US Navy Experimental Diving Unit

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John C. Ratliff

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David,

I was able to see a more recent study of fin efficiency, and found this quote:
The Apollo fin possesses the lowest Froude efficiency, probably due to the split in the fin’s blade. The split allows water to “pass through” it instead of having the water pass over the surface to produce the desired pressure gradient between the attacking and leeward surfaces. The Apollo (Taped) and Quattro fins each have Froude efficiencies well above 60%. The common characteristic between these two configurations is that both have flanges along the lateral edges of the blade to direct flow to the fin tip which acts as dykes to channel the flow along the fin’s surface and ultimately being ejected from the TE.
Here is the study:
http://archive.rubicon-foundation.org/xmlui/bitstream/handle/123456789/3936/12841609.pdf?sequence=1

This seems to confirm my work over these decades on the "scoop fin" concept.

SeaRat
 

sealark

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full.jpg I made a 250 and 285 ft air dive's in that chamber back in 1966. On our duty nights we were tasked with cleaning up the EDU chamber that killed the divers from the O2 fire.
 

David Wilson

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David,

I was able to see a more recent study of fin efficiency, and found this quote:

Here is the study:
http://archive.rubicon-foundation.org/xmlui/bitstream/handle/123456789/3936/12841609.pdf?sequence=1

This seems to confirm my work over these decades on the "scoop fin" concept.

SeaRat

Looks like an excellent academic piece, John, from the University of Buffalo, providing chapter and verse on the science underlying fin efficiency. I'm glad it gives credence to the principles of your scoop fin design. The North Dakota State University website has another comparative analysis of fin performance from around the same time, 2002-2003, at Fins -- In depth (2002).
 

John C. Ratliff

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View attachment 434304 I made a 250 and 285 ft air dive's in that chamber back in 1966. On our duty nights we were tasked with cleaning up the EDU chamber that killed the divers from the O2 fire.
Oh my, I had not heard of this O2 fire and the loss of the divers. I don't think it was even covered by Ben Hellwarth in his book, SEALAB (I'm checking now--'couldn't find it in that book). This is the undersea equivalent of the Apollo I fire and the loss of three astronauts, Grissom, White and Chaffee (from memory--I'll have to check). Thank you for bringing it to our attention.
SeaRat
 
OP
Akimbo

Akimbo

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Akimbo

Akimbo

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I just stumbled across this video. I haven't seen it since First Class Diving School when it was a 16mm film.


The opening scenes are of an operational diesel boat parked on the bottom rather than an actual disabled sub.

Compare that to the salvage of the Russian submarine Kursk in 2001.

 

Pressurehead

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https://www.shearwater.com/products/teric/

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