30 or 40 lb wing?

[Dive Right In Scuba.]

Would you mind explaining the downsides of "hybrid monstrosities"? For someone looking at their first BP&W, with an eye to diving doubles in the future, a hybrid sounds kind of nice.

The only real advantage is in saving money. If a wing is too big for the tanks you are using, it will wrap around the tanks and leave your air bubbles in hard to reach places when you are trying to control buoyancy.

 

[divad]

Would you mind explaining the downsides of "hybrid monstrosities"? For someone looking at their first BP&W, with an eye to diving doubles in the future, a hybrid sounds kind of nice.

They're bad at two things at the same time, like a two-headed monster, promising a cheap salvation.

 

[runsongas]

Quick quiz......how does a suit flood make you negative?


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if you lost more than 21 pounds of buoyancy from the suit flood (unlikely, but possible) and had a full 120, you would be more than 30 pounds negative. even fully inflating the 30 pound wing would still leave you negative. it probably would only be a few pounds that you could still swim it up.

 

[Rossia pacifica]

Another question if you don't mind: Why are bungeed wings frowned upon? Is it just the entanglement hazard or is there more?


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[PfcAJ]

if you lost more than 21 pounds of buoyancy from the suit flood (unlikely, but possible) and had a full 120, you would be more than 30 pounds negative. even fully inflating the 30 pound wing would still leave you negative. it probably would only be a few pounds that you could still swim it up.

If your wing can float your rig without you in it, it can float you with a flooded drysuit. Water in water is neutral.

 

[cool_hardware52]

If your wing can float your rig without you in it, it can float you with a flooded drysuit. Water in water is neutral.

Humm, not really. Drysuits don't lose buoyancy because water can get in, they lose buoyancy because the gas trapped in an intact suit can get out.

Consider a BC. Normal function of a bc always results in water entering the BC. This water will reduce the max available lift, but it will not keep the BC from providing lift, as long as the BC can trap a bubble it will provide positive buoyancy. If, OTOH, one was to tear off the corrugated hose from BC it would be unable to trap gas and would provide no positive buoyancy.

Drysuits are no different. When water leaks into a Drysuit is has zero impact on buoyancy for the reason you note, water inside or outside of the suit is of the same density.

A suit failure, for example jumping into the water with the zipper open, blowing out a neck seal, or tearing the suit is exactly the same as tearing the corrugated hose off a BC. The suit can no longer trap gas, and has the potential to lose 100% of the buoyancy the gas trapped in the undergarment provided.

Drysuit "floods" are inconvenient and uncomfortable, but should not be confused with the impacts of a suit that fails in such a way that it cannot trap a bubble.

Tobin

 

[PfcAJ]

Humm, not really. Drysuits don't lose buoyancy because water can get in, they lose buoyancy because the gas trapped in an intact suit can get out.

Consider a BC. Normal function of a bc always results in water entering the BC. This water will reduce the max available lift, but it will not keep the BC from providing lift, as long as the BC can trap a bubble it will provide positive buoyancy. If, OTOH, one was to tear off te corrugated hose from BC it would be unable to trap gas and would provide no positive buoyancy.

Drysuits are no different. When water leaks into a Drysuit is has zero impact on buoyancy for the reason you note, water inside or outside of the suit is of the same density.

A suit failure, for example jumping into the water with the zipper open, blowing out a neck seal, or tearing the suit is exactly the same as tearing the corrugated hose off a BC. The suit can no longer trap gas, and has the potential to lose 100% of the buoyancy the gas trapped in the undergarment provided.

Drysuit "floods" are inconvenient and uncomfortable, but should not be confused with the impacts of a suit that fails in such a way that it cannot trap a bubble.

Tobin

Irrelevant. You can hop in the water with a full wing and just your birthday suit and still float. The drysuit's existence (or not) doesn't really matter when it comes to selecting how much lift you need.

Its gotta have enough lift to float all your business without you in the rig.

If loss of buoyancy from the suit results in you not being able to attain positive buoyancy from the wing, the wing is too small.

 

[cool_hardware52]

Irrelevant. You can hop in the water with a full wing and just your birthday suit and still float. The drysuit's existence (or not) doesn't really matter when it comes to selecting how much lift you need.

Its gotta have enough lift to float all your business without you in the rig.

If loss of buoyancy from the suit results in you not being able to attain positive buoyancy from the wing, the wing is too small.

As I have posted countless times any BC needs to meet two criteria; 1) be able to float the diver's rig, with full cylinders without the diver and their buoyant suit attached, and 2) be able to compensate for the maximum possible change in buoyancy of the diver's exposure suit.

In cold water it is almost always the buoyancy of the diver's exposure suit that determines minimum required wing capacity.

Consider a diver in a suit that is 28 lbs buoyant, doesn't really matter if that's a 7mm farmer john or a shell drysuit with thicker undergarments.

If his rig consists of a Stainless steel back plate harness (~-6 lbs), regulator (~-2 lbs) and negative steel tank (hp 100 ~-10 full) his rig will be about -18 lbs with a full cylinder, and this "rig" will provide about 10 lbs of ballast with an empty tank. A 20 lbs wing will easily float this rig.

However the diver's suit has the potential to lose 100% of the buoyancy it starts with, or 28 lbs. If this diver suffers a total failure of their drysuit, or dives deep enough to compress a wetsuit to the point where is loses more than 20 lbs of buoyancy it should be pretty evident that sizing a wing based only on it's ability to float the divers "rig" is very poor practice.

OTOH if this diver selects a wing that offers enough lift to compensate for the maximum possible change in buoyancy of their suit they will be able to deal with either the compression of a wetsuit or the failure of a drysuit.

Divers use Buoyancy Compensators to compensate for things that change in buoyancy with respect to depth, and that is almost exclusively the diver's exposure suit.

As long as the diver is breathing compressed gas their personal buoyancy won't change WRT to depth, and their cylinders are losing mass as the contents are consumed, that leaves only the changing buoyancy of the exposure suit in need of compensation.

There is good reason why wings get larger the further you get from the equator. The water gets colder, and the exposure suits required are more buoyant. More buoyant suits require greater Buoyancy Compensation.


Tobin

 

[PfcAJ]

As I have posted countless times any BC needs to meet two criteria; 1) be able to float the diver's rig, with full cylinders without the diver and their buoyant suit attached, and 2) be able to compensate for the maximum possible change in buoyancy of the diver's exposure suit.

In cold water it is almost always the buoyancy of the diver's exposure suit that determines minimum required wing capacity.

Consider a diver in a suit that is 28 lbs buoyant, doesn't really matter if that's a 7mm farmer john or a shell drysuit with thicker undergarments.

If his rig consists of a Stainless steel back plate harness (~-6 lbs), regulator (~-2 lbs) and negative steel tank (hp 100 ~-10 full) his rig will be about -18 lbs with a full cylinder, and this "rig" will provide about 10 lbs of ballast with an empty tank. A 20 lbs wing will easily float this rig.

However the diver's suit has the potential to lose 100% of the buoyancy it starts with, or 28 lbs. If this diver suffers a total failure of their drysuit, or dives deep enough to compress a wetsuit to the point where is loses more than 20 lbs of buoyancy it should be pretty evident that sizing a wing based only on it's ability to float the divers "rig" is very poor practice.

OTOH if this diver selects a wing that offers enough lift to compensate for the maximum possible change in buoyancy of their suit they will be able to deal with either the compression of a wetsuit or the failure of a drysuit.

Divers use Buoyancy Compensators to compensate for things that change in buoyancy with respect to depth, and that is almost exclusively the diver's exposure suit.

As long as the diver is breathing compressed gas their personal buoyancy won't change WRT to depth, and their cylinders are losing mass as the contents are consumed, that leaves only the changing buoyancy of the exposure suit in need of compensation.

There is good reason why wings get larger the further you get from the equator. The water gets colder, and the exposure suits required are more buoyant. More buoyant suits require greater Buoyancy Compensation.


Tobin

Maybe I'm not writing simply enough.

If the wing can float all your stuff without you and your suit, then it can float it without the buoyancy provided by the suit... If it can do that it HAS to be able to compensate for the maximum possible change in buoyancy of the diver's exposure suit. The max possible change in a drysuit would go from +28lbs (or whatever) to zero, which would be neutral.

Criteria 2 is just a rehash of criteria 1. If a wing can't do 1 it can't do 2.

Its a little late in the evening, but I think that in your above example, the tank, reg, and plate = -18lbs. The suit is +28lbs. -18+28=10. You'd need ~16lbs on the belt to compensate for the remainder and the gas from an empty tank to be neutral with an empty. -18+(-16)=-34. I believe 35lbs to be the required wing size, thereabouts, which can certainly float your rig and weightbelt or however you choose to mount your weights without the diver present.

 

[Flipmode85]

Thanks for the answers!
I want the tecline donut 15 (30lbs) or the tecline donut 17 (40lbs)

12 litre steel single tank.
I have a drysuit, primary cablelamp and a weightbelt with 8 kg lead.

Many people say go for the 30 lbs its more then enough.
Others say go for the 40 lbs.

Really dont know anymore. So many People so many opinions i understand.

But its a lot of money for me and since its my first bP/w i really want to make a good choice!