Wing size/lift calculation questions.

OK, so there's a lot of philosophies out there about what the size an air cell should be for different applications.
It is mentioned that a wing or air cell has to do two things, compensate for the added weight when a suit compresses at depth and it has to be able to float a rig on the surface.

My question is when did these rules come into play and who says?

I see the first thing as true, an air cell is designed to compensate for the added weight caused by suit compression at depth.
I do not agree however with the statement that a wing has to float a rig on the surface.
Years ago divers used no BC's so they didn't have any compensation at depth except for their lungs and they certainly didn't have any floatation to keep the rig on the surface and they dove just fine. Later the horse collar came along which in time allowed for depth compensation but still no floatation of the rig at surface.
Finally a jacket comes along that depth compensates but being an all in one unit now has the by product of being able to float on it's own on the surface via the inflated bladder.
Now days there are a multitude of different systems including old school stuff, plain jacket BC's, weight integrated jacket BC's, back inflate weight integrated BC's, BP/W BC's, and now user set up weight integrated BP/W BC's.
So somewhere in all this came the rationalle that the tank rig system had to be able to float on it's own. I even remember in PADI open water they had us do a BC remove and put back on on the surface with the rig floating around. I was using a rear inflate at the time and got so frustrated trying to put the thing on inflated that I finally let all the air out to be able to put it on.

I have used a 4 pound backplate with an HP steel tank wearing a thick 7mm suit, 20 pound weightbelt and an 18 pound wing and had plenty of depth compensation diving as deep as I need to go. The wing was responsible for covering the compression of my suit which was probably around 10 to 12 pounds of loss. An 18 Lb wing worked fine with room to spare. However the rig would not float well on the surface with a fully inflated wing and it would slowly make it's way down. Maybe those Oxycheq wings are not rated right because a steel 120 with a 4 pound plate should be less than 18 pounds in water but who knows .

Let's say I was using a 6 pound plate, same 120 tank, but I had extra weights on the plate lets say 4 pounds, and a two pound tank weight, and now a 12 pound weightbelt and the same 18 pound wing. Essentially nothing has changed underwater, I should still have enough depth compensation to do the dive. However now on the surface that rig will drop like a rock. So with the float the rig on the surface theory I should have to step up the wing to 30 or even 40 pound size because remember even with the first rig it was negative and made it's way down. So now stepping up the size of the wing just to see it float on the surface means I need a much bigger wing which also means more drag and more air sloshing around. I'm still only needing 10 to 12 pounds lift to cover crush but Now I have that small amount of air wandering from side to side in a big floppy wing, just so I can float it on the surface, Really???

There are times I dive with no BC at all. How do you suppose I am to float a steel tank and plate on the surface with NO wing, but I can dive just fine?

Good topic. I got my wing with the same buoyancy as my old jacket on the "if that worked before it should work now theory". I rarely have much air in it unless deep but it barely will float the rig if the tank is full, an extra clip and it's on the bottom.

ZKY:

Later the horse collar came along which in time allowed for depth compensation but still no floatation of the rig at surface.

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My first "horse collar" was more of a Mae West was made for surface floatation only with a CO2 cartridge for emergency inflation. It probably gave 5 or 10# lift so you would not have to work to stay on the surface in an emergency, the inflation tube was a modified tire valve to orally inflate.



The newer horse collars that you are describing are like this:



Click on them for a larger version, I smalled them too much.

Bob
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I may be old, but I’m not dead yet.

It's a very good question to state.

If I can speculate a bit, I think I'm a bit too young to provide any first hand insight =P.
As diving became more popular you got more divers who were less fit or less in tune with water activities. The float your rig or float your person was probably added as a safety/liability requirement, to allow for a safety net for all divers/students regardless of swimming ability. I mean let's be honest, without it diving could not gain the wide range of customers it has now. There would be no profit if only the fittest could dive.

With the advent of integrated weights you now have the possibility of a cold water diver sporting all 25lbs in their BC. And with new divers today being overweighted and on their knees, I think this has led to more modern BC's sporting higher lift capacities than probably needed.
This I think has led to "float your rig" becoming more prevalent than "float your person".

g1138:

It's a very good question to state.

If I can speculate a bit, I think I'm a bit too young to provide any first hand insight =P.
As diving became more popular you got more divers who were less fit or less in tune with water activities. The float your rig or float your person was probably added as a safety/liability requirement, to allow for a safety net for all divers/students regardless of swimming ability. I mean let's be honest, without it diving could not gain the wide range of customers it has now. There would be no profit if only the fittest could dive.

With the advent of integrated weights you now have the possibility of a cold water diver sporting all 25lbs in their BC. And with new divers today being overweighted and on their knees, I think this has led to more modern BC's sporting higher lift capacities than probably needed.
This I think has led to "float your rig" becoming more prevalent than "float your person".

Click to expand...

This is just what I was thinking. In the past weak swimmers need not apply to scuba class. Gear was what it was and a diver had to be a strong swimmer. As to horsecollar vests. My 1st was a short gray UDT vest that I would add air to orally at depth and vent during ascent. A skill I use today with my orally inflated SMB, the inflating part anyway. Today we have "disabled" divers (weird term) without BC's that could float a person, lead weights and tanks that wouldn't be possible.

What do you do when you find the 30lb weight belt you just must bring home? Oh yeah you max the wing and go into your drysuit for buoyancy underwater (Mind you I had double 100's that were full, so air was a non issue for at least three hours).

How about kayak diving or diving off of a small boat, as we both do? If you clip your kit off to a tag line you are being darn trusting it will be there when you go to pull it onboard.

All I ask of my singles wing is for it to float my full HP130 at the surface. Nothing more. I used to dive pretty much the same setup with a smaller wing and it was annoying as it would sink with the tank full. So if I threw it overboard to don it, I would have to pull up on the tag line to locate my BP/W underwater.

Surface floatation is definitely a convenience but not absolutely necessary.
I am able to don a tank with no floatation device off my kayak.
Off a small boat might be different, but once in the water the same technique is used.

What would I do if I wanted to lift a 30# weight belt off the bottom that I found? I would employ a lift bag. If I didn't have one I would leave it behind and come back later with a lift bag. Not the best idea in the world to lift heavy items using your BC or drysuit.

g1138:

It's a very good question to state.

If I can speculate a bit, I think I'm a bit too young to provide any first hand insight =P.
As diving became more popular you got more divers who were less fit or less in tune with water activities. The float your rig or float your person was probably added as a safety/liability requirement, to allow for a safety net for all divers/students regardless of swimming ability. I mean let's be honest, without it diving could not gain the wide range of customers it has now. There would be no profit if only the fittest could dive.

With the advent of integrated weights you now have the possibility of a cold water diver sporting all 25lbs in their BC. And with new divers today being overweighted and on their knees, I think this has led to more modern BC's sporting higher lift capacities than probably needed.
This I think has led to "float your rig" becoming more prevalent than "float your person".

Click to expand...

Actually, I don't really think using a rig that floats or sinks really makes a difference wether the diver is fit or not as long as the overall weighting is correct.
Once underwater it's all the same. On the surface while the rig is on it's all the same too. Only once the rig comes off do things change.
I think some of these new style weight integrated rigs with huge air cells of 50 to70 lbs of lift are rediculous. But if they are after floating the rig with the worst case scenario of using huge steel tanks and enough weight to sink the titanic then I suppose that's how they have to be. It just seems like a hell of a lot of extra air cell to get in the way for one percieved convenience.

On a side note about overweighting.
What happens when an inflator comes undone or breaks off from the wing with that much weight on? Does the diver get towed straight to the bottom?

ZKY:

Not the best idea in the world to lift heavy items using your BC or drysuit.

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Agreed, but it was a lot of lead $$$, and since we were at Van Damme the average depth was under 30ft. There really wasn't much danger involved. Weren't you there or were you diving somewhere else that day? (It was the Albion trip) The SMB/lift bag I typically carry isn't good for much more than marking my position at the surface.

ZKY:

On a side note about overweighting.
What happens when an inflator comes undone or breaks off from the wing with that much weight on? Does the diver get towed straight to the bottom?

Click to expand...

That is where a drysuit is nice for redundancy. Then once at the surface, if needed, away goes the weight belt.

Are there really BC's for recreational diving with more than 45lbs of lift?

I guess with a full HP130 and 25lbs of lead, it would take one heck of a wing to float it. Another good reason for a weight belt to split up the weight.

ZKY:

Actually, I don't really think using a rig that floats or sinks really makes a difference wether the diver is fit or not as long as the overall weighting is correct.
Once underwater it's all the same. On the surface while the rig is on it's all the same too. Only once the rig comes off do things change.
I think some of these new style weight integrated rigs with huge air cells of 50 to70 lbs of lift are rediculous. But if they are after floating the rig with the worst case scenario of using huge steel tanks and enough weight to sink the titanic then I suppose that's how they have to be. It just seems like a hell of a lot of extra air cell to get in the way for one percieved convenience.

On a side note about overweighting.
What happens when an inflator comes undone or breaks off from the wing with that much weight on? Does the diver get towed straight to the bottom?

Click to expand...

Well I think you maybe forgetting about shores divers that might swim longer distances. We need flotation.

That's what the ditchable weights are for, quick release buckle........ Then again when I use my double LP90's I don't use weights at all which is why I have a lift bag in case the wing goes south.

Peter_C:

What do you do when you find the 30lb weight belt you just must bring home?

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Um….that’s what the 16ft SMB is for.

Peter_C:

Are there really BC's for recreational diving with more than 45lbs of lift?

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Actually I remember my dad finding a 75lb BC on ebay. Forgot the manufacturer but the model was called Recon. It was a tech inspired recreational BC for single tank diving. Size small

ZKY:

Actually, I don't really think using a rig that floats or sinks really makes a difference wether the diver is fit or not as long as the overall weighting is correct.

Click to expand...

It makes a difference if the said diver can't thread water for a period of time. Having some flotation for the surface swim can put a diver at ease, especially if the diver can't swim all to well.

ZKY:

On a side note about overweighting.
What happens when an inflator comes undone or breaks off from the wing with that much weight on? Does the diver get towed straight to the bottom?

Click to expand...

Yup, diver goes bye bye, unless he/she remembers to ditch.


I'm not saying this is the right course of action for the scuba world, but it is the "fad" (if I can even use the term) that has taken hold at the moment.