Seumas

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The great thing about Mark Chirnside's discovery about the three bladed central propeller is that it gives us hope that somewhere there are still some more secrets and surprises regarding RMS Titanic lurking in a dusty box or cob webbed file cabinet waiting for someone to find them. :)
 
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Bob_Read

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Charley: I know of no speculation about Titanic having a three bladed center propeller before Mark made his discovery. Like a lot of things on Titanic, there was no written documentation or photos so we just had to extrapolate on the basis of early Olympic knowledge. Mark’s discovery is the only evidence we currently have about Titanic’s center propeller.
 

Mike Spooner

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The Olympic well may have an three bladed centre propeller in the wars years and changed back to a four bladed propeller after the war years.
The is mention of increase vibration using the three blades over four blades. Yet I didn't see any comments made by Titanic of the centre propellers vibration. Another factor on Olympic. Do we know if there was any different in fuel computation between a three or four bladed propeller!
Yes it will be a great discovery if the sea bed is removed from Titanic centre propeller and put to bed of any further discussion on the matter.
 
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Bob_Read

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Olympic received her 3 bladed propeller in March 1913. The Olympic experiment most likely was short because we have film of a new Britannic in dry dock with a four bladed center propeller.
 
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Bob_Read

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There was probably some increased vibration but another factor may have been that the propeller just didn’t provide much increased performance.
 

Mike Spooner

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Just another angle on Olympic. If is to use an three bladed propeller and Britannic is used a four bladed propeller. It still gives them an opportunity to compare the performance between the two ships.
 
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Bob_Read

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Mike: They already knew how a four bladed propeller performed on Olympic during her first 18 months of service. Since Britannic had a four bladed propeller, Olympic probably had a 3 bladed propeller les than two years at most.
 
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Mike Spooner

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Bob: As any new class ship propeller changes wasn't new. So I don't blame them trying out a three bladed as to a four blades. But at the end of the day more blades smoother the performance.
 

Mike Spooner

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I would agree as you know a one blade is more efficiency, that if you can put up with the vibration. You would of thought two blade was the answer! But really never took off with large ships. Horses for Courses!
 
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A comparison of the propellers used on Olympic and Titanic.
1576786413514.png

Notice that the total area and pitch for the center props were the same despite one being 4-bladed and the other three bladed. Titanic's 3-bladed prop was slightly larger in diameter by 3%. For the area tobe the same, the blade widths on Titanic's 3-bladed prop had to be about 29% greater than the blade widths of Olympic's 4-bladed prop. It probably looked something like this:
1576787877446.png
 
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Mike Spooner

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Its hard to believe that extra 6 inches on diameter can make up the same sqft from a four blades to a three blades.
Whilst on the subject centre propellers. I have notice on Olympic the mark numbers in feet are not there behind the propeller. Looks like a wear plates had been added!
 

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Charley Smith

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Its hard to believe that extra 6 inches on diameter can make up the same sqft from a four blades to a three blades.
Whilst on the subject centre propellers. I have notice on Olympic the mark numbers in feet are not there behind the propeller. Looks like a wear plates had been added!

I think the blades had to be wider also, not just larger diameter. As you say - 6 more inches wouldn't have done it.
 

Charley Smith

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Here's some interesting changes made to the Olympic Class wing propellers:



rms-olympic-white-star-line-in-dry-dock-in-southampton-T8KEPE.jpg


On the starboard side is an original Olympic propeller - notice the very slender, conical hub. Now, notice the port propeller with the man climbing on it. Is this the one borrowed from the unfinished Titanic? Notice the hub.





olympic-lost-propeller-blade-300x284.jpg


Here's another shot of the thrown port blade before repair. You can clearly see the mounting bolts are ripped - again notice the slender central hub of this propeller.






.png



Here's a later photo - notice the hub is beefier much more rounded. This is not the same.



92fbbd684530480282ab5e88c5f2213f.jpg



And lastly - Titanics starboard propeller on the wreck. This is not the same as early Olympic photos.
 

Mike Spooner

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Hi Charley,
Do known what year and month the first photo was taken? As I see the centre propeller has been removed.
 

Charley Smith

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Hi Charley,
Do known what year and month the first photo was taken? As I see the centre propeller has been removed.


No sorry - this is what would be interesting to know, hopefully someone else on here might chime in with more info and ideas.....

In the first photo, it looks like a lot of general work is being done - obviously painting and the center propeller is removed. I wouldn't expect that from an emergency repair due to a damaged propeller. They'd want her back in service making money and not ruining the schedule. Still, I never noticed the hub differences before.

I believe the Hawke collision damage was confined to the starboard shaft & tunnel (aside from the major hull punctures further forward). So this starboard propeller may be original and the port one a whole propeller replacement from another incident - like a thrown blade perhaps.

From the photos, I would also question whether the blades could be interchangeable between the two seemingly different designs. The mounting base of each blade looks much 'flatter' on the slender hubs compared to the others where the base seems to be thicker and more rounded to fit the contour.
 

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