how far will a ship roll without capsizing? - Page 4 - PeachParts Mercedes-Benz Forum

Skippy · #46 04-09-2011, 06:36 PM

The projos weigh around 2700 lbs, so yes but it would have to be one of the lighter ones. I'm picturing an old Falcon coming down from the sky and landing in front of the Capitol.

kerry · #47 04-09-2011, 07:10 PM

Quote:

Originally Posted by R Leo

Not exactly so...they definitely are ballasted to keep the wheels in the water when the bunkers are light but I guarantee you they aren't ballasted to recover from a roll because there's no reason to ever worry about roll on an inland waterway...there's no swell.

The pics you speak of was the Towboat Cahaba being pulled under the Rooster Bridge by her tow on the Tombigbee River near Demopolis,AL. The only reason she survived and didn't sink like a stone was because the engine room hatches were closed and the only reason she didn't get rolled all the way over was because she'd fueled earlier in the day and had 20,000 gallons of diesel in her bunkers acting as ballast.

Plus it was only the bridge that was hold the tug over on it's side.

That footage is verification of one of the golden rules of river canoeing--never lean upstream.

kip Foss · #48 04-09-2011, 08:23 PM

My uncle was the capt. of the destroyer Emmons in the N. Atlantic during WWII. He told me that many of the tin can type ship could roll so far over that they would take green water down the stack and put out the boilers. I think that it would have to be over more than 45 degs.

t walgamuth · #49 04-09-2011, 11:38 PM

That would be over 90 degrees if the ocean was calm....of course if it were calm it would not be rolling over!

dynalow · #50 04-10-2011, 07:59 AM

Here's an interesting story by a ship captain on experiencing parametric rolling

http://kennebeccaptain.blogspot.com/2010/01/parametric-rolling-of-car-carrier-in.html

Check this video of the cruise ship Voyager doing some serious rolling.
same site People flying around like bowling pins.

http://www.itk.ntnu.no/ansatte/Holden_Christian/prof/files/inside.mp4

Soooo, the moral of the story is......

It is important for masters to know and understand the
mechanism of parametric rolling. This is because when
conditions for parametric rolling exist the worst possible action
to take is to put the ship’s head to sea and reduce speed. In
normal circumstances putting the ship’s head to sea and
reducing speed is the textbook response to navigation in bad
weather, but in conditions of parametric rolling it will only make
the rolling worse. Conditions for parametric rolling can be said
to exist when the wave length is approximately equal to the
ship’s length and the wave period of encounter is half the ship’s
rolling period. The period of encounter will depend on speed. (p.6)

http://www.standard-club.com/docs/MM_Nov02_disc.pdf

kip Foss · #51 04-10-2011, 10:56 AM

If the ocean were calm the vessel would not be rolling. He was talking about the North Atlantic in mid-winter.

check out this. http://www.youtube.com/watch?v=N7ASvFEmMuk&feature=related

Remember that WWII destroyers and destroyer escorts were very narrow and lacked the stabilizing ability that new vessels have.

Emmerich · #52 04-10-2011, 01:51 PM

The CB is relatively constant no matter how far a ship leans, and the ability to roll/recover is not significantly related to that.

A ship (or object) has primary and secondary stability. Primary is the resistance to rolling at all. Secondary is after it rolls to a certain point, will it roll over. These are dependent on hull shape and other factors like if there is a skeg. You have to factor in the forces applied to the ship and for how long.

Also, as an example, the angle of the water surface is critical. If you have a ship sitting flat on the water but the water is tilted at 30 degrees on the side of a wave, using your method, it will not roll over.

Basically inertia is your friend.

Quote:

Originally Posted by rocky raccoon

A ship has two critical dimensions related to the capsizing moment.

(1) The Center of Gravity; Cg
(2) the Center of Bouyancy; Cb

Cb is the center of gravity of the volume of water displaced by the ship.
A ship is designed so that the Cb is below the Cg on the same vertical line when the ship is upright. It is then stable. As a ship rolls, the Cb moves outward from the vertical line and rises toward the Cg. Once the Cb rises ABOVE the Cg the ship will not recover from the roll.

IRT to deck guns simply sitting in recesses in the deck, I don't know for sure but it sounds unlikely. The recoil forces and rotational forces of big guns would require them to be firmly mounted. If not so mounted normal movements, however small, would at best destroy accuracy and at worst damage the ship structure.

Warships are simply heavily ballasted to keep that Cb low.

t walgamuth · #53 04-11-2011, 11:51 PM

Quote:

Originally Posted by kip Foss

If the ocean were calm the vessel would not be rolling. He was talking about the North Atlantic in mid-winter.

check out this. http://www.youtube.com/watch?v=N7ASvFEmMuk&feature=related

Remember that WWII destroyers and destroyer escorts were very narrow and lacked the stabilizing ability that new vessels have.

Amazing! I hope the men on that ship had places to sit and strap themselves in!

chilcutt · #54 04-11-2011, 11:54 PM

Quote:

Originally Posted by t walgamuth

Amazing! I hope the men on that ship had places to sit and strap themselves in!

I was thinking the same thing..like, "What did the crew do..turn cartwheels"?

Skippy · #55 04-11-2011, 11:55 PM

Generally, no, at least in most parts of the ship. Last deployment I worked with a recovering fleeter who used to be on a sub tender. She said they had a strap attached to your rack so you could strap yourself in and not get tossed out while you were sleeping. I don't know if they had those in WWII though.

kip Foss · #56 04-12-2011, 12:03 AM

As the European war wound down my uncle took the Emmons to the Pacific where it was sunk by a Kamikaze. He was severely burned but recovered. He died in 1997 I believe. The Emmons reunion is the longest still active reunion in the Navy.

R Leo · #57 04-12-2011, 10:19 AM

Quote:

Originally Posted by Skippy

Generally, no, at least in most parts of the ship. Last deployment I worked with a recovering fleeter who used to be on a sub tender. She said they had a strap attached to your rack so you could strap yourself in and not get tossed out while you were sleeping. I don't know if they had those in WWII though.

About 15 years ago I went offshore to do some work with Dad on R/V Lone Star and had an interesting 'out of bunk' experience.

Lone Star was Rice University's seismic/oceanographic research vessel and had originally been a oil rig crew boat. Because it had been significantly modified over the years with an elevated work deck and a-frame at the transom it had a lot of top hamper and a pronounced, lazy roll.

We shoved off from TAMU Galveston's dock about 10pm, headed for a site about 30mi offshore to do some vibracore samples. I stayed up for an hour or so, hanging out in the pilothouse until we had crossed the bar and things seemed to settle down. Went below to catch some winks had barely dozed off only to find myself sailing through space and landing on the deck in a heap. No straps on that bunk...just a low fiddle that I'd rolled right over on the way out.

Once we passed the jetties and out into the ground swell she kicked up pretty good and dumped my a&& like a rank horse. I realize now that we were probably dealing with the parametric rolling spoken of earlier in the thread.

dynalow · #58 04-12-2011, 02:04 PM

Quote:

Originally Posted by Skippy

Generally, no, at least in most parts of the ship. Last deployment I worked with a recovering fleeter who used to be on a sub tender. She said they had a strap attached to your rack so you could strap yourself in and not get tossed out while you were sleeping. I don't know if they had those in WWII though.

We didn't have straps or any such thing on my bird farm, but you sure would have felt these wave slaps where my rack was.

(way up forward, right below the flight deck.

)

Here's a real clip.
Haze gray and underway...

http://www.youtube.com/watch?v=5AGEpBjcZ4s

Skippy · #59 04-12-2011, 03:10 PM

So you got to sleep under the steam cats? Sounds like prime real estate-not.

dynalow · #60 04-12-2011, 11:08 PM

Quote:

Originally Posted by Skippy

So you got to sleep under the steam cats? Sounds like prime real estate-not.

Like anything else. you got used to it. But the bow sure shook with a bang when a big bird like an A-3 or an RA-5C got shot off. You could almost tell what type of plane was going up by the thrust and shake.
http://www.youtube.com/watch?v=CJL_rgRwAvM&feature=related
Coming off a midwatch trying to sleep during the day was the biggest challenge. That's when most flight ops happened.

It was a long hike to the mess decks from up there though

...and to the Geedunk

.