WW2/Korea TF sustainable speed

Seen lots of sources on the Internet that identify maximum sustainable speed of Essex carriers and supporting ships in the Task Force as 30 knots. But I don't see anywhere how long "sustainable" means. 4 hours? 8 hours? A day? Multiple days?

Eventually destroyers and the other smaller ships in the TF would run out of oil, clearly.

Is there a wear and tear component that forces them to reduce speed?
 
WW II warships, with few exceptions, were driven by turbine engines, which could run flat out until the fuel ran out. The "crack" liners of the Atlantic run would do that, sustaining 30+ kts for the entire trip. Weather of course made a difference; in December 1941, Enterprise was delayed 24 hours in returning to Pearl Harbor by adverse weather.

However, on a really long run, such as Kido Butai's trip to and from Hawaii, the TF would run slower to stretch the fuel supply.

The exception was ships with reciprocating engines. Some older dreadnoughts had reciprocrating engines: USS New York and USS Texas, IIRC. Also, though, the 50 Casablanca-class escort carriers. Reciprocating engines in operation slam weight back and forth, which inevitably shakes the engines loose on their bedplates. Run reciprocating engines too hard and too long, and they break down. The reciprocating-engine ships of the RN were noted for being able to run flat out for only a relatively short time (maybe as little as eight hours; I can't remember or find a reference) before the engines fell apart.
 
The numbers may be a bit wishy washy and it's not totally WW2/Korea but when HMS Ark Royal was tasked to put a demonstration flight over Belize in 1972 it first had to steam for 1500 miles at a dispatch speed of ~26 knots (top speed 29kts) and drew the fuel down to 55% of bunker capacity. They normally never went below 80% of fuel capacity so they blended aviation fuel into the bunker fuel, as a result they didn't have to use water as ballast and then clean the bunker tanks afterwards.
 
Thanks, Gentlemen. Useful stuff. Have to remember about adding seawater to maintain ballast. Read a bit the other day about a destroyer doing that during Halsey's typhoon. Have to go back and check if it mentions whether their fuel status at the time had much to do with it.
 

CalBear

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Speed, or more properly, rate of advance, for a carrier group, is largely impacted by wind direction. The carrier has to me moving into the wind to properly conduct flaght operations (a 15 mph headwind with 30 knots of ship speed provides a LOT of additional lift for heavily laden aircraft). If the carrier is sailing with a following wind it will need to set course 180 degrees away from its destination one hour in three (or less with early WW II fighters/dive bombers) greatly lowering average rate of advance compared to a force moving into the wind. There are also other factors that can greatly impact rate of advance, the most significant being zig-zagging. A zig-zagging formation will cover close to double the distance moving from point A to point B than one maintaining a direct course. There is also the matter of escorts. Destroyers can make 7-10 knots more than CV (depending on class of both ships), but the DD rarely moves in anything even similar to a straight line, and a DD uses fuel at a spectacular rate while at top speed while starting with less fuel to begin with.

When coupled with the need to refuel escorts the TF rate of advance will, in general, be half to two-thirds of the "top speed" of the slowest ship in the formation
 
WW II warships, with few exceptions, were driven by turbine engines, which could run flat out until the fuel ran out. The "crack" liners of the Atlantic run would do that, sustaining 30+ kts for the entire trip. Weather of course made a difference; in December 1941, Enterprise was delayed 24 hours in returning to Pearl Harbor by adverse weather.

However, on a really long run, such as Kido Butai's trip to and from Hawaii, the TF would run slower to stretch the fuel supply.

The main exception was ships with reciprocating steam engines, which are much more economical at low speeds. Some older dreadnoughts had reciprocating engines: USS New York and USS Texas, IIRC. Also, though, the 50 Casablanca-class escort carriers. Reciprocating engines in operation slam weight back and forth, which inevitably shakes the engines loose on their bedplates. Run reciprocating engines too hard and too long, and they break down. The reciprocating-engine ships of the RN were noted for being able to run flat out for only a relatively short time (maybe as little as eight hours; I can't remember or find a reference) before the engines fell apart.
 
There is almost no wear and tear on a turbine. Turbine generators run for years at a time at full output between refueling on nuke plants. Propulsion turbines are basically the same, except they are attached to a reduction gear. Reduction gears are tough pieces of equipment. I was on several 25-30ish year old subs and the reduction gears where fine. The moored training subs in Charleston have reduction gears that are going on like 60 years old. Riding on an oil wedge bearing, there is no metal to metal contact anywhere in a turbine. If a battle group is not launching planes as CalBear noted, then they can just go fast. They would slow down to perform underway refueling of the escorts. Modern battle groups have to do the same thing since only the carrier and attending SSN are nukes. When crossing an ocean we would run our sub at flank for days/weeks at a time. Only slowing for a quick trip to PD and back down.
 
Speed, or more properly, rate of advance, for a carrier group, is largely impacted by wind direction. The carrier has to me moving into the wind to properly conduct flaght operations (a 15 mph headwind with 30 knots of ship speed provides a LOT of additional lift for heavily laden aircraft). If the carrier is sailing with a following wind it will need to set course 180 degrees away from its destination one hour in three (or less with early WW II fighters/dive bombers) greatly lowering average rate of advance compared to a force moving into the wind. There are also other factors that can greatly impact rate of advance, the most significant being zig-zagging. A zig-zagging formation will cover close to double the distance moving from point A to point B than one maintaining a direct course. There is also the matter of escorts. Destroyers can make 7-10 knots more than CV (depending on class of both ships), but the DD rarely moves in anything even similar to a straight line, and a DD uses fuel at a spectacular rate while at top speed while starting with less fuel to begin with.

When coupled with the need to refuel escorts the TF rate of advance will, in general, be half to two-thirds of the "top speed" of the slowest ship in the formation

Thanks, CalBear.

I figured there was lots of zigzagging, but didn't realize it would almost double the distance.

I do wonder for example what the average speed/speeds would have been for the task forces supporting the Doolittle Raid. I'd think they would have wanted to have gotten in and then back out as fast as possible.
 

CalBear

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Thanks, CalBear.

I figured there was lots of zigzagging, but didn't realize it would almost double the distance.

I do wonder for example what the average speed/speeds would have been for the task forces supporting the Doolittle Raid. I'd think they would have wanted to have gotten in and then back out as fast as possible.
The Doolittle TF managed a rate of advance of around 24 knots en route to the strike (winds in the northern Pacific tend to blow East to West and somewhat to the Southwest, roughly the direction the TF was heading). The trip back, after the Japanese were alerted and trying to chase them down, the rate of advance was closer to 17 knots (wind was going in the wrong direction and additional ASW defensive measures were needed since IJN subs would be on the alert)
 
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