I recently heard a claim that Titanic was adjusting course continually throughout the night and a final course correction some time after 11 pm put her on course with the iceberg. Sounds like bull to me, but I'd rather have the knowledgeable weigh in than assume.
jim, i'm sorry for the delay answering your post. Business comes before titanic these days.
No problem David. Wish I had a similar diversion but time won't damn-well stand still. Anyway, I'll answer as before; drab bits between your blue-coloured words of wisdom.
the standard compass was mounted on a non-magnetic platform (the platform itself had no maganetic "signature") some 15 feet above the superstructure. This was an obvious attempt to reduce the influence of the ship's own steel on the instrument, although its construction would not have eliminated what maritime navigators call "deviation."
Standard procedure in ship construction.
the positioning of this platform amidships also is an obvious attempt to reduce the ship's influence on the compass by placing about the same amount of iron ahead of as behind that instrument.
I agree. But more of an inconvenience than anything else. Two ruddy-great funnels ahead and astern limiting the azimuth efficiency.. One question still intrigues me. Why, if there was that big fat chunk of metal right ahead of him, would an experienced QM like Olliver look up when he heard 3 bells?
all well and good, but the location was decidedly unhandy and, in my opinion, was one of the factors influencing the events of the evening.
Well David, I know what you mean but you know, I don't agree with you.
your discussion of compass comparisons is more detailed than the requirements in the imm/white star line rule book.
Actually I was simply remembering how it was when I was a callow youth.
In a cargo ship with reduced bridge staff, you did not have time for such nonsense. In a passenger ship there would be no need for it. In the latter, when you did have the extra hand or three, you were continuously checking compass error. Mostly by taking azimuths at regular intervals or by known transit bearings. In more recent times checking was done using the gyro and comparing it with all the other compasses. In any case, the 30 minute rule you mention does not make sense unless they continuously knew the error of the standard compass.
" because the wording requires a 30 minute interval, that would not have changed with the alteration of the crew's clock by that 24 minute retardation."
Yes it would David. Simply because it's the information gleaned in that last 15 minutes of a watch which is of greatest importance to the on-coming OOW - the the man doing the relieving. Further back in Watch time is old history.
this is not a minor matter because it explains why olliver was on the compass platorm and why boxhall was coming out of the officers quarters when the lookouts sounding three strokes on the crow's nest bell.
Actually olliver told the court exactly what he was doing at that time. I quote:
"I had just performed an errand and was entering the bridge when the collision occurred.....I happened to be looking at the lights in the standing compass at the time. That was my duty, to look at the lights in the standing compass, and I was trimming them so that they would burn properly."
In a vessel with oil lamps. That was standard practice, David. It was done usually by the 'farmer'... the name given to the QM who did not have steering duties during the watch. It was only basically relevant to the use of the compass during the hours of darkness and nothing to do directly with a compass check.
you are correct I should not have said the ship was "making good" a course of 266. Properly stated it was simply steering that course.
Correct! A course can only be determined as having been 'made good' if it is one measured between 2 known positions.
The 5:45 or 5:50 turn at "the corner" (different people remembered different times) was not a navigational "fix." even so, it appears that boxhall used "the corner" as the starting point for a new leg of dead reckoning. This is not the best navigational practice, but it seems to have been what was done that night."
If you read the evidence again, David; you'll find that Boxhall did not use The Corner as a start point. In fact, he and Pitman were of the opinion that at 5-50pm, Titanic had turned later than she should have done. If that was the case then she turned south and west of it and the position used by Boxhall was a distance south and west commensurate with the course and speed he used from Noon that day. Likewise, Pitman would use a different position for the turn at 5-50pm to calculate a DR for use with the 7-30pm celestial observations. For this reason, I agree with your observation that..
It was the only way a DR could be established to be used in conjunction with a star sight calculation we have no proof of exactly where (lat/lon) the ship actually made the course change assigned to "the corner," so any forensic reconstruction of boxhall's work contains this "fudge factor." [/COLOR]
You go on.....
I would like to say that he corrected his work using the 7:30 stars shot by lightoller, but there is absolutely no proof of that, either. In fact, none of the surviving officers could even recall the lat/lon of that celestial fix.
In fact, the only person with intimate knowledge of the 7-30pm position would have been Boxhall. All the relevant calculations were in his work book which went down with the ship. However, 3rd Officer Pitman would have started on these sights and in 20 minutes, (by 8pm when he was relieved by Boxhall) would have had enough information to give the following evidence on Day 7 of the US Inquiry:
"4422. Do you know how these [7-30pm] observations located the ship? A: - Yes; right on the track.
All he needed was one good latitude and one good longitude - a first fix if you like? From there he would have calculated the bearing of The Corner. If he got 085 degrees True he would be able to say that she was right on the line
I personally doubt that resolving of Lightoller's sights was completed, or if it was the information was not used by Boxhall in Titanic's dead reckoning -- but I can't claim that as a fact.
If he did not complete these calculations then Boxhall was 'knitting' a very elaborate deception when he described how he gave the results to Captain Smith then watched while the latter laid then off in his personal chart. That was about 9-30 pm that night
The course change I propose at 11:30 pm in April 14th time was made while he [Pitman] was off duty and (presumably) asleep.
The evidence is against you, David. The man on the wheel categorically stated that there had been no alteration of course before impact. I quote from Day 3 of the UK Inquiry, QM Robert Hichens in the stand:
" 940. Was there anything on the course-board to indicate the course you were to steer? A; - Yes, N. 71Âº.
941. That was on the course-board? A: - That was on the course-board, the steering compass.
943. Up to the time of the collision did she vary from her course at all? A: Not that I am aware of,......"
I think that's fairly conclusive , David. Don't you?
Another point is the time when Captain Smith entered onto the bridge. He did so moments after impact. If Titanic was in the process of turning when she hit the iceberg and was turning as a results of master's orders, then Smith would have remained on the bridge during the turn or he would have written a turn order in his night order book. If he did so, he would have informed Lightoller who would have signed that order and passed it on verbally to Murdoch at 10pm
Apart from the foregoing, my experience tells me that if Captain Smith was going to alter course to take the ship further south, he would have done so the minute he received the results for the 7-30pm calculated position. Boxhall said he stood by the captain's chart room as the latter pricked-off that very position on his chart. It is totally illogical for him to have waited for another hour or so and another 22 + miles closer to danger before altering to avoid it.
Titanic sent out two different lat/lon positions in distress calls. The first was given to marconi operator Phillips by captain smith and the second by Boxhall. These two sets of coordinates are 20 minutes of steaming apart at boxhall's stated 22 knots.
True! However there is nothing to connect the two.
Boxhall's CQD was obtained by the use of the 7-30pm sights position. Smith used the false 8 pm DR position to determine his CQD.
Boxhall's CQD was to the northward of the wreck site while that of Smith was in the same latitude as the wreck site.
Boxhall use a speed of 22 knots while Smith must have used a speed of 22.25 knots.
Smith's coordinates are within the error limits of 1912 navigation the predicted longitude of true midnight for titanic --2447 hrs in April 14th time or 0000 hrs April 15th.
Predicting the position of a ship at midnight is and was not normal practice unless there is a planned course change at that time. If you look at the evidence, you will see that there were two predicted times for arriving at the ice region. These were 9-30 pm (Lightoller) and 11 pm (Moody). We know that some time before 10 pm, Lightoller and Captain Smith discussed the time of arrival at the ice region. Since Smith had the coordinates for the 7-30pm sights by that time; is it conceivable that he would not then have made a decisive course alteration to the southward?
According to Boxhall, Smith used n 8 pm DR which was 20 miles in error. i.e. 20 miles behind the real position. I suggest to you that in fact, the 8 pm DR used by Smith was 20 miles ahead of the proper DR for that time.
You will remember that both Boxhall and Pitman belived Titanic had gone further on than the intended turning point at 5-50pm that night. In fact, Pitman thought she had overshot by some 20 miles. It was Pitman who was responsible for calculating the 8pm DR. I rest my case!
Boxhall's coordinates indicate that he simply "backed up" the ship's position by 20 minutes (the difference between 11:40 pm and the crew's midnight change of watch) on a reciprocal of the 255 course which the ship took after 11 pm April 14th time. I make this claim based on the fact that the reciprocal 075 crosses the 266 track line at exactly the ship's dead reckoning position for 11:30 pm april 14th.
Boxhall used a time of 11-46 pm for his CQD calculation, not 11-40pm.
When such a position is calculated, it is the estimated position where the ship finally comes to a halt; never moved again and finally disappeared. It is the position to which all potential rescuers should head. It was not the position where the initial impact took place. Boxhall would have worked-out what happened in the 6 minutes following impact.
He used that dead reckoning track to begin the new 255 course after 11:30 pm.
I ask again, David: why on earth would Captain Smith decide to alter course at 11-30pm?
If he believed Titanic was up to longitude 49 West at 9-30pm then he would also believe that 2 hours later, at 11-30pm she would be at least 44 miles farther on and at 50 West.
If he believed Moody's version then he would have believed that Titanic was at 49 West at 11 pm and at 49-15 West 30 minutes later at 11-30pm.
In fact, if we are right about the clock alterations then I believe she was at 49 West just after 10 pm that evening and at 11-30 pm was at 49-41.7'West. At midnight, she as at 49-55.5'West. Four minutes later, she hit the iceberg and swerved south before turning westward and stopping.