Why are the submarines' propellers covered or removed while out of the water?.?

Question

Can you get any information about a submarine just out of a propeller?.

I wonder because seems hard to find pictures of a submarine with the propeller visible at all, if present.

Answer 1

For the same reason that the below-water-line view is covered on America's Cup racers... SECRECY.

Answer 2

Propeller technology is very important for submarines striving to be as silent as possible and as it is so "state of the art" the prop is usually hidden when the boat's in dry-dock.  In addition, the opportunity is often taken to remove the blades for polishing, dressing out small nicks etc., all in the quest for efficiency and silence.

Answer 3

It's all about keeping the secret of the proprietary design.

Remember the good old days when they would drape the hulls of the 12 meter America's Cup boats? That winged keel was the best kept secret next to Deep Throat.

Answer 4

They are a special design, constantly being worked on so they produce no cavitation or noise.  All ships can be identified by their noise signature by good sonar personell.  Subs go to special lengths to remain silent for obvious reasons, hence their prop designs are top secret.

Answer 5

The s***w, as the propeller is called, is specially designed and its configuration is classified.

Answer 6

The prop design is normally secret, and I am only aware of a few pictures of in the civilian literature, most recently the ones that ended up on google earth.

Here are some pictures:

http://cryptome.org/boomer/boomer-refit....

HTH.

Regards, Dan.