Electronics at sea

[gildasd]

In navigation, yes, but nobody in their right mind does that by hand now. Log book in Kn because that’s the rule

In dynamic positioning (moving slow and highly precise), it’s all metric Meters per minute and so on.

In the bowels of hell (machinery space) where I spend all my days chilling out, apart from compressed air fittings... I think it’s all metric.

That said, I use imperial in furniture as it far easier to balance shapes and work in fractions to do that.
It is probably is due to the base 12 or something.

And I find it normal to be able to work in both.

[Herr R aus B]

I guess, it's just comfortable what you are used to :-) I would be all confused with inches, feet, 16th of an inch and bla... :-) and didnt that one mars probe crash because of the imperial system? ;-)

Never ending discussion :-)

And - before studying at the university i was working in plumbing - funny mixture... steel pipes, fittings and their threads all in imperial, copper stuff all metric... makes nice brass adapters from imperial stuff to metric stuff :-) and my bike? everything metric except the f*** shimano hubs... imperial nuts... almost not to distinguish from metric ones and then of course all wrenches slip... yes - of all ppl the japanese also got stuck with the ancient system :-)

and now for the discussion of pi vs. tau :-)

[apis]

It's about standardisation. There are big benefits if everyone use the same system of units. (Currently it's only Liberia, Burma and the USA who are not using SI.) The longer one waits to transition the more it's going to cost and the longer before everyone can benefit from having the same system of units. Why north americans prefer the old imperial/colonial system to the modern metric has always been a mystery to me. (There is nothing that prevents anyone from using fractions in the metric system, so that is a moot point.)

[gildasd]

As for fractions in furniture.
If I want something hand size, solid for normal use and elegant, 1 1/4inch x 1/2 inch. And that is a fraction of standard stock take smoothing and cutting (ie minimal wastage).
So yeah, I can do it mm (I would if in metal...) but if I actually have to work conveniently and fast, not so good,

But yeah, horses for courses.

[ivaylo]

SI all day, every day!

Except where more convenient for the mind units exist:
 - I’d rather tell you how old I am in years than in seconds (some of these years were different lengths too)
 - for some reason the size of the milky way sits better in my brain as 100K light years than in however many AU (or another non SI unit astronomers use is parsec)
 - degrees for everyday measurements, radians only for calculations with frequencies and such
 - etc, etc, same with the spherical measures we use for navigation on earth
Again, grew up with and love metric, there should be standards, SI is the best, but I would retain a little bit of humanity.

[apis]

If I want something hand size, solid for normal use and elegant, 1 1/4inch x 1/2 inch.

I'm probably missing the point here but you can do fractions with metric as well:
1 1/4 inch x 1/2 inch = 3 7/40 cm x 1 27/100 cm, the numbers are not as nice and round because we had to convert from inches, but you could easily have for example 3 1/8 cm x 1 1/4 cm (or 1/3 dm x 1/8 dm)?

[gildasd]

If I want something hand size, solid for normal use and elegant, 1 1/4inch x 1/2 inch.

I'm probably missing the point here but you can do fractions with metric as well:
1 1/4 inch x 1/2 inch = 3 7/40 cm x 1 27/100 cm, the numbers are not as nice and round because we had to convert from inches, but you could easily have for example 3 1/8 cm x 1 1/4 cm (or 1/3 dm x 1/8 dm)?

Yes and no.
Yes in theory, but no in practice as in practice, there is no 1/4cm mark in readily available measuring tools (speed squares, tapes, laser, depth gages etc) and in wood work you work to a line, not down to a measurement (in most cases)... you dont do parts that are 16,891mm (as with metal) but 1’1/64 to the knife mark, then if you need to adjust, you plane it down micron by micron until the fit is tight.
And the plans are done in fractions, with no rounding.
Except in cabinets... as the appliances are made to fit in 30, 60, 90 or 120cm units!
It might not make sense in a conversation, but in practice chopping miter joints or slabbing lumber, it does.
 
Anyway, got back on the vessels today, in dry dock somewhere south of Istanbul.
I allready stink of diesel as a duplex filter was more dirty than expected, and the compressed air blew the leftover fuel up instead of through the filter.

[schmitt trigger]

Speaking of Metric vs Imperial usage in the US:

While almost everything is sold in Imperial units, have you noticed that drugs are almost always traded in Metric? 

[Seph.b]

- degrees for everyday measurements, radians only for calculations with frequencies and such

I use both imperial and SI units in the same project without any problems. Each have their own use cases. Both make sense.

Degrees seem like the most arbitrary unit ever though, base 360 really!? Radians are so logical and easy to use. 1pi is a straight line, 1/2pi or 3/2pi is square, anything in between is easy to recognize in both faction and decimal form. I normally use degrees if I have to work with others, but my brain just works in radians by default.  I guess degrees make since on a clock, global positioning or astronomy, but that is about it.

[Eka]

It's about standardisation. There are big benefits if everyone use the same system of units. (Currently it's only Liberia, Burma and the USA who are not using SI.) The longer one waits to transition the more it's going to cost and the longer before everyone can benefit from having the same system of units.

A high percentage of US auto and farm manufacturing is now metric so they can also sell to the world markets.

Why north americans prefer the old imperial/colonial system to the modern metric has always been a mystery to me.

Plain and simple. Canada switched to metric a year or so before the US was planning on, and the cries of how hard it was caused congress to scuttle the plans to go metric. Really &^$%*(& sucks!!!!

[ivaylo]

- degrees for everyday measurements, radians only for calculations with frequencies and such

...
Degrees seem like the most arbitrary unit ever though, base 360 really!?...

Look at the number of divisors of 90 - https://www.dcode.fr/divisors-list-number
The Babylonians used a base-60 counting system, same reason.

[apis]

Degrees seem like the most arbitrary unit ever though, base 360 really!? Radians are so logical and easy to use.

Radians has its mathematical advantages but I always felt a cycle (turn) was the most natural unit for angles (i.e. 400 gon = 360 deg = 2pi rad = 1tau rad = 1 cycle).

[Herr R aus B]

This is all off off off topic now :-)

[ebastler]

This is all off off off topic now :-)

Yes indeed... I think the connection to your original topic is that while at sea, you have a lot of time to let your thoughts roam. 

[Herr R aus B]

This is all off off off topic now :-)

Yes indeed... I think the connection to your original topic is that while at sea, you have a lot of time to let your thoughts roam. 

that would imply, everybody involved in this thread were at sea ;-) i personally am back ashore since 2 weeks - unfortunately :-)

[towlerg]

I know it's off topic but I'd like to resond to the SI mafia.

In terms of seamanship the metric system is terrible. The natural measure of speed is the knots ie 1 nm/hour. You use calipers to get 1 nm from the vertical axis of the chart, it's just so easy. Everything related to speed follow from that. Don't even go there with windspeed in mtrs/second or whatever the metric drones at the met office use, it's just plain daft, nothing in the real world gives a sense of that number. What the hell do they measure tidal flow in?

As for depth, 2 meters is 1 fathom so who cares.

BTW The Mars climate orbiter didn't crash because of the imperial system but beacause one team used metric and the other used imperial and the conversion was not accurate enough.

On the subject of inaccuracy did they stuff up the measurment of the planet that the meter is based on? I see that now the meter is defined as the length of the path travelled by light in a vacuum in 1299 792 458 second (doff cap to goggle), what an oddly un-si number.

[schmitt trigger]

SI mafia....

Before you accuse me of anything, I live in the US and I use feet, inches, gallons, miles and degrees Fahrenheit every single day of my life.
And as others have mentioned, for woodwork, Imperial makes sense. Same with seamanship, employ Imperial if that makes the life easier..

However, at work and for any engineering assignment I use metric.

Your assessment of the Mars Orbiter clearly indicates the reason that for engineering and scientific research, all the units should be Metric.
Regardless of what Trump says, in this global interconnected world, the USA requires to collaborate with many other nations, METRIC nations.

The USA cannot force the 99%of the world to employ units which only make scientific calculations far more difficult.

[Ian.M]

As for depth, 2 meters is 1 fathom so who cares.

That's nowhere near good enough for anything except deciding how much chain to payout when anchoring.   Assuming a vessel that's crew customarily work in metric units, they'll have about 8.5% less actual depth than they expect.  If you are operating in shallow channels, that 8.5% can be critical e.g. if Squat effect is involved.   

A far safer quick conversion from fathoms to meters is to subtract 10% after the conversion above, so multiply by two then subtract  a tenth of the result.   The 1.6% error in the result is in the safe direction i.e. more water than you think you've got under you.

Similarly, going the other way from meters to fathoms, dividing by two then adding a tenth only overestimates the depth by less than 0.6% - far less than the safety margin one needs due to various other factors.

[ivaylo]

This is all off off off topic now :-)

Not really. Some of us own boats, live on boats, etc. Thanks for starting this thread. It exposed how much many of us engineers focus on their own little area and underestimate problems solved in different but not that fat disciplines.

[Herr R aus B]

BTW The Mars climate orbiter didn't crash because of the imperial system but beacause one team used metric and the other used imperial and the conversion was not accurate enough.

That's what I meant :-) You are really taking the stuff seriously, hm? :-) But then:

As for depth, 2 meters is 1 fathom so who cares.

It is 1,852m and if you took 10fm, the difference would add up to almost 1,5m which might be crucial in some situations - so if you take the stuff so seriously, do it consequently :-)

I never thought, talking a small travel electronics assortment would end up in yet antoher of these never ending, fundamentalistic - say religious? - discussions... MAFIA??? Can I close my own thread??? :-)

[Herr R aus B]

Regardless of what Trump says, in this global interconnected world, the USA requires to collaborate with many other nations, METRIC nations.

Did he announce the U.S. leaving scientific standards now as well? Did I miss something? :-)

[rdl]

...
I never thought, talking a small travel electronics assortment would end up in yet antoher of these never ending, fundamentalistic - say religious? - discussions... MAFIA??? Can I close my own thread??? :-)

No need for concern, it's not unusual here for a thread to end up as Linux vs Microsoft, Imperial vs Metric, Apple vs Everything Else, and so on. Must be a corollary to Godwin's Law or something.

[towlerg]

That's nowhere near good enough for anything except deciding how much chain to payout when anchoring.

You either operate in a lake or run aground alot. By the time you add tides, weather conditions and local odities I'm be amazed if I could predict depth tp within 10%.


My point, is that it's stupid to shoehorn SI into an application where it is inferior, just because of "SI is best" dogma. Like all people I buy stuff in liters and kilograms and I don't have any problem with that although perhaps the most importat change we made was decimaliation.

[ebastler]

Regardless of what Trump says, in this global interconnected world, the USA requires to collaborate with many other nations, METRIC nations.

Did he announce the U.S. leaving scientific standards now as well? Did I miss something? :-)

How about an import tariff on all products using metric dimensions? 

[Ian.M]

That's nowhere near good enough for anything except deciding how much chain to payout when anchoring.

You either operate in a lake or run aground alot. By the time you add tides, weather conditions and local odities I'm be amazed if I could predict depth tp within 10%.

On the contrary, depths can be predicted to within a couple of decimeters for the current tidal cycle, correcting for meteorological effects by comparing the calculated tide against the actual tide at nearby tide gauges.

Its not unusual for very large vessels passing through restricted dredged channels (e.g in the Solent and entrance to Southampton water where the channel has a maintained depth of 12.6m - approx 6.9 fathoms) to operate with only a few meters clearance,  waiting in a designated anchorage or holding area in the approaches until the combination of the port authorities current tide gauge reading, and the predicted rise of tide during the expected time to reach the start of the maintained depth channel allows sufficient depth under the keel.  Their maximum speed through the channel is tightly constrained by the clearance and the squat effect.  When you are working with clearances of a few meters, loosing a meter of that clearance due to bad maths in a units conversion is potentially disastrous, as if the vessel enters the channel with too much speed for the clearance, handling will be severely compromised, and if as a result the vessel looses control, a grounding at speed is highly likely.

Of course its very different for recreational small craft - very few have a draft exceeding 3m, so in most circumstances, depth is of little concern unless inshore of the 5m contour, and if in less than 5m, the inaccuracies due to meteorological effects, without actual tide heights from port control, can easily exceed 10% of that.