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Sailing in tide..quiz.
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    Posted: 03 Oct 17 at 10:22pm
Originally posted by A2Z

Originally posted by Sam.Spoons

Sorry Doug, I was trying to answer mozzy's 'supplementary question'  Smile Not sure I have the answer right but based on 'conveyer belt' theory?
This conveyor belt theory. Why is it assumed all boats drift downtide at the speed of the current?  Isn't that like assuming all boats can run downwind at windspeed?
All boats do drift down tide at the speed of the current. Unless you're sailing them through the water. In which case they will move in a direction over land which is the sum of those two vectors (the tide and the sailing).

Trust me, when the wind drops to nothing, and the tide is flushing out the harbour, all the boats, 49er to oppie, all drift out the harbour with equal hopelessness! 


Edited by mozzy - 03 Oct 17 at 10:24pm
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Post Options Post Options   Quote Guests Quote  Post ReplyReply Direct Link To This Post Posted: 03 Oct 17 at 10:14pm
Originally posted by Sam.Spoons

Sorry Doug, I was trying to answer mozzy's 'supplementary question'  Smile Not sure I have the answer right but based on 'conveyer belt' theory?
This conveyor belt theory. Why is it assumed all boats drift downtide at the speed of the current?  Isn't that like assuming all boats can run downwind at windspeed?
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Posts: 6499 		Post Options Post Options   Quote iGRF Quote  Post ReplyReply Direct Link To This Post Posted: 03 Oct 17 at 10:04pm
Originally posted by mozzy


Originally posted by Sam.Spoons

Assuming the tide slackens across the whole course? No windshifts? And they were sailing at exactly the same speed? B would have to take avoiding action to avoid hitting A (still on Starboard)?

Spot on! A would hold a 1 metre is lead and B would have to avoid. 


Agreed, but then B could still short tack, onto the starboard layline and force A behind and round first

Edited by iGRF - 03 Oct 17 at 10:05pm
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Posts: 3401 		Post Options Post Options   Quote Sam.Spoons Quote  Post ReplyReply Direct Link To This Post Posted: 03 Oct 17 at 10:04pm
Originally posted by mozzy

Once I did lay a finish mark that dried out... oops, I did get a fair bit of stick for that. But there is no rule that the course has to be on the water!

I remember Raceboards Open Meetings at Morecambe many years ago, I got there early one year and helped set the course marks with the aid of a wheelbarrow (and, incidentally, collect them the same way after the event)  Tongue happy days......
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Posts: 3401 		Post Options Post Options   Quote Sam.Spoons Quote  Post ReplyReply Direct Link To This Post Posted: 03 Oct 17 at 9:55pm
Sorry Doug, I was trying to answer mozzy's 'supplementary question'  Smile Not sure I have the answer right but based on 'conveyer belt' theory?

Edited by Sam.Spoons - 03 Oct 17 at 9:56pm
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Post Options Post Options   Quote Guests Quote  Post ReplyReply Direct Link To This Post Posted: 03 Oct 17 at 9:49pm
Originally posted by Sam.Spoons

Assuming the tide slackens across the whole course? No windshifts? And they were sailing at exactly the same speed? B would have to take avoiding action to avoid hitting A (still on Starboard)?

Spot on! A would have a one meter lead and B would have to avoid. 


Edited by mozzy - 03 Oct 17 at 10:06pm
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Post Options Post Options   Quote Guests Quote  Post ReplyReply Direct Link To This Post Posted: 03 Oct 17 at 9:46pm
Dougaldog, I love your optimism and faith in race officers! But the scenario is only a bit of fun to illustrate a point. Out of all the unrealistic things about it (no shifts, same boat speed, no gust etc etc) a race officer setting an unintentionally bias line is about the most realistic. 

Sounds like you did an excellent job at the event you ran though. 

When I'm race officer at my club I just guess the course by eye. As long as they can cross the line it's all fair; everyone has the same opportunity to choose the correct end. 

Once I did lay a finish mark that dried out... oops, I did get a fair bit of stick for that. But there is no rule that the course has to be on the water!

I doubt anyone takes floating wind readings for club racing, for instance, and lots of club will be working off fixed lines anyway!
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Posts: 356 		Post Options Post Options   Quote Dougaldog Quote  Post ReplyReply Direct Link To This Post Posted: 03 Oct 17 at 9:30pm
Sam - as soon as the line was closed we were off....Of course, taking readings from a moored boat works fine on a pond....

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Posts: 3401 		Post Options Post Options   Quote Sam.Spoons Quote  Post ReplyReply Direct Link To This Post Posted: 03 Oct 17 at 9:23pm
Assuming the tide slackens across the whole course? No windshifts? And they were sailing at exactly the same speed? B would have to take avoiding action to avoid hitting A (still on Starboard)?
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Post Options Post Options   Quote Guests Quote  Post ReplyReply Direct Link To This Post Posted: 03 Oct 17 at 9:15pm
Originally posted by iGRF

Impossible scenario, both boats start on port?

You got me! I've edited to starboard. Both boats start on starboard and sail on starboard until the tide slackens and B tacks. 
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