Airplane props CAN cavitate, they just call it stalling, or in a more technical term: Departure of boundary layer.

On a screw, tip speed is the #1 worry and source of problems. Above when I said they would make them as large as they can so they turn slower? It is tipspeed of the screw that they are trying to bring down.

I always wondered what that inflatable boot was for? Is that supposed to stop flooding if the shaft somehow became disengaged from the reduction gears and managed to back its way out of the boat?

It's an auxillary seal. If the shaft falls out, it's end of show for the boat.:o

What we would call a real bad day at sea.

Boy is THAT the understatement of the year. Didn't this almost happen to one boat? The shaft broke something like 3 feet from the shaft seals. The rest fell out of the back of the boat. I can imagine the shock when they found out how close they came to death

I found it. It was the USS Tullibee

http://navysite.de/ssn/ssn597.htm


We had a leak of the primary and secondary seals once. We had to rig drain lines all the way to condensate bay drain funnels to keep up with it. Any deeper than 400 or so feet and we had to run the darin pump full time at low speed to keep up. If you answered any kind of bell you had to have a raincoat in shaft alley.

It was amazing, during that time EVERYONE in the engineroom knew how to inflate the shaft seal without having to follow a procdure. Even the RO's knew how to do it. As a side note here: If you are on the inflatable seal, you are not turning the shaft. It is a desperation last chance device.

Very quickly off topic.

Tullibee seems an interesting boat. Any good photos and line drawings of her?

http://upload.wikimedia.org/wikipedi...SSN-597%29.jpg

Odd boat. One of a kind. Nuc, Turbo-electric drive, no reduction gear (if I remember right).

keep up he good work guys..what do I need to run this sim?

I was a qualified throttleman on a 688 myself but it looks like bubbleheads got you guys covered and its been a couple years for me but I really want to play with this thing....:p

http://www.commanders-academy.com/comsubsim :arrgh!:

PS: now I hope it was repeated enough (together with my sig).

OK posting this here as the bubble heads will see it.

In the sail of a submarine, the bit of the sail they all stand in when transiting on the surface, is it covered up with a hatch when the submarine submerges or is it not?

I'm making my model of and Oscar II and I want to sort out the sail bridge. I know the Russians have a windscreen that can be raised but I can't make out from drawings and photographs if there is a cover that maintains the lines of the sail.

I would have thought yes, because having a large hole I'd have thought would have caused noise due to water swirlling around.

Cheers

US subs have a non-watertight streamlined cover that closes these holes over.

What makes the noise is not som much the swirling but the 'coke bottle effect'. You know, take a empty coke bottle abd blow across the top and you get a tone.

US boats are dang near paranoid of this potential problem. I would presume the the other subs in the world are as well. You get GREAT low hrz tonals off of them.

Cheers. I fugured there would be. Now I just have to incorporate it into the model.

New version 9b of comsubsim was released. Check the WIKI:

http://www.commanders-academy.com/comsubsim

Hi Xabba you asked about hatches that cover the sail-bridge on subs. Well I've gone though just about all the pictures I have along with a few videos of subs diving and found some that show subs with these covers in use.

The subs that I've seen using them include US SSN from 688s on, Russian subs with out a foul weather bridge these incl. the Akula, Sierra, and Alfa. Japanese SSKs have them too. French Agostas don't nor does my fav the Kilo. Here are a couple pics

http://www.commanders-academy.com/tl...e/PDVD_002.jpg

http://www.commanders-academy.com/tl...e/PDVD_003.jpg

http://www.commanders-academy.com/tl...ierra%20II.jpg

And for the USS Tullibee

http://www.commanders-academy.com/tlamstrike/SSKN.jpg

It is actually a metal blanking plate if you will on hinges. you swing it to cover the hole that allows you to stand inside the sail. When you swing it closed there is simply and pin or pins that are inserted to hold the "clamshell" closed so that it is streamlined. Used to be a common problem for a pin to not be inserted and rattle around as submerging creating a rattle the even the most deaf sonarman would immediately recognize.

But did these covers open outwards or inwards? The reason I ask is that whenever I see pics of surfaced boats with crew on or masts up these covers are nowhere to be seen.