Extra ship's propellers?

[dgadee]

Reading again Moya Crawfords 'Deep Water' (and her husband's book too) and they mention that in salvaging ships there was usually one or more spare blades/props. Was it so common to lose these or just difficult to get replacements after launch?

 

[Poignard]

Reading again Moya Crawfords 'Deep Water' (and her husband's book too) and they mention that in salvaging ships there was usually one or more spare blades/props. Was it so common to lose these or just difficult to get replacements after launch?

Some of the ships I was on in the Merchant Navy carried a spare propeller, made of steel.

 

[Biggles Wader]

Just fwd of the ensign staff on the poop deck sits the spare prop. We also carried a spare anchor mounted against the focsle bulkhead. MV Olivebank 1970s

 

[RunAgroundHard]

The reason was simple. Getting a propellor made, was difficult as stock of certain shapes was not held. Also shipping from a manufacturer to a foreign country, could take a long time, before airfreight was common. This could result in cargo delivery delays, or loss of cargo, that could cost penalties or losses to charterer, ship owner.

I sailed with my father on European coastal trade and all his ships carried spare propellers, in steel, as mentioned by @Poignard.

Today, the trend has come back with high cost azimuthal thruster blades being carried as spares. The Queen Mary 2 carries spare blades on her decks which passengers can walk around. They are huge and probably a custom design.

My drill ships carry spares but held in a warehouse. We would ship to nearest port with suitable facilities and change out, likely in the water, not dry dock. The thrusters are designed to be dropped through a well, and lifted to, from underside to barge, or dock side.

On large single screw container ships, bulk carriers, there are often pad eyes, on the hull, above the water line, either side of the rudder area, for thus very purpose, where the screw would be removed from the shaft.

 

[Snowgoose-1]

Just fwd of the ensign staff on the poop deck sits the spare prop. We also carried a spare anchor mounted against the focsle bulkhead. MV Olivebank 1970s
View attachment 191825View attachment 191825

Ships were much more prettier than they are now.

 

[wonkywinch]

Cunard's QM2 has some spares on the bow, affectionately referred to as the "Commodore's Cufflinks".

 

[dgadee]

The reason was simple. Getting a propellor made, was difficult as stock of certain shapes was not held. Also shipping from a manufacturer to a foreign country, could take a long time, before airfreight was common. This could result in cargo delivery delays, or loss of cargo, that could cost penalties or losses to charterer, ship owner.

I sailed with my father on European coastal trade and all his ships carried spare propellers, in steel, as mentioned by @Poignard.

Today, the trend has come back with high cost azimuthal thruster blades being carried as spares. The Queen Mary 2 carries spare blades on her decks which passengers can walk around. They are huge and probably a custom design.

My drill ships carry spares but held in a warehouse. We would ship to nearest port with suitable facilities and change out, likely in the water, not dry dock. The thrusters are designed to be dropped through a well, and lifted to, from underside to barge, or dock side.

On large single screw container ships, bulk carriers, there are often pad eyes, on the hull, above the water line, either side of the rudder area, for thus very purpose, where the screw would be removed from the shaft.

How often would they be needed?

 

[RunAgroundHard]

How often would they be needed?

No idea. They would come under a capital spares (sometimes called insurance spares) classification, high value, long lead items based on low probability high cost events to company. When tendering for a service, this type of capital spare is checked by the tendering company as the consequences of failure are very high costs.

In my industry, there is a mandatory 5 yearly survey and we also deploy significant conditioning monitoring strategies employing OEM services (Rolls Royce) to remotely check functionality remains within parameters, which means we can increase mean time between failure and plan for change out.

They get damaged typically when approaching ports and strike the seabed, rarely in use in open water. I have not known any to be damaged at sea. Rather I am aware of fires in the thruster bay caused by HV transformers and bearings overheating, which is far more likely than a damaged blade. However, if a blade, or propellor, was damaged, typically on a contract with a day rate of $750k, where NPT allowance is limited to a few days, without a spare propellor (or blade), could be looking at 3 to 4 months manufacturing, shipping, fitting and testing; clients would also be very pissed off at delays to their wells and overhead costs for other 3rd parties et cetera. With a spare propellor, (or whole azimuth thruster pod in my case) ignoring transit time to / from an area where the change out could be done, you are looking at 5 days to drop and refit with all the set up time included. Transit time, including coming off a well, would be the big time factor.

 

[dgadee]

Thanks. Very interesting.

 

[veshengro]

A few of the Tramp ships I sailed in carried a spare prop, often on the top of the Poop Housing. They traded to places where if a prop was damaged and needed replacing waiting times for a replacement could be weeks.

 

[Daydream believer]

I know what you all mean--I used to carry a spare prop spring for my seagull 40+. Only needed to clip the beach when coming ashore & it could take 12 mins to replace. Deadly if near closing time

 

[Frank Holden]

Not unknown for them to just fall off. Company I was with in the early 70's had that happen to a 30,000(?) ton bulker in mid Atlantic.
Just reading the other day that war built Liberty ships had an issue with them falling off as with the mass production they didn't have the skills to put them on proper and there were electrolysis issues twix phosphor bronze prop and steel shaft.
Going back to the 60s sailed with a 2/0 who had been on a ship that shed a single blade mid ocean. He said the instant vibration was something else.
Cairncross Drydock in Brisbane had an assortment of props to suit a number of big ships in the NQ bauxite trade. I guess there was a saving in having one spare prop for 2 sisters trading locally.
I recall the shipping press back when I used to pay attention would in their 'sales for breaking' listings make special note if the spare prop was phosphor bronze rather than steel.
Joined one ship that had damaged her prop in Fremantle and had sailed with a steel one for about a year 'til next drydock. Tips of the blades were like swiss cheese.
Changing without drydocking involves ballasting by the head until tail shaft was well clear of the water. Remove section of tail shaft in engine room, draw shaft into ER and so on.
Propeller Change

 

[Daydream believer]

Just reading the other day that war built Liberty ships had an issue with them falling off as with the mass production they didn't have the skills to put them on proper and there were electrolysis issues twix phosphor bronze prop and steel shaft.

I am suprised that liberty ships were bothered about electrolysis over the life of the ship during the war. Bearing in mind the % sunk must have been high & over 6 years did electrolysis really come to a head. Did many survive the war & go on to plying their trade as cargo vessels? Or were they scrapped?

 

[bikedaft]

I am suprised that liberty ships were bothered about electrolysis over the life of the ship during the war. Bearing in mind the % sunk must have been high & over 6 years did electrolysis really come to a head. Did many survive the war & go on to plying their trade as cargo vessels? Or were they scrapped?

Of the nearly 3,000 Liberty ships built, 200 were lost during World War II to enemy action, weather and accidents. Only two are still operational today, the SS Jeremiah O'Brien and the SS John W. Brown.

from Liberty Ships and Victory Ships, America's Lifeline in War (Teaching with Historic Places) (U.S. National Park Service).

pretty sure many went on for some time after the war. i would have guessed at higher than 7% too...

 

[Frank Holden]

I am suprised that liberty ships were bothered about electrolysis over the life of the ship during the war. Bearing in mind the % sunk must have been high & over 6 years did electrolysis really come to a head. Did many survive the war & go on to plying their trade as cargo vessels? Or were they scrapped?

About 2700 built, about 300 were war losses. The props dropped off early in their life , from Sawyer and Mitchell's 'The Liberty Ships' - 'propeller-dropping occurred quite frequently. The latter problem arose simply because of the mass building of the ships. Previously a ship's propeller was fitted tightly to the shaft without the use of a gland sealing ring, but such a tight fit was not readily achieved during mass production, and when not achieved corrosion often resulted as steel and bronze came together'.
After the war many went into the US reserve fleet but quite a few were 'sold foreign'. I saw the last UK flagged one - 'Sandsend' - in Capetown in about 1966 and an Italian flagged one in Bandar Mashur a few years later discharging pipes and stuff for the oil industry. Round the Cape from Europe at 10 knots - that must have been fun.
I think late 60's was the end of them in trade but it took a while to scrap all of the ones in the reserve fleet.

 

[veshengro]

I was in a Shaw Savill ship out of the Royal Albert Dock with a bloke who had been torpedoed in a Victory Ship. A convoy from Canada and they were caught to the West of Ireland. Luckily the torpedo just blew the bow off the ship and after some pretty heroic damage control jinks they kept her afloat and made The Clyde. His great yarn was that in under three weeks John Browns Yard had cut the remains of the bow off and welded a new one in place, and he sailed for Liverpool as soon as the paint was dry.
Another interesting point he mentioned was that when the torpedo struck the ship 'went out of shape' and a lot of the accommodation interior doors got stuck and wouldn't open or close properly and they remained wonkey until the end of the voyage