Hogarthian rig balancing

[Patrick Kuehn]

This might not be an appropriate question for the advanced board, but I'd like an advanced person to answer.

I'm primarily diving wet in Southern California in a 7mm suit. I use a wing and stainless steel back plate. I'm usually diving a big single steel tank like an HP120, sometimes a spun steel Asahi 120 that is -5 lbs buoyant empty and -13 lbs when full. Assume my suit is maybe 16 lbs buoyant and compresses and my gas weighs ~8 lbs.

I'd like to be able to float my rig and gear without me in it which can be around -24 lbs buoyant. So, I figure I should have a wing with enough capacity to do that.

I figure I need enough wing lift to:
1) compensate for protection change (16 lbs worst case)
2) at least equal the weight of the gas I will consume, so I can start the dive that negative and stay neutral at my safety stop
3) float the rig if I'm not in it

My question is, why are positively buoyant floatation materials not attached to a HOG rig to adjust rig buoyance in a less flocculating, more fail safe, and more streamlined manner than through an air inflated wing? It seems like the optimal wing size is achieved when the rig's buoyancy is equal to the potential worst case buoyancy loss.

I'm imagining a non-compressible positively buoyant material (no change at depth), which I can permanently attach to my rig. In my case, I'd add 6-8 pounds of lift.

 

[tech3324]

I'm imagining a non-compressible positively buoyant material (no change at depth), which I can permanently attach to my rig. In my case, I'd add 6-8 pounds of lift, or whatever it took to me to get neutral at my safety stop with a 15-20 lb wing.

Wouldn't that fixed 6-8lbs of buoyancy be equivalent to removing 6-8lbs of weight from your rig?

 

[tbone1004]

because that would only work for a non-balanced rig to make it balanced. If the wing is designed properly a 30lb wing shouldn't have any measurable amount of drag more than a 20lb wing because they typically get longer rather than wider

 

[211ratsbud]

Wouldn't that fixed 6-8lbs of buoyancy be equivalent to removing 6-8lbs of weight from your rig?

Aluminum or kydex plate and a little better tank selection (different manufacturers 120) would put him dead on I believe.

 

[Patrick Kuehn]

Thanks all.
Tech 3324: Yes, except I can't remove more weight from my rig. There is no lead in that setup.

DanaHunt: I definitely could do that and am trying to choose between a Faber or Worthington HP 100 to cut 3-5 lbs. The 120 Asahi is too much of a load, and drags my butt down and messes up my trim.

tbon1004: Makes sense. I do like the idea of balancing in a way that isn't susceptible to a puncture like a wing bladder is.

 

[tbone1004]

so this is going way back to the basics but buoyancy is created by displacing water with something of a different density. In the case of something like lead, it is displacing less water than it weighs so it sinks, but in the case of air it is displacing more water than it weighs so it floats. In order to compensate for buoyancy you can either create something like a submarine ballast tank that takes in water or releases water in order to create buoyancy in a rigid container, or you can take a flexible container, and inflate it accordingly. Your regulator is more than capable of working with something like a submarine ballast tank because it would work essentially the same as a wing, but it would be fairly large and incredibly complicated to get it to balance. I.e. you would have to have a rigid tube on either side of the tank with a balancing mechanism for the water and air to balance. It would also be rather expensive to design and develop because it would have to be pressure rated, would have a lot more failure points, etc etc. Possible, yes. Practical? Oh he77 no....

Experience says you shouldn't need any more than a 30lb wing for that setup, and in the case of something like the DSS LCD30, there really aren't that many more streamlined wings on the market because it is as long as it is. This is ideal for a multipurpose wing and is the one that I have for my personal singles setup, which also uses a SS backplate, 5mm suit with hooded vest in my case, and a PST HP120 tank.

 

[Patrick Kuehn]

I'm actually doing it without a problem with a 26 Torus right now without any problem. The rig just barely floats without me in it.
I should just switch to a Faber 100 and pick up 5 lbs of buoyancy. The 120 hurts my back.

 

[tbone1004]

how overweighted are you in the current tanks? I.e. are you adding any lead to your rig anywhere?

 

[Bob DBF]

I'm imagining a non-compressible positively buoyant material (no change at depth), which I can permanently attach to my rig. In my case, I'd add 6-8 pounds of lift.

Products | DeepWater Buoyancy

If these guys don't have it off the shelf, they can do custom work.



Bob

 

[Lorenzoid]

Aluminum or kydex plate and a little better tank selection (different manufacturers 120) would put him dead on I believe.

Is this not the answer? Replacing the steel plate with an aluminum or kydex plate would remove 4 lbs. or so.