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      A Few Simple Rules   05/22/2017

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Kiwing

Maximum VMG

Maximum VMG   45 members have voted

  1. 1. The maximum VMG upwind?

    • Less then or equal to 25 knots
    • More than 25 knots.
  2. 2. Maximum speed downwind?

    • Less then or equal to 35 knots
    • More than 35 knots.

Please sign in or register to vote in this poll.

35 posts in this topic

What will the VMGs be this time regardless of wind conditions?

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Wow 25 knots VMG upwind, I thought that was a little too high but !!!

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35 knots VMG down wind would be pretty amazing !!

 

Must be doing 50 knots or thereabouts, to achieve that

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I think they are capable of touching 34 knts upwind, at an AWA of about 24deg - footed slightly hot. Downwind, someone might top ETNZ's AC72 record 47.9 knts (was it .9?) but not by much. I doubt we will see 50 broken in this cycle, the foils won't be designed for the (yes original) SF upper wind range possibilities.

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34 implies if True wind is from the mark approx 31 knots VMG ??

 

Am I right?

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Don't understand your question but VMG is a simple formula given boatspeed and degree to the mark.

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Don't understand your question but VMG is a simple formula given boatspeed and degree to the mark.

 

Which you provided and the poll is about VMG (to the next mark is assumed) and I have attempted to calc the VMG.

 

Or did you mean 34 knots VMG?

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34 implies if True wind is from the mark approx 31 knots VMG ??

 

Am I right?

No. That would be the case if True Wing Angle was 24, but he said AWA was 24

 

ETA, we would need to know wind speed or something else to calculate the VMG/VMC

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In the ACWS Race Data the highest speeds were on approach and bearing off around Mark 1, and the highest VMGs downwind were shortly after. The fastest event was sailed in Bermuda and I crunched the numbers and then posted some graphics showing all that.

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34 implies if True wind is from the mark approx 31 knots VMG ??

 

Am I right?

No. That would be the case if True Wing Angle was 24, but he said AWA was 24

 

ETA, we would need to know wind speed or something else to calculate the VMG/VMC

 

 

If we assume 10 knots for wind speed (34/3) what would VMG work out ?

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Boatspeed at 3xTWS downwind works only to a certain point, the graphs will show it being below around 15.

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In the ACWS Race Data the highest speeds were on approach and bearing off around Mark 1, and the highest VMGs downwind were shortly after. The fastest event was sailed in Bermuda and I crunched the numbers and then posted some graphics showing all that.

 

Sorry to be a pest but where? I did not see it?

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In the ACWS Race Data the highest speeds were on approach and bearing off around Mark 1, and the highest VMGs downwind were shortly after. The fastest event was sailed in Bermuda and I crunched the numbers and then posted some graphics showing all that.

Sorry to be a pest but where? I did not see it?

Get out the binoculars, it is way far past the transom wake.

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I think you need to add 10 kts ( or more to the DW one ) to both your categories... providing we get ideal conditions, which are probably 17+ kts of wind. I sense both the existing barriers listed are already history.

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^

I sense the upwind one will be hard and the rest seem to suggest that.

 

And I just found a graph of VMG for AC34 which shows they both topped 37 Downwind which also seems to be agreed by the crowd. They only just clocked 20 in AC34 upwind.

 

May be I should change down wind to 45 knots ?

 

But we were entertained for a couple of days and the real thing will hit the screens in the next couple of days - no time for play!

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34 implies if True wind is from the mark approx 31 knots VMG ??

 

Am I right?

No. That would be the case if True Wing Angle was 24, but he said AWA was 24

 

ETA, we would need to know wind speed or something else to calculate the VMG/VMC

 

 

If we assume 10 knots for wind speed (34/3) what would VMG work out ?

 

34kts and an AWA of 24 degrees is not mathematically possible with a wind speed of 10kts. True wind speed would have to be over approx 13.8kts to even be theoretically possible. And even above guessing a wind speed would produce greatly differing VMGs so no point trying to guess I'm afraid

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In the ACWS Race Data the highest speeds were on approach and bearing off around Mark 1, and the highest VMGs downwind were shortly after. The fastest event was sailed in Bermuda and I crunched the numbers and then posted some graphics showing all that.

Sorry to be a pest but where? I did not see it?

Somewhere around this post. They look much more amateurish in hindsight than how I remembered, another poster put up far more polished charts of much the same data, later in the probably the same thread. AC45Fs, at ACWS Bermuda

 

The nice gybe by SWE in R3 L6 headed to the finish line, beating USA and winning the Bermuda event. The minimum speed through that gybe was 18.06 knots, at timestamp: 2015-10-18 15:22:54.797

 

SWE_R3_L6.JPG

 

 

The TWA/TWS numbers charted somewhere there had the usual caveats, being off an upwind weather station etc.

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DDWFTTW?

It's possible on Ice boats and land sailboats, and that funny prop driven thing that proved it a few years back....

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Surely this has to be VMG to the wind.... lets say a average wind of 18 knots.

 

VMG to the mark means nothing if you missed a few shifts

 

Lets face it a slower boat can win a race by hitting the correct shifts and pressure lines... and doing good turns.

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^Its pretty hard to be hitting the shifts if you are the boat behind being covered by a faster boat ahead.

@TeamNZ=clueless

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Two boats starting equal at a mark. The first boat to the next mark will be the boat with the best VMG to that mark, regardless of which boat has the best VMG relative to the wind?

 

The things we do to entertain ourselves while ETNZ does not reveal it's next amazing innovation !!!

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^Its pretty hard to be hitting the shifts if you are the boat behind being covered by a faster boat ahead.

@TeamNZ=clueless

done a bit of sailing. If The slower boat wins the start?... comprehendo?...

 

Or even, if the slower boat breaks a cover.

 

Or. They have a split side start...

 

These boats will not be tight covering, lee bowing, or slam dunking like the 12s.

 

Stick to the rubber duck in the bath dude... thats challenging enough fot you!

 

Fuck your dumber than i thought.

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Two boats starting equal at a mark. The first boat to the next mark will be the boat with the best VMG to that mark, regardless of which boat has the best VMG relative to the wind?

 

The things we do to entertain ourselves while ETNZ does not reveal it's next amazing innovation !!!

So boat A gets to the mark first because Boat B sailed into a hole but was faster?

 

VMG to a mark is not a measure of speed but a measure of speed and angle to the mark, wind angle and pressure, tactics, reliabilty, tackng speed,...

 

It means nothing in the context of a whole leg in the course!!!!!

 

It is a good measure of a moment within a leg where you need to know if you are on the favouable tack or gybe to the mark.

 

TeamNZ is right. VMG to the wind is a better way of comparing boats speed versus angle. After all wind shifts! But the mark stays put.

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No point of having a good VMG relative to the wind if you are travelling away from the mark !!???

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Depnds if your neasuring speed and angle v the other influences on a leg.

 

To the wind is a better measure of VMG ( how fast and high you can sail)

 

To the mark adds the dimensions of tactics, tacking speed, wind pressure variances, etc

 

To the eind shows better data in relation to speed and angle. This can then show if you are better or improving relative to previous boats, setups, and data. There are less variables to contend with too.

 

VMG to a mark counts when racing . But there are so mant variables that " on board" data can never prove what was the key things thet made you fast.

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Velocity made good. Has the sense of relative to where you are going?

 

Relative to the wind seems fallacious ??

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By definition: Vmg = Vs * cos ( Twa )

 

I'm thinking Twa will range from 60° in the lower wind range to 45°-ish in the upper wind range.

 

Upwind Vs probably not over 30 kts sustained. Therefore max upwind Vmg 30 kts * cos ( 45° ) = ~21 kts.

 

Also, leeway accounted for in Twa but leeway may be highly variable and could be positive or negative.

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Seems weird that if the wind changes to 45 degrees one side of the next mark and you are on the wrong side of the wind then you could be making good Vmg relative to the wind but not getting any closer to the Mark !!!

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VMG = Velocity Made Good (towards True wind)

VMC = Velocity Made on Course (towards where you want to go)

 

They are often mixed up, sometimes harmlessly, sometimes from ignorance of the difference.

 

Which matters depends on the question.

For this thread VMG is the one that makes sense.

VMC will vary between the 0 (just before tack onto layline) and the boat speed (when laying the mark)

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^^That's Vmc. The thread question involves Vmg.

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Wow I think I shall stick to sailing my Laser which is true seat of the pants stuff !!

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Wow I think I shall stick to sailing my Laser which is true seat of the pants stuff !!

Actually if you learn VMC theory then it can help dinghy sailing in some cases- forex where the wind is shifty and unpredictable

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