For decades, it was simply assumed that Titanic's propeller configuration was the same as her sister Olympic's. This assumption became accepted as fact.
The evidence we have available today is to the contrary:
- Harland & Wolff's records for the completed Titanic state she had an increased pitch on the port and starboard propellers, as well as an enlarged diameter centre propeller with three blades instead of four. These records came to light in 2007 and were made publicly available in 2008;
- The papers of a turbine specialist working for John Brown & Co., who were subcontracted to build Olympic and Titanic's turbine engines, strongly support the Harland & Wolff evidence. These were uncovered by Joao Goncalves and made publicly available in 2020.
This dossier groups together everything you might wish to know - in one place.
RESOURCES - AT A GLANCE
Above: An artist's illustration of how Titanic's propeller configuration appeared, based on the Harland & Wolff documentation which came to light in 2007. (Courtesy Vasilije Ristovic, 2019)
'The Mystery of Titanic's Centre Propeller' (2008)
Evidence from Harland & Wolff's records that Titanic was completed with a three-bladed centre propeller
This article outlined the discovery of primary source documentation from Harland & Wolff with Titanic's propeller specifications. Their records state that her port and starboard propeller blade pitches were increased and that her centre propeller was enlarged, with three blades instead of four, compared to Olympic's 1911 configuration.
In hindsight, the use of the word 'mystery' in the title is rather over-dramatic, because the Harland & Wolff evidence is clear that Titanic had a three-bladed centre propeller. It is the best source material we have. Unfortunately, familiarity bias (the tendency to believe what we already believe to be true) can be hard to overcome. Prior to that time, everyone apparently accepted the assumption she had a four-bladed centre propeller without question, yet since 2008 nobody has been able to provide any evidence at all to support that assumption.
Titanic's Centre Propeller: The Stephen Pigott Evidence (2020)
Evidence that proposals for both a three-bladed and four-bladed centre propeller were under consideration c. 1910.
This article analysed a discovery by researcher Joao Goncalves of a notebook in the papers of Stephen Pigott, a turbine engine specialist who worked for John Brown & Co. The Clyde shipbuilder was subcontracted by Harland & Wolff to work on the low pressure turbines for Olympic and Titanic and they shared their experience and turbine technology with them.
The notebook in Pigott's papers includes two proposed centre propeller configurations for the two White Star liners: a three-bladed and a four-bladed one. These are identical to the centre propeller configurations for each ship in the Harland & Wolff records, in terms of the propeller diameters and the area of the propeller blades. (The sole difference is that the pitch of the propeller blades was changed on the completed ship).
'RMS Titanic Reflections: Deep Conversations Episode 1' (2021)
In this video, Bill Sauder discusses the evidence concerning Titanic's centre propeller configuration and explains the nature of propeller design in 1912.
The Object On the Barge - Part 1 (2021)
Sam Halpern's article analyses 'The Object On the Barge' photographed in February 1912. His article includes 3D CAD models - the result of painstaking work by Tony Taylor - of the four-bladed centre propeller Harland & Wolff recorded for Olympic and the three-bladed centre propeller Harland & Wolff recorded for Titanic. The models are based directly on the recorded specifications.
How do these models match up with the object in the photograph? Sam concludes: 'What is lying on that barge is a three-bladed propeller that happens to line up nearly perfectly with the three-bladed CAD model built in accordance with Harland & Wolff design specifications regarding number of blades, diameter, pitch and blade area for Titanic’s center propeller'.
The Object On the Barge - Part 2 (2021)
Sam Halpern's follow up article includes an analysis of the photograph to try and ascertain the size of the object. His central conclusion is that the propeller in the photograph had a diameter of 16.95 feet, which is 'is amazingly close' to the 17-foot diameter of Titanic's centre propeller in Harland & Wolff's records.
Although Titanic is one of the best-documented ships in history, there are some glaring gaps in our knowledge where researchers have previously been forced to rely on the assumption that her configuration was identical to her sister Olympic. Plenty of areas of the ship were not photographed. Titanic’s propellers were not photographed after installation. Photographs of her older sister are often used as a substitute, but they are not always captioned clearly enough to explain that they are Olympic images which have been used to stand in for Titanic. The consequence has been a great deal of confusion. Simply doing a Google search for 'Titanic's Propellers' produces plenty of images which are Olympic or, even worse, other ships entirely!
A NEW DISCOVERY (2007-08)
Until 2007, everyone apparently assumed Titanic’s centre propeller was the same as her sister ship Olympic’s: a four-bladed configuration, in contrast to the three-bladed propellers on the port and starboard side of the ship. However, that year I became aware of a Harland & Wolff engineering notebook that recorded the engineering particulars of each successive ship they completed, including their propelling machinery and propeller specifications. The notebook recorded Titanic’s propeller specifications in detail and stated clearly that she was fitted with a three-bladed centre propeller. It also gave details of tweaks to Olympic's propeller configuration during 1911 and early 1912. It is the only contemporary primary source which records the number of blades on Titanic's centre propeller. This information was made available in an article, ‘The Mystery of Titanic’s Centre Propeller’ published in the Titanic International Society's Voyage journal in 2008 and subsequently online at Encyclopedia Titanica.
EIGHT YEARS LATER (2016)
In many ways, the wording of the original article comes across as somewhat hesitant. Part of the reason was the possibility that additional information might come to light, contradicting the new evidence. It didn't: since the article was published, nobody has come forward with any photograph that might have existed in a private collection of Titanic’s propellers after installation. In fact, the new information that has become available only reinforces the conclusion that she was fitted with a three-bladed centre propeller. There is, in truth, no 'mystery'.
It had always been understood by researchers such as Bruce Beveridge that Olympic had been fitted with a three-bladed centre propeller during her 1912-13 refit. Researcher Bob Read provided further confirmation in a 2016 article: ‘Unravelling the Mystery of Titanic’s Centre Propeller’.
Similarly, at a presentation given in Belfast in April 2015, Simon Mills noted that there is evidence Britannic was envisaged with a three-bladed centre propeller during an early phase of her construction in c. 1912-13.
There should, therefore, be nothing surprising or extraordinary about Titanic being fitted with a three-bladed centre propeller. Shipbuilders of the period were constantly seeking to find the optimal propeller design to combine efficiency, benefiting speed and fuel economy, and minimal vibration, benefiting passenger comfort. A good example is all the changes Lusitania and Mauretania underwent during their early years of service, not to mention the changes to Olympic (and Titanic’s) port and starboard propellers as the shipbuilder adjusted the pitch of the blades.
Whatever the pros and cons of the three-bladed centre propeller’s performance on Olympic after the 1912-13 refit, it seems any benefits were outweighed by the negatives. She subsequently reverted to a four-bladed configuration and Britannic was completed with a four-bladed centre propeller as well. This is visible in period film from 1914, as well as on Britannic's wreck today.
Nonetheless, we now have clear evidence that all three ‘Olympic’ class ships were either:
- fitted with a three-bladed centre propeller (Titanic);
- fitted with a three-bladed centre propeller for a period (Olympic); or
- envisaged with a three-bladed centre propeller at an early stage in construction (Britannic).
As Bob Read wrote in his article:
'For those who are reluctant to accept a three bladed centre propeller on Titanic, they must consider the fact that there is absolutely no evidence that Titanic ever had a four bladed centre propeller'. [my emphasis]
TWELVE YEARS LATER (2020)
Joao Goncalves' discovery of a notebook in the Stephen Pigott papers demonstrated that both three- and four-bladed centre propeller designs were being explored for Olympic and Titanic while both ships were under construction. The two design proposals are virtually identical to the centre propellers fitted to each ship according to Harland & Wolff's records, with identical diameters and area of propeller blade - the sole difference is that the pitch was adjusted subsequently.
Frequently Asked Questions:
Q. You said that there are no known photos of Titanic’s propellers fitted, but there are many in books and online.
A. Unfortunately all these claims are incorrect. The original photographs taken for Harland & Wolff by R. Welch were all given a unique reference number. The details of each glass plate negative were recorded alongside the reference number, including a description of the subject of the photograph and the date that the photograph was taken. By looking up the contemporary reference numbers, it’s possible to identify the photographs taken of Olympic’s propellers, including when they were fitted in 1911, when a blade from the port side propeller was being replaced in March 1912, and when she was at Belfast for an overhaul in January 1924.
These Olympic photos are well-known and have been used in books, websites and documentaries to stand in for Titanic. The captions rarely make it clear. Unfortunately the fact that they are Olympic photographs tends to go unnoticed. (In fact, the 1924 photograph is one of the most famous: it shows shipyard workers standing on the dry dock floor with Olympic’s three enormous propellers towering above them. It is often used to illustrate Titanic and it appeared on an enormous banner promoting the salvaged Titanic artefacts when they were displayed in Amsterdam in 2013-14, but few people realise it was an Olympic photo taken 13 years after Titanic sank!)
There were also physical differences between Olympic and Titanic in 1912, which confirm the photograph reference numbers. There was a small zinc plate fitted above the centre propeller aperture: on Olympic, it had eight rivets but on Titanic it had only five. This is clear in early Titanic construction photographs before her propellers were fitted.
Q. But every depiction of Titanic shows her with a four-bladed centre propeller? James Cameron’s film, for example.
A. As explained above, until 2007 it was perfectly reasonable to assume Titanic had a four-bladed centre propeller just like Olympic. However, historians have to be open-minded and change their views to reflect new evidence.
Q. What about the propeller photographed sitting beside the dry dock in February 1912?
A. This was discussed briefly in my 2008 article. However, as Bob Read points out:
Some have assumed [my emphasis] that this propeller is Titanic’s center propeller. Additionally, this photo has been analyzed and there are those who believe it is a three bladed propeller and others who believe that it is a four bladed propeller. I have dismissed this photo as any kind of useful evidence because even if the number of blades could be reliably determined, there is still no way to positively identify it as a center propeller for Titanic. [my emphasis] Further, even if it was a center propeller for Titanic, there is no way to determine whether it is a propeller which has yet to be installed or one which has been removed.
Q: The wreck has been explored, photographed and filmed - doesn't this provide an answer?
A. Although the port and starboard propellers were forced upwards when the ship's stern slammed into the ocean floor, Titanic’s centre propeller is buried in the seafloor. The wreck is therefore of no assistance unless a future expedition is able to explore beneath the mudline.
Q. What does it matter?
A. It illustrates the need to re-examine everything we think we know about Titanic and her sister ships. Even to someone interested in the subject, it might seem there is little or nothing more to learn, but how many other beliefs are merely assumptions which have become accepted as fact through the years?
To those interested in the technical or engineering aspects of the ship, it's new information which needs to be incorporated into any analysis of her propelling machinery and performance. More generally, it's an interesting bit of trivia for Titanic geeks!