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Historical Units of Measure


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I just acquired a slew of invaluable reference books from a member and while looking through one book (Historic Ship Models by Wolfram zu Mondfeld, pg 66)  I stumbled onto a chart of historical units of measure.


The unit of measure was standardized across the board with the introduction and acceptance of the metric system in 1799. (no surprise to me)


Many countries were using the foot (and inch) as their unit of measure but the actual distance that comprised a foot differed between various countries. (again no surprise to me)


What surprised me was to learn that the English foot (12 inches) was established to have been (on average?) 308.0 millimetres prior to this date.


Today (as of the standardization made in 1799) it is 304.8 mm ............... a difference of 3.2 mm shorter than earlier dates.


This doesn't seem like much but a ship measuring 168 feet long in 1786 might be 168 x 3.2 = 537.6 mm = 21 (and a wee bit) inches longer today using the measuring stick of that day!


One of them hemmm moments.


Here I thought the change from the Julian calendar to the Gregorian calender in 1582 might have mixed up a few historical dates.




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Switching between measurement systems can get confusing.  When I was a young engineering student one of my professors would give us problems in off the wall units and require us to report the results in other off the wall units like furkins per furlong.  I have run across at least 4 different "feet" measurements; standard, english, swedish and french.  I am sure there are others as well as units like cubits and chains.

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Hello Alan,


I took my own copy of Wolfram zu Monfeld "Historic Ship Models"  and opened it at page 66, and found the said list of different measurements. I believe we have the same book, is it the one published by Sterling Publishing Co, Inc. NY?  


There's indeed a list which gives the English foot to be 308.0 mm, but I wonder if this is right. To my knowledge, the dimension of English foot did not change at least from the 17th century until nowadays, so if they did change anything into the 19th century it was the way they "translated" it into a meter, not the dimension itself. 


Moreover, in my calculations I always use the English inch of 25.4 mm yet I have an old Hütte engineer's manual which I have inherited from my father which gives one English inch to be 25.399956 mm. The difference is very small, yet as you said, if you add many inches together, it can get a significant amount. 


This only happens if you work your model metric and always try to "translate" your measurements from the old imperial units into milimeters.


Here is the really nice part when working with imperial units: if you use an imperial scale and use a measuring tool divided in inches and fractions of an inch, working for example your model to a scale of 1' = 1"  your model will always be true to its scale of 1:12. Moreover, if instead the English foot you will use a measuring tool divided into French feet or Swedish feet to measure a plan which is made into these units, the model will still be 1:12. Of course, this only works if that unit is sub-divided into 12 inches. It will not work for the Amsterdam foot which was divided into 11 duimen. Don't ask me why, and moreover, how on Earth they managed to divide that foot into 11 equal parts :D  


So if using a different foot or a different way of translating your foot into milimeters, your model will still be accurately proportioned (supposed you made it accurately) only the scale which you know to be a true 1:48 may in fact be 1:51.5 or 1:46,79 or something like that. It's just a question of numbers. This applies as well with the old Navy Board models, many of which are known to be built in 1:48 scale, yet if measured carefully, some of these models show not to be built at a true 1:48 scale but to a slightly different scale, depending on which measuring tools the model maker used and how accurately these tools were made. 






you have an abstract of the measuring ways used in Europe from the early times (it is a wiki source so use with the due caution as it is known for the wikipedia sources not to be always reliable) and here:




a review of the measuring system in Spain in early 15th century. 


Hope this helps!

Edited by Doreltomin
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Indeed they are the same book and same table!

Looking at your link to Wikipedia, it gives examples of the foot measurement having been standardized at even an earlier time (Henry III) and becoming 11/12ths of what it had been.


My understanding is the metric system nailed everything down and created a world wide standard where no one could be short changed.  After all a foot was originally the measurement of the length of a standard foot... I wear a size 11 so if I were to measure something I might get more of it than my very good friend and neighbour Pierre who wears a size 9-1/2


An inch was the width of the thumb.  If I hit my thumb with a hammer and it were to become swollen.... you get my point.


The Merchant I am sure would find a way to use the system to his advantage.


I believe the French established the standard to eliminate the confusion and did indeed find the average English foot to be what was reported, equal to 308 mm in their new and improved international system of measurement (SI units)  and then in there "right and might" of the time decided they would re-invent it to be 304.8 mm.   After all Napoleon did have very high aspirations!




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I am quite sure that foot/millimetre conversion factor in Mondfeld's book is a misprint.


Actually, the UK, Canada and the USA are metric, but most don't know. I forgot since when exactly, but the foot and the inch are defined by a fixed ratio to the metre. The metre in turn is defined through a physical constant (not the old platinum-iridium bar in Sevres anymore). So, if the metre would change in absolute length, the foot and the inch would too ...


BTW until the late 19th century each state and often each town in continental Europe had their own measurement system, there were different feet in Hamburg, Bremen, Frankfurt, Danzig, St. Petersburg to name just a few coastal towns. The same for volume and weight measures. When reading old plans, one has to verify which foot was used. For instance, in 17th century Brandenburg ships were built with Amsterdam foot not Brandenburg foot as measure, because the master shipwright was Dutch.



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In the US, the foot is based on the International Foot which = 0.3048 meter.  The US foot is essentially the same - the conversion just takes it to 10 decimal places (1 US Foot = 0.3048006096 meters).  For those of us geeky enough to want more info, the National GS has a PDF format document from the National Bureau of Standards in 1959 (NBS is now NIST) called Refinement of Values for the Yard and Pound that defines the "U.S. Survey foot" as 1200/3937 meter or 0.3048006096 meters. For more detail on the SI units, see http://www.nist.gov/pml/wmd/metric/metric-program.cfm


The SI meter is now defined as the length of the path traveled by the light in vacuum during a time interval of 1/299,792,458 of a second.

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Just for the record, the traditional standards for the exact length of an inch have varied in the past, but now the imperial or US customary inch is defined to be exactly 25.4 mm.


To 'convert' that and divide 1 by 25.4 (mm to inch) results only in an approximation.


I believe this has been accepted universally.

Note that the inch is defined in terms of the metric system and not the other way around.


BTW Wayne, the 'standard foot' would then be 12 x 25.4 = 304.8 mm or 0.3048 meters exactly, and not with all those extra numbers at the end. What you were using was, I believe, an old 'standard'.

Edited by Modeler12
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There were many 'feet' of different lengths in Europe prior to the metric system. An Amsterdam foot was different to a Swedish foot, and so on….

Just an anecdote: When I was growing up in Holland, my mother would always buy her cloth (yardage) from the tallest sales lady on the open market. Why, I asked. Because she has the longest arms. The cloth was measured in 'el' which is the distance from the tip of the outstretched hand to the shoulder.

My mother would end up with a fraction more cloth as long as the price was the same.


Actually the el was later defined but varied from town to town. See Wikipedia, if interested.

Edited by Modeler12
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Wayne, had those numbers ready to post and talked myself out of it. What you posted is correct and when dealing with large numbers of feet like State Plane Coordinates the minute difference between exactly and 10 digits does have a effect on where you find yourself in a rectangular grid. Oregon uses the International Foot, our neighbors use the US Survey foot when dealing with the State Plane Coordinate System as do most States. Need to know what definition you are working with across a state wide grid. The differences  produce undetectable differences in the model ship world.


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Jud, what you are referring to are the 'standards of the US Survey foot'. Those were kept by a few states in the US because the map coordinates were all based on the old standards and it would be too costly to convert those old maps and survey data.


It is not, in my opinion, relevant to making measurements of model ship details.


For more details go to:


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Kind of depends on the definition of 'using'


Where many countries have adopted the metric system, common usage is still predominately Imperial.


The US being a good example.


And also different Industries confuse the issue further, the Aircraft Industry will never move away from using feet for Altimeters.


That would lead to unacceptable risk when trying to convert, imagine 'reduce you height to 2000 metres' -whoops.


I remember hearing a tale of a certain African country, when moving from driving on the left to driving on the right followed the rule: cars change on Monday, Trucks on Tuesday, Bicycles on Wednesday :D  :D 

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In my dept at my job we use 3 measurements.  Metric, decimal. and standard.  It depends on who the customer is.  There are only 2 people there who can work with that confusion all the time.  As a result we have three rulers and we just convert  otherwise.  I wish it was just one of them.

David B

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