Quiz: What was 12.5 fathoms in 1949

[FullCircle]

...and is now 15 fathoms?

and your bonus question is:

what relationship is twice the square root of the depth of water in fathoms?

 

[onenyala]

Quiz

Hand lead line ?

 

[andygc]

1. A shackle of anchor cable
2. Don't know

 

[sailorman]

1. A shackle of anchor cable
2. Don't know

you appear to be correct

shackle 27.43 m 15 fathom = 1 shackle
30 yards = 1 shackle Shackles were a measure of the length of cable. According to a 19th Century Seamanship Manual, ships were usually equipped with 12 shackles of bower cable where each shackle was a 12.5 fathom length. These 12.5 fathom lengths were joined by shackles (hence the name) and by swivel links to overcome twisting. When paying out the anchor cable, counting the number of shackles passing gave a measure of the length used. In 1949, the Royal Navy switched from 12.5 fathom shackles to 15 fathom shackles. Modern heavy mooring chain is usually sold in 15 fathom lengths or 'shots'. The specification sheets quote the number of links per shot. Here is a formula for calculating the amount of anchor chain to put out in your warship: Twice the square root of the depth of water in fathoms = the number of shackles of cable.

 

[FullCircle]

1. A shackle of anchor cable
2. Don't know

Andy 1. is correct....

 

[FullCircle]

you appear to be correct

shackle 27.43 m 15 fathom = 1 shackle
30 yards = 1 shackle Shackles were a measure of the length of cable. According to a 19th Century Seamanship Manual, ships were usually equipped with 12 shackles of bower cable where each shackle was a 12.5 fathom length. These 12.5 fathom lengths were joined by shackles (hence the name) and by swivel links to overcome twisting. When paying out the anchor cable, counting the number of shackles passing gave a measure of the length used. In 1949, the Royal Navy switched from 12.5 fathom shackles to 15 fathom shackles. Modern heavy mooring chain is usually sold in 15 fathom lengths or 'shots'. The specification sheets quote the number of links per shot. Here is a formula for calculating the amount of anchor chain to put out in your warship: Twice the square root of the depth of water in fathoms = the number of shackles of cable.

Well Googled Roger....

 

[sailorman]

Well Googled Roger....

i never woz any good a Cricket

 

[tobble]

I'll have a guess at 2. - wave speed or maybe frequency

 

[Ludd]

bonus bonus question--

Well Googled Roger....

WHO sang "Goodbye,Google-eye"?

 

[planteater]

Google knows the answer to number 2!

 

[Pye_End]

Andy 1. is correct....

Wasn't 2. correct as well?

 

[sarabande]

I know this is not the answer that Full Circle is seeking, but it is correct.

Take 36 fathoms, for instance. Its square root is 6.

2 x 6 =12.

36 fathoms is also 216 feet, which is also - correctly ! - the reversed figures in the previous line.

So the relationship which is twice the square root of the depth of water in fathoms is that square root of arbitrary depth times two is graphically the reversed conversion of the arbitrary figure to feet.

Simple, innit ?

(and yes, I have been sitting in a tractor for 7 hours today, shifting buckets of snow and big bales of silage, so my mind is frazzled.)


EDIT. Sudden thoguht. Something about the depth that a wave "feels" the ground beneath it, and starts to change profile.

 

[andygc]

Wasn't 2. correct as well?

It was absolutely spot on - I didn't know ... but I do now.

So I need to remark my chain in fractions of a cable, reset my echo to fathoms, get out my square root tables, and I'll be all hunky-dory for optimal anchoring ... I haven't got a warship, but I do have a particularly pretty and entirely lawful ensign.

Hmm - 8 January - this combined anchoring and ensign thread's a bit late starting.

 

[peterb]

So I need to remark my chain in fractions of a cable, reset my echo to fathoms, get out my square root tables, and I'll be all hunky-dory for optimal anchoring ...

It's not all new. Back in the 1980s(?) the RYA's courses for Day Skipper and Coastal Skipper had a formula for anchor cable scope of twelve times the square root of the depth. Initially they didn't specify the units to be used, but later on they specified metres. At that time the RYA's cruising generalissimo (or should that be admiralissimo) was Bill Anderson, ex RN, where this formula seems to have originated.

I leave it to someone else to work out whether twelve times the square root of the depth (scope and depth both in metres) is the same as twice the square root of the depth (scope in shackles, depth in fathoms).