Diving Performance - Beyond Drag (article Series And Discussion)

[John C. Ratliff]

Revan,

This is another hard-shell BC, but without the constant volume that the Dacor Nautilus CVS used. It was manufactured by White Stag for just a little while. It is simply a repository for air, at ambient pressure. Add the air, and if you want to remove it, simply do a surface dive and it flows out holes in the bottom of the unit. It is a very simple unit, but actually fairly effective. It has about 15 pounds of buoyancy.

Concerning the Dacor Nautilus CVS, it was patented in September 1978, and so is now available for copying. It would be fairly easy to get a smaller one, such as the White Stage version, into a CVS by simply adding a small regulator, a water intake valve, and overpressure relief valve. Here is the Dacor CVS patent. Here's a short video of me using the Dacor Nautilus CVS with a double hose regulator. This will also give you an idea of the currents I deal with in the Clackamas River.

SeaRat

 

[ronscuba]

What do you guys think about the small 17 lb wings ? My wife and I use them, they provide enough lift for us.

One has an outer cover and the other is single layer. Do you think trying to secure them down to the backplate or wrapping closer to the body will make a difference ?

 

[REVAN]

What do you guys think about the small 17 lb wings ?

It looks pretty good if you need the BC. It looks like a nice simple harness. I'd ditch the BC and just use the harness except for when I'm wearing more than 3mm of neoprene.

 

[John C. Ratliff]

When the water temperature in the Clackamas River reached 65 degrees F, I simply wore a hood and my wet suit vest, without a BC. Here I'm diving a single 72 steel tank, with a very old Broxton DA Aqualung regulator (U.S. Divers Company's first regulator), a few weights and my minimum equipment (mask, snorkel, fins, booties, and a knife). Note that with the double hose regulator between my shoulder blades, the tank is barely visible in the current.

I think if you are required to have a BC, Ronscuba, the 17 pound wing is more than adequate.

SeaRat

PS, this was a trash dive, and I have a yellow net bag with me, which you see in the second photo. Oh, and the mask is a Champion Deluxe Mask from U.S. Divers Company, last made in the 1970s.

 

[REVAN]

Do you think trying to secure them down to the backplate or wrapping closer to the body will make a difference ?

Anything you can do to keep the BC close to your body will help. You could try bungees or some other method of holding it down. The main thing is to not have it floating up around the tank if there is a little air in the bladder.

What brand is that unit? The wing reminds me of a Deep Sea Supply product. Does the wing detach allowing you to use just the harness? It looks like a pretty nice setup.

 

[ronscuba]

Yes, they are both DSS wings. I can see larger wings creating a lot of drag resistance. But being only 17 lbs lift, they are very small and I was wondering if the benefit of securing them down is worth it.

Water temps 80 and above, I don't wear a wetsuit. I could dive without the wing, but I am negative buoyant at the start of the dive. Full tank, valve, regulator, etc., is enough to make me sink without any additional weight.

 

[REVAN]

Full tank, valve, regulator, etc., is enough to make me sink without any additional weight.

Are you using steel tanks?

 

[ronscuba]

Aluminum 80, no wetsuit, I don't need any extra weight. An exhale brings me down.

I think a full al 80 is -2 lbs. Regulator, tank bands, and bcd hardware probably is another -2 lbs. My BCD is webbing, wing, hardware, softplate, no padding.

 

[REVAN]

It sounds like it might be a neutral 80 as opposed to a standard 80. Even so, I wouldn't think you'd need a BC to prevent being too heavy unless there is a steel plate hidden somewhere in that slick little harness. It looks like just a harness, with no plate.

For diving no BC, you should sink when you exhale. You want to be neutral with no less than 3/4 lungfull at the beginning of the dive. At the end of the dive, you will be about neutral with 1/4 lung full.

 

[REVAN]

I should point out that you usually want to shoot for the same buoyancy principles above if you are using a wetsuit, except that you want this to hold true at 15 to 20 feet depth (where you do your safety stop). Without a wetsuit, the depth is irrelevant, so you can get your weights trimmed out near the surface. Once you know what you need diving skin, you just need to figure out what the added buoyancy of your wetsuit is at 15 to 20 feet depth to add the compensating weight for the wetsuit. It will be about 2/3 to 3/4 the buoyancy measured at the surface.