Rocket Ascents... Can divers breach like a fish (split from Accident in Mich)

[lamont]

Besides we are trying to strealine our diver for his 21 ft/second ascent (If you don't know where that figure came from look at posts #55 and #155). That puts us very much in the same speed realm

why am i reading this thread?

we need an icon for a trainwreck or an accident on the side of the road...

 

[JeffG]

why am i reading this thread?

we need an icon for a trainwreck or an accident on the side of the road...

LOL...Should be a propeller head icon.

 

[Snowbear]

why am i reading this thread?

we need an icon for a trainwreck or an accident on the side of the road...

It's a SCUBA board. Sheesh! For the folks who think they can escape a shark by streamlining, how about this one...

 

[PavoDive]

I still don't see how this relates to a submerged object with no waterline or wave hight ...
Air is compressible , water is not. so I dont see how this can directly relate to an object under the water that does not have this air/water interface. Anyone have an explanation for this ???
DB

DB, water resistance has basically 3 components: frictional, wave-making and eddy-making. As you say, if the body is UW, then you can disregard wave-making resistance (unless you're talking about supersonic velocities, quite an absurd; or if you're submerged but close enough to the surface to create a wake).

However, frictional resistance and eddy-making resistance will increase exponentially with the speed, so there will be a point where any added force will add no speed (mathematically it will, but it's so small you can simply forget about that). As somebody pointed out, the only way you can move pass that speed is by changing the design (in submerged subs the Length/beam ratio isn't as important --in terms of resistance, that is-- as in surface hulls; the factor here will likely be the cross sectional area and the smoothness of the lines).

So even if you have that Hammer-tank assisted backwards emergency ascent, that won't propel you pass the terminal velocity

I personally don't give his theory a dime, but if the guy who started this thread is right, then I'll better don't buy oversized BCs... I'm afraid I could reach the escape speed and end up floating in outer space, full diving gear and all :icon28:

I can't believe I gave two hours of my life to all this non-sense... At least I had some good laughs

 

[serambin]

OOPS! see other reply.

Thanks,

Stan

 

[serambin]

The dimples are an effort to shrink that low-pressure region he was talking about.

Golf balls have dimples so they will go faster. Tennis balls have fuzz for the same reason. I gave a brief quasi-technical explanation of what's happening in a previous post.
. . .

(more-or-less)

Na, golf balls have dimples for two reasons -

1. They act a 'purchase' on the air. Just like a seam on a baseball, dimples increase air resistance so as the golf ball rotates with under spin, it is actually curving upward (like a fastball, only faster). This allows for lift and increases the distance the ball flies. I've heard that without dimples, the maximum distance on a well struck driver would be less than 150 yards off the tee.

2. Girl golf balls think they look cool on the guys. :14:


Stan

 

[serambin]

I still don't see how this relates to a submerged object with no waterline or wave hight ...
Air is compressible , water is not. so I dont see how this can directly relate to an object under the water that does not have this air/water interface. Anyone have an explanation for this ???
DB

You are correct when you say water is not compressable (or at least not very). This means an object must 'move' the water out of the way when passing through it. Where does the water go? It goes around the object. At the back end of the object the water swirels around the object and this increases drag or reverse pressure. Just like a boat on top of the water. The only thing you can do to substantially increase this maximum velocity is to increase the water line length allowing for more velocity before the wave reaches the backend of the object.

In another post someone calculated the maximum speed of a free diver with a lift bag at over 8 MPH. The increase in LWL would not seem to increase the terminal velocity to that amount, but if he is correct, something is happening.

Stan

 

[Butch103]

WOW !!!! I actually read all 23 pages......It is still BS.....

 

[MXGratefulDiver]

WOW !!!! I actually read all 23 pages......It is still BS.....

Train wrecks are fascinating ... aren't they ...

... Bob (Grateful Diver)

 

[serambin]

WOW !!!! I actually read all 23 pages......It is still BS.....

I'm sure the the BS you refer to is - Best Stuff. :bang: