How do you measure a boat

DAKA

DAKA

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I have thought about how to accurately ascertain Berthing length.

Weights and measure go to a lot of trouble to check fuel pumps and scales to make sure consumers dont get overcharged so how should berthing masters go about it,

On the hard

Plumb line from the anchor and davits but the tape will bend around the chocks ?

what about when the boat is moored in a finger pontoon that barley makes midships ?


I herd of one 'Blond' using a tape on board around the Rubbing strake /forums/images/graemlins/laugh.gif

Is there a way to accurately measure a boat that is in effect moving ?
 
Method 1

Put crew member in a dinghy, moored up securely with a theodolite.

Motor past aforesaid dinghy at a fixed speed. Get crew member to time point of bow passing to stern.
Repeat 3 times to ensure accuracy. /forums/images/graemlins/smirk.gif


Calculate legth by speed / time

Method 2

Moor up somewhere with detailed google earth coverage. Wait till next time piccie taken. Calculate boat length by comparison with a known fixed length (width or nearest pub, etc.
/forums/images/graemlins/smirk.gif
 
As you said, plumb line from the fwd and aft extremities, and measure the distance between.

That's how I measured Play d'eau.

If the chocks are in the way, mark the ground and measure when the boat is moved away.
 
Extend line between plumblines along the ground from ends of boat.
Draw perpendiculars from the two plumblines (triangulate to make sure they are perpendicular).
Measure equal lengths along the perpendiculars and mark points.
Measure distance between marked points.

Alternatively, read numbers on side of boat and hope.
 
Hard when you have a Shetland 570 though.....

The Rio 700 is a snip at 7.2 metres though.... /forums/images/graemlins/grin.gif
 
For a Seamaster 30 I was charged for 10m - which = 32.8 ft.
For a Project 31 I was charged for 10.5m = 34.4 ft
For a Princess 37 I was charged for 12m = 39.3 ft
 
Generally in the YC bars boats tend to be 4ft longer counting bow fenders and bathing platforms and dingy's in tow, BUT in the marina office they seen to be at least 4ft shorter.
/forums/images/graemlins/laugh.gif
 
The Marina office is the only place you don't hear people boasting about the length of their Boat, in fact.... /forums/images/graemlins/laugh.gif
 
After the US of A removed the selected availability, I made a test with two gps measurements - bow and aft - taken one just after the other, with many satellites in sight, and with the same instrument.
I wouldn't call it an 'accurate' measurement of course, but you'd be surprised by how close to reality the resulting LOA actually is.
I was obviously moored, but in theory this method could work also while cruising, provided that the course and speed are steady enough...
There are sat compass built around this principle, capable of 0.5 degree accuracy with different measurements taken within just a 30" or so radome!
 
Fortunately, the Dutch are very much more relaxed about such things to the extent that I have to admit engaging in a most childish game with some Harbour Masters I've met. When he comes round in the evening for the harbour dues, the conversation goes something like this

Normal pleasantries then 'How longa da schipp?
'I'm not sure Havenmeester, how long do you think it is?
'About 15 metres'
'Nonsense, its nearer 11'
'I am going to charge you 13'
'Thank you Havenmeester'

He departs with a grin, everyones happy, especially as we both know he was very nearly right with his first estimate!!
 
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