What water sees.

[tursiops]

tursiops,

This precisely is the value, and fun (in my opinion), of these types of discussions/exercises. Anyone can assign different values to the parameters and thereby gain insight by the effects that obtain. Helps inform the discussion. No absolutes, correct?

Safe Diving,

rx7diver

No, sorry, not interested. To many real things to discuss without inventing angels on the head of a pin.

 

[dmaziuk]

This is the part that is not so obvious, I think. You increase buoyancy by displacing more water (with air). The fact that the jacket BC poofs out around the entire torso (from the diver's front, from his/her back, and under both arms), it really doesn't need to poof out very much to supply a lot of buoyancy.

On a perfectly spherical diver of uniform density, I assume? Indeed it (either BC) doesn't need to poof out very mush in order to work as you describe, it only needs to poof out to fully inflate the entire bladder. Otherwise the air goes up goes up and forms a bubble at the highest point. Or at least that's what air in water does on my planet.

 

[rx7diver]

Otherwise the air goes up goes up and forms a bubble at the highest point. Or at least that's what air in water does on my planet.

Absolutely. And anyone who remembers the graphics in the old Scubapro catalogs will remember that Scubapro touted this "feature" as being extremely advantageous/desirable.

Safe Diving,

rx7diver

 

[Skeptic14]

I don't see anything scientific/definitive/useful about this, just seems like you picked numbers you liked to draw some ellipses?

I imagine if you wanted people to give this consideration and start a discussion a good place to start would be explaining what measurements and methods were used to obtain the ellipse equations you've plotted...

Also, I'm no expert in fluid dynamics but I'm pretty sure you've ignored them for this demo/premise/theory...

 

[rx7diver]

I don't see anything scientific/definitive/useful about this, just seems like you picked numbers you liked to draw some ellipses?

I imagine if you wanted people to give this consideration and start a discussion a good place to start would be explaining what measurements and methods were used to obtain the ellipse equations you've plotted...

Also, I'm no expert in fluid dynamics but I'm pretty sure you've ignored them for this demo/premise/theory...

Skeptic14,

Absolutely nothing scientific/definitive here. Nor intended. No premise/theory, either. "Useful" is in the eye/imagination of the beholder, I would think.

And, yes, all I did was draw some ellipses. Eyeballed mostly. The tanks have outer diameter 7.25" (like an Luxfer Al 80 or a PST HP 65/80/100/120). The heads are a bit bigger (because IRL they are, I think). As mentioned, the tubes on the Wings have diameter 4" (because 2 is a nice, whole number). The shoulders/torso of these divers look a bit extreme (but, like with the tubes, I simply used nice numbers).

Source code is included, so anyone can rescale and/or tighten things up as he/she likes. Or graph using a different software. Not difficult. (Nothing about ellipses is difficult, maybe, I think.) But not what was intended for these simple graphics that resulted simply by me spending a few minutes playing with/learning/investigating a new piece of software.

Safe Diving,

rx7diver

 

[rx7diver]

I spent a bit more time thinking about this. I recruited my daughters. They measured my shoulder width, and I measured their heads. Then I rescaled my graphics a bit.

Also, recalling several posts I made in a SB thread (Using "fuller" tanks.) discussing smaller, higher pressure cylinders, I superimposed an 8" OD tank and a 6" OD tank on the graphic.

Revised graphic is attached.

I find these graphics compelling.

Safe Diving,

rx7diver

 

[Nemrod]

Calculate the flat plate area?

We do not move through the water in perfect horizontal trim, the wing is partially blocked by the torso.

I suspect in your presentation the wing/BP has more flat plate area exposed to the water.

N

 

[tursiops]

By "compelling" you mean they lead you to some conclusion? What do you conclude?

 

[rx7diver]

We do not move through the water in perfect horizontal trim, the wing is partially blocked by the torso.

Nemrod,

I concur and have a hand-drawn side-view sketch showing this. Next version of this graphic I will try to drop the scuba units down a bit below the divers' shoulder silhouettes. Things get a bit tricky, though, since the height the tank is worn (i.e., how low the tank is worn down the diver's back) becomes a factor. And, of course, the torsos and legs become more of a factor, too. The engineers on here would probably do this kind of thing with much less effort, and much better, than I ever could, but, hey, this is fun.

Safe Diving,

rx7diver

 

[rx7diver]

I added a third diver (a third configuration), to my graphic. This diver is wearing "baby doubles" (OMS/Faber LP 46/50 doubles, OD = 5.5") and a BP/W.

Safe Diving,

rx7diver