First thoughts and questions about singles rig

[cool_hardware52]

tbone,

This is the DSS forum. I know you mean well, but I have a specific method for calculating weighting and buoyancy, adding new factors can lead to confusion.

My standard method for divers using buoyant suits and single tanks is to adjust their buoyancy so they are eye level as the surface with no gas in their wing and a full tank.

That already accounts for the mass of their head.


Personal buoyancy will impact total ballast, but it need not be compensated for, as it does not change WRT depth.

Tobin

 

[elgoog]

just being irritating, but change rental steel tanks to 11lbs since the larger HP tanks are around 11 when full. Also factor in weight of your head, which is 10lbs when doing that calculation. Tobins basic calculation is fairly spot on, but you need to factor the 10lbs for your noggin, and whatever ballast is offset by your natural buoyancy and your exposure protection to make sure it can keep you at the surface. You'll be fine more than likely with a 30lb wing, but it good to keep the whole picture in view when you are doing these calculations. This really only becomes a factor if like me, you dive a 18lb travel wing for singles with a transpac, you have to make sure the rig is less than the 18lbs. Now I don't have a SS plate, so that's 5lbs, out, and I don't have weight plates, and I naturally sink, so I have to be careful diving that wing with steel tanks and I flat out can't dive it without exposure protection to help offset some of the weight because I usually sit VERY low in the water when the tanks are full.

The weight calculation above was just for the gear that is attached to the harness, not my body, exposure suit or anything else that's on me. The weight calculation was to make sure that the entire rig won't sink (with the BC fully inflated) when I drop it in the water first and then hop in after it to don in the water (or the other way around if I'm taking it off before getting into a boat/kayak)

I didn't account for my head's buoyancy as the general expectation would be that when I push my rig over the gunwale/dive platform, my head's not going to go with it

 

[cool_hardware52]

The weight calculation above was just for the gear that is attached to the harness, not my body, exposure suit or anything else that's on me. The weight calculation was to make sure that the entire rig won't sink (with the BC fully inflated) when I drop it in the water first and then hop in after it to don in the water (or the other way around if I'm taking it off before getting into a boat/kayak)

I didn't account for my head's buoyancy as the general expectation would be that when I push my rig over the gunwale/dive platform, my head's not going to go with it

I have specific method for determining buoyancy and required wing lift I use to explain my recommendations to my customers. You approach may also be valid, but I try not to confuse people about what is already a poorly understood, but very basic element of scuba.

Tobin

 

[elgoog]

I have specific method for determining buoyancy and required wing lift I use to explain my recommendations to my customers. You approach may also be valid, but I try not to confuse people about what is already a poorly understood, but very basic element of scuba.

Tobin

The method I was using here was your "Any BC needs to be able to float your rig with a full tank" - just described by me in a very haphazard and roundabout fashion.
Apologies for any confusion.

 

[cool_hardware52]

The method I was using here was your "Any BC needs to be able to float your rig with a full tank" - just described by me in a very haphazard and roundabout fashion.
Apologies for any confusion.

No worries, my comments were not directed to you.


Tobin

 

[Hatul]

tbone,

This is the DSS forum. I know you mean well, but I have a specific method for calculating weighting and buoyancy, adding new factors can lead to confusion.

My standard method for divers using buoyant suits and single tanks is to adjust their buoyancy so they are eye level as the surface with no gas in their wing and a full tank.

That already accounts for the mass of their head.


Personal buoyancy will impact total ballast, but it need not be compensated for, as it does not change WRT depth.

Tobin

Maybe I'm missing something but it seems to me that at the beginning of the dive with no air in the wing you should be about 5 lbs negative-- so you would just sink. With your method above, you're actually positively buoyant when head is submerged at the surface.

 

[tbone1004]

the point there is that as you are at eye level with a full breath, most people have about 4lbs of buoyancy in a "full breath". Normal tidal volume is just over 1lb of buoyancy, but a "full breath" is closer to 4lbs, so it is close being right. You also some suit compression at 15-10ft of depth so you might be a little floaty and breathing on the very top of your lungs, but it's just to get close.

 

[cool_hardware52]

Maybe I'm missing something but it seems to me that at the beginning of the dive with no air in the wing you should be about 5 lbs negative-- so you would just sink. With your method above, you're actually positively buoyant when head is submerged at the surface.

Minimum ballast means the least I need to allow me to hold a shallow stop with an empty tank. Even if I'm a few lbs positive at the surface at the start of the dive it's really no big deal to swim down a few lbs. Example would be a buoyant suit and smaller volume cylinders.

Being over weighted is a safety issue. Being over weighted increases the problems associated with either a buoyancy failure (wing failure) or a panicked diver that does't ditch, doesn't fill his bc etc.


Not sure why so many feel compelled to complicate a pretty simple concept.

Tobin