{Stus-List} Nexus system - VMG vs WCV - report

Bill Bina billbina at sbcglobal.net
Mon Jun 29 13:17:18 CDT 2009


I don't race, I cruise, so the mark is often 100 miles away anyhow! LOL

Bill Bina

Dennis C. wrote:
> Bill,
>  
> You are correct if you're using WCV (waypoint closure velocity) also 
> known as GPS VMG, not VMG (wind).  If you're racing to windward and 
> set the actual mark as your waypoint in your GPS, as you approach 
> either windward layline, WCV (GPS VMG) will tend to decrease.  When 
> you reach the layline, WCV will equal 0 because you are proceeding 
> perpendicular to your course to the mark.  This may help a racer know 
> when to tack to the mark but won't take current into account.  It also 
> assumes the boat tacks through exactly 90 degrees.  I use the time 
> honored technique of sighting along the wheel.
>  
> So, if you want to use a GPS to calculate VMG towards the windward 
> mark, once the course is set by the race committee, set a relative 
> mark on the race course bearing 100 miles out like you said.  :)
>  
> Dennis C.
> Touche' 35-1 #83
> Mandeville, LA
>  
>  
>
> ------------------------------------------------------------------------
> *From:* Bill Bina <billbina at sbcglobal.net>
> *To:* cnc-list at cnc-list.com
> *Sent:* Monday, June 29, 2009 11:43:15 AM
> *Subject:* Re: {Stus-List} Nexus system - VMG vs WCV - report
>
> I have been told that to get accurate VMG, you need to set the "mark" 
> at an imaginary point about 100 miles beyond, and aligned with, the 
> actual mark.
>
> Bill Bina
>
>
> Dennis C. wrote:
>> Dwight,
>>  
>> In the Nexus vocabulary, VMG is both VMG to windward and VMG 
>> downwind.  Both show as a positive number.  We maximize it.  
>> Downwind, we find that we sail a little bit "hotter" than boats which 
>> are more windward/leeward designs.  That is, our gybe angles are wider. 
>>  
>> When racing downwind, we set one of our multidisplays to show 
>> apparent wind on the top line and VMG on the bottom.  Once we 
>> optimize VMG, we can then gybe to the same apparent wind angle on the 
>> opposite gybe and the VMG should be close to optimized given no 
>> difference in wave angle, etc.  At this point we usually switch to 
>> watching the windex on the masthead because it's more responsive.
>>  
>> In shifty conditions, we have been known to put the top line while in 
>> wind mode on true wind angle because we feel wind shifts will be seen 
>> quicker.  True wind angle (TWA) is the angle between the true wind 
>> direction and the boat's heading.
>>  
>> Dennis C.
>> Touche' 35-1 #83
>> Mandeville, LA
>>
>> ------------------------------------------------------------------------
>> *From:* dwight veinot <dwightveinot at hfx.eastlink.ca>
>> *To:* cnc-list at cnc-list.com
>> *Sent:* Monday, June 29, 2009 11:17:08 AM
>> *Subject:* Re: {Stus-List} Nexus system - VMG vs WCV - report
>>
>> Dennis
>>
>>  
>>
>> VMG (wind) would be helpful in determining the optimum point of sail 
>> when going to weather but do you know if it is useful to determine 
>> the optimum jibe angle when sailing downwind.  I haven’t checked that 
>> out yet with my instruments which are new to me this year but I would 
>> expect something like a minus number and that  larger negative 
>> numbers would be faster?  Is VMG(wind) a shortened way of saying VMG 
>> to windward.  Do you know what the Nexus system outputs for VMG wind 
>> on a downwind jibe?
>>
>>  
>>
>> Dwight Veinot
>>
>> 1974 C&C 35, Alianna
>>
>> Head of St. Margaret's Bay, NS
>>
>>  
>>
>> ------------------------------------------------------------------------
>>
>> *From:* cnc-list-bounces at cnc-list.com 
>> [mailto:cnc-list-bounces at cnc-list.com] *On Behalf Of *Dennis C.
>> *Sent:* June 29, 2009 12:58 PM
>> *To:* cnc-list at cnc-list.com
>> *Subject:* Re: { Stu s-List} Nexus system - VMG vs WCV - report
>>
>>  
>>
>> Dwight,
>>
>>  
>>
>> I think you're correct.  The compass shouldn't be needed.
>>
>>  
>>
>> Dennis C.
>>
>>  
>>
>>  
>>
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>>
>> ------------------------------------------------------------------------
>>
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