what would the auto pilot do if a collision occurred ?

we see the Crystal changed heading from 68 deg to 112 deg from time 127 to 130

would autopilot do such a turn ?

diff topic:

have been looking at the Crystal pics more.

very rough estimate:

from water line to top of the bow rail is about 41 feet

8 meter draft would mean there is 26 feet of Crystal underwater. Besides the bulbous bow, don't know how much of that draft added to the underwater damage



Crystal had a gash across the very front of the bow. The gash is mostly on the port side. It is about 21 feet up from the water line

This message has been edited. Last edited by: sdy,

The Collision caused the turn, not the autopilot. The autopilot on ECDIS could do such a turn if you programmed your route that way intentionally, but not as sharply as on the AIS. Well, the entire reason Costa Condordia sank was because it couldn't turn sharp enough to miss the island, similar sized ship as the freighter, pull up it's AIS track to compare the turns. We studied that in length in my HELM class recently.

When the autopilot encounters an unusual strong force causing the boat to turn, the boat will turn quite a bit, then it takes a minute to figure out what happened and then will start working it's way back to course. If it is too far off or too hard to get it to course it will alarm and stop steering entirely. With ECDIS it should not stop working entirely, but will take a few minutes to go right back to the course line it was on.

On a yacht, I've used all of the different brands of autopilots. Ships usually use the same ones we do such as Furuno. For example if you're on a twin engine boat at 8 mph and you take one engine out of gear, the boat will naturally make a fairly hard turn in the direction of the engine you took out of gear. Put Port engine in neutral, vessel will turn to port........what will happen on autopilot is it still will turn to port and probably make a 60-90 degree turn before the autopilot stops the turning motion a minute later, then the autopilot will slowly start working it's way back to starboard and may take 1-5 minutes to get back on your course heading.

Trust me on this one. Everyone on board the Crystal felt and heard the collision inside of the ship, there is no doubt in my mind that it was felt like rearending the car in front of you at 20 mph.

I think the bulbous bow hit the destroyer hull first and rolled the destroyer susper structure towards the crystals bow and caused that to collide but the super structure kept the bulbous bow from peeling away more of the destroyers aluminum hull..... Aluminum is no match for steel in a collision.

CNN update -

Navy is working the theory that 5 of the 7 may have become 'incapacitated' as soon as the collision happened.

It may never be known if anyone was still alive when the hatch was shut.

I thought these paragraphs were worth noting:

The official also noted the Navy is trying to corroborate accounts which suggest that the two sailors who weren’t almost instantly “incapacitated” attempted to help the other five escape the incoming water.

“But at some point the ship somehow lost communication,” with the two sailors and they also perished, according to the official. All seven were found dead in the flooded area.

The official emphasized that the Navy will wait for all the investigations to be completed before coming to any conclusions about the actions of the crew and decisions over citations for heroism or potential disciplinary action.

The official also strongly emphasized that no judgments are being made about the timing of the decision to shut the watertight hatch. It is also not clear if those on the bridge called the commanding officer as the crisis unfolded.

http://fox61.com/2017/06/23/ne...led-oakville-sailor/

quote:

Originally posted by jimmy123x:
Aluminum is no match for steel in a collision.

The only aluminum in the Fitzgerald is in the funnels, we were assured about a week ago.

quote:

Originally posted by jimmy123x:

I think the bulbous bow hit the destroyer hull first and rolled the destroyer susper structure towards the crystals bow and caused that to collide but the super structure kept the bulbous bow from peeling away more of the destroyers aluminum hull..... Aluminum is no match for steel in a collision.

The hull is steel.

Aluminum is used above the main deck in the superstructure to save weight and increase speed of the vessel.

quote:

Originally posted by JALLEN:

quote:

Originally posted by jimmy123x:
Aluminum is no match for steel in a collision.

The only aluminum in the Fitzgerald is in the funnels, we were assured about a week ago.

You are correct. The USS fitzgerald is steel hull and steel superstructure according to what I just looked up. They may use aluminum in areas of the superstructure to save weight. I assumed the entire superstructure was built out of Aluminum on the hull and superstructure to save weight (for more speed and also so they could carry more gear/weight). I don't know how much aluminum is used in it's superstructure. I do know you cannot weld aluminum to steel and they cannot be touching, they need to be isolated due to galvanic corrosion and they use a synthetic material in between the two metals.

That being said, the bulbous bow is the strongest part of the hull on that entire freighter.

http://www.nvr.navy.mil/SHIPDE...PSDETAIL_DDG_62.HTML

quote:

Originally posted by jimmy123x:
I think the bulbous bow

There's a huge piece protruding from the bow of the cargo ship under water we're not seeing.

quote:

Originally posted by braillediver:

quote:

Originally posted by jimmy123x:
I think the bulbous bow

There's a huge piece protruding from the bow of the cargo ship under water we're not seeing.

Someone posted a picture of the Crystal light on cargo (a few pages back) that shows the bulbous bow which is mostly out of the water when the vessel is light.....and completely underwater when the Crystal is loaded with cargo.

this is DDG 62 in drydock a year ago (July 2016)

The dome under the bow is the SQS-53 hull sonar

This message has been edited. Last edited by: sdy,

quote:

Originally posted by jimmy123x:
I do know you cannot weld aluminum to steel and they cannot be touching, they need to be isolated due to galvanic corrosion and they use a synthetic material in between the two metals.

You most certainly can weld the two together....you just have to use a "datacoupler".

The USCG has over 80 ships with steel hulls and aluminum superstructures...they are joined with a datacoupler-which is literally a strip of the two types of metal that were compressed under explosives; such that the two metals are now one....when the side of the metal strip is unpainted you can actually see the two different types of metal.

Regarding the photo sdy posted above, I'm a little surprised there isn't a tarp or something keeping eyes away from the hull.

detailed pics of the SQS-53 and the transducer structure are on the open net

even details on transmit characteristics

quote:

Originally posted by sdy:
detailed pics of the SQS-53 and the transducer structure are on the open net

even details on transmit characteristics

Interesting. I thought all that was double top secret requiring the Secret Squirrel decoder ring.

quote:

Originally posted by MikeinNC:

quote:

Originally posted by jimmy123x:
I do know you cannot weld aluminum to steel and they cannot be touching, they need to be isolated due to galvanic corrosion and they use a synthetic material in between the two metals.

You most certainly can weld the two together....you just have to use a "datacoupler".

The USCG has over 80 ships with steel hulls and aluminum superstructures...they are joined with a datacoupler-which is literally a strip of the two types of metal that were compressed under explosives; such that the two metals are now one....when the side of the metal strip is unpainted you can actually see the two different types of metal.

Love the truth bombs getting dropped in here.

quote:

Originally posted by ulsterman:

quote:

Originally posted by sdy:
detailed pics of the SQS-53 and the transducer structure are on the open net

even details on transmit characteristics

Interesting. I thought all that was double top secret requiring the Secret Squirrel decoder ring.

I've been in quite a few dry-docks over the years and Navy ships are always hidden.

quote:

Originally posted by jimmy123x:

quote:

Originally posted by JALLEN:

quote:

Originally posted by jimmy123x:
Aluminum is no match for steel in a collision.

The only aluminum in the Fitzgerald is in the funnels, we were assured about a week ago.

You are correct. The USS fitzgerald is steel hull and steel superstructure according to what I just looked up. They may use aluminum in areas of the superstructure to save weight. I assumed the entire superstructure was built out of Aluminum on the hull and superstructure to save weight (for more speed and also so they could carry more gear/weight). I don't know how much aluminum is used in it's superstructure. I do know you cannot weld aluminum to steel and they cannot be touching, they need to be isolated due to galvanic corrosion and they use a synthetic material in between the two metals.

That being said, the bulbous bow is the strongest part of the hull on that entire freighter.

http://www.nvr.navy.mil/SHIPDE...PSDETAIL_DDG_62.HTML

Why not look it up before you post so you know what you are talking about?

The link you gave says it is all steel, hull and superstructure.

It seems like a lot of what you know ain't so.

Crystal bow flares out significantly.
Crystal is about 100 feet wide




My guess right now is that initial contact was at the top of the bow where the rail is bent back.

edit: after looking at more pictures, it sounds misleading to say the bow rail hit before the bulbous bow. The bow rail and bulb probably hit at virtually the same time.



If the estimate of the height is correct (at 41 feet) that means the very initial contact was rather high on DDG 62.

edit: other pictures show the Crystal draft at 9 meters rather than 8. That would make the height from water line to bow rail to be about 38 feet

edit: it looks like the bulb projection starts at just below the 8 m draft point. So the bulb may have penetrated DDG 62 at 3 to 4 feet below the water line. How much lower the penetration would be depends on the complete shape and depth of the lower part of the Crystal


At 18.5 knots Crystal was doing 31 feet /sec


If the 44 deg course change of Crystal was due to the collision then DDG 62 would likely experience a large reaction too.

Since Crystal didn't slow hardly at all, have been wondering what the sequence was for the 2 ships to disengage. Perhaps DDG 62 was physically displaced (violently pushed away)after a very brief time from the collision.

This message has been edited. Last edited by: sdy,

Does this help?

Those last two pics of the Crystal really put it in perspective. Wow.

that's the best pic yet of the bulb

If I am reading the draft indicators correctly there is still another 13 feet or so below the pic to the bottom of the hull.