lift capacity needed for cold, open water diving with side mounted doubles

[babycover]

I'm diving with dry suit all year around and what I found is more often than not, when i finished my dive,the 2 tanks usually have 300psi each. maybe a bit too low, but i rather be a bit negative when i'm at safety stop than positive.

 

[Kazeone]

Would anyone ever need more than 45lbs of lift diving sidemount in a wetsuit? My backmount doubble’s wing has 65lbs for obvious reasons mentioned earlier. Being new to sidemount the amount of lift needed = not so obvious. thanks

 

[rjack321]

Would anyone ever need more than 45lbs of lift diving sidemount in a wetsuit? My backmount doubble’s wing has 65lbs for obvious reasons mentioned earlier. Being new to sidemount the amount of lift needed = not so obvious. thanks

No because in a wetsuit you don't want to be carrying big steel tanks and lots of stages because you wont be able to swim all that up from depth with wetsuit compression...

In a wetsuit you will be using 2x al80s plus perhaps an al40 or al80 stage. That's about the max weight of gas you can safely carry in a wetsuit. 3x 80s is about 27lbs (11kgs) of gas which is reasonably held up with 45lbs of lift with some reserve to get your head above water.

 

[gextyr]

FWIW, I use an 18lb wing for single (HP100) backmount diving (wet or dry). That's about the smallest amount of lift I could find in a wing, and I still need some lead to be neutral. I wish I could find a smaller one. I typically use an aluminum backplate and a rash guard, because I live in FL, so the wing (and my love-handles - hah!) is my _only_ positive buoyancy. I love the 18lb wing. It is perfect. I can't imagine why anyone would want a 30-45lb wing for single tank.

Now, for sidemount with stages, I am currently using a Hog (nominally 43lb) with the top bungees partially cinched down. The lift is more than adequate when diving a wetsuit, with two HP100s and two AL40s. I don't carry any lead when diving wet, and it works out just right. When I first got it, I cinched down the top all the way, and it was just BARELY enough lift, so I loosened up the top a little to give me a few more lbs of lift.

During my the TDI sidemount course, I was required to dump all air from the BC, and keep my head above water for a few minutes - with a full set of gear (2 full steel cylinders, 2 full aluminum cylinders, regs, reels, etc. - only wearing a 3mil wetsuit - in fresh water.) It wasn't easy, but it was doable... The point is, in an emergency (complete wing failure), I know I can swim my rig up, get to the surface, stay on the surface, and if necessary, casually start ditching cylinders. In a drysuit, I would be wearing ditchable lead, so if my wing failed AND my drysuit flooded, I imagine the scenario would be exactly the same, except it would include me ditching lead at some point. I don't use drysuits all that often, so I feel like I'd need to do some failure drills to be confident.

I suppose someone with less natural buoyancy (aka love handles) might need more lift than me... but I have always been flabbergasted at the amount of lift people think they need. Whatever you decide to do - just make sure you practice with your kit. Make sure you can swim it up with an empty wing, and make sure you can stay on the surface.

 

[almostDIR]

post removed, did not notice first that this was sidemount topic and commented from bp/w POV

 

[W W Meixner]

so i have been doing a substantial amount of reading online about different side mount rigs available and there are a few i am looking at. however, some of them are described as being for warm water diving only, due to the relatively low lift capacity. "they" say that due to the extra weight we need to carry for cold water (because of dry suits, steel tanks etc) that the lift capacity is too low. and everything i have read about choosing a proper sized wing seems to support this thought.

i am confused by this. let me explain why. then you can point out what i am missing and why i obviously have no idea what i am talking about.

i try to weight myself (no matter what type of tank or gear i am wearing) to be neutral (or slightly negative) at 10 or 15 feet with low gas (maybe 500psi if max is 3000psi) and my BC emptied. so at this point obviously the lift capacity is a non issue as i am neutral. so when do i need to add gas to the BC ?? and how much lift do i really need ?? i would need to consider that when full (as opposed to having 500psi) each tank would have maybe 5lbs more gas in it. if diving doubles, thats about 10 lbs. so i need at least 10lbs lift in my wing to counter act that extra 10lbs of gas at the start of a dive. i also need to consider that i want to be able to float comfortably on the surface with my head out of the water. i have seen it mentioned several times online that an average head with a hood on it, adds about 10lbs negative when above the water. so if i use that as a rough guess, that means i now need 20lbs of lift in my wing (10lbs gas + 10lbs for my head) at the start of the dive to be able to float comfortably. so if i had a wing with 20 to 25lbs of lift, i should be fine right ?? i have no intention (at this point) to carry added tanks beyond the two. i don't have to worry (as back mounted double divers do) about whether my wing will float my rig if i take it off. so what am i missing.

no matter whether i am in salt, fresh, diving wet, dry, cold, warm, using steel or allum tanks, i will always be weighted close to neutral with low gas in the tanks at my safety stop depth. the only lift i seem to need is the extra gas weight plus keeping my head above water. apart from that, i can see needing some extra lift possibly for wet suit compression (if i wore a wet suit), but i dive dry. so any compression will be offset by me adding gas to the suit.

now if i was looking at a worse case scenario, and had a flooded suit at my deepest part of the dive, i would be dumping lead anyway to hopefully do a controlled ascent. i would not rely only on my wing lift to get my back to the surface. and if my wing fails, well then the lift capacity becomes irrelevant.

so lets hear it. am i crazy or what ?? what am i missing ??

Rick...

I'm not sure if I'm muddying the water or being of some help...

I dove HP steel 100 PSI doubles for years...and dove with a dry-suit almost full time...

Never used any additional ballast...didn't even own any...

I had two OMS wings...a single 60 Pound lift Ocean...to wear with the dry-suit...and a double 94 pound lift Ocean...when I occasionally did dive with a wet suit...

Primarily cold water...with annual North Carolina charters...where my exposure protection is Carhartt Bib overalls under a long sleeve rash guard...and again...double 94 pound lift Ocean Wing...no additional ballast...

Now with the rebreather which is maybe 60 pounds loaded...with the dry-suit...and 55 pound lift wing...I carry four shot packs...two 6's...and two 4's...20 pounds total...

Hope this helps...

Best...

Warren

 

[Kazeone]

No because in a wetsuit you don't want to be carrying big steel tanks and lots of stages because you wont be able to swim all that up from depth with wetsuit compression...

In a wetsuit you will be using 2x al80s plus perhaps an al40 or al80 stage. That's about the max weight of gas you can safely carry in a wetsuit. 3x 80s is about 27lbs (11kgs) of gas which is reasonably held up with 45lbs of lift with some reserve to get your head above water.

Thanks a bunch. I appreciate it.

 

[Schwob]

now if i was looking at a worse case scenario, and had a flooded suit at my deepest part of the dive, i would be dumping lead anyway to hopefully do a controlled ascent. i would not rely only on my wing lift to get my back to the surface.

Could you all reflect on that particular aspect a bit more?
Why plan (or not?) lift capacity such that one needs to drop weight if the wetsuit floods at depth early in the dive?

 

[rjack321]

Could you all reflect on that particular aspect a bit more?
Why plan (or not?) lift capacity such that one needs to drop weight if the wetsuit floods at depth early in the dive?

Because a drysuit& undergarment in genuinely cold water, takes a ton of lead to sink. Which means a giant wing, and in sidemount the giant wing is even harder to control than in backmount wing and ends up bulging up all over. If its undercontrol with bungies at normal diving volume, then if you try and pump it full with 30lbs more lift the OPV pops. So no a 60lb sidemount wing a) isnt made and b) would be dreadful to try and dive if it were made.

Fortunately drysuits leak but rarely catastrophically flood. But if the neck seal delaminates from the suit (I have seen that happen) you are flooding really bad, like 20+lbs of loft gone. And instant cold water breathing shock.

 

[Schwob]

Because a drysuit& undergarment in genuinely cold water, takes a ton of lead to sink. Which means a giant wing, and in sidemount the giant wing is even harder to control than in backmount wing and ends up bulging up all over. If its undercontrol with bungies at normal diving volume, then if you try and pump it full with 30lbs more lift the OPV pops. So no a 60lb sidemount wing a) isnt made and b) would be dreadful to try and dive if it were made.

Fortunately drysuits leak but rarely catastrophically flood. But if the neck seal delaminates from the suit (I have seen that happen) you are flooding really bad, like 20+lbs of loft gone. And instant cold water breathing shock.

Thanks. You are driving home that thought quite well!
Maybe bring a small lift bag then... or is that condidered not good form and dropping weight it must be?