YM Lies, Damn Lies and Statistics

shaunksb

shaunksb

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Just reading Ym test on one of those lovely Etap's but raised an eyebrow at the owners claims of easily obtaining 8 to 9 knots close hauled. This led me to the back of the artical for the favorite pastime of comparing boat spec's only to see YM at it again at their primary school attempts to convert metric to Imperial.

LOA 10.6m (31'6") - No it's not
LWL 8.7m (26'7") - No that's not right either
Beam 3.5m (11') - Maybe to the nearest foot
Draught 1.6m (6'3") - Way out
Displacement 6940Kg (8619lbs) - not even ballpark!

and if the diesel tank holds 11 Gal (105 ltr) how can the 22 Gal water tank hold 280 ltr?

This has completely ruined my game of top trumps and now I have no idea what is supposed to be right.

On their new 100 point results test I'd give them 1 mark for getting the make right. - Please try harder
 
raised an eyebrow at the owners claims of easily obtaining 8 to 9 knots close hauled.

For gawds sake no one reply yet... I need to make a cup of tea....
 
I thought there might be a simple explanation, such as 11 inches in the YM foot, but the conversion factor ranges between 2.97 and 3.91 ft/m.

Rubber rulers, and elastic tapes ?
 
shaunksb said:
LOA 10.6m (31'6") - No it's not
LWL 8.7m (26'7") - No that's not right either
Beam 3.5m (11') - Maybe to the nearest foot
Click to expand...

Maybe they were quoting the channel M seasonally adjusted figures :rolleyes:
 
With regards to the 8-9 knots... That seems reasonable to me, IIRC the LWL is actually 9,1 m and not the 8,7m quoted) which gives you a hull speed of more than 8 knots, depending on the constant you use. It would probably be fair to use a higher constant (like 1,5) for the Etap, as it has a relatively slippery hull?
(It wouldn't be doing 9 for long periods, though)

So it seems (to me) that the only figures that are useful in YM are the owners estimates :)
 
JomsViking said:
With regards to the 8-9 knots... That seems reasonable to me, IIRC the LWL is actually 9,1 m and not the 8,7m quoted) which gives you a hull speed of more than 8 knots, depending on the constant you use. It would probably be fair to use a higher constant (like 1,5) for the Etap, as it has a relatively slippery hull?
(It wouldn't be doing 9 for long periods, though)

So it seems (to me) that the only figures that are useful in YM are the owners estimates :)
Click to expand...


Maybe they're just confusing boat speed and SOG?

We once 'did' 13.2kts off Alderney - hull speed just over 8kts.
 
DK has been metric since may 4, 1907, but we still (often) use feet when measuring boats - So give it a few more years :D
Agree to the confusion and senslessness, though. :cool:

sailorman said:
The UK has been metric since 1972 isnt about time we stopped all this dual measurement clap-trap. Is is very distracting & senseless
Click to expand...
 
if you were sending very expensive satellites to Mars, you might be concerned about a difference in measurements standards, as in confusing metres and feet.

Then again, closer at home, a rock at 3m, or 3ft... ?
 
sailorman said:
one or the other no need for both all the time especially within text
Click to expand...
I disagree ... for a publication with a wide audience then you do everyone a favour by showing the measurement most applicable to them.
I was brought up on metric, but always think of boats in terms of feet and not meters. Even keel depth is in feet - although water depth is in meters.

I (part) agree with the OP though - if you're going to publish converted figures - make sure they're right!!
 
sailorman said:
The UK has been metric since 1972 isnt about time we stopped all this dual measurement clap-trap. Is is very distracting & senseless
Click to expand...
It has failed to be adopted because it ignores a basic principle that people like to deal in whole numbers between 1 and 100. It's much easier to remember and visualise the difference between a 32ft boat and a 35ft boat than it is when the measurements are expressed as 9.8m and 10.7m. It's nothing to do with familiarity with the system; it's just the way our minds work.
On the continent measurements are normally given as 8m and 45cm or just "8m 45". For some reason in the UK we have chosen to use metres and millimetres which lumbers people with either decimals or uncomfortably large numbers.
 
shaunksb said:
Just reading Ym test on one of those lovely Etap's but raised an eyebrow at the owners claims of easily obtaining 8 to 9 knots close hauled. This led me to the back of the artical for the favorite pastime of comparing boat spec's only to see YM at it again at their primary school attempts to convert metric to Imperial.

LOA 10.6m (31'6") - No it's not
LWL 8.7m (26'7") - No that's not right either
Beam 3.5m (11') - Maybe to the nearest foot
Draught 1.6m (6'3") - Way out
Displacement 6940Kg (8619lbs) - not even ballpark!

and if the diesel tank holds 11 Gal (105 ltr) how can the 22 Gal water tank hold 280 ltr?

This has completely ruined my game of top trumps and now I have no idea what is supposed to be right.

On their new 100 point results test I'd give them 1 mark for getting the make right. - Please try harder
Click to expand...


Mmm, I do understand what you mean. Lets address each of those flaws:

The Etap 35i is:

Length. 10.68 metres
Beam. 3.5 meters
draft is 1.6 meters.
Dry displacement is 5300kg
The fuel tank holds 105 ltrs
The 2 water tanks hold 130ltrs each.

Oh, the speed issue, I'll need to read the article again, 8knts yes in the right conditions, 9? did I say that? Mid 7's is the speed we can maintain, again in the right conditions. Over the land we have hit 12knts.

There was another discrepancy, I was quoted as saying we regularly averaged 6 knts crossing the channel, in fact we regularly average 6.6knts, if you dont believe that, I'm happy for you to read the ships log.

IMG_3042.jpg
 
DJE said:
It has failed to be adopted because it ignores a basic principle that people like to deal in whole numbers between 1 and 100. It's much easier to remember and visualise the difference between a 32ft boat and a 35ft boat than it is when the measurements are expressed as 9.8m and 10.7m. It's nothing to do with familiarity with the system; it's just the way our minds work.
On the continent measurements are normally given as 8m and 45cm or just "8m 45". For some reason in the UK we have chosen to use metres and millimetres which lumbers people with either decimals or uncomfortably large numbers.
Click to expand...

apart from old gits ( me inc.) there have been almost 4 generations through the skool system all taught metric since 72.
 
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