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» Online Classroom   »   » Public Discussion of Inland and Coastal Navigation   » DR and Leeway

   
Author Topic: DR and Leeway
OLowry


 - posted July 11, 2007 07:20 PM      Profile for OLowry           Edit/Delete Post 
I did all the searching on Leeway and am still confused on procedure for taking a "Log Book" enter and then figuring Leeway into it or is it already in it. Lets say the log book entry looks like this"
code:
Time  Log   Course       Wind 
1300 46.5 105°M 80°T @ 10kts

Now we need to Assume 5° leeway

Procedure for plotting above course would be what?

From: Indianapolis, IN
David Burch


 - posted July 11, 2007 07:55 PM      Profile for David Burch           Edit/Delete Post 
Leeway, unlike currents, actually changes your speed through the water, so the speed or distance factor is accounted for automtically by whatever means you use to monitor speed and distance.

What does not show up, however, is the course. The wind will push you downwind by about 5° or so, which means if the wind is northerly and you are sailing say 135, they you will make good a coruse of more like 140.

if you were sailing 270 you would make 265, etc.

so to correct for leeway, use the same distance run, but offset your course to leeward (downwind) by your estimate of the leeway, which can, as explanined in the notes, actually be measured underway.

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in your example, the wind is from 080 and you are sailing toward 105, so you would be slipping 5° leeward to make good 110.

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i checked the notes and in the section we cover this we are also making other corrections so it is not so clear. i will make a new picture and put it here, tomorrow.

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in the meantime, if you search this discussion on leeway you will find this link with a picture and discussion

http://www.starpath.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=17;t=000069#000000

From: Starpath, Seattle, WA


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