Pouring anchor Kenter shackle lead plug - GIF

Pouring anchor Kenter shackle lead plug.

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Previously:

https://www.homemadetools.net/forum/...270#post181006
https://www.homemadetools.net/forum/...079#post103189
https://www.homemadetools.net/forum/...952#post152950
https://www.homemadetools.net/forum/...463#post154816
https://www.homemadetools.net/forum/...516#post127995

Recent aircraft carriers are fitted with 12 shots (180 fathoms, 1080'), at about 10,000 pounds per shot these are very close, if not same size links. Critical to retrieve a 30 ton anchor.

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Originally Posted by Toolmaker51

Recent aircraft carriers are fitted with 12 shots (180 fathoms, 1080'), at about 10,000 pounds per shot these are very close, if not same size links. Critical to retrieve a 30 ton anchor.

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Leagues, fathoms, and now shots. The seafaring community has to accept the blame for some of the more contorted measures of the inferial system.

Am I correct in assuming that the shackles are used to connect 90 foot lengths of chain ? So, each time a shackle shoots by, you count one shot ?

How did the term 'shot' arise ?

One nautical shot equals 90 feet of chain.

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Originally Posted by owen moore

One nautical shot equals 90 feet of chain.

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Thanks for the arithmetic correction.

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Originally Posted by mklotz

The seafaring community has to accept the blame for some of the more contorted measures of the inferial system.

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Is there anything wrong with a nautical mile?
It seems more sensible than - let's say - meter.

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Originally Posted by 12L14

Is there anything wrong with a nautical mile?
It seems more sensible than - let's say - meter.

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The nautical mile is useful because it very closely matches the length of one arc minute on a great circle of the earth. That makes it useful for anyone who must navigate on earth. Like most inferial units, it makes some sense where it's used but it should not be allowed to become part of an intelligent measurement system. Fortunately, it hasn't; one seldom encounters it outside the navigation arena.

My distaste is not based on the unit per se, but on the inconsistent relations between units in inferial systems. The lack of any order to the system means that every unit-to-unit relation must be learned separately and remembered. In an intelligently organized system, e.g. metric, the name of the unit tells you how it's related to all the other units of that class.

Three nautical miles to a league, six feet to a fathom, ninety feet to a shot... It's easy to convince oneself that inferial systems were designed to make learning and using difficult so the old-timers could lord their knowledge over newcomers.

"Shot" relates loosely as a verb and or adjective, not so much only a noun, as a few other terms in mooring.
When a vessel positions over desired anchorage point, the depth is either known by markings on the nautical chart (map) or a sounding. That depth converts to 'shots' needed to lay anchor and the amount of chain (or anchor line) needed to absorb current and tidal changes to not disturb anchor.
Chain runs fast, scary fast. The 'shots' are counted as they zip by to ascertain the correct length is out, because they are painted a different color. Some even use color coding in alternates, mostly depending on how energetic the crew manning the foc'sle are.

Chain is great anchor line, enough laying in a pile below holds position very well, but current/ wind/ tide cause it to drag, hence the anchor aka hook. Many lighter vessels use line, and roughly one foot of chain per length of boat between it to the anchor, the assembly known as the "rode". A ratio of 3:1 is minimal depth to rode length, up to 7:1 or so. Longer it is, makes the 'rode' a shock absorber, while the chain lays on the bottom. Line is usually marked in 20' 'shots' with a band of paint or electrical tape, etc. 'Tackle' is often used to describe the whole assembly.

Speaking of terms, when the connection of 'tackle' to a vessels hull tears free, the tail end you see go over the side is known as the 'bitter end'.
I kid you not.

All in all Mr. K's "It's easy to convince oneself that inferial systems were designed to make learning and using difficult so the old-timers could lord their knowledge over newcomers." is both true and untrue. Every trade has it's own vocabulary, I'd think doctors and lawyers are champions of garbled terms. At the same time, nautical language isn't rich (maybe) to exclude, a lot might be purely it's developed since the first guy went down a river clutching a log. Some nations never ventured beyond sight of their own coastline, others went for broke.

Too, a lot of terms originate out of need for brevity or easy correlation to signals, such as crane operators. So, where leagues (hasn't been used probably since advent of chronometers) described distance, knots referred to speed, fathoms to depth. Separating those may have lent clarity, all potentially being relayed in rapid commands therefore distinct.

“One second of arc of the meridian degree is 100 Greek feet.”
This quotation is from “All done with mirrors” by John Neal

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Originally Posted by Philip Davies

“One second of arc of the meridian degree is 100 Greek feet.”
This quotation is from “All done with mirrors” by John Neal

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Yes, but the Greek mathematicians had small feet, LOL

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Originally Posted by Philip Davies

“One second of arc of the meridian degree is 100 Greek feet.”
This quotation is from “All done with mirrors” by John Neal

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Whose "pous" (Greek for foot) ? As this article...

https://en.wikipedia.org/wiki/Pous

indicates there were many versions, all of different lengths (reminiscent of the cubit confusion).

I love this quote from the article...

"Stecchini and others propose the Greek podes are different sizes because they are divided into different numbers of different sized daktylos to facilitate different calculations."

It's hard to construct a useful measurement system when you can adjust the units to fit the work.

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Originally Posted by Frank S

Yes, but the Greek mathematicians had small feet, LOL

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The Greek foot is 12 English inches. Photo to follow. I’m watching tv.

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Originally Posted by mklotz

It's hard to construct a useful measurement system when you can adjust the units to fit the work.

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Or printing lavatory signs to accommodate multitudinous genders.

Attachment 43378
This is a Roman foot. The Roman foot is 24/25 of the Greek foot. The artefact is in the Ashmolean museum, Oxford. It is 0.96548 feet. It is known as the “Foot of Hercules.” This make Hercules 6’ 9”.

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Originally Posted by mklotz

Whose "pous" (Greek for foot) ? As this article...

https://en.wikipedia.org/wiki/Pous

indicates there were many versions, all of different lengths (reminiscent of the cubit confusion).

I love this quote from the article...

"Stecchini and others propose the Greek podes are different sizes because they are divided into different numbers of different sized daktylos to facilitate different calculations."

It's hard to construct a useful measurement system when you can adjust the units to fit the work.

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There are indeed variations of the Greek foot. Neal explores the ratios between them.

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Originally Posted by Philip Davies

“One second of arc of the meridian degree is 100 Greek feet.”
This quotation is from “All done with mirrors” by John Neal

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Very close, if the Greek foot was close to the inferial foot...

3959 miles (earth radius) * 2pi * 5280 (ft/mile) / (360 * 60 * 60) = 101.34 ft/arcsecond

Of course, we don't know what they used for the earth radius. (At least they knew it was a sphere and didn't think it was flat.)

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Originally Posted by mklotz

Very close, if the Greek foot was close to the inferial foot...

3959 miles (earth radius) * 2pi * 5280 (ft/mile) / (360 * 60 * 60) = 101.34 ft/arcsecond

Of course, we don't know what they used for the earth radius. (At least they knew it was a sphere and didn't think it was flat.)

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Might be my favorite distillation of mathematics, dependent on observation AND science. Epic, with Venetian cartographers and Portuguese sailing captains ignore all of it. Their concept held Earth barely half the actual and proven diameter.

https://www.aps.org/publications/aps...06/history.cfm

How did the mile become 5,280 ft?

The roman mile (mille passus) was exactly 5,000 roman feet. However, the English parliament standardized the mile in 1592 as 8 furlongs. (8 x 660 = 5,280). Yard goods (rope, yarn, etc) were purchased by the mile but taxed by the foot. The new "mile" was about a 5.5% tax increase!

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Originally Posted by Saltfever

How did the mile become 5,280 ft?

The roman mile (mille passus) was exactly 5,000 roman feet. However, the English parliament standardized the mile in 1592 as 8 furlongs. (8 x 660 = 5,280). Yard goods (rope, yarn, etc) were purchased by the mile but taxed by the foot. The new "mile" was about a 5.5% tax increase!

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The Romans had an odometer. The wheels were 4 feet in diameter, according to Vitruvius. He goes on to state that one revolution completed a distance of 12 and one half feet, giving a ratio of pi as 3.125 feet. Evidently, the Romans used a short foot (0.96768 English feet)for the diameter and a longer foot (0.973209) for the circumference. The 22/7 value of pi has been decreased by the same ratio as the value of of circumferential value has been increased. This, John Neal explains, is an example of 175-176 ratio frequently found in ancient measures.

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Originally Posted by Philip Davies

The Romans had an odometer. The wheels were 4 feet in diameter, according to Vitruvius. He goes on to state that one revolution completed a distance of 12 and one half feet, giving a ratio of pi as 3.125 feet. Evidently, the Romans used a short foot (0.96768 English feet)for the diameter and a longer foot (0.973209) for the circumference. The 22/7 value of pi has been decreased by the same ratio as the value of of circumferential value has been increased. This, John Neal explains, is an example of 175-176 ratio frequently found in ancient measures.

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Their odometer also had an ingenious mechanism for dropping pebbles into a container to register miles traveled...

Ancient Rome: The Odometer Of Vitruv | History Of Physics

The Greek, Olympian foot, (taken presumably from the stadium length, divided by 600) is cited as 1.01376 English feet. 6000 of these Olympian feet equals 6082.596 feet. The UK officially defined nautical mile is cited as 6082.56 feet. (Figures taken from Neal’s book)

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Originally Posted by mklotz

Their odometer also had an ingenious mechanism for dropping pebbles into a container to register miles traveled...

Ancient Rome: The Odometer Of Vitruv | History Of Physics

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That New World farmers reused as a seed planting device. That advantageous equal spacing eventually led to mechanization of harvest equipment.

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Originally Posted by Philip Davies

The Greek, Olympian foot, (taken presumably from the stadium length, divided by 600) is cited as 1.01376 English feet. 6000 of these Olympian feet equals 6082.596 feet. The UK officially defined nautical mile is cited as 6082.56 feet. (Figures taken from Neal’s book)

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This from Wikipedia...

A nautical mile is a unit of length used in air, marine, and space navigation, and for the definition of territorial waters.[2][3] Historically, it was defined as the meridian arc length corresponding to one minute (1/60 of a degree) of latitude. Today the international nautical mile is defined as exactly 1,852 metres (6,076 ft; 1.151 mi).

https://en.wikipedia.org/wiki/Nautical_mile

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Originally Posted by mklotz

This from Wikipedia...

A nautical mile is a unit of length used in air, marine, and space navigation, and for the definition of territorial waters.[2][3] Historically, it was defined as the meridian arc length corresponding to one minute (1/60 of a degree) of latitude. Today the international nautical mile is defined as exactly 1,852 metres (6,076 ft; 1.151 mi).

https://en.wikipedia.org/wiki/Nautical_mile

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Correct, mathematically. In practice, rounded to 6000 feet, enabling rapid mental calculations that work with 60 unit time, and divisible degree units of 60. When two 90,000 ton vessels may collide, a few seconds delay can be hazardous.
It impressed me early on, having already begun machining, that navigation was so similar, just different words.

In the mid 70s most all general aviation aircraft converted from mph to an air speed indicator calibrated in knots. Maule aircraft today are the only planes still using mph.

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Originally Posted by Toolmaker51

That New World farmers reused as a seed planting device. That advantageous equal spacing eventually led to mechanization of harvest equipment.

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We learned in school of Jethro Tull’s seed drill, invented 1725, I read. This, it seems used a belt to convey grain from hopper to furrow. I am fortunate that the Museum of English Rural Life is close to my home, in Berkshire, where Tull was born. My late friend, Don Gill, a very skilled craftsman made a model, which is there.

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Originally Posted by mklotz

This from Wikipedia...

A nautical mile is a unit of length used in air, marine, and space navigation, and for the definition of territorial waters.[2][3] Historically, it was defined as the meridian arc length corresponding to one minute (1/60 of a degree) of latitude. Today the international nautical mile is defined as exactly 1,852 metres (6,076 ft; 1.151 mi).

https://en.wikipedia.org/wiki/Nautical_mile

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The Dent dictionary of Measurement gives the following:
UK nautical mile = 6082.66 feet (also called a “geographical mile”
Admiralty nautical mile = 6080 feet (This is found on the Greenwich Observatory website)
US nautical mile (international standard) = 6076.12 feet.
I haven’t got the dictionary, but I view Neal’s figures with caution. There are frequent errors in English and occasional miscalculations, the latter of course are much harder to spot.
The longer mile is apparently due to its being surveyed at a more northerly latitude.

Trying to tie any unit to earth geography is fraught with difficulties. The major problem is the earth's equatorial bulge. It gave the French difficulties when they tried to tie the meter to the equator-to-pole difference. (But remember, the exact value of the base of any measurement system is never important - good measurement systems are dependent on other characteristics.)

The equatorial bulge affects satellites as well. The RAAN (Right Ascension of Ascending Node - the longitude at which the south to north path of the satellite crosses the equator - more here...

https://en.wikipedia.org/wiki/Longit...ascending_node

drifts westward due to the bulge. There is an equation that predicts the drift rate...

https://en.wikipedia.org/wiki/Nodal_precession

as a function of the earth's oblateness.

I was once tasked to provide an improved gravity model that could be used to integrate the satellite's motion without using the drift rate equation. As it turns out, the oblate earth can be accurately modeled as a combination of a perfectly spherical mass with a torus around the equator to mimic the bulge. Then the net gravity acting on the satellite can be computed as a vector addition of the components arising from the sphere and the torus.

Need I mention that computing the gravity field of a torus is a daunting mathematical exercise ? Using the equation is vastly easier.

So what does the lead do?
Hold a pin in place after the two halves of the kenter shackle have been fitted up to each other?

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Originally Posted by CharlesWaugh

So what does the lead do?
Hold a pin in place after the two halves of the kenter shackle have been fitted up to each other?

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It prevents the escape of the tapered pin that secures the parts of the shackle. Near the bottom of this page...

https://wachain.com/kenter-joining-links/

is a diagram that explains how the shackle works and how the tapered pin secures the parts.