Large ships with brass propellers

Looks like one I’ve seen in the display garden at the National Museum of the United States Navy (Washington Navy Yard).

Now let’s get into phosphor bronze. I’m sure you know, Don, but for those members who are saying “phosphor bronze? whatzat?”, phosphor bronze is an alloy of 90%-ish copper, 3.5 - 10% tin, and <1% phosphorus. This stuff has low susceptibility to chemical corrosion in a saltwater environment, a low coefficient of friction, tough (machinability rating = 20 vs. free cutting brass = 100), and resistant to mechanical fatigue (all which makes a preferred material for a ship’s propellers). It has a somewhat odd, albeit pleasant, color:

The phosphorus improves the fluidity of the molten metal, thus cleans up the grain boundaries, improving mechanical properties.

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ADDENDUM: And this is what it looks with a little corrosion:

80,000 pound propeller from the U.S. flag merchant tanker, “American Osprey”.

Don, are you certain that is an adjustable pitch prop & why do you think so?

TomZ2

Looks like one I’ve seen in the display garden at the National Museum of the United States Navy (Washington Navy Yard).

Now let’s get into phosphor bronze. I’m sure you know, Don, but for those members who are saying “phosphor bronze? whatzat?”, phosphor bronze is an alloy of 90%-ish copper, 3.5 - 10% tin, and <1% phosphorus. This stuff has low susceptibility to chemical corrosion in a saltwater environment, a low coefficient of friction, tough (machinability rating = 20 vs. free cutting brass = 100), and resistant to mechanical fatigue (all which makes a preferred material for a ship’s propellers). It has a somewhat odd, albeit pleasant, color:

The phosphorus improves the fluidity of the molten metal, thus cleans up the grain boundaries, improving mechanical properties.

Perfect!  This is what bronze looks like when new. I paint bronze by starting with a coating of "copper".  Testors makes copper paint. I then airbrush over that a light, transparent coat of gloss brown.  I may then weather that with a very light coat of flat green, or a wash of the same. If it is a new, contemporary ship I may stop with the brown.

ddp59

Don, are you certain that is an adjustable pitch prop & why do you think so?

Some signs nearby explained it.  In aviation it would be called "ground adjustable", not something you can adjust in the air.  Adjustment is by removing blade and indexing by one bolt pitch.  Must be done in shipyard.  Apparently the prop style was not successful and this is now a rare artifact.  However, it gives a nice look at heavily weathered bronze.  Usually when a prop is hauled out of water, or sets in air in a drydock, it is not that heavily weathered, but will have a greenish grey patina over the basic brownish copper color of fresh bronze.  If the ship has been grounded for years, the prop may begin to look like this.  If it is really a new ship it will look like the photo of the "phosphor bronze" balls.

I have to think some of the "blame" lies in the "builder's models" out there that often have brass features on them because the modeler made them that way.  Paint schemes on builder's models are generally only "mostly accurate" too--more for the expediency of the builder, who is typically under bot time and budget pressure to turn out the product.

The other driving force, to my mind, would be what paints are commonly available to 80% of the target audience.  So, in the days when the only choices were the teeny glass bottles of Testor's, you had a different pallet than if able to pick and choose across all the Asian paint makers.  (Even though that can have pitfalls, too, consider the color gaffes from early Tamiya Colours or G-S Mr Paint pallets.)

We also probably ought factor in some lack of research (or expedient editing of same)--if you presume monochrome grey, you will opt for more color highlights for less-experienced modelers.

Which is endemic to armor/AFV modeling, with "unpainted" tools called out, and rusty track and the like.  And, that, despite the love an adulation NCOs have for keeping things painted (or in idle hands busy at painting and not running stills or gambling operations).

Applying that logic to ships has always bothered me-but, I grew up around ships, reflexively, I know the decks are a different shade than vertical surfaces, that non-skid is a unique color (and texture) that linoleum is used over steel on a regular basis.  Oh well.  We each bring our life experience to our lives, and they all vary.

TomZ2

 

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ADDENDUM: And this is what it looks with a little corrosion:

80,000 pound propeller from the U.S. flag merchant tanker, “American Osprey”.

TomZ2

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ADDENDUM: And this is what it looks with a little corrosion:

80,000 pound propeller from the U.S. flag merchant tanker, “American Osprey”.

Yes!  This is exactly what the large ship propellers I have seen looked like in service.  That is the shade/tone I strive for.

You know, if people can bronze baby shoes, how hard could it be for the kit mfgs to give us bronze props instead of brass/gold?

CapnMac82

Applying that logic to ships has always bothered me-but, I grew up around ships, reflexively, I know the decks are a different shade than vertical surfaces, that non-skid is a unique color (and texture) that linoleum is used over steel on a regular basis.  Oh well.  We each bring our life experience to our lives, and they all vary.

And I have been around airplanes enough to know that they also feature different tones of weathering on horizontal and vertical surfaces, especially those tied down outside rather than hangered.  Of course, most WW2 planes were tied down outside, so I have always strived to weather with that in mind.  The horizontal surfaces have more caulking of the paint, a lighter color, than the vertical, and the insignia and stuff fades more on the horizontal.

Don Stauffer

You know, if people can bronze baby shoes, how hard could it be for the kit mfgs to give us bronze props instead of brass/gold?

I’ve seen kits that “bronze” plaster castings at craft stores.
They include little bottles like this:

I guess some artistic license is allowed, as no one ever seems to model marine growth either. But point well taken, Don. I get stuff made out of bronze all the time, and have a lot of paint to match it with. In fact, most of the plaques people see around that are supposedly bronze finish are painted. I'll repaint those props on the Emden tonight!

Bill

If you see a bronze propeller in dry dock that has just been cleaned, it is almost a gold color.  Maybe after a few days it gets a patina, but since a ship model sitting on a walnut base is not a realistic setting anyway, I say paint the propeller any color you want.

onyxman

If you see a bronze propeller in dry dock that has just been cleaned, it is almost a gold color.  Maybe after a few days it gets a patina, but since a ship model sitting on a walnut base is not a realistic setting anyway, I say paint the propeller any color you want.

I'd say they look a lot like the photo in TomZ2's first post. Is that a gold color?  I'd say it is closer to copper than gold, but without a reference of both metals to see, maybe some would call it more gold.  May depend on the alloy, too.  There are a number of bronze alloys- some look almost more like steel or aluminum.

Here's a picture of a USCG 65' harbor tug sitting high and dry in a yard.  The prop has been cleaned, but it has a two tone look.  Also notice the location of the sacrificial zinc anodes.

Another comment on that adjustable pitch prop; that is similar in design to modern changable pitch propellors (CPP) used on many large ships, especially gas turbine powered warships.  The effective pitch of the prop blades can be changed by a hydraulic system controlled from the pilothouse or engine room.  Two of the USCG Cutters I served on had CPP, with a pnuematic-hydraulic control system.  The pilot house and main engne room controls used a pneumatic system to adhust valves on "the Ouija board" interface to the hydraulic controls.