Correct. As soon as the astern command is given with the engine turning ahead, on conventional engines (with camshaft) the camshaft and the start air distributor will move to the astern end positions and the braking air will be introduced and fuel introduced when the engines kicks astern at around 20 rpm. Ahead engine speed corresponding to about slow ahead or slightly above should be easily possible to reverse. On the Dali at 8 kts or so, with all electronic timing and start air distributor (no delay) should have possible to start the engine astern if they had stable power.
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Even with a speed of 7-8kn, the flow velocity going over the rudder will be less, because of the wake of the hull, and with the propeller not turning the flow will not hit the rudder straight. I think with the propeller stopped, the flow will be much more disrupted than let’s say, when the propeller is turning at low rpm to push the ship at low speed.
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I think the second blackout in port on DG3 due to insufficient fuel pressure is the causal factor related to both the first and second blackout on the passage. While the report does not mention that the drop in fuel pressure in port is momentary, I think it is a momentary event (probably lasting a few seconds) c causing the engine to sputter with frequency dropping/hunting due to engine speed and also possibly voltage dropping/hunting as the auto voltage regulator (AVR) of the generator does not respond or compensate quickly.
So what could be the cause of the momentary drop in pressure. Cannot be the fuel service tank level low. The fuel circulating booster pumps malfunction or defective can also be ruled out as it would a more permanent condition. Which brings us to a possible malfunction of the auto fuel filter.
It is fair to assume that an automatic back flushing filter would be installed on the fuel line to the engine – possibly one in each of the DG rooms servicing 2 DGs each. These auto filters similar to the Boll and Kirsch design will have multiple cannisters with each cannister housing fine filters. One of the cannisters will be on stby and when the dP across the filter reaches a preset value, the stby cannister is taken into service and the one of the in-service cannisters is now ready for backflush with compressed air, filling the chamber with fuel and then onto a stby status. I have experienced trouble with these types of filters whereby the pressure drops when the stby filter is taken into service either due air in the system due to incomplete filling or a sluggish drain valve that does not close quickly, etc leading to a momentary drop in pressure.
The effect of the above cause is a disturbance on the steady state of the engine and alternator. In port DG3 breaker dropped out either due to low frequency or voltage. In the passage, possibly the same scenario with fuel pressure dropping momentarily with DG3 and DG4 on line. And that too with a lot more load than in port, the voltage and frequency disturbance may be more acute. It is possible that the voltage drop/hunting caused HR1 under voltage coil to ‘buzz’ and drop out. Kind of explains the flickering lights. Also possible the same momentary drop in pressure caused the second blackout as well with the breakers opening. In other words, all these blackouts possibly are initiated by the same causal factor.
Winds were NNE 15-20 when I woke up the morning of the accident on Chesapeake Bay. I believe they had been blowing that way throughout the night.
A port arrival requires an astern test. That involves stopping the engine then allowing the ship to slow to the point the engine will start astern. That’s about 6 kts on the ships I was on. Ship was a bit sluggish with the engine stopped but still had good steerage in light winds and in deep water.
Most senior deck officers would be aware of how the ship responds to the rudder in that scenario. The situation with the Dali would differ of course, being a different ship in a different situation at that specific time and place.
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On the steering gear system with 2 hydraulic power systems and 3 motors (2 pumps feeding one power system) as per the attached and the systems can be isolated in case of a piping failure, the performance requirement for the 3rd motor/hyd power unit is 15 deg to 15 deg in 60 secs at half speed (or 7kts which ever is greater). Possible Dali has this arrangement and SG3 powered from the ESB meets the 15-15 in 60s. The hydraulic power unit 1 with 2 motors will need to meet the 35-30 in 28s at rated speed and summer draft. Makes sense that during maneuvering all three pumps were operational.
Does not really matter if the rudder was essentially useless per the discussion above.
I don’t understand what’s being said here.
According to the formula the Dali (and containerships in general) fits in the category of ships that trim down by the stern.
Are you saying the Dali would have likely trimmed down by the head?
3 posts were split to a new topic: Technical Analysis of NTSB Preliminary Report M/V Deli
“…what is being said here” - where??
“…According to the formula the Dali” … what formula do You have in mind Sir? The formulas I have inserted in my comment ??? - My inserts are from " Browns Almanach" - but there are many formulas : Barras s formula and other , there are formulas that take into account different types of canals ,their shapes ( parameters) . So pls be so kind and pin point the formula You have in mind.
Regarding triming by the head: Yes I am suggesting Dali could have trimmed by the head when underway.
I am a bit disappointed by the report and wonder why her departure draft was given in feet. ( 39.9) , of course there is no problem to convert but her draft marks surely were in mtrs . At the moment of writing this comment I have not checked what was reported earlier from Marine Traffic (Ais). But I will do it later.
So NTSB says it was 39.9 ft EVEN KEEL. But it does not say where this figure comes from. They I think should have given drafts from :
a) loadicator and
b) eyeballed. I do not know if it was eyeballed by chief mate or duty mate and I do not know if it was taken for example from electronic draft indicator because some mates are too lazy to move their asses on land and take a walk. Had in my career several champions like that who did not even check /verify accuracy of such equipment.
But basis the NTSB report and basis it was true (eyeballed) draft fore and aft even keel of 39.9 ft =12.16 mtrs , then yes I do confirm my suspicion and/or suggestion she could have trimmed by the head when underway.
Another issue . I was on many container ships and almost never had I I experienced (coincidentaly) even keel after finishing loading/unloading ops .
I made even keel on very rare ocasions when there was draft issue in port and minimum draft was required for passing a bar or sth like that. Therefore this even keel on dep Baltimore smells badly to me.
Now the cherry on top of the cake.
On my last vessel chartered to Maersk line on East Africa Tanjung Pelepas run via |Mauritius and Madagaskar we were ORDERED by Maersk Mumbai who was our operator to sail with trims by the head as they were doing some effing experiments claiming it is better for fuel economy. I need to dig into my records as I saved some of their tables and explanations.
I Joined the vessel in Mauritius relieving Ukrainian Master who mentioned it to me during handover. The officers (deck/eng) were Ukr, Rus and PH mix and crew all PH. So I asked him how they are handling this situation as requirements were to trim 1-1.5 mtr by the head which I found completely CRAZY .
However the Ukr. Master explained , that they were cheating Maersk line Mumbai by reporting trim by the head on departure but sailing with or close to even keel .Nedless to say they were misreporting same to Greek Owners. One of the reason they did it was that when they tried once to follow exactly Maersk Orders regarding sailing trim the cheng and engine crew complained about an increased alarm in the engine room what meade lifen and work miserable and exhausting.
I followed the example for one month and then decided to finish this nonsense and flately refused to participate in this circus. Made a report to Owners explaining all the reasons but Owners insisted to follow Maersk orders claiming they do not want to purturb and antagonise their VERY PRECIOUS client.
I have refused to follow and Maersk as per Charter Party requested form Owners replacement of an " uncooperative master" . So After 2.5 months I was replaced by another Ukr Master. Interesting enough is that what I found later on ,all expences (hotels , plane tickets etc, etc ) were paid not by Owners/Crew managers but by Maersk -the charterer .
Rgds
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A post was merged into an existing topic: Technical Analysis of NTSB Preliminary Report M/V Deli
Spo
Pain in the butt for the engine room when the vessel is trimmed by the head. All the drains from the spill containments are usually located aft. So leaks splash around and make a mess with the rolling onto the deck outside the containments. Mostly DG containments. Not to mention outlets from tanks - designed for even keel or slight trim aft.
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Exactly .That is what I reported to Greek Owners after interrogating in depth the Ukr.Cheng .We listed all the problems , including measurement of liquids in all the tanks including sump tank. Manual measurements were not a problem as tables had trim correction to 1.5 mtr by the head but all electronic measuring devices were showing a complete B.S. Not to mention steering as vessel reacted clumsily to helm orders .
It was a real nightmare for them so they resorted to cheating. I choose another path to present honest arguments against it and had to say bye bye to another two monts salary. But everybody has his own RED LINE. Mine was there and I decided to hold the line. 
. Another example how commercial or other pressure works in reality.
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According to report pretty much even keel
Why did the vessel drift to starboard? I don’t know.
I’ve never been on a ship of any type which steered straight with 0 deg rudder for an extended period. Some have better directional stability than others.
Even two sister ships will have a slightly different steering tendency.
The same ship will steer differently depending on how its loaded.
Trim by the head? Some are a bit faster, Steering tends to be less effective, More rudder impute required. More or less fuel efficient?
Squat usually has greater effect forward. Inducing trim by the head. Steering less effective. problem solved by reducing speed. This ship was big had a relatively deep draft but was going relatively slow.
Bank effect, again like squat. relative to speed. Big ship narrow channel, not going fast. Nice theory. I don’t by it. Contributing factor, ? Along with wind ect.
I don’t have any local knowledge. A local Pilot probably would know if bank effect was a problem. Even if they didn’t know it was bank effect. A Pilot would know where you tend to get a drift, sheer or wander to a particular side or not.
The chance the ruder was exactly midship at the point when the shit hit the fan. Not high.
The QM was steering a co requested by the pilot. He or She adjusted as required to stay on co.
Even if I bothered to look up the prevailing conditions at the time. I don’t know the port.
Its not unusual for a vessel to require more impute in a narrow channel then open water to maintain a co. There are lots of subtle effects. Even a small current effects how the ship steers.
Knowing a channel or approach you know where you will probably get pushed this way or that way.
Which is why its called local knowledge.
Why do I always get a slight sheer as I pass a particular spot? Sometimes its the current, Sometimes its the wind? Trim, Draft, shape of the bottom, ect.
The problem here without power, there was no way to correct the normal imperfections induced by the prevailing conditions at the time. Result the ships head started to wander. In this case to STRB.
It would be unusual for the ships head not to wander. After a loss of power and steering. Without correction. The factors resulting in the wander of to starboard may have increased the further she wandered of course.
The only thing I can be reasonably confident of. Nobody is going to be able to model it accurately. There are just to many variables.
One of the effects on steering, Prop walk, occurs when you are going ahead. You don’t notice it. The QM or auto adjusts the rudder the counter this effect. Among others.
Stop the prop. No more walk.
Where is the ruder.
The small ruder impute to counter the prop walk is still there.
Did it have an effect? I don’t know.
As per report, without propeller wash, the rudders effect is greatly reduced. Not gone.
Looking at he vessels track. As per report. After loss of power I see no evidence of the effect of propulsion or rudder impute.
I do notice a slight decrease in speed which, I’m not sure of.
I don’t see the effect of a dragging anchor. Until perhaps there might have been a reduced speed very shortly before impact.
To some extent, even after the NTSB figures out all the contributing factors.
This comes down to really bad luck. It happened right in a terrible spot. The time and place where everything added up to hitting the support for the bridge dam near head on.
A bit sooner a bit later. Near miss, Instead it was a direct hit.
Even though timing is everything, Planning could probably have prevented this.
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A post was merged into an existing topic: Technical Analysis of NTSB Preliminary Report M/V Deli
Yes, my mistake. You’ve not included any calculation of block coefficient.
Articles about parametric rolling often use values less the 0.7 for containerships, 0,65 perhpas being typically.
In the case of the Dali the actual value is not known.
That is funny as we were both thinking abt it at the same time .
As I was just about to give You another answer
It is not about mine or your mistake as we both speculate trying to understand Dali phenomenon of loosing steering at abt 8 kts. As per available literature with her Lpp/B ratio she should be very responsive to helm orders when trimmed by the stern , less responsive when at even keel and sluggish or poorly responsive, when trimming by the head underway. Unavailability of prop wash surely negatively affected responces in all 3 cases.
I am not sure but have to check the Ever Given discussion as I think i posted there and attachment by DNV GL regarding new designs of cont vessels where it was clearly stated some may have Cb btw 0.72-0.75.
But may be it will not be necessary to check as I have found another source confirming that value of Cb.
I could not calculate Cb of Dali without hydrostatic data, plus my Lpp of Dali is rather speculative figure based on differences btw LOA and Lpp of other vessels . Hence had to use suplementary data from literature on ship’s handling, that promted me to hypothesise Dali Cb was larger then 0.7 .
Her LOA 299 > Lpp abt 287 ratio to B=48 287/48= 5.98 which is very low in comparison with all my cont vessels . For example my Zim Bejing was 300 LOA Lpp=287 and only B=32.5 Then the ratio Lpp/B was 8.83 . So the diferrence of ratio of Zim and Dali is huge.
Container ships designs have changed over the last 25 years and the hulls seem a lot “bulkier” then slim elegant lines of our younger years.
Here are some designes which I will use as comparison with Dali .
And here are some parameters :
I will leave it to You to calculate the Lpp/B ratio of cont vsl types in the above table and compare it with Dali.
Hence my speculation and extrapolation of plausible Dali Cb to even 0.75 .Of course her true Cb at given draft of 39.9 ft even keel can only be determined precisely having access to her hydrostatic data .
Rgds
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From the report:
The NTSB report is a JOKE.
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