Speed measurements/indicators

[Jim Currie]

No Sam, to be correct, the body of water through which a ship sails, is not a frame but a cuboid which had dimensions equal to the beam as well as the air and water drafts of the vessel.
As you point out, a strong head wind (acting on that part of the vessel above the water) will effect its forward speed and consequently the distance in one direction it will travel. However, by the same token, a head current or any current forward of the beam,s will effect the forward distance traveled.
At least 2 independent and very well qualified witnesses testified to the expectations regarding a current in that area which would have slowed any ship down had they encountered it. At least one source of evidence demonstrates that such a head current existed in the area in question:
Captain Moore of the Mount Temple thought that his ship would pick up half a knot from the eastward setting North Atlantic Current.
Likewise, Titanic's 4th Officer Boxhall also expected such a current and even off set it with a guestimate of reduced propeller slip due to the flat calm which gave him his 22 knot figure he used to calculate the Distress position. He was obviously using a ship speed of 21.5 knots as derived form the Olympic Slip Tables since the ones for Titanic had yet to be completed and he did not use the Patent Log. Had he been using the ones you concocted, he would have used a speed greater than 22 knots to work his distress position.
Then there is the calculated Noon position of the SS Mesaba which put her to the north and east of her expected (DR) Noon position.
I sailed to New York twice a month for over a Year Sam.,I do not remember a single incidence when we did not get a head current of some sort in that area. Explain how it got "switched off" for the passage of the Titanic.

 

[Samuel Halpern]

However, by the same token, a head current or any current forward of the beam,s will effect the forward distance traveled.

That will affect what Georges G. calls speed over ground, not speed through the water, which is what you get by dividing the distance run by log by time. And that's my point that simply fail to understand.

 

[Jim Currie]

The distance run by Patent Log Divided by time is how Lowe arrived at his speed. Over the ground or water would not enter his mind. He would simply assume that Titanic had traveled 125.7 miles since Noon. If she had not altered her course before 6 pm, he would have run on at the same speed and course for another 2 hours to obtain the 8 pm DR. However the coursew was altered before 6 pm so he had to find out a position for where she turned/ The use of the term "At The Corner" is misleading
However, if there had not been any impediment to the forward passage of the ship. and she had made 22 knots as she did up until Noon, then the 6 pm reading would have been 132 miles and Lowe would have used 22 knots to calculate a 5-50 pm turning DR and subsequently, the 8 pm DR

 

[Samuel Halpern]

Or the real log reading put down was something like 135.7 miles since noon and he read the handwritten 3 as a 2. 135.7 miles divided by 6 hrs is a speed of 22.6 knots through the water, which over a 2 hour period gives 45.2 miles by log, totally consistent with Hichens' 45 miles by log reading taken at 10pm, and consistent with the ship carrying 75-76 rpms since noontime Saturday. But I highly doubt you would be inclined to consider that as a possibility.

 

[Jim Currie]

Sam. Navigators in 1912 and right up to and after 1960, worked in exactly the same way/ They used logarithms to the base 10. When Low came on the bridge at 6 pm, the first thing he would do after the handover, would be to find out the speed. We know he got that from the Patent Log because he said so in so many words. His work would be as follows:

Patent Log at 6 pm = 125 .7 Log 2.09934
Run time 6 hours ....................Log 0.77815.
Log 1.32119 = Av. Speed 20. 95 knots.
In fact , Lowe and the others would have used 4 figure logs. I use 5 because I'm used to them and besides that-s how my tables are tabulated/

The logarithm for 135.7 is in fact 2. 2937... nothing like the logarithm for 125.7. Lowe would have spotted that in a New York Minute.

In fact, both Boxhall and Pitman, (Lowe's boss) were using what seems like Olympic Slip Tables and were thinking in terms of 21.5 knots = 75 rpm.. Pitman and Lightoller said as much and you can be sure that's why Boxhall used 22 knots for his distres position. Since Boxhall had worked the 7-30 pm sights and knew the Noon position, you can also be sure that he did not get a 22 + knots average speed from Noon until 7-30 pm sights. He most certainly would have provided that information for Smith before 10 pm that evening. By the way, this is what ships ahead look like from the port wing of the bridge.

That was taken in the Suez Canal. As you can see, the ship right ahead is in the direct line of sight and would be dead ahead to the helmsman and to anyone on the starboard side. No problem with parallax on a ship with a beam such as the one you see above.