Speed measurements/indicators

[Jim Currie]

Actually the log line did not stretch David.

Because it was continually in torsion, it could not be made from normal 3 or 4 strand RH rope. It was a special, braided cotton line which did not twist or stretch. However, it was very prone to kinking therefore it had to be streamed (payed-out in a special way. Instead of just paying out the impeller first and letting it pull the rest of the log line until it was fully out behind the ship, the impeller (fly) was kept on deck until the last moment. The line itself was payed out in a bight until it was all out with one end attached to the taffrail register and the other to the impeller (fly. Then the fly was thrown over board and it fell away astern until the line was fully stretched out to it's full length. Then it would start turning. here's a wee sketch:

In fact, they were unjustly cautious about these things since they worked on more or less the same principle as the engine revs. The biggest problems were caused by being fouled by seaweed of floating debris. In fact, the design did not change very much between the time of Titanic and the time of the old QE2.

Jim

 

[Georges Guay]

Interesting Jim. I own a complete Walker's Cherub III Taffrail Log with its Walker’s Governor Wheels and hundreds of feet of Log Line … ready to go. The instructions in the box cover give a different way of setting the log away, maybe not considering that the line was prone to kinking. There was a piece of natural fiber Log Line in the box. It looks like a double braded anti-torsion line.

 

[Jim Currie]

That extra bit was to attache the governor, Georges. Wish I had £ for every time I streamed one of these beasts when i was an Apprentice. Incidentally, did you ever actually use one in practice and if so, do you r4emember how accurate they were,, even in a cross current?
Here's another unrelated question which I'm sure you can answer.....to the May Flie still swarm in amazing, radar -blinding clouds in the Bay of a Thousand Islands? In 1960, the swarm was so great that they were drifting against the wheelhouse bulkheads and the radar clutter was getting dangerous at one point.

 

[Georges Guay]

I am happy to learn that this piece of log line is to attach the governor wheel to the register. On some other log, it seems that the governor is attached to the register via a dedicated brass hook, which I do not have.

I never had the chance… to use the patent log. But like we discussed previously, it gives the speed through the water. Any current will have to be compensated for to get the speed over the ground. If you have a cross current, I guess you will have to use trigonometry to deduce the current vector that affect the log, in the same manner where you have to find the true wind from the relative one given by the vane on a moving vessel. Deduced navigation they say!

Jim, I once had to dock a tanker vessel by May-June. On final approach, the captain told me that he would prefer we maneuver on the outside bridge wing. I advice him that if he didn’t bother eating flies, it was fine with me. I let him go first and watched him. He came back in almost instantly, spitting flies while trying to free those inside his shirt collar and hairs. Just by the time the master opened the door and latched it, a cloud of flies engulfed the bridge to such an extent, that the wheelsman couldn’t concentrate anymore to steer the ship. Everyone query if these flies were dangerous; if I would’ve said yes, I think they would abandon ship in their gumby suit.

We are not talking about flies here Jim, but rather squalls of flies falling on your head from a low black flies cumulonimbus. But these sweet babies only live 24 hours and their explosion only happen on a very hot and humid days by end of May, early June. Every street light has its own cloud of flies! Fish are jumping out the water all over the place. To tell you the truth, mosquitoes are much worst and along the seaway, they are all over the place when the sun set. Their voracity makes you totally nuts!!!

 

[Jim Currie]

I am happy to learn that this piece of log line is to attach the governor wheel to the register. On some other log, it seems that the governor is attached to the register via a dedicated brass hook, which I do not have.

I never had the chance… to use the patent log. But like we discussed previously, it gives the speed through the water. Any current will have to be compensated for to get the speed over the ground. If you have a cross current, I guess you will have to use trigonometry to deduce the current vector that affect the log, in the same manner where you have to find the true wind from the relative one given by the vane on a moving vessel. Deduced navigation they say!

Jim, I once had to dock a tanker vessel by May-June. On final approach, the captain told me that he would prefer we maneuver on the outside bridge wing. I advice him that if he didn’t bother eating flies, it was fine with me. I let him go first and watched him. He came back in almost instantly, spitting flies while trying to free those inside his shirt collar and hairs. Just by the time the master opened the door and latched it, a cloud of flies engulfed the bridge to such an extent, that the wheelsman couldn’t concentrate anymore to steer the ship. Everyone query if these flies were dangerous; if I would’ve said yes, I think they would abandon ship in their gumby suit.

We are not talking about flies here Jim, but rather squalls of flies falling on your head from a low black flies cumulonimbus. But these sweet babies only live 24 hours and their explosion only happen on a very hot and humid days by end of May, early June. Every street light has its own cloud of flies! Fish are jumping out the water all over the place. To tell you the truth, mosquitoes are much worst and along the seaway, they are all over the place when the sun set. Their voracity makes you totally nuts!!!

I an see there are "no flies on you", Georges.

I note your are still promoting the "speed over the ground" approach. That is a modern concept.
Back in my day and the days of Titanic and patent logs, speed over the ground was not even dreamed about, Speed and distance was relative to points on the water. Only when an unexpected reading was obtained would the effect of current on the log and therefore the ship be detected and even measured. The simple principal was that the Log Rotator, Register and ship all moved through the water for exactly the same distance. Application of time interval between readings indicated speed through the water

 

[Georges Guay]

Ok Jim, I’m gonna give you my trick but don’t tell nobody. I was standing in the corner of the bridge by the very first window; remembering that I was docking the beast. I was then protected from the door wind draft in the same manner as the crow’s nest canvas windshield. As I am an expert with flies as being a sport fisherman, I lit up and pumped out vigorously a big stinky Malboro cigarette. But I must admit that there was a few on my PPU screen, keyboard and in my coffee cup. But they just add taste to that infect instant Nestlé coffee they serve.

Jim, if you divide the distance by the time between two celestial fixes, it gives the speed over the ground. It was a concept widely used at the time. They were probably using both method and compare them to find out if they had applied the proper current effect on the log. For daily average and general speed log inscriptions, they were using speed over the ground. If they couldn’t take any sights for days, they probably had to figure out a calculated speed over the ground derived from a current corrected speed in the water, compare to the average rpm/pitch/slip and or from previous voyages. If not, there would land up with large differences in day to day speeds which could have to be justified. Even in that era, I guess they were trying everything possible to keep away the office nose from the ship’s business.

 

[Jim Currie]

Ok Jim, I’m gonna give you my trick but don’t tell nobody. I was standing in the corner of the bridge by the very first window; remembering that I was docking the beast. I was then protected from the door wind draft in the same manner as the crow’s nest canvas windshield. As I am an expert with flies as being a sport fisherman, I lit up and pumped out vigorously a big stinky Malboro cigarette. But I must admit that there was a few on my PPU screen, keyboard and in my coffee cup. But they just add taste to that infect instant Nestlé coffee they serve.

Jim, if you divide the distance by the time between two celestial fixes, it gives the speed over the ground. It was a concept widely used at the time. They were probably using both method and compare them to find out if they had applied the proper current effect on the log. For daily average and general speed log inscriptions, they were using speed over the ground. If they couldn’t take any sights for days, they probably had to figure out a calculated speed over the ground derived from a current corrected speed in the water, compare to the average rpm/pitch/slip and or from previous voyages. If not, there would land up with large differences in day to day speeds which could have to be justified. Even in that era, I guess they were trying everything possible to keep away the office nose from the ship’s business.

The method of navigating in 1912 was the same right up until RADAR became common on all merchant ships. That didn't happen until well after WW2. In fact, formal qualifications as a Radar Observer on UK Merchant ships did not come into force until mid to late 50s. That's when I got my first one (still have it).
In fact, the navigation on ships such as the Titanic was much more precise than on a lowly cargo vessel, because she had dedicated Navigators... officers whose soul purpose in life was to provide the Master with minute by minute updates on the ship's navigation. Every MN Navigator (myself included) used the Patent Log and we knew it's error at any time throughout the voyage. On Titanic, it was read and the reading recorded every 2 hours throughout the voyage.
We know what the reading was at 6 am on April 14 and immediately after impact with the iceberg. It was 125.7 at 6 pm and 260 at the time of impact. This means she covered a log distance of 134.3 miles on her 265 True track from 6 pm until about 49-56'w. This in turn means that Titanic was at about 46-57 West...about 2,2 miles eastward of The Corner at 6 pm and at about 46-51.5'W ... 3.5 miles more to the East. at 5-50 pm when she turned . i.e. at least 5.7 miles east (and about 3 miles southward) of it. I'm sure you can calculate a position for where she turned.(and point out my errors)
The foregoing only holds good if you understand why 5th Officer Lowe was able to confidently state the speed was.."Twenty-one knots or under; it was really 20.95, about. If the speed had been increased or reduced during the interval when I was off duty, I would have been informed of it. " And you also accept QM Rowe's evidence that "As soon as the berg was gone I looked at the log and it read 260 miles.

 

[Samuel Halpern]

We know what the reading was at 6 am on April 14 and immediately after impact with the iceberg. It was 125.7 at 6 pm and 260 at the time of impact.

The only log readings given in evidence was 260 miles at the time of collision, and 45 miles run between 8pm and 10pm. We were also told the the log was reset at noon. That's the evidence.

 

[Georges Guay]

In fact, the navigation on ships such as the Titanic was much more precise than on a lowly cargo vessel, because she had dedicated Navigators...

They were amongst the greatest dedicated ocean navigators in the whole universe, as they pretend, but they succeeded to deduce a 20 nautical miles soon corrected by a 13 nautical miles offset on their CQD positions, that located Titanic on the west side of the icefield!!! That's what we call precision ...

 

[Georges Guay]

What does mean 260 miles or 45 miles «over the water by patent log» between 8 and 10pm, when a vessel is steaming across chaotic eddies engender by the collision between the Labrador Current and the Gulf Stream?

 

[Georges Guay]

I sailed around Cape of Good Hope many times on board gigantic crude oil carriers. We had all the GPS, DECCA, Satellite Transit, you could dream of. On a few occasions, I got stuck in these colossal eddies without having real knowledge of them. None of these eddies are specifically shown on Pilot Charts. Nobody really knew their existence before NASA produced this visualization using NASA/JPL's computational model called Estimating the Circulation and Climate of the Ocean, Phase II or ECCO2.

The vessel was absolutely impossible to be kept on track. She was drifting from one side to the other very rapidly. My speed over the ground was going up and down. At the end of my watch I had to annotate the logbook with the miles run but in this case, I had to enter the vessel’s progression toward its destination during the course of my watch. I had such a difference with the other mates that the captain asked me later what happened, like traffic. I explained him; he smiled and never heard about it again.

So through eddies, how could you estimate any reasonable distance run over the ground with a patent log to find out where you are on a chart … if I didn’t have any idea of my distance run with all the electronics ? Just good luck !

P.s. My record is 6 miles off track in one hour while crossing the Gulf Stream abeam ... I can tell you that I did not earn a navigator medal that day!!!

 

[Jim Currie]

The only log readings given in evidence was 260 miles at the time of collision, and 45 miles run between 8 pm and 10 pm. We were also told the the log was reset at noon. That's the evidence.

Yes Sam, the only log readings actually stated were as you say, but you know very well that Lowe gave that precise speed when asked and that the only way he could have come up with such a speed was by dividing the patent log reading as noted on the Scrap Log by 6. Truth be known... you do not want to see this because it completely upsets the time of impact theory.
It is not good to ignore evidence or make a preferential selection. Lowe had no reason to make such an exact observation regarding speed except that he was being closely questioned on the matter of ship speed.
You have claimed in the past that Lowe's 162 miles to go from Noon to the 5-50 turn was a typo and should read 126 miles. In fact, if you calculate the GC distance, and subtract the distance already sailed to Noon from Fastnet Rock, you will find that the distance to go from Noon to The Corner was 124 miles , not 126 miles..
Would you be surprised to know that if you take the time to actually plot the evidence of Boxhall and Lowe, rather than dismiss it out of hand, you will find:
A ..That Titanic turned at a point about 6 miles on a bearing of 105 True from The Corner .?
B: That Captain Smith guessed this and altered course to 266 True to bring her back on the line at or near to 7-30 pm?
C.. That the patent log would be reading close to 162 at 7-30 pm

Boxhall did not alter course to 266 True... he found that the ship was on that course when he went on Watch at 8 pm. Only Smith would order such an adjustment and he would only do so if he believed his ship was south of the line.
According to Pitman, the ship was right on the line at 7-30 pm sights. Smith did not know where his ship was at 7-30 pm until well after 9 pm. If he did not order a course change before impact, then Titanic would have hit the iceberg north of the line.

 

[Samuel Halpern]

but you know very well that Lowe gave that precise speed when asked and that the only way he could have come up with such a speed was by dividing the patent log reading as noted on the Scrap Log by 6.

It seems he came up with that by dividing the distance the ship was from the corner at noon by 6 hours. Nothing to do with log readings unless they reduced rpms from 75 down to about 71 for six hours.

 

[Samuel Halpern]

Or try this one.
Suppose the log reading at 6pm was written down as 135.7 miles and Lowe read the 3 as a 2. That gives him a speed by log of 20.95 knots through the water. But the reality was that it was 135.7/6=22.6 knots, or a two hour average of 45.2 miles, which is in line with Hichens' 45 miles by log between 8 and 10pm. The ship was carrying 75 rpms all day.

 

[Georges Guay]

If a vessel steers 266°T at 22.6K by patent log and there is a current setting to 196°T at 1.3K, the course and speed over the ground would be something like 263°T at 23.1K.