Negative slip

spongebob
27th January 2009, 09:39
Negative slip

A recent conversation with an ex naval man brought to mind a time when our twin screw vessel left Auckland for Melbourne and after rounding North Cape we took a course well westward before heading down to our Australian landfall at Wilson’s promontory. For most of the three day run down the Tasman sea the distance traveled equaled or exceeded the theoretical distance due to the pitch of the screws, i.e. three days at neutral or negative slip.
The second mate was an avid navigator, living and sleeping the subject and on asking about this event he claimed to have steamed westward to pick up a seasonal ocean current that gave us this ‘free ride.’
I can appreciate this happening in enclosed waters such as a flowing river or a with a strong tide flow in a narrow strait but my companion is very skeptical about this happening over such a distance.
It happened 50 years ago and the second mate may have been pulling my leg so I would be pleased if some of you Navigational experts could comment..

Bob

Orbitaman
27th January 2009, 10:41
If the ship picked up the East Australian current, the negative slip would be possible as this current runs at two to three knots. However, to take advantage of the current, it would have required a significant deviation from the normal route from Auckland to the Australian coast to take advantage of the current.

In conclusion, it is possible to have negative slip on a three day passage or possibly longer if you do follow one of the advantageous ocean currents. However, in this case, it would be hard to believe that such a deviation would be tolerated by Master or owner!

I was on one ship in the 1980's where the 2nd Mate recorded negative slip for the entire voyage from the Persian Gulf to Jeddah, but that was down to the 2nd Mate having inside information on the engine distance each day and adjusting the ships run accordingly to register negative slip. The poor Chief Engineer couldn't believe it!

Lancastrian
27th January 2009, 13:16
There is no such thing as "negative slip" except as a fictitious entry in Engine Room logbooks. A ship cannot travel further through the water than that which the propeller (or the wind) pushes her. She can of course travel further over the ground if the body of water is moving in the required direction at whatever rate.

Mike S
27th January 2009, 13:33
We had a run heading to Tahiti from Panama on the Rangitane one voyage where the distance made good was further than the old Doxfords had pushed us. Call it what you like but we had an extra 18 hours in Tahiti to show for it.
The Equatorial current was running a "banker" that trip ...... we even topped 19 knots made good one 24 hour run. There was no way the old girl ever managed that in her life!
We even made it into Auckland early!
We carried it almost all the way to the Tuamoto Achipelego and the Fakarava Channel.
Hows that for an old memory! It was 46 years ago........(Smoke)

surfaceblow
27th January 2009, 15:53
I have sent up a lot of negative slip entries up to the Bridge and Master on the Noon Slips. The ship was usually in the Gulf Stream and or had the wind behind the ship.

The only negative slip I did not believe was on ships with controllable pitch propellers you could never be sure that the pitch was constant. Especially on the home bound leg very morning I would have to lower the engine speed and pitch when on bridge control. The throttles seem to move only when the engine room was unmanned according to the data recorder.

I sailed with one Chief Engineer who had his own Chief Engineer's Noon Report printed on the reverse side he had the formulas and constants printed along with his definitions of each term. His definition for slip was Percent Mate inefficiency. His view was positive slip was due to all of the turns that the mates did not record example turning to avoid fishing vessels, turning to return vessel to course line and the Williamson Turn Drill's. Of course back then there was no GPS or Sat Nav's.

I do not remember any one getting mad at the time the deck department was just glad to get the Noon Report. The Chief would nap after lunch so I would fill out the slip before returning to the engine room with the log book.

Lancastrian
27th January 2009, 16:10
The whole problem with slip calculations is that they compare chalk with cheese. What the Engine Distance should be compared with is Distance Through Water but that is not available, (unless you have a very accurate log, which I've never seen), so the 2nd Mate gives the Chief Distance Over Ground which is all that he can calculate with any accuracy, (on a good day before GPS).
To my mind all these figures which have been religiously entered in logbooks over the years are completely meaningless.

Derek Roger
27th January 2009, 16:46
On Brocklebanks Mahsud and Maihar we had KaMeWa CP propellors and they always recorded a negative slip .
The process was to take the "K' reading on the OD box and record it in the log. The "K" reading was then checked against a graph which gave the pitch ; this was then used to calculate the distance etc.
The Graph curves were obviously incorrect . We had discussion with the office and pointed out that the log entries were meaningless and a waste of time but were advised to continue doing the calculations .
Some of the Mates would argue that it was because the CP Propellors were more efficient than a fixed wheel which of course was drivel and caused some heated discusion in the bar when we had nothing else to talk about .

Derek

sidsal
27th January 2009, 18:51
What an interesting thread !! There wasn't anything like negative slip in my day - seems it was a technological development by these clever people !
Talking of useless recording of things - do you remember in the 60-70's when you were returning to the UK by plane the stewardess would hand out cards and you had to fill in name, passport number etc. This often involved digging for your passport etc. When I was in the air taxi business we had to get our 8 passengers (or less) to fill them in and I would take them to an office in the terminal at Manchester (MI6) I believe. I once asked the chap what they did with these thousands of cards. He said - "Nothing - we ditch them when they take too much room up "!!

spongebob
27th January 2009, 21:33
Thanks for all that learned comment. It comes to mind that the second mate, Jack,I cannot recall his surname, later went on to become the chief examiner at the NZ Marine Department in Wellington so his navigational zeal was real.
Mike, I do believe that performance of the Rangitane, she was a great ship.

Bob

Mike S
28th January 2009, 11:34
Indeed she was Bob.......my favourite ship.

I am trying to dig out a picture I had of her alongside in Kingston Jamaica. She looked a picture that day.

Klaatu83
29th March 2009, 19:00
I've seen negative slip occur on a day's run, but rarely for an entire passage unless it was a fairly short passage. When sailing northbound along the U.S. East Coast we used to hold well offshore in order to catch the Gulf Stream which, in places, can be well over five knots. On the other hand, while southbound we used to keep as close inshore as possible in order to avoid the current, or even catch a slight counter-current. The captains used to say that you were too far offshore if you couldn't count the bikinis on the Florida beaches!

Windsor
20th May 2013, 19:12
Joined a ship on the N. Atlantic trade in the sixties. Browsing through Reed's almanac I saw a recommendation that when sailing a great circle from North of Ireland to South of Newfoundland one should keep 15 miles North of the track going West and the same distance South when returning East. (Gulf Stream?) I thought it worth a try. Day one - negative slip and derision from the Chief! The same on each succeeding day. Admittedly my sights were the usual North Atlantic variety,( i.e. sometimes the brightest cloud etc!), but I stuck to my guns, and on making a landfall I was proved right! The same happened on the homeward trip, and on several succeeding voyages, except when the weather was more than usually foul.

Waighty
26th May 2013, 17:21
In Bank Line after loading through the South Pacific islands and heading for Panama it was company policy as I recall to head North Easterly (052 (T) if leaving Apia in Samoa), until picking up the Equatorial Counter Current; it was supposed to speed up the passage.

Klaatu83
26th May 2013, 19:09
I do recall one long passage that we did from Alexandria to Galveston, Texas; which our captain planned via the Straits of Gibraltars, SW towards the Canary Islands, Westwards towards the Bahamas, through "Hole in the Wall" (as we used to call New Providence Passage), and then into the Gulf of Mexico by hugging the Florida Keys as closely as possible to avoid the Gulf Stream. He took full advantage of the prevailing SE "trade winds" and ocean currents, and did everything possible to avoid contrary winds and currents. Our ship, which had a normal service speed of 18 knots, averaged over 20 knots during that passage, and I believe she also achieved a negative slip for the entire passage. It was a good demonstration of what can be achieved, even in modern times with a power-driven vessel, providing a passage is carefully planned to take maximum advantage of favorable winds and currents. I might add that out captain used nothing more sophisticated than a common Pilot Chart to plan that passage.

Andy Lavies
26th May 2013, 20:06
If you could pick up the Equatorial Counter Current (and keep it) it could make a difference of a couple of days in getting to Panama. I can remember taking sights every hour or so when in the expected vicinity to see whether we were making any easting. Must be a lot easier with GPS but would you be allowed to do your own navigation or is it all dictated by somebody, or some computer, ashore.

Andy

oldman 80
27th May 2013, 03:02
Negative slip

A recent conversation with an ex naval man brought to mind a time when our twin screw vessel left Auckland for Melbourne and after rounding North Cape we took a course well westward before heading down to our Australian landfall at Wilson’s promontory. For most of the three day run down the Tasman sea the distance traveled equaled or exceeded the theoretical distance due to the pitch of the screws, i.e. three days at neutral or negative slip.
The second mate was an avid navigator, living and sleeping the subject and on asking about this event he claimed to have steamed westward to pick up a seasonal ocean current that gave us this ‘free ride.’
I can appreciate this happening in enclosed waters such as a flowing river or a with a strong tide flow in a narrow strait but my companion is very skeptical about this happening over such a distance.
It happened 50 years ago and the second mate may have been pulling my leg so I would be pleased if some of you Navigational experts could comment..

Bob

Negative Slip seldom, if ever, occurs in reality.
Where negative slip is recorded it is usually because the Chief Engineer has used the observed days run in his calculation (ie distance between noon sights (or GPS) over 24 hour period) when he should not have done so . !!!!!!!
The slip should be calculated by comparing distance travelled by the propeller with the distance travelled through the water - not over the ground (sea bed). ["Through the water" distance is measured by the ships log - mechanical, electronic, or pressure type.]

(Ouch)

spongebob
27th May 2013, 07:07
The actual situation was that the ship had steamed from a defined point A to a defined point B over several days and the recorded prop revolutions x actual pitch during that time amounted to a lesser distance. Obviously ocean currents and or windage played a part.

Bob

oldman 80
27th May 2013, 07:28
The actual situation was that the ship had steamed from a defined point A to a defined point B over several days and the recorded prop revolutions x actual pitch during that time amounted to a lesser distance. Obviously ocean currents and or windage played a part.

Bob

Thank you for that.
It is just as I have already indicated, the distance between the defined points A & B were obviously used in the Chief Engineers calculation. That distance should not have been used, as it incorporates the effects of current and leeway.
Slip is determined (or should be determined) by comparing propeller distance with the log distance, measured by the ships log.
(Sad)

WilliamH
27th May 2013, 08:48
I am not going to argue over the definition of "slip" but when I was CE I was required to record the difference between the distance traveled by the vessel and the theoretical distance traveled by the engine revolutions (pitch x engine revolutions)' this we called slip, I relied on the Second Mate for distances covered. On many occasions I remember recording negative "slip" so how were the various Second Mates measuring the distance covered. One other point "slip" measured using distance over the ground could be used by Head office engineering staff when arguments arose over a vessels service speed and also indicte that the ships bottom needed cleaning.

oldman 80
27th May 2013, 11:28
I am not going to argue over the definition of "slip" but when I was CE I was required to record the difference between the distance traveled by the vessel and the theoretical distance traveled by the engine revolutions (pitch x engine revolutions)' this we called slip, I relied on the Second Mate for distances covered. On many occasions I remember recording negative "slip" so how were the various Second Mates measuring the distance covered. One other point "slip" measured using distance over the ground could be used by Head office engineering staff when arguments arose over a vessels service speed and also indicte that the ships bottom needed cleaning.

Hmm, I see.
I don't disagree with your comment in quotes.
That doesn't make it right though.
Slip is as I have clearly outlined - determined by comparison of propeller distance with distance "through the water" - not over the ground.
With respect to the 2nd Mates distances - it seems they have not included the log distance along with days run in their noon chit to the Cheng - perhaps because the log was not working, or maybe even, not streamed.
When you were Chief Engineer was that with a Ship Management Company ?
It sounds a bit like it to me.

Derek Roger
27th May 2013, 17:31
Negative Slip seldom, if ever, occurs in reality.
Where negative slip is recorded it is usually because the Chief Engineer has used the observed days run in his calculation (ie distance between noon sights (or GPS) over 24 hour period) when he should not have done so . !!!!!!!
The slip should be calculated by comparing distance travelled by the propeller with the distance travelled through the water - not over the ground (sea bed). ["Through the water" distance is measured by the ships log - mechanical, electronic, or pressure type.]

(Ouch)

Using your stated definition of slip ( with which I do not disagree; although most definitions use the term actual ships speed but fail to indicate how this is to be calculated )then one can Never have actual negative slip as it is impossible to have a propeller with more than 100% efficiency .
It is also something which would only have to be calculated from time to time as a measure of hull condition .The calculation would depend on a ships log of either Sal Log type with pitot tube or a Doppler log .It would not matter that the log had n error as long as it was constant . With a clean hull good sea conditions the slip could be calculated for a particular vessel and used for comparison at a later time to evaluate hull condition .
In my company we were require to make the calculation daily ( which as I said before was a useless piece of information ; in particular with the C.P Props where bye the actual average pitch for the day was a best guess using a chart showing pitch )
On our older ships not fitted with in hull Logs the only time the Taffril logs were streamed was in decent weather so I am sure the bridge "actual speed " was by calculation by observations or dead reconning which made the calculation of slip even more useless due to errors in observation and the effect of tide wind and current .
All I know is that it took me an extra couple of minutes in completing my log before going for a pint before lunch .


Derek

oldman 80
27th May 2013, 18:17
Using your stated definition of slip ( with which I do not disagree; although most definitions use the term actual ships speed but fail to indicate how this is to be calculated )then one can Never have actual negative slip as it is impossible to have a propeller with more than 100% efficiency .
It is also something which would only have to be calculated from time to time as a measure of hull condition .The calculation would depend on a ships log of either Sal Log type with pitot tube or a Doppler log .It would not matter that the log had n error as long as it was constant . With a clean hull good sea conditions the slip could be calculated for a particular vessel and used for comparison at a later time to evaluate hull condition .
In my company we were require to make the calculation daily ( which as I said before was a useless piece of information ; in particular with the C.P Props where bye the actual average pitch for the day was a best guess using a chart showing pitch )
On our older ships not fitted with in hull Logs the only time the Taffril logs were streamed was in decent weather so I am sure the bridge "actual speed " was by calculation by observations or dead reconning which made the calculation of slip even more useless due to errors in observation and the effect of tide wind and current .
All I know is that it took me an extra couple of minutes in completing my log before going for a pint before lunch .


Derek

Ah well, yes of course, the variable pitch prop (Nautical) would definitely be another "headache" when it came to slip calculations.
In aviation it is known as a constant speed prop, as opposed to a fixed pitch prop. Ships of the air, are somewhat different, although in many ways they are not. There are many " parallels " between the two.
A Good posting Derek, - so much of it so true.
With respect to the other guy and management company tactics (William H) all I can say is with regard to the condition of the ships bottom, it was easier to just look at it rather than calculate it. Today, with the availability of mini underwater ROV's, (some very reasonably priced,) that should present little in the way of any problems at all.

Derek Roger
27th May 2013, 22:08
Ah well, yes of course, the variable pitch prop (Nautical) would definitely be another "headache" when it came to slip calculations.
In aviation it is known as a constant speed prop, as opposed to a fixed pitch prop. Ships of the air, are somewhat different, although in many ways they are not. There are many " parallels " between the two.
A Good posting Derek, - so much of it so true.
With respect to the other guy and management company tactics (William H) all I can say is with regard to the condition of the ships bottom, it was easier to just look at it rather than calculate it. Today, with the availability of mini underwater ROV's, (some very reasonably priced,) that should present little in the way of any problems at all.

Agreed ; short dive over the side will reveal all .
Regarding propellers however there is a misconception that all ( solid cast ; for the want of a better word ; are fixed pitch ) Propeller design is such to my understanding a very a very complex science and most modern designs of ( solid ; not controllable ) props have a variable pitch i.e It is not a constant pitch as in the case of an Archimedes Screw ; the pitch by design changes from the hub to the blade tip .
The correct terminology for a Prop . which has the ability to move its blades from Ahead to Astern or anywhere in between is a Controllable Pitch Prop.

My interest in the subject is of local interest here in Rothesay New Brunswick . In 1927 a local man Wallace Turnbull invented the first controllable pitch Prop for Aviation . His original Prop is on a wall in our local airport . I was however also called a Variable pitch propeller and it may well have been a fixed pitch that was controllable .
Therein lies the dilemma of what is the correct name or lack of understanding of the science .
The same applies to aircraft as to marine applications .

Look forward to the views of the experts .

We shall not fall out over the issue ; I will leave that for "The Ashes "

Regards Derek

Rocket_Ron
27th May 2013, 22:22
No Derek. If it can`t be moved its a fixed pitch prop.
It will have a different angle of attack, blade thickness, aspect ratio along its length, but it is fixed.

Derek Roger
27th May 2013, 23:05
No Derek. If it can`t be moved its a fixed pitch prop.
It will have a different angle of attack, blade thickness, aspect ratio along its length, but it is fixed.

So you are saying that all cast ( I e immovable blades are fixed pitch and cannot have a varying pitch from the root ( Hub ) to the tips ???)

Cheers Derek

Rocket_Ron
27th May 2013, 23:30
So you are saying that all cast ( I e immovable blades are fixed pitch and cannot have a varying pitch from the root ( Hub ) to the tips ???)

Cheers Derek

The pitch will (in all probability) differ along the length of the blade. But because they are not variable, they are termed fixed pitch.

Derek Roger
27th May 2013, 23:59
The pitch will (in all probability) differ along the length of the blade. But because they are not variable, they are termed fixed pitch.

The correct definition is Controllable when the pitch can be changed by mechanical means .

Having sailed with many and built a number of vessels the propellers were always designated CP ( Controllable Pitch ) Not VP . Check the likes of LIPS who had many CP systems .

Cisco
28th May 2013, 00:11
This works for me.... http://www.propellerpages.com/?c=articles&f=2006-03-08_what_is_propeller_pitch

Re the distance 'steamed' through the water and the calculation of slip.... pre SAL, Chernikeef, and Doppler logs coming into vogue I rarely if ever sailed on a ship where a Walkers Patent Log was streamed as a matter of course. This of course meant that the calculation of 'slip' was a nonsense, often making little more sense than 'Zanzibar Time'.

oldman 80
28th May 2013, 01:26
This works for me.... http://www.propellerpages.com/?c=articles&f=2006-03-08_what_is_propeller_pitch

Re the distance 'steamed' through the water and the calculation of slip.... pre SAL, Chernikeef, and Doppler logs coming into vogue I rarely if ever sailed on a ship where a Walkers Patent Log was streamed as a matter of course. This of course meant that the calculation of 'slip' was a nonsense, often making little more sense than 'Zanzibar Time'.

Aye indeed.
I Sailed on a few ships back in the early to mid 1960's where the Patent log was streamed - it was very much a cadets job streaming and hauling it.
And then of course there was the old drum type sounding machine which required you to hold a "feeler" on the wire as you let it run to the bottom having armed the lead, and all that stuff.
We all took it very seriously, in the full and certain knowledge that the Orals Examiner of Masters and Mates would throw us out of the orals examination room if we didn't.
Sorry Cisco - but nostalgia may be beginning to flourish once again, both at sea and in the air, so to speak, - despite your feelings on the matter.
Yes indeed, I feel Nostalgia may be returning at last.

spongebob
28th May 2013, 03:22
I have checked my very old diary re this voyage to be reminded that it had more drama than a matter of ‘under screwing’
The MV Kaitoa left Auckland 5/11/59 and arrived Adelaide to load oranges 14/11/59, a long time ago.
I am sure that the chief engineer, a competent man, would have calculated his log report in the correct manner. I recall the event of a fast passage was a frequent discussion in the Mess about the ship having travelled further than the propellers screw motion but as most of you say there is a difference between travel between two fixed points and through the water medium when helpful or hindering currents affect the passage.
It is a long time ago and I am not saying that the daily log recorded ‘negative slip’ but the conversation led by the enthusiastic second mate allowed us to witness this unusual assistance from an ocean current. I guess a European Canal Cruiser would experience the same effect steaming down the Rhine but mid ocean, the effects are not often very noticeable or dramatic.

Bu wait, there is more to recall about this voyage. We sailed from Adelaide on Wednesday 18/11/59 for Lyttelton via a southern route through Foveaux Strait and while heading north up the East Coast in very heavy weather we picked up a May-Day call from MV Holmglen, a coastal trader en-route from Dunedin to Wanganui. We were north of her position and on attempting to go about to join a search we rolled heavily and our cargo of cased oranges shifted enough to warn us back on our original course and to produce a list. This was mainly corrected by pumping ballast as I recall and we were ordered to continue on to Lyttelton until more information came to hand.

Only one call was received from the Holmglen and nothing else emerged as to what went wrong. She was later found sunken about 35 km ESE of Timaru with a loss of all the 15-crew members. An empty lifeboat and three bodies were later recovered.
Something was bugging me as I struggled to recall this drama then I remembered that Holmglen’s normal Chief Officer had been on leave in Wellington and was prevented from re-joining his ship due to the bad weather that closed Wellington Airport, a blessing in disguise. He is my Namesake, Bob Jenkins, now in his eighties and retired in Wanganui.

Google
home engels - Shoreline-man.name (http://www.shoreline-man.name/holmglen/14_homeengels.html) and roll up


Bob

Michal-S
28th May 2013, 12:31
From "Ship Design and Performance for Masters and Mates" by Dr C.B. Barrass (see: attachment).

chadburn
28th May 2013, 13:38
The difference between speed by engine revolutions and a ships actual speed through the water is the "apparent slip" and this is invariably expressed as a percentage of the engine speed in knots.
Should the actual speed be greater than engine speed for any given revolutions there exists what is termed "negative slip" which is found on a ship with a very full Stern profile.

David Campbell
29th May 2013, 01:40
There can be no such thing as "negative slip", it is "apparent negative slip". I was Chief Engineer for 30 years and logged the term every day in my Abstract. Got the days run every afternoon from the 2nd Mate. The only use for it from my obsevation was that when the ship required docking, comparing the slip over a long period, there was a much larger positive slip percentage.

oldman 80
29th May 2013, 02:04
From "Ship Design and Performance for Masters and Mates" by Dr C.B. Barrass (see: attachment).

Oh my god ! This is Nostalgia at its best.
Admiralty Coefficients are back.
It sooooooooooooooo exciting, so it is. (Scribe)

oldman 80
29th May 2013, 03:27
Sorry guys but I just can’t resist it.
Post # 31 has stirred something inside me.
I am minded of that day January 29th 1993, when I was lined up on runway 14 Mackay, in Queensland Australia awaiting clearance for take off.
Beside me sat the CAA Examiner of Airmen, (Mike) who was conducting my final flight test for my Multi Engine Command Instrument Rating. As I sat there making final adjustment to the pitch controllers for each propeller and monitoring each manifold pressure , just awaiting that clearance from the tower, I remember relating some comments to the examiner about propeller pitch, slip, and Admiralty Coefficients. I could sense he wasn’t completely at ease, as he was looking at me sideways with a sort of “ funny look” on his face.
Then Nigel came through on the headset, (another of Australian Aviation greats), “Echo Delta Hotel you are cleared for take off”. As I released the brakes and rammed the throttles open, my examiner, I suspect, knew he was in for a bit of a ride, and, as it turned out at the end of the flight, so was I.
Wow !
What an experience that particular Two hour thirty minute flight test was.
I was 47 years of age, and had 10 years command experience in very large sea going vessels, yet that was the day, and that was the flight when I finally realised what the very limit of my own personal endurance and ability was.
That’s what they do in aviation, they take you to the very limits of human endurance, push you over the edge, and then pull you back again – in a jiffy, - just like that.
At the end of that examination flight, I stepped from that aircraft, shaking a bit, and saturated in perspiration. The examiner then took me by the hand with a big smile on his face and said, “Congratulations , - You have Passed” .
As a mariner many might think the greatest day of my life would have been the day I was finally appointed to Command a rather magnificent Swedish Built O.B.O. of some 105,000 dwt tonnes.
(she was orange, and grey, with some cream)
However that would not be true. The greatest day of my life came 13 years later, as I stepped from that aircraft in Mackay, Queensland , Australia.
What an experience – was that flight test.
It simply blew me away.
That was Mike – one of Aviations finest – I suggest.

Derek Roger
29th May 2013, 03:40
Sorry guys but I just can’t resist it.
Post # 31 has stirred something inside me.
I am minded of that day January 29th 1993, when I was lined up on runway 14 Mackay, in Queensland Australia awaiting clearance for take off.
Beside me sat the CAA Examiner of Airmen, (Mike) who was conducting my final flight test for my Multi Engine Command Instrument Rating. As I sat there making final adjustment to the pitch controllers for each propeller and monitoring each manifold pressure , just awaiting that clearance from the tower, I remember relating some comments to the examiner about propeller pitch, slip, and Admiralty Coefficients. I could sense he wasn’t completely at ease, as he was looking at me sideways with a sort of “ funny look” on his face.
Then Nigel came through on the headset, (another of Australian Aviation greats), “Echo Delta Hotel you are cleared for take off”. As I released the brakes and rammed the throttles open, my examiner, I suspect, knew he was in for a bit of a ride, and, as it turned out at the end of the flight, so was I.
Wow !
What an experience that particular Two hour thirty minute flight test was.
I was 47 years of age, and had 10 years command experience in very large sea going vessels, yet that was the day, and that was the flight when I finally realised what the very limit of my own personal endurance and ability was.
That’s what they do in aviation, they take you to the very limits of human endurance, push you over the edge, and then pull you back again – in a jiffy, - just like that.
At the end of that examination flight, I stepped from that aircraft, shaking a bit, and saturated in perspiration. The examiner then took me by the hand with a big smile on his face and said, “Congratulations , - You have Passed” .
As a mariner many might think the greatest day of my life would have been the day I was finally appointed to Command a rather magnificent Swedish Built O.B.O. of some 105,000 dwt tonnes.
(she was orange, and grey, with some cream)
However that would not be true. The greatest day of my life came 13 years later, as I stepped from that aircraft in Mackay, Queensland , Australia.
What an experience – was that flight test.
It simply blew me away.
That was Mike – one of Aviations finest – I suggest.

Well done ; who cares about slip . Derek

Ian Harrod
29th May 2013, 04:19
In Bank Line after loading through the South Pacific islands and heading for Panama it was company policy as I recall to head North Easterly (052 (T) if leaving Apia in Samoa), until picking up the Equatorial Counter Current; it was supposed to speed up the passage.

And took you into the rain belt for a drop of long overdue fresh water!

NoR
29th May 2013, 10:17
I was on one ship in the 1980's where the 2nd Mate recorded negative slip for the entire voyage from the Persian Gulf to Jeddah, but that was down to the 2nd Mate having inside information on the engine distance each day and adjusting the ships run accordingly to register negative slip. The poor Chief Engineer couldn't believe it!

How did he hide the extra miles?

NoR
29th May 2013, 10:35
In aviation it is known as a constant speed prop, as opposed to a fixed pitch prop. Ships of the air, are somewhat different, although in many ways they are not. There are many " parallels " between the two.
.

A constant speed propellor uses a contant speed unit (CSU) to continually vary its pitch so as to maintain constant rpm.

Not sure if ships had anything like this. If they did I guess it would be based on torque.

chadburn
29th May 2013, 12:21
There can be no such thing as "negative slip", it is "apparent negative slip". I was Chief Engineer for 30 years and logged the term every day in my Abstract. Got the days run every afternoon from the 2nd Mate. The only use for it from my obsevation was that when the ship required docking, comparing the slip over a long period, there was a much larger positive slip percentage.

I was covering all sizes of vessels in my comment, "negative slip" occurs when it is found that the wrong size Prop has been fitted when carrying out Trials covering the range from Slow to Full.

WilliamH
29th May 2013, 14:26
Geordie Chief I don't quite understand what you mean in your last post.
As I see it there is confusion about apparent slip, positive and negative. The confusion comes from the way the speed of the vessel is measured ie. through the water or distance relative to the earth. I studied for my "tickets" at South Shields Marine starting in 1964. At that time the head of Naval Architecture was E.A . Stokeo, he had the usual string of letters after his name but the main one indicted he was a member of Royal Instute of Naval Architects. He gives the definition of apparent slip as (engine revolutions x pitch) minus distance travel by vessel and then he goes on to give two methods of obtaining the distance traveled by vessel. 1 speed through water and 2 speed over the ground but he does not say which method is the correct method to use.

submarine
29th May 2013, 16:26
Hi WilliamH,
I have before me a 1963 Reed's Naval Architecture by none other than E. A. Stokes.
PITCH If the propeller is assumed to work in an unyielding fluid, then in one revolution of the shaft the propeller will move forward a distance which is known as the Pitch.

" If the ship speed is measured relative to the surrounding water, i.e. by means of a log line, the theoretical speed will invariably exceed the ship speed, giving a POSITIVE apparent slip. If, however, the ship speed is measured relative to the land, then any movement of water will affect the apparent slip, and should the vessel be travelling in a following current, the ship speed may exceed the theoretical speed, resulting in a NEGATIVE apparent slip "

His letters, M.R.I.N.A., M.I.Mar.E., M.N.C.E.Inst To add some weight.


Reed's were one of the bibles at the time.

Dave

chadburn
29th May 2013, 16:31
"Apparent Slip" is as you have indicated and calculated by using the ships actual speed through the water. As also indicated Stokes was the "Main "man, however, it is important that before the log line is deployed it must be well wetted and stretched by those intending to deploy it.

Derek Roger
29th May 2013, 16:37
Hi WilliamH,
I have before me a 1963 Reed's Naval Architecture by none other than E. A. Stokes.
PITCH If the propeller is assumed to work in an unyielding fluid, then in one revolution of the shaft the propeller will move forward a distance which is known as the Pitch.

" If the ship speed is measured relative to the surrounding water, i.e. by means of a log line, the theoretical speed will invariably exceed the ship speed, giving a POSITIVE apparent slip. If, however, the ship speed is measured relative to the land, then any movement of water will affect the apparent slip, and should the vessel be travelling in a following current, the ship speed may exceed the theoretical speed, resulting in a NEGATIVE apparent slip "

His letters, M.R.I.N.A., M.I.Mar.E., M.N.C.E.Inst To add some weight.


Reed's were one of the bibles at the time.

Dave

Agree 100% . He does not tell how it should be recorded in a ships log ; obviously there is an option . Still a piece of meaningless information other than perhaps indication the vessel has picked up a favorable current or otherwise if ships speed over the land is being used .
From my recollection in Brocklebanks the distance travelled was from noon position to noon position ie over the ground . Oldman indicates this is not correct .

oldman 80
29th May 2013, 20:48
O.K. lets try another approach - the simplest possible.
Let us assume we have a perfect propeller ie. no slip.
A ship moves through a body of water by a certain distance - lets say " X" nautical miles.
As in this case we have a perfect propeller the distance travelled by the (zero slip) propeller will therefore be "X" nautical miles also.
The fact that the body of water may have moved "over the sea bed" (ocean current) has nothing to do with the determination of slip.
Propeller Slip is a comparison, (if you like) between theoretical distance the propeller should have travelled through the water and the distance it has actually travelled through the water.
The movement of that block or body of water over the sea bed due to ocean current has nothing to do with the matter - absolutely nothing at all.

Edit:- Speed has nothing to do with it either, except for the fact that speed is a direct correlation between distance and time. Speed should not even be mentioned in the argument - to do so only creates confusion, - so why mention it ?

chadburn
29th May 2013, 22:13
Apparent Slip. The difference between speed by engine revolutions and a ships actual speed through the water is the "apparent slip" and this is expressed as a percentage of the engine speed. After you have calculated the engine speed in knots the % slip can be calculated as follows; (engine speed - actual speed) x 100 over engine speed in knots = .

Derek Roger
29th May 2013, 22:33
Agree Oldman ; However the dilemma seems to be whether it should be based on distance over the ground compared to propeller distance or distance the ship has logged through the water compared to propeller distance recorded .
A significant difference .
The first proposal is only of use re fouling ( and would not require logging every day ) .
The second would let the navigator know when he has picked up a good current ; favorable tide or wind or an unfavorable situation ( which seems to make more sense ; otherwise why log it ? )

An interesting discussion ; all I know is that the requirement to log it and put in in my abstract just wasted time in having a beer before lunch .

The text books don't seem to have addressed how it should be recorded .

For my part I am certain it was logged as Prop distance v noon position distance day to day in the company I sailed with .
All this information was sent to head office and I am sure nobody even looked at it yet alone tried to make any sense of it .

We shall not fall out on the issue ( will wait for the Ashes for that one )

Regards Derek

oldman 80
29th May 2013, 22:46
Agree Oldman ; However the dilemma seems to be whether it should be based on distance over the ground compared to propeller distance or distance the ship has logged through the water compared to propeller distance recorded .
A significant difference .
The first proposal is only of use re fouling ( and would not require logging every day ) .
The second would let the navigator know when he has picked up a good current ; favorable tide or wind or an unfavorable situation ( which seems to make more sense ; otherwise why log it ? )

An interesting discussion ; all I know is that the requirement to log it and put in in my abstract just wasted time in having a beer before lunch .

The text books don't seem to have addressed how it should be recorded .

For my part I am certain it was logged as Prop distance v noon position distance day to day in the company I sailed with .
All this information was sent to head office and I am sure nobody even looked at it yet alone tried to make any sense of it .

We shall not fall out on the issue ( will wait for the Ashes for that one )

Regards Derek

If I were a betting man, which I am not, I'd lay my money on what you have said is in fact the reality of the situation you were faced with at the time. However as I have said before, it does not mean it was the correct way of doing it - far from it in fact.
Besides, as a wise man said not long ago (#36) - Who Cares about slip ?

Cheers,
(Pint)

Derek Roger
29th May 2013, 22:46
Apparent Slip. The difference between speed by engine revolutions and a ships actual speed through the water is the "apparent slip" and this is expressed as a percentage of the engine speed. After you have calculated the engine speed in knots the % slip can be calculated as follows; (engine speed - actual speed) x 100 over engine speed in knots = .

Agreed ; The question is was that comparison based on a deck log distance or from noon positions . That seems to be Oldmans point .
My experience was that it was a comparison of prop distance against noon positions ; which was of use to the navigator as to whether the vessel had picked up favorable or otherwise conditions .

The actual Prop distance travelled v Ship distance travelled through the water would not vary over a short period of time therefore why log it daily ?? The only way it could vary is by fouling which takes time or propeller damage .

chadburn
30th May 2013, 13:17
I would think its agreed that "slip" can be affected in a number of ways like fouling, increase with speed, draft and with head winds and seas, all will cause an increase in slip, it will decrease as the bunkers are emptied, reduced speed along with fair winds and seas. In answer to your question, the patent log showing "the actual" distance sailed by the vessel.

peter3807
31st May 2013, 01:45
Negative slip

A recent conversation with an ex naval man brought to mind a time when our twin screw vessel left Auckland for Melbourne and after rounding North Cape we took a course well westward before heading down to our Australian landfall at Wilson’s promontory. For most of the three day run down the Tasman sea the distance traveled equaled or exceeded the theoretical distance due to the pitch of the screws, i.e. three days at neutral or negative slip.
The second mate was an avid navigator, living and sleeping the subject and on asking about this event he claimed to have steamed westward to pick up a seasonal ocean current that gave us this ‘free ride.’
I can appreciate this happening in enclosed waters such as a flowing river or a with a strong tide flow in a narrow strait but my companion is very skeptical about this happening over such a distance.
It happened 50 years ago and the second mate may have been pulling my leg so I would be pleased if some of you Navigational experts could comment..

Bob

Taking the route from Europe to Brazil advantage was gained from the Canaries current until the equatorial counter currents which involved a small amount of allowance for set. You then picked up advantage from the Brazil current. Obviously you were disadvantaged on the return journey.
Routing to the US gulf through the NE Providence channel you took a line to the Florida keys with a large amount of set for the gulf stream to get close to the keys to take advantage of the counter current. From the Gulf at about the Dry Tortugas you set yourself in the main axis of the gulf stream. hung on to your hat and flew along.
When working out my abstracts for the charterers I still don't understand why the Chief got so wound up about slip. He still got a little brown envelope.I didn't.

chadburn
31st May 2013, 12:01
Who care's about slip? The Engineer does, no such thing as negative slip? of course there is especially when the vessel is new as it usually indicates someone has slipped up and the prop fitted is too small.
In regards to why did Head Office want the figures? there is a lot of truth in who were the figures for the ships owners or a Management Company.
Those on the site who sailed under the Israeli Flag in the late 1960's early 1970's and carrying part of an Armoured Brigade as Deck Cargo to Israel will understand why I would used the the Patent Log as the routing to Israel was not exactly direct, there was a lot of zig-zag going on!! My little "Brown envelope" indicted how many Bonds I had bought as part of my pay deal.

Andy Lavies
31st May 2013, 14:45
Large slip - CE teases Old Man. Negative slip - Old Man teases CE. Simple!

Andy

chadburn
31st May 2013, 21:26
Large slip - CE teases Old Man. Negative slip - Old Man teases CE. Simple!

Andy

From one "surfing" to another, 30 years later(Jester)

Derek Roger
1st June 2013, 00:38
No one has yet said how slip should be recorded in the noon log ? except Oldman )
Is it propeller miles against ship position miles ( by observations ) or compared to ships distance by log through the water .
A significant difference .
I wish some of our Master Mariners would comment further .

Derek

eldersuk
1st June 2013, 01:14
All we Chief Engineers and Masters with all our learning cannot agree on how to deal with apparent slip.

I will now tell you the reason for all these figures.

There is a guy in Head Office with a piece of paper divided up into squares and he needs some numbers to put into these squares because that is his job, just to fill his bit of paper. He doesn't give a tinker's cuss if they are positive, negative, admiralty coefficients, crank deflections, specific fuel consumption or whatever, in fact he almost certainly doesn't understand them anyway.

When his piece of paper is full it is filed away, not to see the light of day again until 50 years later when somebody is doing some research in the archives of the Merseyside Maritime Museum or wherever....and HE doesn't understand them either.

That's what all your sweat and worry and wrestling with fractional indices is for.

That's one of the joys of retirement, you can say things like that now, and they can't even stop your pension!

Derek

spongebob
1st June 2013, 01:17
I am beginning to feel the angst and division cause by this thread that I started
a long time ago!!

Bob

submarine
1st June 2013, 01:56
Having been caught up in this thread I have some satisfaction now knowing that as a Jnr.Eng. on the 8 to 12 logging total prop revs. for 24hrs. and passing it upward that I was in at the bottom floor (plates) in its journey to the mysterious head office desk.
Dave

Mike S
1st June 2013, 02:13
To be honest Derek, I don't think it matters a tinkers cuss as to whether it is distance made good on sights or distance by log, they were both a little less accurate at times than desirable. A couple of poor sunsights and no stars for a couple of days and the whole lot was getting a little out of whack. A log reading would have been more like it as it was measuring distance through the water however that literally depended on how long the piece of string was!
Just another useless bit of information to fill in a little square in the log book. (Thumb)

Cisco
1st June 2013, 03:52
No one has yet said how slip should be recorded in the noon log ? except Oldman )
Is it propeller miles against ship position miles ( by observations ) or compared to ships distance by log through the water .
A significant difference .
I wish some of our Master Mariners would comment further .

Derek
I don't think it was ever recorded in the deck log, just in the run book.
Slip should involve distance through the water ie by log....
A Walkers or any other sort of log should by quite accurate... and if there is an error it should be a constant error.
A few weeks ago on my present command I calibrated a new Raymarine paddle wheel log... measure mile sort of thing at slack water on a quiet day... should be pretty accurate now.

Distance made good over the ground can be quite a different animal... think of a 15 knot ship with a 1 or 2 knot favourable or adverse stream . Thats not all that uncommon... the east going stream in about 40S is in the order of 1 knot... 24 miles a day added to a 360 mile run through the water.

Peter Martin
1st June 2013, 09:17
I recall one voyage where, if the CE's calculations were to be believed, the Doxford arrived in port six hours before the ship!!

joebuckham
1st June 2013, 10:23
the slip used, and recorded by the chief on any ship i was ever on was the difference between the geographical distance of agreed consecutive noon positions, whether, deduced reckoning, astronomical positions, true positions or a mixture of them and the engine distance produced by the chiefs mathematics, in multiplying the pitch of the propeller by the revs per min by the number of minutes passed between noon positions.(Thumb)

Cisco
1st June 2013, 10:28
the slip used, and recorded by the chief on any ship i was ever on was the difference between the geographical distance of agreed consecutive noon positions, whether, deduced reckoning, astronomical positions, true positions or a mixture of them and the engine distance produced by the chiefs mathematics, in multiplying the pitch of the propeller by the revs per min by the number of minutes passed between noon positions.(Thumb)

So pretty meaningless then?

I found that most engineers... wonderful people all.... had no real concept of how a ship actually moved across the face of the planet...

Quite often in settled conditions I have heard engineers explain that the behaviour of the engines was due to the current......

Cisco
1st June 2013, 10:40
Moving right along but sticking with stuff that made no sense....
Fresh water abstracts....
I was one a ship once trading between two ports.... FW taken wasn't metered at either end and lots was used for washdowns after discharge.... so for years people had been doing a totally BS FW consumption/taken etc etc abstract.
As mate I took a unilateral decision to stop sending them in... it was 4 months before someone in the office realised that their day was not quite as exciting as it used to be.......

joebuckham
1st June 2013, 11:12
So pretty meaningless then?

I found that most engineers... wonderful people all.... had no real concept of how a ship actually moved across the face of the planet...

Quite often in settled conditions I have heard engineers explain that the behaviour of the engines was due to the current......

yup!! (Jester)

Fred Field
1st June 2013, 11:12
Quite often in settled conditions I have heard engineers explain that the behaviour of the engines was due to the current......

Tongue in cheek
Under certain conditions that is a fact.
Take the Agulas current off the SW corner of Southern Africa. The temperature of that can drop like a whores drawers with the fleet in on pay night (I was once corrected on that expression by a beery old second engineer with 'what makes you think a good ***** wears any laddie?'). On a turbine steamer that can give a significant increase in obtainable condenser vacuum with the corresponding increase in power.
Therefore it could be correct.
As I said, tongue in cheek!

Cisco
1st June 2013, 11:26
Umm....the Aghulas current is warm... things would improve on a steamboat when you hit the cold Benguela off Cape Aghulas or thereabouts ...

Which brings us to the Persian Gulf , the inefficiency of steamboats thereabouts and the increase of internal volume on large tankers...

Early 70s they were having lots of probs with cargo delivered compared with cargo loaded according to ship's paperwork.... you build a ship in sweden in the winter its going to be a lot bigger up the Gulf in summer....

Supergoods
1st June 2013, 11:49
About 25 years ago I was under tow on the Ocean Bounty in the vicinity of Dogger Bank en-route from Bilbao to a location in the Northern North Sea.
There was a strong North westerly wind and progress was a little slow.
The tug, a Maersk 12000bhp if I remember correctly, had a towing speed on this job of 4.5 knots.
The relatively shallow propeller depth caused a lot of slip when going into the weather.
Speeds were 2 knots with the tide and 1 knot astern going against the tide.
That would have made for some interesting slip calculations and it seems, from the earlier posts that the engine distance and the overall distance for the 24 hours would be very different from the six hour figures when going against the tide.

Ian

Fred Field
1st June 2013, 11:49
Umm....the Aghulas current is warm... things would improve on a steamboat when you hit the cold Benguela off Cape Aghulas or thereabouts ...

Which brings us to the Persian Gulf , the inefficiency of steamboats thereabouts and the increase of internal volume on large tankers...

Early 70s they were having lots of probs with cargo delivered compared with cargo loaded according to ship's paperwork.... you build a ship in sweden in the winter its going to be a lot bigger up the Gulf in summer....

I'me going to blame the 'mates' anyway, I was always led to believe it was the Agulas current, but I do know on the steamer I was on we could still tweak the burners down a touch when we hit the cold current, whatever its name was, and still maintain the required 'revs', important on a mail-boat.

On a more practical side, and prompted by your observations about volumetric capacities altering with temperature it would appear that one could get more cold beer in a warm glass than warm beer in a cold glass, assuming the same nominal original capacity. An interesting research project?

Cisco
1st June 2013, 12:09
...it would appear that one could get more cold beer in a warm glass than warm beer in a cold glass, assuming the same nominal original capacity. An interesting research project?
You get the funding... I'll do the research......

Re Agulhas.... what you say is correct but it was when you slipped out of the Aghulas Current that things improved....

Same as why you could go swimming in False Bay with nothing to fear but the Nobby Clarkes while if you went for a dip at Sea Point your goolies would seek refuge alongside your tonsils...

Fred Field
1st June 2013, 12:13
[QUOTE=Cisco;681306]You get the funding... I'll do the research......

[/QUOTE

After me!

Cisco
1st June 2013, 12:25
How does that work?

Just been giving it more thought.... further east of Aghulas not so much the Benguela as the counter currents inshore ... same same running up the east coast of Oz on low powered ships you would duck into every bay to get the counter current... I assume the sea temp was lower.

Back in a mo.... I'll see if I can find a pic of the Falklands Current's temp....

Cisco
1st June 2013, 12:43
This is a bit rough...in fact as rough as guts but you can see the Falklands current ( blue) pushing up to around Mar del Plata... for much of the year it extends as far as Uruguay.... stick in that north bound... go further offshore when southbound...

PS the black bits are where the sea was obscured by cloud....

joebuckham
1st June 2013, 13:32
the actual name is agulhas current(Jester)after the cape

oldman 80
1st June 2013, 14:28
No one has yet said how slip should be recorded in the noon log ? except Oldman )
Is it propeller miles against ship position miles ( by observations ) or compared to ships distance by log through the water .
A significant difference .
I wish some of our Master Mariners would comment further .

Derek

Hmm - not a bad idea I suppose.
Perhaps it would be best if we did that by invading the Engine Room Forum.
Better still perhaps, "All Masters and Mates to the engine room, and all engineers to the bridge."
Actually that is not as daft as it may seem, - provided of course it does not occur simultaneously - on mass, - so to speak.
I used to love spending time down below, whenever I got the opportunity.
Know your ship - that is important, but you certainly will never achieve that, if you confine yourself to the bridge.

Derek Roger
1st June 2013, 15:30
As Chief Eng I did most stand byes on the Bridge with the Old Man . Let the 2nd look after the pit .
Regarding the slip issue it has been a most interesting dialogue with out some or the argument we find in other threads .

oldman 80
2nd June 2013, 01:57
As Chief Eng I did most stand byes on the Bridge with the Old Man . Let the 2nd look after the pit .
Regarding the slip issue it has been a most interesting dialogue with out some or the argument we find in other threads .

An interesting post Derek.
There was a "drift" toward that (Cheng & Oldman on the Bridge) in my latter years at sea. Unfortunately however, or fortunately, which ever way you choose to look at it, my company included in it's operational manuals the specific requirement that the Chief Engineer MUST be in the Engine Room/Local Control Room or Station, when the vessel was on Stand By. That requirement was periodically included and emphasised in routine communications between head office and the ship.
I remember my "Promotion to Command" briefing in Head Office very clearly, face to face with Company Directors, back in 1980. My job, as much as any other, was to ensure my vessel was operated strictly in accordance with the provisions laid down in the Company Operating Procedures Manual, and the Company Rule Book. That was the requirement imposed upon me - that's what I was paid for, and that is what I did, so far as was possible.
There are of course "limits", depending on the circumstances of the case.
In those days, I even remember one instance when a Chief Engineer was on the bridge when a pilot boarded the vessel. He immediately questioned the Chief Engineers presence in the Wheelhouse, and asked to have him committed to "the Pit" , otherwise unberthing would not occur .
That, if my memory is correct, occurred in a USA port, and yet the incident was in Head Office in the U.K.,( via the agents,) within 5 minutes. Fortunately, I had not yet rung S.B.E. as I was discussing a technical matter (which had just become apparent)with the Chief Engineer, which may have caused me not to ring SBE, maybe for at least a couple of hours. In the final event SBE was rung about 25 minutes later - the problem resolved sooner than expected.

I agree with your comments about the nature of the content of this string, and, in considering those comments at length, I ask myself this question, "Could it be we still have some Officers and Gentlemen around after all of these years" - despite "Ship Managers", "Port Captains" (???????) and the like. ?

(Thumb)

Cisco
2nd June 2013, 02:28
our twin screw vessel left Auckland for Melbourne and after rounding North Cape we took a course well westward before heading down to our Australian landfall at Wilson’s promontory. For most of the three day run down the Tasman sea the distance traveled equaled or exceeded the theoretical distance due to the pitch of the screws, i.e. three days at neutral or negative slip.
The second mate was an avid navigator, living and sleeping the subject and on asking about this event he claimed to have steamed westward to pick up a seasonal ocean current that gave us this ‘free ride.’

Bob
I've just re read the OP.....
If you look here http://www.tedperkins.com/nz/rip.htm at the first map you can see that while heading due west from Cape Reinga your ship would have experienced a current athwart the track... maybe the master and 2/0 both had experience of this when running to Sydney and maybe at certain times of the year there was a west going component. Then hanging a left near the Australian coast you would pick up the east coast current so yes all quite plausable. And it would also give you better weather...maybe.
We used to do a similar thing when running from Bass Strait to Fremantle. Shape a course up past Kangaroo Island ( sometimes passing inside KI if the weather was bad) to the latitude of Albany WA. (approx) then steer 270. Better weather and a west going counter current.

Derek Roger
2nd June 2013, 02:42
An interesting post Derek.
There was a "drift" toward that (Cheng & Oldman on the Bridge) in my latter years at sea. Unfortunately however, or fortunately, which ever way you choose to look at it, my company included in it's operational manuals the specific requirement that the Chief Engineer MUST be in the Engine Room/Local Control Room or Station, when the vessel was on Stand By. That requirement was periodically included and emphasised in routine communications between head office and the ship.
I remember my "Promotion to Command" briefing in Head Office very clearly, face to face with Company Directors, back in 1980. My job, as much as any other, was to ensure my vessel was operated strictly in accordance with the provisions laid down in the Company Operating Procedures Manual, and the Company Rule Book. That was the requirement imposed upon me - that's what I was paid for, and that is what I did, so far as was possible.
There are of course "limits", depending on the circumstances of the case.
In those days, I even remember one instance when a Chief Engineer was on the bridge when a pilot boarded the vessel. He immediately questioned the Chief Engineers presence in the Wheelhouse, and asked to have him committed to "the Pit" , otherwise unberthing would not occur .
That, if my memory is correct, occurred in a USA port, and yet the incident was in Head Office in the U.K.,( via the agents,) within 5 minutes. Fortunately, I had not yet rung S.B.E. as I was discussing a technical matter (which had just become apparent)with the Chief Engineer, which may have caused me not to ring SBE, maybe for at least a couple of hours. In the final event SBE was rung about 25 minutes later - the problem resolved sooner than expected.

I agree with your comments about the nature of the content of this string, and, in considering those comments at length, I ask myself this question, "Could it be we still have some Officers and Gentlemen around after all of these years" - despite "Ship Managers", "Port Captains" (???????) and the like. ?

(Thumb)

In my early days ay sea one never saw the Chief down below ; stand bye or otherwise.
The ships I sailed on in latter days were quite sophisticated at the time and the old men were quite happy to have some assistance on the bridge during stand bye . I would always go below before docking but not until then .

Derek

oldman 80
2nd June 2013, 09:53
I've just re read the OP.....
If you look here http://www.tedperkins.com/nz/rip.htm at the first map you can see that while heading due west from Cape Reinga your ship would have experienced a current athwart the track... maybe the master and 2/0 both had experience of this when running to Sydney and maybe at certain times of the year there was a west going component. Then hanging a left near the Australian coast you would pick up the east coast current so yes all quite plausable. And it would also give you better weather...maybe.
We used to do a similar thing when running from Bass Strait to Fremantle. Shape a course up past Kangaroo Island ( sometimes passing inside KI if the weather was bad) to the latitude of Albany WA. (approx) then steer 270. Better weather and a west going counter current.


Well it's all fascinating stuff, I suppose, but absolutely nothing to do with slip, negative or otherwise. There's heaps of potential in it for lengthy discussion on SET and DRIFT - for those so inclined, but it has no relevance to propellor slip.
(Night)

Cisco
2nd June 2013, 10:10
But everything to do with the OP..

'The second mate was an avid navigator, living and sleeping the subject and on asking about this event he claimed to have steamed westward to pick up a seasonal ocean current that gave us this ‘free ride.’
I can appreciate this happening in enclosed waters such as a flowing river or a with a strong tide flow in a narrow strait but my companion is very skeptical about this happening over such a distance.'

So your point, OM80, was what ed zackery?

Cisco
2nd June 2013, 10:14
PS.... not a lot to do with 'set and drift' more to do with passage planning.......

chadburn
2nd June 2013, 19:31
In the Head Office they had slip charts/tables/graphs for a particular vessel where all the information was entered on, they can reverse the info given by using these charts to keep an eye on/calculate the progress of the vessel.
I was always down below when docking/ undocking which in my view was the most critical time.
Long as a piece of string? the length of "string" on a Walkers Log was very critical as I remember, it will underegister if the "string" is too short!

Barrie Youde
2nd June 2013, 20:42
#77

In a long career in pilotage I never heard of any pilot query where the Chief Engineer might be.

Merely whether or not the engines were in working order!

Barrie Youde
2nd June 2013, 21:01
With apologies for going off-thread (if only a little), my mentor as a young man was O.G. Small, who some readers will remember as a Blue Flue pilot at Liverpool. He was a close friend of my father.

Blue Flue ran a joint service to Australia with Shaw Savill. OGS was docking at Gladstone one morning with a Shaw Savill ship, when the Dockmaster (Lockmaster?) on the quayside began calling, "Slow astern together", or words to that effect. Whereon the response from the bridge to the lockside was, "Just a moment, we're about to land a man and send him up to Harland and Wolff for that other engine. This one's single screw!"

randcmackenzie
2nd June 2013, 22:57
In my memory I am quite sure Denholm's regulations (The Green Book) called for the Chief Engineer to be immediately available and on call at Stand By.

Most Chief's I sailed with were very happy to handle the Bridge Control, and a very useful addition to the Bridge team they were.

Any anomalies with the movements resulted in short low keyed conversations with his henchmen below, and anything of concern was passed on.

Had any pilot requested the removal of the Chief or any other from the bridge I would have most certainly demanded another pilot had he insisted, happily I never met one that uncouth!

Barrie Youde
2nd June 2013, 23:08
#86

Many thanks randc.

Quite right, too!

Cisco
2nd June 2013, 23:41
After the fire on Capetown Castle in 1960 I believe Union Castle made it policy that all the senior engineers were not to be down below together at standby.

http://www.unioncastlestaffregister.co.uk/SHIP_CAPETOWN_CASTLE_01.html

oldman 80
3rd June 2013, 00:28
But everything to do with the OP..

'The second mate was an avid navigator, living and sleeping the subject and on asking about this event he claimed to have steamed westward to pick up a seasonal ocean current that gave us this ‘free ride.’
I can appreciate this happening in enclosed waters such as a flowing river or a with a strong tide flow in a narrow strait but my companion is very skeptical about this happening over such a distance.'

So your point, OM80, was what ed zackery?

Precisely as said/typed.
SET & DRIFT - nothing to do with propeller slip.
I can see you are very much the Ship Manager type - " shovelers of confusion - probably chaos as well "
(Gleam)

oldman 80
3rd June 2013, 01:11
In my memory I am quite sure Denholm's regulations (The Green Book) called for the Chief Engineer to be immediately available and on call at Stand By.

Most Chief's I sailed with were very happy to handle the Bridge Control, and a very useful addition to the Bridge team they were.

Any anomalies with the movements resulted in short low keyed conversations with his henchmen below, and anything of concern was passed on.

Had any pilot requested the removal of the Chief or any other from the bridge I would have most certainly demanded another pilot had he insisted, happily I never met one that uncouth!


Ah now that is interesting - the "old green book". - Yes indeed.
By the time I joined Denholm that had been (or was in the process of being) superseded , and replaced by the loose leaf blue plastic covered version.
Obviously there were differences between them - quite considerable in many cases.
Despite the fact that it had been superseded, - the old green version was required to be retained on board - for reference purposes. Like so many other things - "retain on board" - Didn't you notice the apparent clear desks of Ship Managers, and the directors, - come to think of it ??
The Blue coloured version (early 1970's) included an annex in which all officers were required to sign that they had read and understood it. The old green version (1950's/1960's era, did not have such an annex - at least so far as I can remember.
In the case of ships which came into management after the blue version was issued - the old green version was nowhere to be seen. ( As one would reasonably expect )
The blue covered version (1970's version) was in turn in the process of being superseded by another version consisting of several volumes when I was transferred from the home fleet to Hong Kong.
(TDU was deeply involved in that effort, - and it appeared to be giving him some headaches - I recall). Whether that process was ever completed I don't know. DSM Hong Kongs version of the Companies Operating procedures - was a flimsy cheap looking document, consisting very few pages, most of which, " in reality " contained very few procedures at all.
In addition, there was only one copy on board, unlike the home fleet where all Senior Officers had copies.

With respect to the "uncouth pilot" - as you put it, - well I didn't interpret his comments as being uncouth at all. Quite the contrary in fact, and in the final event, the Chief went below, and resolved the problem very quickly, indeed much quicker than initially expected.


Edit:- This really has nothing to do with slip - but that's the way that it goes.

Derek Roger
3rd June 2013, 01:52
Well it's all fascinating stuff, I suppose, but absolutely nothing to do with slip, negative or otherwise. There's heaps of potential in it for lengthy discussion on SET and DRIFT - for those so inclined, but it has no relevance to propellor slip.
(Night)

Was the SET not your hair do ? Regarding Drift I shall have to think about that one .

oldman 80
3rd June 2013, 07:01
Was the SET not your hair do ? Regarding Drift I shall have to think about that one .

Hair Do ? Highly unlikely.
Drift ? Good idea, - I suggest.

It's the distance through the water that counts, compared with theoretical distance travelled by the propeller i.e. = Revolutions x pitch.
That's slip.

Fred Field
3rd June 2013, 22:05
After the fire on Capetown Castle in 1960 I believe Union Castle made it policy that all the senior engineers were not to be down below together at standby.

http://www.unioncastlestaffregister.co.uk/SHIP_CAPETOWN_CASTLE_01.html

On the steam UC mailboats it was 'all hands and the cat' below at departure from Southampton this thinned out a bit once we had cleared the 'dock area' and nothing had 'dropped off or otherwise malfunctioned'. Most arrivals and departures had the 'top four' (Chief, First, Senior Second and Extra Second) 'in the pit'. This was because most scheduled arrivals and departures were at 06.00. This was the Senior Second's watch and he had a J/2/E in the boiler room, the Extra Second (me) had the 12-4 so we either had a brief break before we 'went down' again or just stayed 'down': Chief was in Engine Room and First in the boiler room Second Electrician in the engine/boiler room, Chief Electrician went to the SG compt. A normal machinery spaces watch was 5 engineers and 4 ratings.