Knots per Hour

[Rocky]

Why use it in 2003?

[John Bell]

Why use it at all?

knot - nautical miles per hour

then knots per hour = nautical mile per hour per hour, which sounds to me like a really arcane unit of acceleration. ;)

If we really wanted to get with the rest of the world, we'd be talking in kilometers per hour.

Not picking on you Rocky, but 'knots per hour' is one of those terms that really bugs me.

[Rocky]

Picky picky. All right, the nautical mile has a better reason for living than the land mile, which is about 796 feet shorter, so why don't we use it on land?

[ 04-04-2003, 08:36 PM: Message edited by: Rocky ]

[Nicholas Carey]

Originally posted by Rocky:
Why use it in 2003?Because one nautical mile is defined as 1/21,600 of the earth's circumference (360*60 giving 21,600)—1 minute of arc, about 6,076.1 feet, more or less.

[John Bell]

No, not splitting hairs, Rocky, just trying to help you get it right. My copy of Chapman's (61st Ed.) says "the phrase knots per hour is a mistake." (p. 429)

A nautical mile is 6076.1 feet which is equal to one minute of latitude, which is useful in navigation.

The same question could be asked as to why use statute miles?

[JeffH]

Yup. The better question would be "why is the U.S. still stuck on the imperical system in 2003?"

[John Bell]

Now, if you're navigating the inland waters of the US, e.g. the Mississippi River, the Intracoastal Waterway, or on the Great Lakes, all distances are given as statute miles, so there's no reason to use knots or nautical miles there.

As for why the US hasn't dropped our antiquated measurement system? Damifino. Why do we still have paper one dollar bills instead of the dollar coin? At least we don't have shillings and guineas! ;)

[Mike Field]

The nautical mile (and hence the knot) is not really an Imperial measure, for the reasons given above. Hence it can't really be metricated.

When all the metric conversion stuff was published here in Oz at changeover time, the fact that the nm and knot would remain unchanged was explicitly pointed out.

(Mind you, I'm a bit surprised that the fans of the French Fad didn't try to metricate the nm anyway. The found no difficulty in doing it with the dimensionless unit of parts per million.)

Decimal currency is one thing. Decimalised everything else is another. I've long admired you in the US for sticking with the Imperial system. Maybe it's because I'm at heart a reactionary?
.

[ahp]

One mile equals 1000 double paces by a standard (Roman Army) walker. It is metric, see!

[seafox61]

america is a big country 3 thousand miles acrost who wants to giger it at 5500 kilometers?

a mile is a good mesure you look at something and you know its about a mile, the range your round will fly out of yor 22 cal rifle. but a klick? wqhats a silly little click? our farms ara a quarter section being a half mile on a side ( or better yet a full section that is a mile on a side)
what is really strange is metric plywood its about an inch and ahalf shorter and 3/4 inch narrower. shucks with people getting bigger wish they would go to 5 feet by 10 fet as the standard

now that would make things intresting wouldn't it ???
jeffery

[Ken Hutchins]

The one thing that really gets me is the penny and the nickle. I say round every price to the nearest dime. That is something I really appreciated when I visited the land of OZ.
But what can we expect from a country that has a stock market that only recently did away with fractions. tongue.gif Maybe there is hope that someday we will convert to metric.

[landlocked sailor]

Peter Spectre dealt with this very issue (knots per hour) several years ago in his wonderful "On the Waterfront" column; sadly, now gone from the pages :( His final conclusion is that both 'knots' and 'knots per hour' are acceptable although the latter never sounds right to me. Rick

[ahp]

It certainly should not sound right. Knots are the first derivitive of distance by time, or velocity. Knots per hour is the second derivitive of distance by time, or acceleration. How many of us care about our boat's acceleration?

[Scott Rosen]

I love knots. I hate metric. Miles, yards, feet, inches, ounces, pounds. I love 'em all.

Knots per hour sounds lubberly to me.

When some asks, "how far?" The answer is __ miles, or __ nautical miles. (Both refer to nautical miles.)

[Rocky]

That's right, metrics are for weenies. You can go 100 in your Yugo on a litre for a euro. They're only superior in the use of hand tools. 13's too small, gimme a 14, or is that a 19/32?

[ 04-06-2003, 09:09 AM: Message edited by: Rocky ]

[Tom Lathrop]

If you go back to the original way of determining boat speed, they counted the number of equally spaced knots on a chip log line in one turning of a small sand glass. That makes it knots per unit time which sounds an awful lot like "knots per hour". It may sound awkward to us but there is nothing wrong with it.

Some of us old codgers still use a chip log to calibrate knotmeters, that is I did until I got my new WAAS GPS.

[JAX]

^^^Knots are the first derivitive of distance by time, or velocity.^^^

No, velocity is a vector (meaning it has both speed *and* direction). Knots is just speed.

[Nicholas Carey]

Originally posted by Mike Field:
I've long admired you in the US for sticking with the Imperial system. Maybe it's because I'm at heart a reactionary?.Nah...it's just US (so to speak) and Kuwait these days, left using the Imperial system of weights and measures.

That's the real reason we came to their rescue 13 years ago.&mdash. they're our compardres in marching to the beat of a different drummer. :D

[Rocky]

Are there any GPS's that will tell you your speed in knots?

[Donn]

My handheld GPS does. So does the speedo on my sounder.

[Mrleft8]

The newly sharpened blade on my table saw cut 15 knots per hour yesterday...

[Leon Steyns]

It's just something you grow up with - metrics or imperial. In both cases, the nautical mile is respected. I'd say: keep it that way. (as for the knot, as for the foot describing boat lenghts).

The grown up people decided in the SI units system that speed is defined in meters per second.

Greets, Leon Steyns.

[Rocky]

On that subject, why are latitude and longitude divided into 60? Could they be divided into 100? Surprised Marat didn't try to do this! Or did he? Wasn't there a book just out about a group of Frenchmen trying to develop the metric system at the height of the Terror?

[ 04-06-2003, 10:39 AM: Message edited by: Rocky ]

[JimD]

Originally posted by Mrleft8:
The newly sharpened blade on my table saw cut 15 knots per hour yesterday...Mrleft8, that sounds like awfully knotty wood to be building a boat with :D

[Johannah]

Don't remember what Marat thought, but the metric system is a product of the Enlightenment and was defined during the Revolutionary period. The poor souls who set the standard for the meter had to contend with enraged peasants and fickle political winds while measuring the defined arc of the earth's circumference that goes through Paris. Part of the reason the US never adopted the metric system beyond technical application is that the arc measured was a French one, really, I am not kidding about this. Other countries also backed off because the fundamental unit was to be defined relative to a line through France (and partly into Spain). A funny/awful story with astronomers trooping through the mountains trying to avoid pitched battles and brigands. One finally was lost while trying to remeasure a problematic area.

The 360 and 60 divisions for time and circles originated in, are you ready for this, Mesopotamia. The Revolutionaries of France tried to impose a 400 degree circle but it was widely loathed and didn't last long. The Meter measurement team used superb instruments for measuring angles called repeating circles. The instrument maker made them each a pair of instruments, one using 360 and one using 400 degrees.

[ 04-06-2003, 12:53 PM: Message edited by: Johannah ]

[John B]

It's not metric or ( versus)imperial. Knots match your chart.Your chart is calibrated in nautical miles for a reason. end of story.
Our metric charts show depth in metres as opposed to fathoms, that's all.

[Mrleft8]

They were very small knots....

[ahp]

While we are all at it, knots (speed) is the count of actual knots tied in a line attached to a chip, that runs out in the time that it takes the sand to run though the timing glass. How far apart are the knots and what is the time interval? My book by Carl Lane, which has this info, is in a box somewhere.

JAX I stand corrected, you nitpicker, velocity is a vector and speed is a scalar.

[Donn]

"..they usually had ropes that had knots every 50 feet and a sand glass that measured half a minute. If you work out the math you will convince yourself that the number of knots that went overboard in half a minute is exactly the number of nautical miles per hour the ship was cruising at. For example, if 10 knots went overboard in half a minute, then the ship was moving forward at the speed of 10 knots or 10 nautical miles per hour (which would be about 11.5 standard miles per hour.) "

http://www.physlink.com/Education/AskExperts/Images/ae400b.gif

more.. (http://www.physlink.com/Education/AskExperts/ae400.cfm)

[Phil Young]

So its really Knots per half minute, rather than knots per hour. 10 knots per hour would be terribly slow.

[Sailing-Randy]

Okay, I'll weigh in for my once-in-awhile.

Yesterday I had the metric discussion witho someone off forum. I remember that the USA officially adopted the metric system back in the 1880's or something like that. Any have any solid evidence on that?

I also know that it is extremely difficult to change the way people think. For my Dad it was nearly impossible to think in metric terms when he was building something. However, as a man who began flying at 40, went on to teach jet pilots instrument flying, he was able to learn a whole lot if it made sense to him. For me I can understand when you say it's about 40 miles over to there. But if you tell me in Kilometers, I will stare at you blank faced until someone can get my mind thinkiing of the conversion rate. Then, and only then, might my face light up with understanding.

I have often said with only part of my tongue in cheek that the hardest thing I do is change my mind. Tis true for all of us I am afraid.

Even my wife, who is a RN Flight Nurse and who thinks in metrics whenever hse on the ship and filing reports, still spaeks in miles-per-hour and cooks with the regular "American" measuring cups.

So why don't they teach this stuff to the kids in school. They do at times, they have tried at times, but unless they want to create a generational stir over something that doesn't really matter, unlike condoms and pre-marital sex, why bother? :D

[Johannah]

If you are enjoying this discussion, especially the laments about how hard it is to think in different measurement systems, you might enjoy a book called "The Measure of All Things". Gives the history of the development of the metric system and is NOT dry reading. tongue.gif

[John B]

the first question is why we use knots per hour in 2003.
Then it's wound off into the semantics of whether the phrase 'knots per hour' is redundant... a duplication, which it is. like calling fuji ama,mt fuji ama.

The answer is that we have knots because it is derived from the calibration used to measure the earth. degrees of latitude are broken up to represent nautical miles. to navigate on the sea you need to know how far you are going and how fast you are going. you get your dividers out, you scale off the latitude , and the chart tells you distance. Each degree is what... 60 nautical miles. That's why NM are different from miles in the first place.It has nothing to do with the metric system.

[Nicholas Carey]

Originally posted by John B:
The answer is that we have knots because it is derived from the calibration used to measure the earth. degrees of latitude are broken up to represent nautical miles. to navigate on the sea you need to know how far you are going and how fast you are going. you get your dividers out, you scale off the latitude , and the chart tells you distance. Each degree is what... 60 nautical miles. That's why NM are different from miles in the first place.It has nothing to do with the metric system.But...

Even though the nautical mile lies outside SI, the NIST has standardized the nautical mile for use with SI as exactly 1852 metres (app. 6076.11549 feet, more or less :D ). See http://physics.nist.gov/cuu/Units/outside.html for more information.

And NIST defines knot as 1 nautical mile per hour or (1852/3600) m/s.

[ 04-08-2003, 08:37 PM: Message edited by: Nicholas Carey ]

[John B]

I'll make some notations on my chart. :D

"how far we going this afternoon?"

"ooooo 25,928 metres to Garden Cove, be there in 2 hours"

LOL.

[Nicholas Carey]

Tee-hee http://www.speakeasy.org/~ncarey/images/smileys/devil.gif

[R.I.Singer30]

A land mile is measured on a flat plane.Since the earth is curved, the knot measures the arc also. 1knot=1.2 miles. Fom ocean level you can only see 5 miles do to the arc of the water/earth's surface.So it's actually a different measurement.

[ 04-09-2003, 07:48 AM: Message edited by: R.I.Singer30 ]

[Johannah]

John B. nautical miles and the metric system are related by underlying philosophy rather than by units. The meter is defined as a fixed segment of the earth's meridian just as the nautical mile is. NM is defined in terms of degrees and meter in terms of distance but they are both defined segments of the same thing. The metric system is named for the fact that it is based on defined measurements of supposedly objective reality. The definition of NM derives from the "metric" movement. Using the term "metric" for the gram/meter system exclusively is relatively modern usage.

[Ian McColgin]

Whoops, lets not get lost -

"Knots" means nautical miles per hour.

Depending on the size of the vessel, the log line may be knotted at different intervals and run for a longer or shorter time. The size of log convenient to a frigatte would be a bit cumbersome on a small sloop.

We can tease that "knots per hour" is really a unit of acceleration, but there really is no such unit in actual use.

The meter was meant to have a relationship of equator to pole - I've forgotten the number but they were wrong anyway - and now is derived from a different standard anyway.

Since the earth is not a sphere, even the nautical mile, which is at least more closely attuned to our watery world, is still not perfect.

But it's very nice.

Just as the mile from mille, 1,000, really derived from 1,000 standard Roman Army paces, a pace being a left and a right. Another nice human measure.

A year or so back Brion Toss had an entertaining colum that I thought was repeated here on how all practical carpenter types like SAE style measure better than metrics since dividing and subdividing in halves and thirds is versitile and easy to keep in the head.

Rather like the superiority of points of the compass vs degrees, especially once you learn the trick of converting any course into its normal on either side or its recipricol.

There was an entertaining thought of number reform that I think Charles II of Sweeden wanted - a base 64 so that things were both divisable and square rootable and you'd not have to bounce between decemals and non-reducing fractions. But someone convinced him that while he was a genius, no one else would even memorize all the number names, much less the basic arithmatic tables.

[Nicholas Carey]

Originally posted by Ian McColgin:
The meter was meant to have a relationship of equator to pole - I've forgotten the number but they were wrong anyway - and now is derived from a different standard anyway.1/10,000,000 of the distance from the Equator to the North Pole on the Paris meridian was the original spec, but hardly 'wrong', using the technology available c. 1795, the error was less than 0.02 percent (two one-hundredths of 1 percent.)

That's 0.2 mm or 0.007874 ins.

Not too shabby for a low-tech, 18th century solution and one with a cumulative error built into the process.

[Bruce G]

I've learned more on this one strand than I have on the entire Bildge. Wow!

[Ian McColgin]

You're right, that is nice and close.

Everyone with sextants and charts marked in radians now switch to kilometers . . .

We'll have the international raft up in Thermidor.

[Nicholas Carey]

I just stumbled across this little gem, courtesy of Google: Of special interest is the Greek Olympic foot, 12.15in., used for the lay-out of the Parthenon. This is a geodesic unit which divided a minute of arc on an assumed spherical Earth into 6000 parts, with 600 to a Stade for one tenth of a minute.

This was remarkably close to our nautical mile, and of comparable accuracy to the original measurement for the metre, which is 0.2mm shorter than was intended.The more things change...

[Ian McColgin]

Amazing what those ancients could do observing the sunlight in a well.

An aside most likely familiar to most on this forum: The bit about Columbus championing the round world against some flat earther's is dead wrong. All educated folk knew our orb was orbish.

Columbus had his own calculations (supported by a minority of previous learned gents) as to the size of the earth. He was in fact very very wrong, which is why that long continent we live on got in his way. I'm not sure that Isabella thought he was actually right as that it made sense to get him on his way and out of court. . .

[Johannah]

Ooof, Ian. Watch the jokes, please. I was reading along without ill effect until hitting your "raft-up in Thermidor" comment and fell out laughing. Riposts come to mind (remember the days of the week? Or the ever popular 10 hour day?) but I will restrain myself. Thanks for the laughter. This is a nifty discussion. tongue.gif

[Bayboat]

The origin of the English statute mile, still the preferred measure of distance in the United States, lies in the length of the long stick (the rod, eventually standardized at 16.5 feet) used since ancient times to prod the oxen while plowing. It was also used to measure plots of land, leading to the English furlong (660 feet)and acre (43,560 square feet). I presume that "mile" derived from the French "mille," but the standard based on Roman paces did not transfer to England with the term.

[Gary Bergman]

I like knots... a mast hitch is my favorite.....whoops :D

[Meerkat]

There is a system in use that divides the circle into 400 units (more accurately, it divides the angle subtended by a right angle into 100 units). I think it's more widely used in Europe than in the US and even then only by specialists (civil engineering?). It's called the Grad system and the unit of measure is the grad. My HP calculator will do math in degrees (decimal and degrees, minutes, seconds), radians and grads.

[ahp]

How about cicular mills, or artillary mills?

[Kevin Zembower]

Originally posted by Ian McColgin:

Rather like the superiority of points of the compass vs degrees, especially once you learn the trick of converting any course into its normal on either side or its recipricol.
So, what is the trick? I thought you just had to memorize all 32 (64 with halves?).

Thanks.

-Kevin Zembower

[Wild Wassa]

This has been an interesting thread ?, ... it has made me rethink the dimensions of my boat.

The boat is now, LOA 0.00026 of an INM
and her sail area is 1/184th of an acre.

These new realizations will help me because I'm always looking for 0.00018 of a knot every time I touch my boat. 0.00018 of a knot is a 'long way' at the end of a dinghy race that may last 2hrs 30mins +.

Warren.

ps, When are the Yanks going to start calling it an International Knot, :rolleyes: .

[ 04-12-2003, 07:23 PM: Message edited by: Wild Wassa ]

[On Vacation]

ps, When are the Yanks going to start calling it an International Knot

Frankly Warren, in our little world, we do just fine getting from point A to point B. :eek:

[Tom Lathrop]

Hey Oyster. I lost contact info with you. Send me an e-mail or give me a call.

[Ian McColgin]

For traditionalists, the 'trick' is to put recipricol terms.

Obviously the recipricol of North is South.

So too, the recipricol of southwest by west is northeast by east (SWxW to NExE).

G'luck

[Ken Hall]

Originally posted by Phil Young:
So its really Knots per half minute, rather than knots per hour. 10 knots per hour would be terribly slow.Ah, that explains why I nearly starve to death every time I go sailing.

[John B]

So when the guy I'm about to get into some conflict with , told me to 'go and get knotted 'the other day he actually meant.........?

[Kermit]

But the change I want is in the calendar. While it makes sense to me that a week is a quarter of a lunar month, seven days is awkward to divide up. I've been advocating for a shift to an eight day week, easily divided into four day units. Then you'd get four days at work followed by four days off. Great weekends for whatever you do with them, and the business world could more easily schedule workers' time. I'll implement this as soon as I'm chosen Almighty and Benevolent Planetary Poobah. All in favor?

[Ian McColgin]

Bobbing this back to the surface as I just read Ken Alder's "The Measure of All Things" (The Free PRess, NY, 2002) that marvelously accounts for the 'error' in Mechain's measurements at the south end of the arc from Dunkirk to
Barcelona that led to the meter error. And how Delambre hid it.