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Baltimore's Key Bridge struck by cargo ship, collapses

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Re: Baltimore's Key Bridge struck by cargo ship, collapses

#781

Post by snarf21 »

TaylorAlexander wrote: post #66

Somehow I find it surprising how completely the bridge collapsed after the damage. I understand that a container ship collision is serious, but you could imagine a scenarios where the bridge slumps or buckles but doesn’t just disintegrate like that. It’s surprising that ships capable of doing this damage were probably regularly driving past it, and its safety as a thoroughfare depended entirely on those collisions no…

Is there a reason we don't force ships above a certain side to always approach a bridge like this perpendicular in the main channels? Seems like a trivial thing to implement immediately and makes this never happen again.

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#782

Post by not2b »

xp84 wrote: post #753
1letterunixname wrote: post #722

Earlier quoted context omitted.

I hope the next POTUS makes good on Biden's promises because Baltimore and Maryland will need federal assistance since they can't afford such a burden. And I assume there will lawsuits to recover costs as this caused economic damage and risk to life (8 people unaccounted for at current time).

I'm kind of confused how a President can promise something like that. He doesn't have any power to appropriate money, and given his party's lack of control of Congress, I'd argue he can't promise anything. Not to mention that one can scarcely find a "bluer" area than Baltimore -- I would assume that the most proudly right-wing politicians would be more than happy to let Baltimore suffer to score points with their pol…

He'll need to get Congress to pass an appropriation, yes, this is his way of putting pressure on them to do it. I think that there are emergency funds already appropriated that he can immediately tap, but they would fall way short of the cost needed to build a new bridge. The damage here doesn't just affect Baltimore, the national economy is affected.

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#783

Post by OJFord »

pixl97 wrote: post #687
OJFord wrote: post #518

Earlier quoted context omitted.

AIUI most souls on the bridge were construction workers filling potholes, not drivers. But either way I'd have thought a certain amount of horn blowing would catch my attention just for being out of the ordinary, even though it's also not ordinary for ships to (need to) signal me.

Ya the people on the bridge would have less than 4 minutes to figure out the ship is crashing then to clear 2500 feet of bridge. When you're working with construction equipment you'd probably not notice till you had seconds left.

4 minutes is a lot longer to save your life than nothing? And do you really think that's the answer, that was the calculation on the ship - well they only have 4 minutes until we hit anyway, so there's nothing they can do, not worth it?

I wasn't criticising anyone, I was 1) asking if that happened; 2) asking why it might not have.

I think the answer is much more likely that the loss of power disabled the horn (as others have suggested) than that the crew thought it wasn't worthwhile because there was insufficient time for anyone on the bridge to fare any better anyway!

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#784

Post by ChainOfFools »

efitz wrote: post #767
jameshart wrote: post #748

Earlier quoted context omitted.

Isn’t there a pretty big difference in how much rudder authority you get between just making way astern, and having the engine in full reverse while still traveling forwards at seven knots?

It's complicated. The rudder is a wing, it's just vertically oriented and underwater. The rudder is capable of stalling, just like any wing. The rudder only produces lift related to the flow of water over the rudder. The lift produced by the rudder is what is experienced as turning force. The tiller or wheel changes the angle of attack. I used to helm a racing sailboat with a high aspect (long & narrow) rudder. It co…

I'm only a minimally experienced (coastal cruising) sailor so there's plenty of things I don't know, but this is the first time I've heard the rudder as a wing (lifting surface) rather than as a neutral control surface.

It sort of makes high-level sense that a lifting bias could in theory work as a counteraction to propwalk. But the terminology is a bit confusing because aerodynamic lift is a byproduct of air being a compressible medium, whereas water is not. Maybe lift means something different when we're talking about water?

At any rate in scenarios where the prop is not engaged, which in a sailboat is most of them, I don't think I've ever noticed a tendency for heading to track predominantly one way or the other, in circumstances where it seems that would be very pronounced and hard to miss, like extended running downwind. Is the lifting body rudder mainly a performance boat thing? Or perhaps am I just so used to trimming this bias out that I don't recognize where it's coming from?

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#786

Post by efitz »

Arrath wrote: post #739
ProllyInfamous wrote: post #648

Earlier quoted context omitted.

As an inland armchair-captain, I want to admonish that tugboats should probably always be stationed around bridges to intercept such off-course mariners.

It seems much more reasonable to only disengage the tugboats that were already helping the container ship get under way once it clears navigation hazards like the bridge, instead of keeping 24/7 quick-response tugboats at the bridge that try to intercept an out of control ship in a bare few minutes.

Moving large boats across water is slow. The Francis Scott Key bridge was 8600 feet long, or 1.4 nautical miles. AFAICT there were just over 4 minutes from the time that the first power outage started until the ship struck the piling.

A modern harbor tugboat can go perhaps 15 knots. In 4 minutes this means it would travel 4 nautical miles, at the very best (running start in correct direction).

So let's say that there would have been 4 minutes for a tugboat to (1) become aware of the problem, (2) travel to the location of the ship, (3) figure out what it needs to do, (4) maneuver into position [keeping in mind it might need to move to the other side of a 900' ship moving 8 knots] and (5) move the ship. And this assumes that the tugboat was idle in the first place.

There just would not have been enough time to do anything meaningful if the tug wasn't already right at the ship, on the correct side.

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#787

Post by nemanja »

mcv wrote: post #616
wlll wrote: post #573

Earlier quoted context omitted.

> in my experience with a 40ft sailboat with a single propeller you have absolutely no rudder authority while reversing. In general it depends on the rudders and the boat. Longer keeled boats don't respond well in reverse at all but more modern boats (like mine, 1990) will do better but will still need some way to have steerage. I can certainly manouver around the marina in reverse, it's just harder than forwards and…

Going backwards in the marina I often steer on the engine rather than the rudder (though I keep the rudder aligned with the engine of course). Obviously that's in a tiny sailing boat with an external engine, but I thought large ships also often have a steerable front propeller to assist with steering and mooring. Although maybe these very large ships use tugboats for that.

Well if you keep rudder aligned with the engine (i.e. parallel) you are really using both, not just the engine.

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#788

Post by quasarj »

adameasterling wrote: post #752
boringg wrote: post #397

This is a tragedy for those involved. My rough calculus points that the amount of force of this collision is on par with a large scale natural disaster. Everyone being surprised at the bridge collapsing needs to reconcile with the amount of force that struck the bridge - it is a truly significant amount of Newtons that hit the bridge. More than a train going from full speed to a full stop. Unbelievable amount of forc…

> Everyone being surprised at the bridge collapsing needs to reconcile with the amount of force that struck the bridge ... I am also a bit surprised at how many people don't grasp this or grasp engineering, magnitude of forces and design principles. A spokesman for CalTrans claimed today that Bay Bridge could have taken the same hit without damage, thanks to fenders that protects all pylons for all bridges in the San…

"A ship traveling at 8 knots" is a meaningless statement. You need to know how bit the ship is...

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#789

Post by elihu »

paddy_m wrote: post #568
araes wrote: post #541

Earlier quoted context omitted.

Current personal suspicion after watching your linked video (excellent discussion by the wgowshipping author) is: Catastrophic engine failure (1:24) causing wide scale power loss. No rudder control, rudder drift, and ship alignment drift (1:24-1:25:30) Power restored and ship reengages prop with bad ship/ruddder alignment (1:25). However, ship is now pushing itself into a further bad turn. Pilot likely stomps the bra…

On ships like this the propulsion is separate from the steering. There is a separate rudder that is close to, but not attached to the prop and propshaft. The propshaft is fixed. The rudder doesn't just "restart in a random position" it would remain in the previous position unless there was a physical piece that broke in the rudder gear. The fact that ship was able to reverse hard ( as evidenced by the slowdown), indi…

Do big container ships like this typically just have a standard propeller/rudder without some kind of directional thruster to assist in maneuvering?

https://en.wikipedia.org/wiki/Voith_Schneider_Propeller

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#790

Post by ElijahLynn »

ajdude wrote: post #481
jxdxbx wrote: post #136

Not that it matters to anyone else, but having driven across that bridge dozens of times with my kids, this is just shocking. It’s one of the main corridors in the area. Thank god it happened in the middle of the night, though that’ll be no consolation to the families of those who may have died.

I was incredibly worried about my dad, he's a truck driver and drove that bridge just an hour prior to this happening. I'm hearing there were at least 20 cars and a truck on the bridge, plus construction workers, at the time; my heart goes out to those families

There is a semi-truck that enters from the right just before the crash at https://youtu.be/N39w6aQFKSQ?t=299 (4m59s). And some more vehicles that follow after. Doesn't seem like they stopped "all" traffic as is claimed.
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