OT: Are ship propellors still made of bronze. (2024)

I used to see the multi ton bronze propellers at a shop in Oakland. That shop is closed now. Are the biggest ship propellors still bronze? back it in the day I think part of the reason was to make the machining and repair work easier.

They must have had some kind of fancy tracer mills with lots of math involved. A stainless prop might be no cheaper to cast or forge in those sizes. I would hate to think what a galled prop that size would take to pull off the shaft.
Bill D.

My guess is yes. Stainless steel is attached by saltwater (the cloride ion).

Tom

I recently watched some program about the largest cargo ship being built.

Two bronze propellers - because just one would be so large it would break the surface and lose efficiency.

Two years in development, computer modeled, then water tunnel tested for cavitation and so on.

Both cast and machines in bronze, $ Million bucks each or something like that.

ratbldr427 said:

I at first thought they were welding a broken blade back on but came to realize that they were creating the missing blade with weld!I wondered how much rod and at what the cost was,

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Yeah, I didn't think of that. If a blade hits something an breaks a blade, you probably don't recover the missing part very easily.

bosleyjr said:

Yeah, I didn't think of that. If a blade hits something an breaks a blade, you probably don't recover the missing part very easily.

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If its multi tons of bronze and in shallow enough waters you sure as hell do!Divers and a small crane barge are not all that costly.

Someday you will just have to click PRINT.

And that is not far from the truth.

"Someday you will just have to click PRINT.

And that is not far from the truth. "

OK, I'll say it - WTF?

GregSY said:

"Someday you will just have to click PRINT.

And that is not far from the truth. "

OK, I'll say it - WTF?

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I think he is thinking 3D PRINTER.

The props on my 65 foot Viking MY (with two Detroit 12V71TA diesels) were made of bronze. I had a "never used" matching spare set under the master bed... thinking they cost previous owner around $18,000 a pair, so can't imagine the cost of larger ship props.

An alternative to buying a spare set is to "rent" a set from Sam's Marine.....i.e. they keep your specific bore, diameter, pitch, blade number, etc set in their inventory ready to ship to a haul out yard at a moments notice for a nominal fee per month. Otherwise you might end up waiting for a month to have a set built if the originals were damaged beyond repair.

The theory is the "moments notice" never actually happens and once you sell the boat and stoping paying the rent, Sam's then can sell the set, or just keep in inventory for the next boat that needs that size. They typically don't buy the props new but buy used sets cheap as they become available to them. In fact it was tempting to sell my spare set to them as having a spare set doesn't add much to the value of a yacht since most buyers don't think about such things too much. But they would have been such a PITA just to get them out from under the bed, up the spiral staircase, etc, I just let them go with the boat (plus I think my particular buyer actually did care there was a nice spare set)

Most boats I looked at before buying the Viking had a spare set but the spares were always not exactly the right diameter and/or pitch and looked well used...but were way better than nothing for "get home" purposes. Mine was one of the few that had a pristine new set that matched perfectly. A big advantage of that is one could swap out with just one haul out, and then when originals are repaired they become the "spare" set......whereas with "get home" props you are talking two haul outs to get matters back to status quo.

(although it is possible for an experienced diver to switch out props underwater... but in this case we are talking props that are much too heavy for one person to lift...so the "in water" procedure involves using floats tied to a blade to try and achieve neutral buoyancy... sounds like a major PITA compared to doing it on land, but it can be done)

As an aside, buying that boat was by far the stupidest decision of my life... took two years to sell it. But that's another story...

During WWII, my uncle was a rigger in one of the San Francisco ship yards. He told me of a prop replacement that he worked on that turned out to be a little scary.

The crew started using kerosene salamanders to heat the prop nut cap so they could melt out the tallow filling so they could unbolt and remove the cap.

Each ship carried a custom 6-point slugging wrench for their prop nut. The crew would use a chain fall to take up the slack, then beat on the wrench with a chain supported battering ram.

The next step was to use a hydraulic prop puller. At the same time, they'd heat the prop hub with salamanders.

This ship's prop wouldn't budge. When lunchtime came around, the entire shipyard stopped. About halfway through lunch, the prop suddenly popped off, and wobbled across the dry dock, smashing everything that it touched.

It turned out that no one had remembered to release the hydraulic puller when they broke for lunch. My uncle told me that since the prop was scrap, no one raised a stink about it.

He also commented that same job saw someone on board use one of the heads (washrooms). This was a giant no-no when the ship was in dry dock since the waste treatment in those days was a pipe straight through the hull. He got hit. He climbed up into the ship, and couldn't find anyone near the toilet, so he unbolted it and used a broomstick to ram every pair of coveralls he could find as far down the pipe as he could - then he went back to work. He told me that he often wondered how long it took them to figure out why the plumbing was plugged.

Bill D said:

Also do the big ships still carry a spare propeller on deck? Not many ships ever did. I suppose the ones on a fixed route would not while those that circled around the world and had no fixed home port would want to carry a spare. Too big to ship by air so you could wait weeks for delivery even if it on the shelf ready to go.

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Dunno but hopefully the larger ship keels are way deeper than the end of a prop blade. My 65 Viking was such that the tip of a prop was about the same as the bottom of the keel....so if one ran aground one can bend a prop blade (which happened to me during Hurricane Matthew)...amazed me they designed the boat that ridiculous but that tidbit didn't sink in my brain until after I had bought it.

In contrast the prop on my Jeanneau sailboat is probably two feet higher than the bottom of the keel (plus it's a folding prop...less resistance under sail)

Nearby we had a prop foundry from Wartsila I was invited by a ex college who started working there to see a big propeller poured
Very impressive Total pour was 110ton of CuNIAl IIRC
But anyway Outside they had a big yard with huge props ready to be shipped Those were spares they held in stock for customers

Peter

Milacron said:

......
As an aside, buying that boat was by far the stupidest decision of my life... took two years to sell it. But that's another story...

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There are two best days in owing a big boat.
The day you buy it....... and the day you sell it.

Bob

CarbideBob said:

There are two best days in owing a big boat.
The day you buy it....... and the day you sell it.

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Heard that cliche a few hundred times...not always true with boats I have owned in the past...but in this case, 10x true....elation seeing the wire for that thing show up in my bank account ! Coincidentially the boat just left the marina today for more northern waters... good, as I cringed a bit every time I walked past it for the past few months even after it was no longer mine !

Funny, I just happened to be walking the dog when I saw it at the fuel dock this afternoon and snapped the attached photo....found out later the new owner pumped in 500 gallons.. main tank held twice that much....aux tank held another 300...

I'm currently the master on a 128' river tow boat with stainless props. Designed specifically for river and inland waterways but we've also operated extensively in salt water. We ground the boat on tidal flats every year to inspect hull and props. No issues with corrosion in many years.

The props operate in tunnels beneath a swept up stern section. At rest with normal draft, our props are 1/3 out of the water. A rectangular trunk is built into the hull section above the props with a removable "plug" shaped to the tunnel section. Remove the plug and 1/3 of the prop is accessible above water. A walkway may be suspended in the water behind the prop. Working with waders, it is a simple matter to cut out fouled lines or remove the shaft nut and pull the prop and lift out the top.

Boat is flat bottomed so no keel. We often operate with a couple feet (or less) under the boat. Prop tips clear the sea bed by 6".

Arguably not a ship but not small either. All early 50's OEM.