AA Butterfly versus CNv LCD wind calculation

Thanks for confirming my question that a fixed magnetic compass provides the fastest and best wind speed/direction calculation. It is also impressive how much others have done (even 20 years ago) to build algorithms which calculate great wind info without the fixed compass.

Racing sailboat instrumentation today (and for the past 20 years or so) is also extremely advanced at calculating "true wind speed" and "true wind direction." Imagine how important it is for a sailing team to understand what the "TRUE" wind direction and speed actually is! The funny thing is that on a moving sailboat (especially a fast moving sailboat) "true" wind direction and speed is actually very difficult to calculate accurately. Modern boats are accelerating and decelerating rapidly and make almost constant course adjustments. Modern sailboats are very high performance, especially downwind, especially multihulls or foiling boats. This performance (huge advanced sailplans, lightweight and powerful and efficient hull shapes) create racing sailboats which develop significant "apparent wind." Apparent wind essentially "bends" the true wind forward as the boat builds speed as much as 120 degrees from the "true" direction as the boats forward speed creates considerable additional wind energy. This energy fluctuates greatly as the boat changes speed and direction to maximize its speed as the true wind changes. Accurate true wind speed and direction data is extremely important for calculating what polar speed is optimum and (equally important) for what tack is favored towards the next mark (SMG, speed made good and SMGT, speed made good (optimum) other tack). The sailors are constantly referencing key instruments for optimum heading (apparent wind angle) and boatspeed in order to stay on the optimum polar heading and speed. This is exactly the same as when a glider references "speed to fly" and changes pitch (1 dimension vs 2 on a sailboat) to stay at the optimum polar speed for the current lift shown on the speed to fly vario. Sailing teams spend many, many thousands of dollars buying and countless hours optimizing these instruments (just as glider pilots do) but sailors actually have a much more critical tactical need for the instantaneous and accuarate true wind data.

For whatever it is worth.

Sean

On Thursday, September 22, 2016 at 10:25:34 AM UTC-4, Sean wrote:
Thanks for confirming my question that a fixed magnetic compass provides the fastest and best wind speed/direction calculation. It is also impressive how much others have done (even 20 years ago) to build algorithms which calculate great wind info without the fixed compass.

Racing sailboat instrumentation today (and for the past 20 years or so) is also extremely advanced at calculating "true wind speed" and "true wind direction." Imagine how important it is for a sailing team to understand what the "TRUE" wind direction and speed actually is! The funny thing is that on a moving sailboat (especially a fast moving sailboat) "true" wind direction and speed is actually very difficult to calculate accurately. Modern boats are accelerating and decelerating rapidly and make almost constant course adjustments. Modern sailboats are very high performance, especially downwind, especially multihulls or foiling boats. This performance (huge advanced sailplans, lightweight and powerful and efficient hull shapes) create racing sailboats which develop significant "apparent wind." Apparent wind essentially "bends" the true wind forward as the boat builds speed as much as 120 degrees from the "true" direction as the boats forward speed creates considerable additional wind energy. This energy fluctuates greatly as the boat changes speed and direction to maximize its speed as the true wind changes. Accurate true wind speed and direction data is extremely important for calculating what polar speed is optimum and (equally important) for what tack is favored towards the next mark (SMG, speed made good and SMGT, speed made good (optimum) other tack). The sailors are constantly referencing key instruments for optimum heading (apparent wind angle) and boatspeed in order to stay on the optimum polar heading and speed. This is exactly the same as when a glider references "speed to fly" and changes pitch (1 dimension vs 2 on a sailboat) to stay at the optimum polar speed for the current lift shown on the speed to fly vario. Sailing teams spend many, many thousands of dollars buying and countless hours optimizing these instruments (just as glider pilots do) but sailors actually have a much more critical tactical need for the instantaneous and accuarate true wind data.

For whatever it is worth.

Sean

Makes huge sense in sailing where every shift matters.
I'm still trying to understand why fast response wing information is as important as this thread seems to imply.
FWIW
UH

I suspect the Butterfly has a large bias for the ASI input, but for sure things would be improved with calibration.

I believe there is only one yacht processor that does it to a similar level as the Butterfly. Mostly, people just use simple trigonometry and damp inputs and results.

I agree UH. I dont think real time wind data is all that critical in a glider.

Sure its nice to have, but as I see it, little advantage can be gained by having slightly better wind accuracy than another guy.

Maybe I just dont live on the ridge enough.

Realtime wind sure is useful flying shear lift.

On Thursday, September 22, 2016 at 6:07:56 PM UTC-7, Sean wrote:
I agree UH. I dont think real time wind data is all that critical in a glider.

Sure its nice to have, but as I see it, little advantage can be gained by having slightly better wind accuracy than another guy.

Maybe I just dont live on the ridge enough.

I did meet a pilot I respect with both installed. He mentioned the fast accurate wind of the butterfly helped him decide which way to turn when entering a thermal. He liked the wind indicator for many other reasons as well.
I'm still trying to understand why fast response wing information is as important as this thread seems to imply.
FWIW
UH

On Thursday, 22 September 2016 23:47:15 UTC+3, wrote:
I'm still trying to understand why fast response wing information is as important as this thread seems to imply.
FWIW
UH

It is hard to explain to pilots who have never seen how wind changes around thermals and especially cloudstreets. We have had very accurate variometers for decades so we are used to look at clues from variometer when approaching thermal. Those same clues are visible also with horizontal flow around thermal. There cannot be vertical disturbance without corresponding horizontal disturbance in flow. Think which is easier to measure when you are 100m from thermal, you cannot measure lift (yet), but wind tells you that something is happening nearby.

How do you use this instant wind info?

Sean, while I enjoyed the sailing tangental as I too am a sailor (year around) I think you have made a logic jump in "confirming my question" at the same time using non-standard phrasing

From this discussion I had gleaned that the Butterfly is the only instrument that actually has all the goodies to be an inertial nav unit. The Butterfly inertial nav, with it's 3D accelerometers, gyros on a multiple chips... is the most accurate way to measure wind.


On Thursday, September 22, 2016 at 7:25:34 AM UTC-7, Sean wrote:
Thanks for confirming my question that a fixed magnetic compass provides the fastest and best wind speed/direction calculation. It is also impressive how much others have done (even 20 years ago) to build algorithms which calculate great wind info without the fixed compass.

On Friday, September 23, 2016 at 10:26:40 AM UTC-4, Jonathan St. Cloud wrote:
Sean, while I enjoyed the sailing tangental as I too am a sailor (year around) I think you have made a logic jump in "confirming my question" at the same time using non-standard phrasing

From this discussion I had gleaned that the Butterfly is the only instrument that actually has all the goodies to be an inertial nav unit. The Butterfly inertial nav, with it's 3D accelerometers, gyros on a multiple chips.... is the most accurate way to measure wind.


On Thursday, September 22, 2016 at 7:25:34 AM UTC-7, Sean wrote:
Thanks for confirming my question that a fixed magnetic compass provides the fastest and best wind speed/direction calculation. It is also impressive how much others have done (even 20 years ago) to build algorithms which calculate great wind info without the fixed compass.


@Jonathan - CNv too - see T8's post. Just not currently used.
@xcnick - I don't want to be in thermal with your friend who's looking at his vario to see what the wind is joining in... or joining the same thermal from another direction.

I've not flown with the Butterfly, but I'm very happy with the wind the CNv-XC gives me.

Dan