to make you neutral (the weight of the gas carried will be compensated by the BCD). You may require slightly less weight due to the loss of the manifold but it will still be similar. When you add up all the stage rigging and stuff it's still close. For cold water/drysuit SM I use a SS backplate with a UTD 50# wing. There are lots of options to place lead, I use about 30-38 lbs depending on tanks.

Frederic Page is a good instructor in Montreal, he can answer a lot of questions for you. fred@unifiedteamdiving.com


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[CGE925]

Weighting for SM is similar to BM, but do not factor in the neg (if neg) weight of the tanks as they can be removed/shared unlike BM. The balanced rig calculation works in SM as well, add up all positive and negative then determine lead requirement to make you neutral (the weight of the gas carried will be compensated by the BCD). You may require slightly less weight due to the loss of the manifold but it will still be similar. When you add up all the stage rigging and stuff it's still close. For cold water/drysuit SM I use a SS backplate with a UTD 50# wing. There are lots of options to place lead, I use about 30-38 lbs depending on tanks.

Frederic Page is a good instructor in Montreal, he can answer a lot of questions for you. fred@unifiedteamdiving.com


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Thanks for the confirmation, looks like I'll still be lugging around quite a bit of lead. I've decided to ditch the weight belt and try a DUI weight harness to carry the weight on the shoulders instead of the hips. Still, not having to carry around 60+ lbs of tank and BP/W and hoist it onto my shoulders will be a blessing.

 

[tbone1004]

If you need 30lbs of lead, you need the SMS100 for safe buoyancy in open water. Remember, your head weighs approx. 10bs and you need to keep it above water. 20lb of lead *remove 5lbs switching to twin steels* + 20lbs of tanks *average steel tank full plus regulator is about 10lbs negative when full* +10lbs of head is 50lbs so you are cutting it close with the SMS100 on total lift, SMS75 at 40lbs of lift just isn't going to cut it, especially with AL tanks. You have a drysuit so that helps and gives you some lift redundancy. Remember that most wings for drysuit steel doubles are around 60lbs of lift for use in open water where you need that extra lift to keep you above water.

Diving aluminum tanks in your situation is definitely the wrong way to go about life. Going to double LP50's gets you 20 cf more gas, takes 5lbs off of your weight belt compared to a single AL80, and the pair of 50's weigh as much as a single 80, so you don't add any extra weight on land.

Diverite and Hollis both have weight plates for the Nomad and SMS75/100 and that would be your best bet for sidemount. Weight belt would add too much weight on your torso and would put you in bad trim so the weight plate allows you to put the heavier weights closer to your head and move down from there.

good luck

 

[Sidemount_Stu]

I think moving to steel tanks would be the way forward for you. If you make the decision for open water diving that you won't be handing off a tank then you can safely include the cylinder weight in your personal weighting. Unless you are doing tight space advanced wreck penetration or cave diving with small restrictions, you shouldn't need to hand of your tanks anyway. I use 2 x 12l steel tanks and with my xdeep stealth harness I only need 2kg weight for cold water Drysuit diving. It's incredibly comfortable and relaxed too!
Choose your configuration in the diving you intend to do, as this will influence inclusion or not of tanks in your personal weighting plan.

 

[oreocookie]

Jeff, between a single BM AL80 and sidemount AL80, I need more weight because I'm weighting for two near empty tanks instead of one. At some point I'll switch to steels to drop a bit of that weight.

I tried on an SMS75 last week and to be honest, the SMS100 is, in my mind, the more comfortable of the two. If you want to see one before you buy, we can show it to you next time you come in to get your tanks filled (and I'll pretend I didn't read your intention to buy online). We've pretty much always got at least one person working who's able to talk about sidemount.

Liz

 

[CGE925]

Jeff, between a single BM AL80 and sidemount AL80, I need more weight because I'm weighting for two near empty tanks instead of one. At some point I'll switch to steels to drop a bit of that weight.

I tried on an SMS75 last week and to be honest, the SMS100 is, in my mind, the more comfortable of the two. If you want to see one before you buy, we can show it to you next time you come in to get your tanks filled (and I'll pretend I didn't read your intention to buy online). We've pretty much always got at least one person working who's able to talk about sidemount.

Liz

;0) As far as tanks go, I'll probably stick with the AL80s for now and carry the extra weight, while I absorb the four figure cost of the new harness and two regulators I also need to buy. I also tried on the 75, but didn't try the 100 yet, and it seemed fine, but I am reading a lot of commenst that the new 75 "fixes" a lot of the shortcomings of the older 100. As to buying online, the price instore when I was in yesterday, for the 50, 75 and 100 are, surprisingly virtually identical, but I can get the 75 from DGEx on sale for $160 less. That being said, your price for the 100 IS good, so I may go that route, once I find a buyer for my now superceded Halcyon Infinity. I have to research the 75 vs 100 differences first. For now, I'll be doing the SM course with Gary in rentals.

 

[tbone1004]

call Edd Sorenson and do yourself a favor through all of this process. He'll help you immensely in making sure that A. he doesn't get undersold because he hates that, but b. and more importantly that you get the right gear you actually need

 

[Dhboner]

I just made the switch to sidemount. In my backmounted set-up I had two AL80's and when diving dry I needed the 6lb steel backplate, a 12lb V-weight and another 10lbs in weight in harness mounted pouches. For sidemount I have switched to steel 100's and now I dive my SMS 75 with no additional weight.

Bob (Toronto)