"Why Flank Speed?" Topic

Anyone know why the max speed of a ship is called "flank speed"?

I found this on the web:

It's that flink-flank noise the engine makes.

Dear Word Detective: Where did the term "flank speed" come from? It is used by both Navy and merchant vessels as the absolute maximum speed for a vessel. -- Len Sutter, via the internet.

Oh boy, a nautical question. We love nautical questions around here, because no matter how diligently I research my answer, I can always look forward to receiving lots and lots of reader mail correcting me. I don't even mind the fact that many of my correspondents see fit to question whether I, personally, have ever actually seen a boat. I just find the enthusiasm with which they say it inspiring.

Onward. As you say, "flank speed" is the absolute maximum speed of a vessel, faster, in fact, than "full speed," which itself is only one-eighth faster than "standard speed" for the vessel. Unfortunately, while I have found many references explaining what "flank speed" is, none of them feels it necessary to explain where the term itself comes from. But I think that once we trace the history of the word "flank" itself, we'll be able to concoct a reasonable theory about "flank speed."…

word-detective.com/041899.html

Anyone heard any other reasons?

--Tom

If a ship was heading with its bows facing the side of an enemy ship it would take a full broadside yet only able to reply with its forward guns – so it needs to close with the maximum speed?

Windward – The definition you have found is & does seem correct though i believe the term itself derives from when destroyers, when they arrived in the latter years of the 19th century at that time known as torpedo-destroyers, used to charge into combat to deliver their deadly cargo into the flanks of an enemies ship.

Black Tower – this manuever is know as crossing the 'T' & any ship that found itself in such an unfortuneate position deserved to get pounded.

A "flanking attack" is not a naval maneuver. The preferred position was with your side to the enemy's bow or stern, which gave you an advantage in firepower, so there would be no rush to get into the side-to-side position and lose that advantage. If your ship was the one with the bow or stern facing the enemy, you'd put your helm over, not increase speed.

Also, the term would have been meaningless before the age of steam, so it can't date back very far.

I thought that I heard this order given in the movie The battle of the river Plate

The British ship was out gunned and IIRC the order flank speed was given to allow it to close with the enemy so it could get into range with its guns
Hence it is a maximum speed to use in an emergency

I don't know, but having owned sailboats, if I were to guess, I would say that a sailing vessel's fasted possible speed is made on a "broad reach". A broad reach is when the wind is coming over the flank (aft quarter) of the ship.

I don't know for sure but I think it comes from ships in line abrest making a wheel like this link explains:

link

The ships need to move at different speeds (outer faster then inner) and if the inner ships slow down they become easy targets. If the formation is at full speed going into the wheel I assume they would need a term to describe the increased temporary speed for the outer (flank) ships, ie.. flank speed. In a battle I am sure that the outer ships would be pushing their engines to the limit, especially if they were something like a torpedo boat rushing in to deliever a torpedo at a battleship that could sink them with one lucky hit.

Just a thought.

Flank speed is a function of the boat going at maximum output in a straight line with both flanks (sides of ship) going at literally the same speed. If the boat is at maximum output but is turning the boat will go slower because of water resistance etc. SO if you want to maximum speed you go at flank speed which means you are not turning and you have maximum output. SO at flank speed the boat seems ( and actually does) go "faster" than "maximum" speed which contemplates turning etc.. Flank speed is the outside limit of speed because it is not a manueverable boat but is attaining distance to (or away from) someting else in the minimum amont of time.

I have just gone down the corridor to talk to the Royal Navy Chief Instructor for Tactical Communications. (If he don't know, nobody does!) He's never heard of flank speed, but the highest speed rung on in order to move rapidly to take station in a new formation, to deliver an attack, shelter from blast, or whatever, is known as 'Stationing Speed'. Hope this helps.

Flank speed is a USN term, definitely, but don't know where it comes from.

>>>Flank speed is a USN term, definitely, but don't know where it comes from.<<<

Hollywood?

Well, the EOT on my boats said 'Flank', but they were both fairly new (oldest was commissioned in 1986)

>>>Flank speed is a USN term, definitely, but don't know where it comes from.<<<

Hollywood?

Nope. Ned Beach uses it in "Run Silent, Run Deep". He also notes that, at least in the the Pacific Fleet Submarine Force, there was actually one speed higher than Flank – All Ahead Pearl Harbor.

I've always heard the answer the earlier poster gave and it makes sense. . .

The ship on the end of a formation in line abreast will have to move faster than those towards the middle when turning. Hence 'flank' speed.

"It is used by both Navy and merchant vessels as the absolute maximum speed for a vessel. -- Len Sutter, via the internet."

As ex-MN and RNR(rtd) it is an expression that I've never heard except in Hollywood films. I would therefore assume that it is a USN expression. Any of your explanations may be true.

According to ORIGINS OF SEA TERMS (John G. Rogers, ISBN 0-913372-31-5)… "FLANK SPEED: Maximum possible speed. This term is mainly naval, and probably originated with our [USN] destroyers before or during World War I. It was the speed required to get to a new position in a formation or convoy in the shortest possible time, also to outflank enemy ships."

Yes, I understood it to be a derivatiion of 'outflanking speed' which would concur with Rich's explanation. My uncle (ex naval, HMS Helford) also thought it was a USN term from their submarine arm and referred to getting ahead of the target (outflanking) at maximum speed to reach the best position and set up for a flank shot.

Flank speed is indeed a US Navy term.

When ships go ahead at 'full speed'they are using the prescribed full speed recommended for the engines. However most warships and submarines could actually go a bit faster than the recommended speed, should it be necessary.

So if a US Captain gave the order 'Full ahead'he meant full speed as per recommended for that ship.

However if he gave the order Áll ahead flank'or 'Flank Speed'he was pretty much telling the engineering staff to pull out all the stoppers. Or in motor vehicle terms….put the pedal to the floor!

Flank was that little extra reserve to get a ship out of trouble, or as has been said to get ahead of an enemy (or away if it was bigger)

The Oliver Hazard Perry class frigates are listed as having a top speed of 27 knots. But while spending some time at sea on one I was assured by the engineer that if necessary, he could probably get another three knots out of her.

The British seem to have referred to it as 'All ahead emergency'. This was used at the Battle of the Falklands in WW1 when the British cruiser HMS Kent exceeded her designed speed by more than two knots. Which was all the more remarkable because for the couple of years before that, her best speed was supposed to be a couple of knots LESS than her designed speed.

If I recall correctly, in 1940, when the German Scharnhorst and Gneisenau were surprised off Norway by HMS Renown they increased to full speed. The weather was very bad so both sides were struggling to make their best speed. But after a 15" shell struck home the German Admiral ordered 'emergency speed ahead' and the two Battlecruisers then reached their best speed as per the designers….which they technically should not have been able to do in the weather conditions.

So 'Flank speed' is an emergency or urgent speed. The term is American. But I believe the explanation by David Raybin is pretty correct.

Ships doing that risk damage to their machinery, and if doing it in heavy seas, they risk damage that way too.

THINK SCOTTY to Captain Kirk!

"She'll no be able t'keep this up Cap'ain"

Engineers are born conservatives and worriers….which is why that part was put into Star Trek. Plus in the steam age, a lot were Scotsmen.

Technically speaking, on some nuc powerplants, there's actually a speed above flank: Battleshort.

Flank speed, while pushing the equipment *hard* will not cause permanent damage if you slow down every 6-8 hours. You're still observing the normal operating redlines.

Battleshort means 'push things until they break.' For example, say your powerplant has a 5x safety factor built in (what you call rated power is only 20% of capacity, if you have no margin for surges). Running at battleshort means reducing the safety factor, possibly to zero. Instead of running at say, 200psi, you're running at more than 400psi. 200rpm on the shaft? No, try 325rpm (and cavitating like a banshee).

Battleshort *will* reduce the operating life of whatever plant you're pushing that hard.