posted 11-06-2007 12:57 PM ET (US)            

He's got to mean "knots per hour". He cant mean kilometers. Knots would put him at 40.25 mph, which I would imagine that boat could do all day long.

posted 11-06-2007 01:05 PM ET (US)            

http://www.boattraderonline.com/addetail.html?79927391

this particular one has twim Yamaha 4 stroke 250's, it's cruises at 30-40mph and top end is 53mph.

posted 11-06-2007 09:32 PM ET (US)            

A remarkably inaccurate statement from you, Jim! Where did you pull that from?

Boat speed is measured however you like. Around here (the Pacific Northwest) there there seems to be about equal numbers of boaters who prefer MPH vs. knots. The never-ending debate about which unit of measurement is "correct" is a bore.

Sd,

posted 11-07-2007 12:34 AM ET (US)            

Any boatie worth his salt should know what they mean.

posted 11-07-2007 08:28 AM ET (US)            

Of course, Jim can set whatever convention he sees fit for his website.

The problem siguy is having is that there is no such thing as "knots per hour". A knot means "nautical miles per hour", so speed should simply be stated in knots.

posted 11-08-2007 09:07 AM ET (US)            

The propeller dimensions were only specified as 14-3/4 and 21. Again, I imagine this was intended to convey their size using inches. But this could also be centimeters. And again we use inches for this unit.

If there is to be total freedom in expression of dimensions in any unit one chooses, as suggested for the speed being free to be expressed in either statute miles per hour or nautical miles per hour, I don't see why there ought not to be the same freedom for the horsepower and the propeller dimensions. Let's have those in kilowatts and centimenters, if you like.

Personally, and as the moderator, I don't like that situation. It would just be confusing and make the units have little meaning for most readers. And this is the same basis why I made the statement I did regarding the speed.

Tom asks: "Where did [I] pull that from?"

posted 11-08-2007 11:24 PM ET (US)            

I pulled it from my responsibility as the moderator to provide some uniformity to the discussions regarding which dimensions ought to be used. We use statute miles per hour for discussing our boat speeds, and it is done for the same reason that we use horsepower to measure the engine power, and inches to measure the propeller dimensions. There are very valid and reasonable alternative units for all of these measurements, but we don't use them because we don't want the discussion to turn into an unfamiliar soup of mixed dimensions and units."

Jim,

That's fine. but that is not what you wrote. You stated that MPH are used (with one exception) as a matter of convention. This is simply not so. It is not true within recreation boating. It is not even true within the borders of the United States. As a matter of fact, units of speed are not uniformly used here on continuousWave if a review of the archives is any indication.

I think what you were trying to express is that you would prefer that participants here used miles per hour (MPH) as the standard unit of speed measurement. I'm with you on using MPH in our discussions, that is my preference as well.

posted 11-09-2007 08:52 AM ET (US)            

In UNITED STATES COAST PILOT 6 which covers the Great Lakes, I found this declaration under the subheading "Distances" in Chapter 1--General Information.

"Coast Pilot volume 6 is in statue [sic] miles unless otherwise stated. A statute mile is 5,280 yards [sic], or about 0.87 nautical mile."

However, in UNITED STATES COAST PILOT 7 which covers the California coast, in the same section it states:

"Distances

"These are in nautical miles unless otherwise stated. A nautical mile is one minute of latitude, or approximately 2,000 yards, and is about 1.15 statute miles."

In COAST PILOT 6 there are many references to limitations on vessel speed and they are all given in miles per hour, e.g.:

"A speed limit of 4 mph is enforced in River Rouge and Short Cut Canal 21. (See 33 CFR 162.130 through 162.140, chapter 2, for navigation regulations.)"

However, on the Canadian side of some waterways, the speed are given in knots:

"Canadian regulations specify a speed limit of 8 knots for vessels of 15 gross tons and over in Amherstburg Channel."

However, in my brief scan of these publications nowhere did I observe the use of the acronym "KPH", which seems to be mainly an invention of the original author in this discussion and as far as I can tell is not in general use by mariners as an abbreviation for "knots per hour."

posted 11-09-2007 09:13 AM ET (US)            

CONTINUOUSWAVE does accept the use of many common acronyms, but it also accepts the common meaning of them as being understood. So when one writes about "MPH" we assume it means miles per hour and not "Master of Public Health" at least when talking about the speed of a vessel.

In the case of KPH it is particularly strange that one would use it as an acronym for speed to mean knots-per-hour because there is of course the immediate confusion with kilometers-per-hour, also a speed measurement. Further, the word "knot" is commonly understood to mean "nautical miles per hour", so interpretation of KPH to mean "nautical miles per hour" requires that we abandon the most common meaning of "knot" and turn to some alternative meaning such as "nautical mile."

If anyone can cite any example of where "knot" has been used in prior discussions here to mean "nautical mile" instead of "nautical mile per hour" I would be pleased to acknowledge them, but as far as I can tell, this was a first.

posted 11-09-2007 04:41 PM ET (US)            

As for you Binkie, you must immediately report to Duke University to undergo an intensive course of political correctness indoctranation. Until you comply, I won't read any more of your posts.

posted 11-10-2007 10:22 PM ET (US)            

I live in Australia and we switched to the METRIC system over 35 year ago and we still use MPH for speed , cubic inches & horse power for capacity in the marine industry because all our engines come from the good ole USA plus when we talk part sizes and clearances we still use thousands of an inch because the metric conversion converts to ridiculously long decimal point number that we don't even understand.Kilowats & Kilometres per hour are only widely used in our car industry as these come in from all over the world but the die hard mopar style enthusiast still quote the old system.

(I think Jimh has hit it on the head, this is a freshie vs saltie thing)..... I agree and my comments are based as from coastal perspective.

posted 11-11-2007 02:05 PM ET (US)            

Many would consider "Piloting, Seamanship and Small Boat Handling", by Charles F Chapman, to be something of a bible on most aspects of recreational boating...it has been in print for decades and is updated frequently, and is used by the United States Power Squadrons as well as various branches of the U.s. Navy and Coast Guard. "Chapman Piloting", at least in an older edition I have in front of me, specifically points to the use of MPH instead of "knots" as an example of a novice mistake in terminoligy...along with other examples such as calling the galley a "kitchen" or referring to a chart as a "map".

Clearly, the KPH term used by the original poster is incorrect. It is also clear that jimh can make MPH the standard for use on this site if he chooses to, and there may be good reasons to do so. MPH is certainly a measure that we all are familiar with from land travel in the USA, and I have used MPH in discussions here frequently. But the statement "Boat speed is measured in miles per hour, unless you are engaged in a long ocean voyage" is not at all correct.

Given that jimh generally like this site to be proper and accurate, down to correct punctuation and grammar, I am surprised that he wants us to avoid the use of the correct nautical measure on this site.

John

posted 11-11-2007 03:34 PM ET (US)            

Do you keep time onboard in "bells"? Stop at local noon to take the altitude of the sun as it passes your meridian?

Perhaps you measure your engine speed in propeller shaft RPM?

Should wide-open-throttle become "all-ahead-full"?

posted 11-11-2007 09:24 PM ET (US)            

As others have pointed out, using MPH versus knots may vary on fresh versus salt water, as well as with the size of the boat...I've never heard anyone quote the cruising speed of a yacht in any measure other than knots, but trailer boaters frequently use statute MPH.

posted 11-11-2007 10:51 PM ET (US)            

Jim, being a great-lakes sailor, is used to using statue miles for both distance and speed. Those on the right and left coasts are much more likely to use nautical miles and knots.

I believe that this odd situation came about because historically, the rivers - and by extension, the great lakes - were considered the domain of the Army Corps of Engineers, which, for obvious reasons, used the "land mile". The waters of the Atlantic and Pacific Oceans, being the domain of the US Navy, used the "sea mile".

posted 11-12-2007 01:28 AM ET (US)            

"Coast Pilot volume 6 is in statue [sic] miles unless otherwise stated. A statute mile is 5,280 yards [sic], or about 0.87 nautical mile."

I am sure they meant a statute mile is 5,280 feet. Heck, even the government can make a mistake now and then.

posted 11-12-2007 05:03 AM ET (US)            

Important thing is that everybody knows what unit we are talking about.

Personally I prefer knots, because when we are talking speed measured by knots, for example 20knots, I immediately understand how fast/slow that is. If we are talking about miles or kilometers per hour, I always have to convert that reading in my mind as knots before I really understand how fast/slow the velocity of the boat is.

However, I think it is a bit weird that MPH is preferred speed unit in this forum, because I see knots as the only correct unit when talking a speed of a boat, but it is ok for me if someone else like to use for example mph.

posted 11-12-2007 08:55 AM ET (US)         

I went to every manufacturer of marine equipment that produces speed measuring devices and not one of them has a gauge, display or device that shows a knots per hour measurement. You can buy any number of them that will provide the requested speed information in MPH, KPH or KTS.

Whew!

posted 11-12-2007 09:22 AM ET (US)            

But when operating in waters that are inside a particular country, it is not unusual for speed and distance measurements to conform to the preferred unit of that country. For example, when we navigated the historic Rideau Canal in Ontario, Canada, this summer, we found that speed limits were posted in kilometers per hour. Cf.:

http://www.tc.gc.ca/acts-regulations/GENERAL/c/csa/regulations/001/ csa005/csa5-c.html

When we saw posted speed limits of 8-kilometers-per-hour, we did not get offended and wonder why these poor misguided people weren't using nautical miles per hour, we just slowed down to 5-MPH and continued our pleasant trip.

The length of a nautical mile comes from a minute of latitude, and you might say it is a natural length. A statute mile of 5,280-feet is not quite as natural a dimension. There is a good discussion in Wikipedia

http://en.wikipedia.org/wiki/Mile

which notes,

"The statute mile is the distance typically meant when the word mile is used without other qualifying words..."

That interpretation is used here. If someone says their boat goes 33-MPH, that is taken to mean 33 statute miles, never nautical miles. If someone gives their vessel speed in nautical miles per hour, I usually convert it to statute miles per hour so that there is some consistency to our discussions and to avoid confusion. When someone gives their boat speed in knots, I hope they are using the term correctly to mean nautical miles per hour, and proceed on that basis.

If someone gives their boat speed in "KPH" I assume they mean kilometers per hour. Wikipedia agrees; see:

http://en.wikipedia.org/wiki/KPH

It is quite common in my experience to see speeds for boats given in kilometers-per-hour, as much of my actual boating is done on inland waters of Ontario, where kilometers-per-hour are the official unit of boat speed. I do not really think there is anyone who can make a serious argument that one ought to interpret KPH as knots-per-hour where knot no longer has its standard meaning but becomes "nautical mile."

posted 11-12-2007 09:44 AM ET (US)            

Most ocean-going vessels--the ones that use knots for speed measurement--travel at quite moderate speeds, typically less than 10-nautical-per-hour, and the difference between 10-nautical miles and 10-statute miles is not huge, being only about a mile and a half. One can shift units of measurement at these speeds and not be off by much.

Many Boston Whaler boats attain speeds of over 40-MPH, and at this speed the difference between expression in statute miles and nautical miles begins to become more significant. A speed of 40-knots is 46-MPH. At these speeds a change in boat performance on the order of 6-MPH is very significant and often crucial to the discussion of whether or not the boat is performing up to its expectations. Therefore, as the speed being discussed increases, I find it becomes more important to clearly distinguish which unit of measurement is being used. And similarly, it become more important that a common unit be used in such discussions, otherwise the reader is going to be presented with data that varies considerably depending on the unit.

posted 11-12-2007 02:35 PM ET (US)            

In Wikipedia, it says that one knot is equal to one nautical mile per hour.

posted 11-12-2007 04:28 PM ET (US)            

So what knots has to do with this. As we know speed is distance divided by time. Time is measured with hours and distance is nautical mile. Those factors makes speed as a knot which is nautical mile/hour. So knot is based on natural units. That makes sense, right?

The most important question is, what we benefit of this? Nautical charts contains latitudes and longitudes. You can see latitude scale (degrees and minutes) in a side of chart. So based on that, you can "pick" one minute there and easily use it as a distance unit when measuring distances from chart. When you are navigating at sea, you need to know at least three things; distance, speed and bearing. You measure the distance and bearing from chart and take a look of your speed meter to figure out your speed. Then you put distance and speed to formula: distance/speed=time and as a result you can estimate your travel time. With this information and by using chart, compass and speed meter, you can navigate where ever you want to go. Without electronic divices.

But if you dont use correct units when calculating these things you get wrong results and most likely you are lost very soon. Abviously you can calculate these things by using statute miles and mph, but then you first must get distance from the chart as nautical miles and convert it as statute mile if you like to use mph as a speed unit. That is totally unnecessary conversion and when ever you convert something, errors can happen and then you distance, time and speed calculations give wrong result and soon you dont know where you are at the sea.

Ok, that is all about traditional navigation by using chart, protractor and compass. Nowdays allmost all boats are equipped with electronic navigation devices (mostly GPSs). Because of that it is not really necessary to do traditional navigation and you can use what ever unit you want. Chartplotter shows how to go the place where you are going and the same device show your speed in what ever unit you want. The only problem is what to do when electronic gizmo breaks and you have to figure out how to go back home from the sea. Then it is really good thing if you can navigate traditional way.

posted 11-12-2007 06:19 PM ET (US)            

Since he was complaining of ONLY getting 35-38 KPH (22-24 MPH) it makes sense that he meant kilometers per hour.

I would not think he would complain of 35-38 knots (40-44 mph).

My 2 cents.

posted 11-12-2007 09:40 PM ET (US)            

Here is a press release from Mercury Marine which mentions boat speed records:

"Mercury Marine established five new world kilo bass boat speed records Monday, November 4, 2002, on the Tennessee River in Clifton, Tennessee....McClain flew through the traps at an average speed of 102.099 mph to set a new 1500 lb. Pro Stock Bass 200 world kilo speed record on his first attempt! ....Nichols made four runs in a Mercury Racing OptiMax 250XS Bullet 20CC bass boat to set a 104.483 mph world kilo bass boat speed record in the newly established 1800 lb. Pro Stock Bass 250 outboardclass.... McClain quickly hammered out a new 1400 lb. Pro Stock Bass150 class record with an average speed of 92.103 mph....Nichols made four passes to achieve a best of two-pass average speed of 105.020 mph....[another boat] blistered through the traps averaging 99.191 mph...to set a new 1400lb. Pro Stock Bass 175 class record."

posted 11-12-2007 09:48 PM ET (US)            

It could be better argued that distance measurements around a sphere ought to be measured in units of radians. See:

http://en.wikipedia.org/wiki/Radian

"History--The concept of radian measure, as opposed to the degree of an angle, should probably be credited to Roger Cotes in 1714.[1] He had the radian in everything but name, and he recognized its naturalness as a unit of angular measure."

posted 11-12-2007 10:01 PM ET (US)            

21,600-nautical miles / 2*pi radians= 3,437 nautical miles/radian

So a boat speed of 1-Kn would be

1-nautical-mile/1-hour X 1-radian/3,437-nautical-miles = 0.00029-radians-per-hour.

posted 11-12-2007 10:44 PM ET (US)            

My perception of boaters in the United States that pilot little (under 30 feet) Boston Whalers and use knots as a measurement of speed is that they are trying to impress someone. Kind of like a college professor trying to wow the coeds.

This is especially true if they pilot boats in FRESH water.

posted 11-20-2007 09:21 PM ET (US)            

See http://en.wikipedia.org/wiki/Gallon

Because aircraft move through air, they often measure their air speed as opposed to their ground speed. It seems incongruous that an aircraft would measure its ground speed in a nautical unit. If they do, perhaps they ought to call it their "ocean speed" instead. How aircraft measure speed is probably an interesting discussion, but I do not see the applicability here.

posted 11-21-2007 06:38 PM ET (US)            

You can override the factory setting and change it it MPH. I did NOT get the paddle wheel transducer as I am using it on a motorboat, not a sailboat (and it was larger and more expensive than the already-larger transducer I did buy).

I am with JohnW, I think MPH has evolved for novice boater's (but I do like WT's "impress the co-eds" point as well). I like KNOTS, it distinguishes the activity being measured from NASCAR or Jonathan Papelbon's fastball.

posted 11-22-2007 11:49 AM ET (US)            

I've used knots on my Dad's boats since the mid-60s. Everybody was using knots, nobody used mph (that I knew, but I only boated saltwater).

MPH became popular when boat manufacturers started putting speedometers in boats that said mph, suddenly that's the only reference boaters had regardless if they were old timers, novices, saltwater or freshwater.

Nautical charts are printed using minutes of latititude - the nautical mile. Does it make sense to use a nautical chart and then convert to miles per hour? Then again, few use charts and most/many rely on their electronics that can give them knots or mph. 2manyboats has the best unit of measure in dollars per mile. Regardless of nautical mile or statute mile, $ per mile will continue to grow.

The Great Lakes have historically used miles per hour. What units are the charts printed in?

JimP

posted 11-23-2007 10:29 AM ET (US)            

When I go to my local lake there is a sign informing me there is a speed limit of 40-MPH on the lake, which I think you will find is in reference to statute miles.

Jim's point about the dial calibration of the pitot-tube speedometer in use for the past 50 years is an excellent observation. They are all calibrated in miles per hour. I do not think I have ever seen one calibrated in knots. Small boats, and particularly small outboard boats which travel at relatively high speeds, used that instrument and its unit of measurement for decades prior to the widespread adoption of GPS speed measurement in the last few years.

If you bought a taft rail log to tow behind your vessel to deduce your speed it probably did not read directly in a unit of speed and needed to be converted. The conversion table probably offered a choice of units.

Most all speed measurement devices which are electronically based have a calibration setting to select the unit from several choices. I do not find it particularly authoritative that the newest manufacturer to enter this market, Garmin, choses a particular unit as the default setting in their software setting. As far as I am concerned, Garmin, as a manufacturer of marine electronics, is the new kid on the block.

Navigation charts for inland waters, and particularly for rivers, are often not presented with a north-up orientation. On such charts there is not a scale of latitude printed on the left-hand and right-hand borders of the chart. As a result, there is no convenient way to use the markings of latitude as a distance chart. It is also quite common that details of harbors are presented in very large scale drawings often called "plans" (to distinguish them from charts) and these usually lack any scale of latitude on the borders. Such charts will include a distance scale, and generally it is calibrated in statute miles.

Everyone is perfectly free to choose a unit of speed measurement for their boat that pleases them, but, as the moderator of this discussion I find statute miles per hour to be the most appropriate unit, and in the interest of keeping the discussion consistent, I convert all other data offered to statute miles per hour. As far as I am concerned, it offers the least confusion. There are too many folks who are actually measuring in MPH but go around spouting "knots" because they think it is more proper or more nautical.

posted 11-23-2007 11:41 PM ET (US)            

"Everyone is perfectly free to choose a unit of speed measurement for their boat that pleases them, but, as the moderator of this discussion I find statute miles per hour to be the most appropriate unit, and in the interest of keeping the discussion consistent, I convert all other data offered to statute miles per hour. As far as I am concerned, it offers the least confusion. There are too many folks who are actually measuring in MPH but go around spouting "knots" because they think it is more proper or more nautical."

Hmmm, just so I understand the rules, does that mean that the forum moderator prefers "front and back" over "bow and stern" or "fore and aft"? Should we refer to the boat as "left and right" vs "port and starboard" because our only reason for using them is "more proper or nautical"?

While the MODERATOR finds Garmin to be the "new kid on the block", I would venture to say that Garmin holds a comparable percent of the market, with regard to Raymarine, Lowrance or other major GPS manufacturers, in the sizes of boats we all are referring to. Moreover, most "paddle wheel" transducer manufacturers products are referred to in "KNOTS" and that is not limited to the newcomer, Garmin.

(Perhaps it is more orchestrated than that and Garmin is just sending these out in KNOTS to sabotage the moderator's preference to using MPH.....)

Maybe, to keep it really simple and consistent, I should refer to the helm as the steering wheel, keeping Dale Earnhart, Jr and I on the same page.

posted 11-25-2007 11:35 PM ET (US)            

Charts & Coast Pilots for the inland river systems and the great lakes are printed giving distances in STATUTE MILES, as was indicated earlier in this thread.

posted 11-27-2007 08:56 PM ET (US)            

Greenwich Sidereal Time = 1.00273790935 × Universal Time

posted 11-28-2007 04:06 PM ET (US)            

Until relatively recently in its history, humankind measured time by the rotation of the earth, using the visual positions of the sun, moon, and other celestial bodies as they traveled across the sky. Two kinds of such astronomical timekeeping are sidereal time and solar time. Sidereal time is measured with respect to the distant stars, while solar time is measured with respect to the sun. A solar day lasts from the time at which the sun is directly over a given point (for example, the Prime Meridian at Greenwich, England), until it is next over that same point.

A sidereal day lasts from the time at which a distant star is over a given point until it is next over that point. Because the motion of the earth in its orbit around the sun is negligible with respect to a distant star, but not with respect to the sun, a sidereal day is about four minutes shorter than a solar day.

posted 11-30-2007 09:18 AM ET (US)            

This was confirmed when I saw the afore-mentioned Walmart road map lying open in the boat, clearly having been the navigational chart of choice.

posted 11-30-2007 02:43 PM ET (US)            

According to Chapman's Piloting, Seamanship and Small Boat Handling: 1 Knot = 1.15 MPH. The terms comes from an old technique they used to use to calculate speed. They would throw a log chip attached to a line off the stern and count the knots in the line for a predetermined amount of time.

Little tid bits of information that I picked up getting my CG Master's License. Most of it is not relevent today as modern electronics has taken all of the guess work out of navigation. But, it is good to know when the batteries die and you have to pull out the charts an dividers.

posted 12-01-2007 11:59 AM ET (US)            

Historically, however, I think the nautical mile comes after the league. I believe that this is apparent in many references:

"20,000-Leagues Under the Seas" wrote Jules Verne, not 20,000 nautical miles.

Emily Dickinson wrote:

Exultation is the going
Of an inland soul to sea,
Past the houses -- past the headlands --
Into deep Eternity --

Bred as we, among the mountains,
Can the sailor understand
The divine intoxication
Of the first league out from land?

And, ahem, I believe the league is based on the statute mile.

So, if historical use is to be the determining factor, it looks like naught for knot.