They
Were Gradually Working Her Up
We know from the
testimony of J. Bruce Ismay that the Titanic started out running at 70
revolutions per minute after leaving Queenstown. We also know that 70 rpm
corresponds to about 20.7 knots through the water.[1]
The distance between Daunt’s Rock Lightvessel, the starting point of the
transatlantic part of the voyage just outside of Queenstown, and Fastnet light, a lighthouse situated on a small
isolated rock off the southwest coast of Ireland, is a run of about 55 nautical miles.[2]
At 20.7 knots, it would take 2 hours and 40 minutes to make that distance.
Since departure at Daunt’s Rock was noted at 2:20 p.m., an arrival time at
Fastnet of 5:00 p.m. would therefore be expected. It is interesting to note
that Sir James Bisset, Second Officer on the rescue ship Carpathia in
1912, wrote in his 1959 book Tramps and Ladies that the Titanic
“had Fastnet rock abeam at 5 p.m.” which is something he may have heard in
conversations with Titanic’s surviving officers on the way back to New
York.[3]
According to Ismay’s
recollection, the revolutions carried on Friday, the second day out, were
increased to about 72 rpm. At 72 rpm the ship would be making 21.2 knots
through the water. If that increase in revolutions began on Thursday evening at
the beginning of the First Watch (the 8 p.m. to 12 a.m. watch), then the
average speed through the water between 2:20 p.m. GMT Thursday, April 11, and
local apparent noon Friday, April 12, averages out to 21.1 knots,[4] just slightly better than the derived 20.98
knots average speed over ground for the 484 mile run from Daunt’s Rock to her
April 12 noon position.
Friday evening, April
12, Captain Smith sent a position report from the Titanic to the La
Touraine for 7 p.m. GMT. It read:
Titanic 'To Captain La Touraine,’ Thanks
for your message and information my position. 7 p.m. G.M.T. Lat. 49.45; long.
23.38. W. Greenwich; had fine weather; compliments. - Smith
The difference between
the time given in the La Touraine message (7 p.m. GMT) and the time for
local apparent noon (1:24 p.m. GMT) was 5 hours 36 minutes. The distance from
our noon position for April 12 (50° 06’ N, 20° 43’ W) to the position in the La
Touraine message (49° 45’ N, 23° 38’ W) is 114.6 miles. The
speed over ground calculates out to 20.5 knots for that period of time. But if
Ismay was correct, and the Titanic was carrying 72 revolutions per
minute, then the ship should have been making about 21.2 knots through the
water all that afternoon. The difference between 21.2 knots through the water
and 20.5 knots over ground suggests that the ship was under the influence of a
relatively strong easterly component of the North Atlantic drift at that time,
something that is quite reasonable and not at all unexpected during a westbound
voyage.
We also have from the
testimony of Fireman Frederick Barrett that another double-ended boiler was lit
up some time on Friday. What time that boiler was connected on line is not
known, but we know from Barrett that it takes close to 12 hours to bring a
boiler on line after it is lit. Adding just one more boiler to the 20
double-ended boilers they already had connected up on Friday increases the
overall steam supply by 5%. Thus the power delivered by the boilers for the
same firing rate would go up by about 5% which would result in an increase in
revolutions from 72 rpm to about 73 rpm keeping the same firing rate.[5]
This means that the speed of the ship would have gone up from 21.2 to 21.5
knots. If we assume, as they would later do on Sunday, that this extra boiler
was lit about 8 a.m. Friday morning and then connected up around 8 p.m. that
Friday night, then we get a weighted average speed through the water for the
second day out from Queenstown of 21.4 knots. With an overall average speed
over ground of 20.91 knots from noon Friday to noon Saturday, we find that the Titanic
was still under the influence of an easterly current drift of about a ˝ knot on
its second day out. Clearly, the North Atlantic Drift was having a noticeable
affect on the progress of the ship this particular day. It is little wonder
that the purser told second class passenger Lawrence Beesley that the 519 mile
run for the second day was somewhat disappointing.[6]
For the third
day’s run of 546 miles, from noon Saturday to noon Sunday, we have information
from both Ismay and Barrett that the revolutions were increased to 75 rpm. This
was the minimum revolutions that was called for on Saturday, and Barrett said
that he heard of no complaints afterward. It is therefore reasonable to assume
that they were making 75 revolutions or better most of the time. We really
don’t know what time this increase in revolutions took place, but what we do
know is that from noon Saturday to noon Sunday the ship averaged about 22.06
knots over the ground. Carrying just 75 revolutions, the ship would have been
making about 22.0 knots through the water. But we also know from Fireman
Hendrickson that at 4 p.m. Sunday afternoon the ship was making 76 revolutions,
and Fireman Thompson said that they had actually posted 77 revolutions down in
the stokehold at 3 p.m., just an hour earlier. And all of this was before two
or three more double-ended boilers were connected up that night at 7 p.m. At 76 rpm the ship would be making about 22.2 knots through the water, and at 77 rpm
she would be making about 22.5 knots through the water. So an average of 22.06
knots over ground for the third day out, from noon Saturday to noon Sunday,
certainly looks quite reasonable.
Finally, an increase
in revolutions of about 2 rpm had taken place on Sunday night after additional
double-ended boilers that were first lit up Sunday morning at 8 a.m. were put
on line at 7 p.m. that evening.[7]
Taking an average between 75 and 76 rpm from 12 noon until 7 p.m., and then
allowing an increase to an average between 77 and 78 rpm from 7 p.m. until the
collision at 11:40 p.m.,[8]
we get a weighted average of 22.3 knots through the water from noon to the time
of the collision. This result happens to match very well with the taffrail log
reading of 260 nautical miles through the water observed by QM George Rowe at
the time the accident happened, the distance run in 11 hours and 40 minutes
since noon. The distance over ground
from noon the collision point was 258 nautical mile which works out to a speed
made good of 22.11 knots.
[3]
Sir James Bisset (in collaboration with P. R. Stephensen), Tramps and Ladies,
first published in the United kingdom by Angus & Robertson, 1959.
[4]
Assuming they increased the revolutions from 70 to 72 at 8 p.m. on Thursday,
then the ship’s average speed through the water for the first day out from
Queenstown becomes 20.7 knots times 5 hours 40 minutes, plus 21.2 knots times
17 hours 24 minutes, all divided by 23 hours 4 minutes (the total elapsed time
from departure at Daunt’s Rock on April 11 to LAN on April 12). This results in
an average speed through the water of 21.1 knots.
[5]
The required power goes up approximately as the cube of the speed. Thus the
speed goes as the cube-root of the power.
[6]
Lawrence Beesley, The Loss of the S.S. Titanic – Its Story and Its Lessons,
Houghton Mifflin Co., 1912, Chapter II.
[7]
The connect time came from Fireman Alfred Shiers. The additional boilers being
lit came from Firemen Frederick Barrett and John Thompson. Several passengers
(Lawrence Beesley, Mahala Douglas, George Rheims, and Henry Stengel) noted the increase in revolutions of the
engines late that night. There was other supporting evidence of this as well
including the increase in pressure shown on the boiler gauges.
[8]
Adding additional boilers on line does not necessarily mean an instantaneous
increase in boiler pressure or speed. These boilers would be connected up at
the same pressure as the other boilers that were already on line. Because of
the increased number of boilers connected up, the flow rate of steam from any
given boiler would drop allowing for the pressure to build up to a new
steady-state value assuming the furnace firing rates remained the same. On
these Olympic class ships the furnaces could be fired every 8, 9, 10, 12, 15,
20, 25, or 30 minutes as set by the engineers. For the same furnace firing
rate, the boiler pressure would have to increase until a new steady-state is
achieved, at which point the engines would be running faster and boiler
pressure would level off at the new increased value.