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Hello,
I noticed that when switching from 'magnetic' to 'true' mode in Expedition the layline times ("Tm on P", "Tm on S", "Td R Prt", etc) are different than the What-if? numbers.
I'm using Expedition v.10.2.9 together with deckman and dfw2exp.
With deckman in MAGNETIC mode; dfw2exp in magnetic mode ("Heading, twd and cog in degrees true" unchecked) and "Magnetic mode" in expedition/settings/system checked the layline times in the number box and in the What-if? Window are same:
With deckman in TRUE mode; dfw2exp in true mode ("Heading, twd and cog in degrees true" checked) and "Magnetic mode" in Expedition unchecked the times differ:
I positioned the boat in an area with relatively high magnetic variation so the effect is quite obvious.
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In the two pictures above the Leeway angle is -38.8°. Could somebody please explain how this angle is calculated? With a Course of 52.1° and a TWD of 10°, I'd expect a TWD of -42.1°. This TW angle is shown in deckman.
In a second example I entered an offset of 3° in Deckman's "adjust wind angle"-correction table for the prevailing wind speed/wind angle. This changes the TWA in deckman to 45° and the TWD from 10° to 7°. But the TWA in Expedition remains almost the same. It differs now more than 6 deg from the TWA in deckman:
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Not answering your questions, but have you selected expedition to calculate twa, tws, leeway or any other variables?
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Layline times and What-if? are now (v.10.2.11) showing the same numbers, also when in TRUE mode.
Just out of curiosity: Which mode (magnetic or true) are you guys using and why?
@Campbell: I didn't find a setting in Expedition where I could enable or disable to calculate any of these variables.
As far as I understand all variables are directly imported from deckman through Dfw2Exp. All variables (TWD, Course, Heel, Leeway,..) show exactly the same values as in deckman. Exception: TWS is alway slightly less in Expedition (up to 0.2kn). TWA in Expedition should be 'Course' minus 'TWD' but that is not the case (in deckman it's correct).
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Seems odd, but first of all lets check Exp Calibrations and Calculations. Available in the drop down menu 'Instruments'
[img] ,h_392,al_c,usm_0.66_1.00_0.01/3a4a49_f338fceeb5204034b17db8fc1ce4edd7.png[/img]
[img] ,h_296,al_c,usm_0.50_1.20_0.00/3a4a49_b6365284212b45359dd714a9fbc7f68c.png[/img]
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Campbell,
thanks, that solved it!
I was just aware of "Exp calibrations" which I was always accessing through 'Settings / Racing / Start calibration values'.
Checking now after your hint 'Instrumens / Exp calculations', "Twa &tws'" was selected. Deselecting it solved the issue.
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nav wrote:
Campbell,
thanks, that solved it!
I was just aware of "Exp calibrations" which I was always accessing through 'Settings / Racing / Start calibration values'.
Checking now after your hint 'Instrumens / Exp calculations', "Twa &tws'" was selected. Deselecting it solved the issue.
Great! One of those traps I have fallen into in the past!
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