Best guess, will I be too heavy with this tank?

[certainmisuse]

I say "guess," because a proper weight check should be performed, but I need the guess for an initial purchase. Background: I only plan to do shallow warm water diving in the future. Despite that, I have a BP/W setup with stainless steel backplate, because I want to minimize lead on the waist. Now, I'm looking for a tank to use in the pool mostly, and I would like it to be light in mass (out of water) because I'm having some back trouble at the moment. I currently like this steel tank, but at -7 lbs full buoyancy (in salt), I'm worried I will be too heavy with only a 25 lb wing. Using the excel calculator that some folks use for estimation, I have some lift to spare, but I'm cutting it close. Also, I could throw on my 3 mm wetsuit to help add a bit more positive buoyancy if need be. What say you? Another option is something like this Al tank, but I prefer the steel if possible given that it's lighter (out of water) and slightly larger air capacity, the money difference is not a major concern.

Side note: LeisurePro should really include a bouyancy table for tanks that are sold together using a drop-down menu of options. A range of values (minimum and maximum) doesn't do much good if you are buying a tank that is not one of the two extremes.

 

[kelemvor]

I assume you're talking about the FX71DVB? It's only -1.4lbs empty. How negative is your steel plate?

Personally, I've always dived wings that are bigger than I need. I don't get the streamlining that many rave about but buoyancy is a non-issue. I got a freedom plate last year and I'm going to experiment with smaller wings this year. Therefore, I'm curious to see what those more experienced with small wings have to say in answer. I know I'd be nervous diving a 25 with steel plate and tank. That doesn't mean it will be a problem though.

Do you have any backup buoyancy options? Decent sized dsmb maybe? drysuit?

I'm pretty sure all the DIR types tend to eschew the use of steel tanks. Expect to see that in the responses. I'm not saying they're right or wrong but generally they seem to have a strong preference for AL from what I've seen.

 

[tursiops]

I'm pretty sure all the DIR types tend to eschew the use of steel tanks. Expect to see that in the responses. I'm not saying they're right or wrong but generally they seem to have a strong preference for AL from what I've seen.

This sounds backwards, except for stage/deco bottles.

 

[1atm]

I think thats very hard to say, with the limited info you have given. Having some more info about a known configuration that has you properly weighted (tank, plate, weights, suit, fins, regs, ...) would allow some degree of extrapolation, but even then it would be hard.

But some food for thought, because you are really asking two questions here:

1. Will you be able to set this up as a balanced rig, ie get close to neutral with empty tanks so you can hold a stop at the end of your dive, and be able to swim up a full tank in case you lose the wing
2. Does the wing have enough lift to make you neutral with full tanks at depth

Regarding #1: this depends on your body ... an average person of normal weight (european definition ...) would be arguably close to neutral in only a swimsuit. Some folks might be a bit positive, some a bit negative, but probably not much. That as a given, adding steel plate, steel tank, regs etc without anything to compensate would make you very negative. So either go drysuit, or reduce weight (Al tank, Al/carbon plate, etc). But this is theory, only a weight check would tell
Regarding #2: if we assume you yourself are neutral-ish, total of full tank, steel plate etc comes out <25 so alone the wing would have enough lift, but not enough to support you and a assist a buddy with failed wing. With brings us back to #1, balanced rig

 

[certainmisuse]

I assume you're talking about the FX71DVB? It's only -1.4lbs empty. How negative is your steel plate?

Personally, I've always dived wings that are bigger than I need. I don't get the streamlining that many rave about but buoyancy is a non-issue. I got a freedom plate last year and I'm going to experiment with smaller wings this year. Therefore, I'm curious to see what those more experienced with small wings have to say in answer. I know I'd be nervous diving a 25 with steel plate and tank. That doesn't mean it will be a problem though.

Do you have any backup buoyancy options? Decent sized dsmb maybe? drysuit?

I'm pretty sure all the DIR types tend to eschew the use of steel tanks. Expect to see that in the responses. I'm not saying they're right or wrong but generally they seem to have a strong preference for AL from what I've seen.

Backplate is the standard SS DiveRite, it's 5.5 lbs on land. You are right, the tank is -1.4 lbs empty, but ~-7 lbs full (both in salt water). I won't be using a drysuit, but will eventually get a good dsmb as you mention.

What is their (DIR's) concern with steel? I don't want to hijack my own thread here, but curious.

 

[1atm]

This sounds backwards, except for stage/deco bottles.

Well they eschew steels when paired with wetsuits (this boils down to the balanced rig point above). With a drysuit you want steels for backgas, Alu for stages

 

[johndiver999]

Your bc lift requirements are going to be dictated in this case by the wetsuit used, not the tank. For a 3 mm suit it should be sufficient; but that doesn’t mean that an al plate would be a better choice for a pool

 

[tursiops]

I say "guess," because a proper weight check should be performed, but I need the guess for an initial purchase. Background: I only plan to do shallow warm water diving in the future. Despite that, I have a BP/W setup with stainless steel backplate, because I want to minimize lead on the waist. Now, I'm looking for a tank to use in the pool mostly, and I would like it to be light in mass (out of water) because I'm having some back trouble at the moment. I currently like this steel tank, but at -7 lbs full buoyancy (in salt), I'm worried I will be too heavy with only a 25 lb wing. Using the excel calculator that some folks use for estimation, I have some lift to spare, but I'm cutting it close. Also, I could throw on my 3 mm wetsuit to help add a bit more positive buoyancy if need be. What say you? Another option is something like this Al tank, but I prefer the steel if possible given that it's lighter (out of water) and slightly larger air capacity, the money difference is not a major concern.

Side note: LeisurePro should really include a bouyancy table for tanks that are sold together using a drop-down menu of options. A range of values (minimum and maximum) doesn't do much good if you are buying a tank that is not one of the two extremes.

Yes, you'll probably be too heavy...with a steel backplate, that steel tank, and no wetsuit. The full tank plus reg plus backplate is about 14-16 lbs negative; what is going to offset that? An almost full wing?

 

[1atm]

... what is going to offset that? An almost full wing?

Exactly that, which brings two challenges:
1. You make your life harder than necessary, because the more air in your wing the more difficult it is to manage buoyancy
2. You may not have enough lift to support yourself and a buddy, in case buddy loses buoyancy

 

[certainmisuse]

I think thats very hard to say, with the limited info you have given. Having some more info about a known configuration that has you properly weighted (tank, plate, weights, suit, fins, regs, ...) would allow some degree of extrapolation, but even then it would be hard.

But some food for thought, because you are really asking two questions here:

1. Will you be able to set this up as a balanced rig, ie get close to neutral with empty tanks so you can hold a stop at the end of your dive, and be able to swim up a full tank in case you lose the wing
2. Does the wing have enough lift to make you neutral with full tanks at depth

Regarding #1: this depends on your body ... an average person of normal weight (european definition ...) would be arguably close to neutral in only a swimsuit. Some folks might be a bit positive, some a bit negative, but probably not much. That as a given, adding steel plate, steel tank, regs etc without anything to compensate would make you very negative. So either go drysuit, or reduce weight (Al tank, Al/carbon plate, etc). But this is theory, only a weight check would tell
Regarding #2: if we assume you yourself are neutral-ish, total of full tank, steel plate etc comes out <25 so alone the wing would have enough lift, but not enough to support you and a assist a buddy with failed wing. With brings us back to #1, balanced rig

Great thoughts. Here are more details:

- Diving plans and profile: warm water and < 50ft, majority <30ft
- Dive Rite travel wing, 25 lbs
- Dive Rite SS backplate, 5.5 lbs (out of water)
- Dive Rite standard harness
- Regs: MK17/G260, R195 (these are not purchased yet, but likely)
- Diver: 6' 3", 175 lbs, nearly nuetral buoyancy
- No lights (for now)

I should also mention I am considering returning the 25 lb wing and getting a 30 lb wing. I know it's only 5 lbs more, but I don't plan to do any extreme diving so I don't need to look like an astronaut.