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converting from AWS to TWS rule of thumbs?


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#1 allen

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Posted 21 April 2012 - 04:51 PM

Sailing without fancy instruments but wanting to know what the true wind speed is has led me to try and come up some rules of thumb. My boat is a conventional 36 foot sloop and these rules of thumb were developed for the speeds my boat goes in the given wind and point more or less. They assume you can read the apparent wind angle off the mast head fly to within 5 degrees or so. They tend to be within about 5% accurate or 1/2 knot at 10 knots which is close enough.

I am wondering if anyone else has come up with rules of thumb for doing this.

Here are mine. Some are sailing points, some easy to measure points for pre start calculations.

Close Hauled TWS = AWS - 3/4 * Boat Speed
75 degrees apparent wind TWS = AWS
90 degrees apparent wind TWS = AWS + 1/4 * Boat Speed
135 degrees apparent wind TWS = AWS + 3/4 * Boat Speed
DDW TWS = AWS + Boat Speed (obvious)

#2 I'moutahere

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Posted 21 April 2012 - 08:33 PM

Sailing without fancy instruments but wanting to know what the true wind speed is has led me to try and come up some rules of thumb. My boat is a conventional 36 foot sloop and these rules of thumb were developed for the speeds my boat goes in the given wind and point more or less. They assume you can read the apparent wind angle off the mast head fly to within 5 degrees or so. They tend to be within about 5% accurate or 1/2 knot at 10 knots which is close enough.

I am wondering if anyone else has come up with rules of thumb for doing this.

Here are mine. Some are sailing points, some easy to measure points for pre start calculations.

Close Hauled TWS = AWS - 3/4 * Boat Speed
75 degrees apparent wind TWS = AWS
90 degrees apparent wind TWS = AWS + 1/4 * Boat Speed
135 degrees apparent wind TWS = AWS + 3/4 * Boat Speed
DDW TWS = AWS + Boat Speed (obvious)

If you have a log and wind speed & compass you can do it easily on paper as a vector.

Attached File  AWA-TWA.png   10.84K   20 downloads

#3 barney

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Posted 21 April 2012 - 09:17 PM

DDW TWS = AWS + Boat Speed (obvious)


This may be overly optimistic, DDW is more like:


Boat speed = 3/4 * TWS , up until hull speed,

Boat speed = 1/2 * TWS , planning

You might feel that there's no apparent on deck level (my Finn's windex is usually spinning), but wind speed is measured up high (10m).



#4 allen

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Posted 22 April 2012 - 04:09 AM

I need to clarify.

The question was if you measure Apparent Wind Speed (AWS), how do you estimate TWS easily, quickly, and close enough without doing vector math. Not how fast can your boat go. I assume you know how fast your boat can go by looking at the knot meter. I listed some ways of doing it that are pretty accurate but wondered if anyone else has a method that they can do in their head without pencil and paper on the water.

I have a calculator that can do it exactly but you need a computer and internet connection to use it. Not exactly on the water stuff. My link


Allen




#5 condor

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Posted 23 April 2012 - 08:31 PM

Years back, we solved the problem by learning the Beaufort sea states for various wind strengths. You can tell the TWS pretty well with a look at the sea state.

Some wind, no caps - under 8 knots.
Small caps beginning to show - 8-10.
Caps getting well-defined, bigger - 12-15.
Lotsa caps, good-sized - 15-18.
Waves leaving streaks - about 22+.

There are Beaufort strength charts that show pics of the the associated sea states. Wikipedia has some shots, although from a large ship.

Here's one that describes the sea states.
http://www.spc.noaa....o/beaufort.html

[story]
We were cleaning out a storage locker for a 60 footer program many years ago (CCA days). Found a bag labelled 'Force 9 Spinnaker'. Bag was heavy canvas and inside was a very heavy tarp, about 5' by 5'. Someone's idea of humor in storage.
[/story]

#6 Oxygen Mask

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Posted 26 April 2012 - 12:56 AM

I need to clarify.

The question was if you measure Apparent Wind Speed (AWS), how do you estimate TWS easily, quickly, and close enough without doing vector math. ...


I look at the surface of the water, the way it's been done for a thousand years. It's quite accurate. ;)

#7 Balder

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Posted 26 April 2012 - 04:42 AM

Years back, we solved the problem by learning the Beaufort sea states for various wind strengths. You can tell the TWS pretty well with a look at the sea state.


+1


Years back, indeed - over 100 years! Damn, your OLD!

#8 LeCanard

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Posted 26 April 2012 - 03:32 PM

And if you want to know the VMG quickly, you can use one of these fine Yacht Performance Calculators from a certain instrument manufacturer.

/LC

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#9 allen

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Posted 26 April 2012 - 03:41 PM

And if you want to know the VMG quickly, you can use one of these fine Yacht Performance Calculators from a certain instrument manufacturer.

/LC


That is in fact what I am trying to do. My interest in getting an accurate wind velocity is based on needing a good wind reading to make this calculation.


Allen

#10 in_TO

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Posted 26 April 2012 - 04:18 PM

Not sure if these posts help:

http://forums.sailin...dpost&p=1387579

http://forums.sailin...indpost&p=97684

#11 allen

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Posted 26 April 2012 - 04:22 PM


And if you want to know the VMG quickly, you can use one of these fine Yacht Performance Calculators from a certain instrument manufacturer.

/LC


That is in fact what I am trying to do. My interest in getting an accurate wind velocity is based on needing a good wind reading to make this calculation.


Allen


By the way. My version of that calculator for upwind is HERE. The problem with this calculator is that it requires a different piece of paper for every true wind speed. That is a problem on the water. My solution to that was that once you get close (using the above tool), you can use THIS tool. With it you can adjust your heading and see which exceeds the number in the table by the most. That then is your maximum VMG heading.

#12 allen

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Posted 26 April 2012 - 04:27 PM

Not sure if these posts help:

http://forums.sailin...dpost&p=1387579

http://forums.sailin...indpost&p=97684


Thanks for the links. The calculation is not the problem. I have a calculator HERE
The problem is that the math is a bit difficult to do on the water in the pressure of a pre-start. What I want is something fast but more accurate than sea state. That is why I did a ton of calculations to come up with the rules of thumb I put in this thread. I was looking for some indication that others use similar methods or have better ones.

Allen

#13 I'moutahere

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Posted 26 April 2012 - 06:25 PM


Not sure if these posts help:

http://forums.sailin...dpost&p=1387579

http://forums.sailin...indpost&p=97684


Thanks for the links. The calculation is not the problem. I have a calculator HERE
The problem is that the math is a bit difficult to do on the water in the pressure of a pre-start. What I want is something fast but more accurate than sea state. That is why I did a ton of calculations to come up with the rules of thumb I put in this thread. I was looking for some indication that others use similar methods or have better ones.

Allen

Why do you need to know what the true wind speed is?

#14 allen

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Posted 26 April 2012 - 06:38 PM



Not sure if these posts help:

http://forums.sailin...dpost&p=1387579

http://forums.sailin...indpost&p=97684


Thanks for the links. The calculation is not the problem. I have a calculator HERE
The problem is that the math is a bit difficult to do on the water in the pressure of a pre-start. What I want is something fast but more accurate than sea state. That is why I did a ton of calculations to come up with the rules of thumb I put in this thread. I was looking for some indication that others use similar methods or have better ones.

Allen

Why do you need to know what the true wind speed is?


Well... I want to know for sail selection although perhaps I could use sea state. Second my target boat speeds are and some of my VMG tools are based on true wind speed. Finally, I think it nice to be able to convert from apparent wind speed to true wind speed with a simple formula if it can be done. I mean, wouldn't it be nice to take out your pocket wind meter and be able to read true wind? To do that precisely you need boat speed and apparent wind angle and a little vector math. But given that my boat goes a fairly predictable speed for a given wind speed and heading, I was able to reduce the complex math into the approximation given and get within about 5%.

#15 I'moutahere

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Posted 27 April 2012 - 06:47 PM




Not sure if these posts help:

http://forums.sailin...dpost&p=1387579

http://forums.sailin...indpost&p=97684


Thanks for the links. The calculation is not the problem. I have a calculator HERE
The problem is that the math is a bit difficult to do on the water in the pressure of a pre-start. What I want is something fast but more accurate than sea state. That is why I did a ton of calculations to come up with the rules of thumb I put in this thread. I was looking for some indication that others use similar methods or have better ones.

Allen

Why do you need to know what the true wind speed is?


Well... I want to know for sail selection although perhaps I could use sea state. Second my target boat speeds are and some of my VMG tools are based on true wind speed. Finally, I think it nice to be able to convert from apparent wind speed to true wind speed with a simple formula if it can be done. I mean, wouldn't it be nice to take out your pocket wind meter and be able to read true wind? To do that precisely you need boat speed and apparent wind angle and a little vector math. But given that my boat goes a fairly predictable speed for a given wind speed and heading, I was able to reduce the complex math into the approximation given and get within about 5%.

I think you will sail faster if you forgot all about trying to guess what the wind speed is and just concentrated on sailing the boat - and looking outside of it.

Sail selection? If your heeling too much, reduce or flatten sail.

edit .... the best your "pocket anemometer" will do is tell you what the wind speed is at boom height. Not where the sails are.

#16 allen

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Posted 28 April 2012 - 05:38 AM





Not sure if these posts help:

http://forums.sailin...dpost&p=1387579

http://forums.sailin...indpost&p=97684


Thanks for the links. The calculation is not the problem. I have a calculator HERE
The problem is that the math is a bit difficult to do on the water in the pressure of a pre-start. What I want is something fast but more accurate than sea state. That is why I did a ton of calculations to come up with the rules of thumb I put in this thread. I was looking for some indication that others use similar methods or have better ones.

Allen

Why do you need to know what the true wind speed is?


Well... I want to know for sail selection although perhaps I could use sea state. Second my target boat speeds are and some of my VMG tools are based on true wind speed. Finally, I think it nice to be able to convert from apparent wind speed to true wind speed with a simple formula if it can be done. I mean, wouldn't it be nice to take out your pocket wind meter and be able to read true wind? To do that precisely you need boat speed and apparent wind angle and a little vector math. But given that my boat goes a fairly predictable speed for a given wind speed and heading, I was able to reduce the complex math into the approximation given and get within about 5%.

I think you will sail faster if you forgot all about trying to guess what the wind speed is and just concentrated on sailing the boat - and looking outside of it.

Sail selection? If your heeling too much, reduce or flatten sail.

edit .... the best your "pocket anemometer" will do is tell you what the wind speed is at boom height. Not where the sails are.


I worry about this stuff because it helps me win races, but thanks for your comment.

#17 Irish River

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Posted 28 April 2012 - 06:28 AM

If you have your polars, then work backward. Our instruments are rarely in great calibration, but we know the boat speed is pretty accurate. Just match up AWA with speed you are trying to sail. Should get you +/- a knot of TWS.

On our boat the down wind the boat speed should be 7.65k at 148 deg AWA, at 14 knots TWS. If we can't hit those #'s it's not blowing 14 knots.

#18 allen

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Posted 28 April 2012 - 02:32 PM

If you have your polars, then work backward. Our instruments are rarely in great calibration, but we know the boat speed is pretty accurate. Just match up AWA with speed you are trying to sail. Should get you +/- a knot of TWS.

On our boat the down wind the boat speed should be 7.65k at 148 deg AWA, at 14 knots TWS. If we can't hit those #'s it's not blowing 14 knots.



I must admit that I have target boat speeds in terms of apparent wind speed but it is still nice to be able to get true wind speed from a hand held instrument.

Let me talk a bit about the accuracy of this measurement. In comparing a hand held instrument that can be held 8 feet of the deck or about 11 feet off the sea surface one might expect it to read about 65% of the 100 foot wind. That would compare with a mast head wind read that was reading 85% of the 100 foot wind. I might ask the question of what height do you care about? Perhaps it is the center of effort of the sail, say 20 feet above sea level where the wind is about 72% of the 100 ft wind. Maybe higher. But if it is these numbers then the hand held reading is about 10% low and the mast head reading is about 15% high. The mast head reading is also influenced by the boat heal, which the hand held reading is not. That might be a 10% error. There is also the issue of the reading being influenced by being close to the sails. Masthead readings need to be compensated for heading as wind coming off the main going down wind can change the reading a couple of knots. The bottom line for me was that making readings from a moderately priced mast head readout was likely no more accurate than a hand held readout. It I wanted to pop for a full setup costing many thousands of dollars, I could get more accuracy. But then I would be spending lots of money to get a slightly more accurate reading and slowing my boat down (weight aloft) in the process. I decided that it would be better to focus on other things, and spend my money on new sails instead of obsessing over instrumentation. So I spent $60 and bought a hand held meter that could take averages to remove the variations of my old meter from wind gusts and called it good.

Another point is that I really don't care what the wind speed is high up. I care about how to sail my boat, what its targets are. If I always calibrate everything for the same height, that error will fall out. In other words, if we know that when the hand held wind reads 14 we set the boat up a certain way for best performance, that is all we need to know.

A final point. I raced on a J-105 last evening. He has 5 TacTick readouts. One was TWS. It was amazing to me how different the reading was on different tacks when going back over the same place in the pre-start. At one point he was reading 20 knots TWS but the sea state was a 3 or 4 and definitely not a 5. It was much calmer than the practice session on the T-10 I did the previous evening where I made a reading of 18 knots using the calibration factors at the start of this thread. This reinforced my opinion that the $60 hand held was the right decision.

The data on wind shear is from the chart on this page that I did for someone who was interested in wind sheer.

Allen



#19 Irish River

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Posted 28 April 2012 - 03:36 PM

I can't see a hand held being that accurate. There's too many variables. Angle to the wind, being the big one. Most wind anemometers are independent of wind direction, your arm is not going to be able to adjust to changing AW. Slight angles might affect your readings. The other issue is wash from the sails. If you take hundreds of measurements and calibrate them against a known wind speed, you might be able to empirically remove some variables.

Not saying you go out and spend money on instruments, but some are better at removing the variables then others.

#20 allen

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Posted 28 April 2012 - 04:16 PM

I can't see a hand held being that accurate. There's too many variables. Angle to the wind, being the big one. Most wind anemometers are independent of wind direction, your arm is not going to be able to adjust to changing AW. Slight angles might affect your readings. The other issue is wash from the sails. If you take hundreds of measurements and calibrate them against a known wind speed, you might be able to empirically remove some variables.

Not saying you go out and spend money on instruments, but some are better at removing the variables then others.


It looked like the ones that could do better than my hand held and concluded they would be about $4 grand. They need a gyro to measure heal angle and a computer unit to figure out the math. I basically agreed with other posters that my energy would be better spend elsewhere.

In terms of pointing the wind instrument at the wind. If you hold it square to your body and have the same wind in each ear, I think you can get very close. I would think you could get within 10 degrees and if it is a cos function, that is only a 2% error. I don't know if anyone has studied errors vs where you make the measurement other than the instrument guys who only care about masthead placements. I know that the racers use long extensions on their masthead sensors so it is an issue even up there. We just measure on the stern and try and be away from the sails. It isn't the biggest problem I have, others are bigger.

#21 bbr

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Posted 28 April 2012 - 09:15 PM

Well... I want to know for sail selection although perhaps I could use sea state. Second my target boat speeds are and some of my VMG tools are based on true wind speed. Finally, I think it nice to be able to convert from apparent wind speed to true wind speed with a simple formula if it can be done. I mean, wouldn't it be nice to take out your pocket wind meter and be able to read true wind? To do that precisely you need boat speed and apparent wind angle and a little vector math. But given that my boat goes a fairly predictable speed for a given wind speed and heading, I was able to reduce the complex math into the approximation given and get within about 5%.


If you're using a handheld wind meter your apparent wind speed will be wrong right off the bat (way too low), and the apparent wind angle will be just a wild guess at best... combine that with a half-assed formula for determining "true wind" and what you will get is just junk... you'll be totally wasting your time...

Like johnnysaint said, you're much better off forgetting about the "numbers" and just concentrate on sailing the boat...

Bill

#22 Oxygen Mask

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Posted 29 April 2012 - 03:22 AM

If you're using a handheld wind meter your apparent wind speed will be wrong right off the bat (way too low), and the apparent wind angle will be just a wild guess at best... combine that with a half-assed formula for determining "true wind" and what you will get is just junk... you'll be totally wasting your time...

Like johnnysaint said, you're much better off forgetting about the "numbers" and just concentrate on sailing the boat...

Bill


Yep. On both counts.

If you feel it really helps, and you're so anal about calcuations that you need to do all that crap, how can it possibly be acceptable to use guesses, approximations, and erroneous data?

I've known a few sailors over the years who had to do all that math rather than rely on what the behaviour of the boat and wind and water tell you, and not one of them ever amounted to much of a race winner, or even much of a decent sailor for that matter.
While you're taking readings and consulting your charts, your competitors have already passed you.
Sail the boat. Learn the feel of it, it will tell you what it needs. Every time.

#23 allen

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Posted 29 April 2012 - 03:30 AM


If you're using a handheld wind meter your apparent wind speed will be wrong right off the bat (way too low), and the apparent wind angle will be just a wild guess at best... combine that with a half-assed formula for determining "true wind" and what you will get is just junk... you'll be totally wasting your time...

Like johnnysaint said, you're much better off forgetting about the "numbers" and just concentrate on sailing the boat...

Bill


Yep. On both counts.

If you feel it really helps, and you're so anal about calcuations that you need to do all that crap, how can it possibly be acceptable to use guesses, approximations, and erroneous data?

I've known a few sailors over the years who had to do all that math rather than rely on what the behaviour of the boat and wind and water tell you, and not one of them ever amounted to much of a race winner, or even much of a decent sailor for that matter.
While you're taking readings and consulting your charts, your competitors have already passed you.
Sail the boat. Learn the feel of it, it will tell you what it needs. Every time.




For the last two years since I have played attention to this stuff I have won most of the races I have entered both handicap and one design.

#24 I'moutahere

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Posted 29 April 2012 - 04:06 AM



If you're using a handheld wind meter your apparent wind speed will be wrong right off the bat (way too low), and the apparent wind angle will be just a wild guess at best... combine that with a half-assed formula for determining "true wind" and what you will get is just junk... you'll be totally wasting your time...

Like johnnysaint said, you're much better off forgetting about the "numbers" and just concentrate on sailing the boat...

Bill


Yep. On both counts.

If you feel it really helps, and you're so anal about calcuations that you need to do all that crap, how can it possibly be acceptable to use guesses, approximations, and erroneous data?

I've known a few sailors over the years who had to do all that math rather than rely on what the behaviour of the boat and wind and water tell you, and not one of them ever amounted to much of a race winner, or even much of a decent sailor for that matter.
While you're taking readings and consulting your charts, your competitors have already passed you.
Sail the boat. Learn the feel of it, it will tell you what it needs. Every time.




For the last two years since I have played attention to this stuff I have won most of the races I have entered both handicap and one design.

How long have you been sailing?

#25 allen

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Posted 29 April 2012 - 05:17 AM




If you're using a handheld wind meter your apparent wind speed will be wrong right off the bat (way too low), and the apparent wind angle will be just a wild guess at best... combine that with a half-assed formula for determining "true wind" and what you will get is just junk... you'll be totally wasting your time...

Like johnnysaint said, you're much better off forgetting about the "numbers" and just concentrate on sailing the boat...

Bill


Yep. On both counts.

If you feel it really helps, and you're so anal about calcuations that you need to do all that crap, how can it possibly be acceptable to use guesses, approximations, and erroneous data?

I've known a few sailors over the years who had to do all that math rather than rely on what the behaviour of the boat and wind and water tell you, and not one of them ever amounted to much of a race winner, or even much of a decent sailor for that matter.
While you're taking readings and consulting your charts, your competitors have already passed you.
Sail the boat. Learn the feel of it, it will tell you what it needs. Every time.




For the last two years since I have played attention to this stuff I have won most of the races I have entered both handicap and one design.

How long have you been sailing?


As long as I can remember, maybe 60 years. I have owned Papoose since 1989. I have been racing since 2004. Started winning races in 2009.




#26 I'moutahere

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Posted 29 April 2012 - 06:22 AM





If you're using a handheld wind meter your apparent wind speed will be wrong right off the bat (way too low), and the apparent wind angle will be just a wild guess at best... combine that with a half-assed formula for determining "true wind" and what you will get is just junk... you'll be totally wasting your time...

Like johnnysaint said, you're much better off forgetting about the "numbers" and just concentrate on sailing the boat...

Bill


Yep. On both counts.

If you feel it really helps, and you're so anal about calcuations that you need to do all that crap, how can it possibly be acceptable to use guesses, approximations, and erroneous data?

I've known a few sailors over the years who had to do all that math rather than rely on what the behaviour of the boat and wind and water tell you, and not one of them ever amounted to much of a race winner, or even much of a decent sailor for that matter.
While you're taking readings and consulting your charts, your competitors have already passed you.
Sail the boat. Learn the feel of it, it will tell you what it needs. Every time.




For the last two years since I have played attention to this stuff I have won most of the races I have entered both handicap and one design.

How long have you been sailing?


As long as I can remember, maybe 60 years. I have owned Papoose since 1989. I have been racing since 2004. Started winning races in 2009.

60 years. and it took you 58 years to get to the point of thinking about AW/TW?..?????????????????

#27 isma

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Posted 29 April 2012 - 06:25 AM

60 years. and it took you 58 years to get to the point of thinking about AW/TW?..?????????????????

Seriously, take the dick out of your mouth when you type. You are an A+ asshole.

#28 I'moutahere

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Posted 29 April 2012 - 06:29 AM


60 years. and it took you 58 years to get to the point of thinking about AW/TW?..?????????????????

Seriously, take the dick out of your mouth when you type. You are an A+ asshole.

Fuck off troll!

This thread is about stuff that is WAAAAY beyond your comprehension.

#29 isma

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Posted 29 April 2012 - 06:39 AM



60 years. and it took you 58 years to get to the point of thinking about AW/TW?..?????????????????

Seriously, take the dick out of your mouth when you type. You are an A+ asshole.

Fuck off troll!

This thread is about stuff that is WAAAAY beyond your comprehension.


Simple vector math...I teach math you dumbshit. It takes two minutes to create a spreadsheet in excel that takes apparent and kicks out true. And despite teaching math, I am really a physicist.

Go back to cocksucking.

#30 I'moutahere

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Posted 29 April 2012 - 06:45 AM




60 years. and it took you 58 years to get to the point of thinking about AW/TW?..?????????????????

Seriously, take the dick out of your mouth when you type. You are an A+ asshole.

Fuck off troll!

This thread is about stuff that is WAAAAY beyond your comprehension.


Simple vector math...I teach math you dumbshit. It takes two minutes to create a spreadsheet in excel that takes apparent and kicks out true. And despite teaching math, I am really a physicist.

Go back to cocksucking.


Then read the whole fucking thread, troll. Though I doubt you would understand any of it,

#31 isma

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Posted 29 April 2012 - 06:48 AM





60 years. and it took you 58 years to get to the point of thinking about AW/TW?..?????????????????

Seriously, take the dick out of your mouth when you type. You are an A+ asshole.

Fuck off troll!

This thread is about stuff that is WAAAAY beyond your comprehension.


Simple vector math...I teach math you dumbshit. It takes two minutes to create a spreadsheet in excel that takes apparent and kicks out true. And despite teaching math, I am really a physicist.

Go back to cocksucking.


Then read the whole fucking thread, troll.

And you'll go back to cocksucking.

The thread has no purpose. Allen had already worked out the trig approximations and for some reason started this stupid thread. More instruments...more potential failures. But you wouldn't get that.

#32 I'moutahere

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Posted 29 April 2012 - 06:52 AM



The thread has no purpose. Allen had already worked out the trig approximations and for some reason started this stupid thread. More instruments...more potential failures. But you wouldn't get that.

Best shut your trap troll. You are already proving you don't know shit from clay, and your only reason to post in this thread is to stir shit.

#33 isma

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Posted 29 April 2012 - 07:05 AM




The thread has no purpose. Allen had already worked out the trig approximations and for some reason started this stupid thread. More instruments...more potential failures. But you wouldn't get that.

Best shut your trap troll. You are already proving you don't know shit from clay, and your only reason to post in this thread is to stir shit.

I keep forgetting you are the Oracle for all things sailing...so step up and share.

#34 allen

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Posted 29 April 2012 - 07:11 AM

60 years. and it took you 58 years to get to the point of thinking about AW/TW?..?????????????????


Johnysaint,

Well, not exactly. Like I said, I have been racing since 2004 and only occasionally at first. It is only the last couple of years that I started thinking about target boat speed as being so important. Previous to that I did just the looking around and sailing the boat as has been suggested. This TWS/ AWS question is just a small part of the target boat speed question, a very small part. So I guess you could ask why it took me 4 years to start thinking about target boat speed. I guess the answer is we had to work through the more significant issues we had with the boat the most extreme being getting new sails. The North Sails just didn't cut it strangely enough. The Quantum sails are much superior. Probably relates to my boat being unique and the Quantum salesman taking the time to get them right. (I think there were 7 re-cuts on 5 new sails) I must also say that it isn't easy to get a 55 year old boat to be competitive with more modern boats and it has taken a long time to work out some of the structural issues with the boat so we didn't rip it apart sailing it hard. Below is a picture of my boat leading a T-10 and a C&C-41 into the first mark for your reference.

Posted Image

#35 I'moutahere

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Posted 29 April 2012 - 07:14 AM





The thread has no purpose. Allen had already worked out the trig approximations and for some reason started this stupid thread. More instruments...more potential failures. But you wouldn't get that.

Best shut your trap troll. You are already proving you don't know shit from clay, and your only reason to post in this thread is to stir shit.

I keep forgetting you are the Oracle for all things sailing...so step up and share.


I was aware of how to work out AW/TW when I was about 16 & sailing skiffs. That was a fucking long time ago - more than 50 years. So I have probably forgotten more about sailing than you have ever learnt.

Anyone who thinks that the time to change sails is at a given wind speed is barking up the wrong tree.

#36 I'moutahere

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Posted 29 April 2012 - 07:24 AM


60 years. and it took you 58 years to get to the point of thinking about AW/TW?..?????????????????


Johnysaint,

Well, not exactly. Like I said, I have been racing since 2004 and only occasionally at first. It is only the last couple of years that I started thinking about target boat speed as being so important. Previous to that I did just the looking around and sailing the boat as has been suggested. This TWS/ AWS question is just a small part of the target boat speed question, a very small part. So I guess you could ask why it took me 4 years to start thinking about target boat speed. I guess the answer is we had to work through the more significant issues we had with the boat the most extreme being getting new sails. The North Sails just didn't cut it strangely enough. The Quantum sails are much superior. Probably relates to my boat being unique and the Quantum salesman taking the time to get them right. (I think there were 7 re-cuts on 5 new sails) I must also say that it isn't easy to get a 55 year old boat to be competitive with more modern boats and it has taken a long time to work out some of the structural issues with the boat so we didn't rip it apart sailing it hard. Below is a picture of my boat leading a T-10 and a C&C-41 into the first mark for your reference.

Posted Image

A pretty boat. From your post I gather the guys at Quantum gave you something (maybe polars) regarding when to change sails re TWS. That would only be an aproximation - a guide. You don't have the means to get TWS or AWS, so the best you will have is a guess.

I trust you will be aware that 20 knots in a hot off the land breeze is considerably weaker than a 20 knot cold (maybe snow threatening) northerly? So if the boat is going slow & laying over, flatten the main and/or change down headsail- don't waste time trying to figure out if the TWS has reached a specific number that your tables suggest you should change sails.

#37 isma

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Posted 29 April 2012 - 07:52 AM

Anyone who thinks that the time to change sails is at a given wind speed is barking up the wrong tree.


Shit, something we agree on...what's the world coming to. I still think you and DoRag should do a Thelma and Louise off a cliff.

#38 allen

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Posted 29 April 2012 - 07:55 AM



60 years. and it took you 58 years to get to the point of thinking about AW/TW?..?????????????????


Johnysaint,

Well, not exactly. Like I said, I have been racing since 2004 and only occasionally at first. It is only the last couple of years that I started thinking about target boat speed as being so important. Previous to that I did just the looking around and sailing the boat as has been suggested. This TWS/ AWS question is just a small part of the target boat speed question, a very small part. So I guess you could ask why it took me 4 years to start thinking about target boat speed. I guess the answer is we had to work through the more significant issues we had with the boat the most extreme being getting new sails. The North Sails just didn't cut it strangely enough. The Quantum sails are much superior. Probably relates to my boat being unique and the Quantum salesman taking the time to get them right. (I think there were 7 re-cuts on 5 new sails) I must also say that it isn't easy to get a 55 year old boat to be competitive with more modern boats and it has taken a long time to work out some of the structural issues with the boat so we didn't rip it apart sailing it hard. Below is a picture of my boat leading a T-10 and a C&C-41 into the first mark for your reference.

Posted Image

A pretty boat. From your post I gather the guys at Quantum gave you something (maybe polars) regarding when to change sails re TWS. That would only be an aproximation - a guide. You don't have the means to get TWS or AWS, so the best you will have is a guess.

I trust you will be aware that 20 knots in a hot off the land breeze is considerably weaker than a 20 knot cold (maybe snow threatening) northerly? So if the boat is going slow & laying over, flatten the main and/or change down headsail- don't waste time trying to figure out if the TWS has reached a specific number that your tables suggest you should change sails.


Thanks,

I have not thought about the air density issue you have raised. I race on San Francisco Bay. Hot = no wind. Snow = Well, it doesn't snow. Point is that the weather is pretty much always the same. With this boat, we drop the traveler to flatten the main and bubble it using the sheet to keep the heel at 25 degrees. The full batons help with that a lot.

There are no polars other than the ones I have created from my own measurement on the water. This is an old boat and nobody has polars for it. Mine are based on the measurements I take and the processes I have worked out. They have helped, that is all I can say. I don't claim that they are prefect as they are not. I just have worked out processes to make it possible to use them on the water. I found the Hawk calculator interesting although not sure it is any easier to actually use on the water than what I have worked out but I am studying it. It is surprisingly difficult to do even the simplest math during a race. Doing vector math on graph paper just isn't going to happen on the water. Too much other important stuff happening like keeping the trim correct.

We have three jibs, a 90, a 130 and a 155. The 90 is mylar and the other two Dacron. Quantum said the 155 is good to 12, the the 90 picks up at about 15. We find that 130 is almost useless as the boat can't point with it. I am still trying to work out the switch point between the 90 and the 155 and not sure the 130 has a place. The 130 may be useful depending on the course as a reaching sail so that we might give up a little on the initial short beat to have a better sail on the next leg. As you know, it is not as simple as taking a wind reading and looking on a chart and picking a sail. But it is helpful to know the true wind even if it is at boat level as that is where we always take it. In other words, if 15 TWS at 10 feet off the water was too much wind for a sail last race, why would I think it would not be too much wind this race even thought someone on this thread told me that my reading was wrong?

This thread has a lot of interesting comments. There are people telling me that my 10 feet off the water reading is useless because it is too low. Other people tell me to look at the sea state, which is 0 feet off the water. I understand wind sheer and that my reading would not be the same at different altitudes but it is my reading and it is valid data.



#39 I'moutahere

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Posted 29 April 2012 - 07:58 AM


Anyone who thinks that the time to change sails is at a given wind speed is barking up the wrong tree.


Shit, something we agree on...what's the world coming to. I still think you and DoRag should do a Thelma and Louise off a cliff.


Fuck off idiot. I've seen your posts here & there. You contribute absolutely NOTHING to any thread. You are just a pathetic shit stirrer, and that is the only reason you post anything.

#40 I'moutahere

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Posted 29 April 2012 - 08:11 AM




60 years. and it took you 58 years to get to the point of thinking about AW/TW?..?????????????????


Johnysaint,

Well, not exactly. Like I said, I have been racing since 2004 and only occasionally at first. It is only the last couple of years that I started thinking about target boat speed as being so important. Previous to that I did just the looking around and sailing the boat as has been suggested. This TWS/ AWS question is just a small part of the target boat speed question, a very small part. So I guess you could ask why it took me 4 years to start thinking about target boat speed. I guess the answer is we had to work through the more significant issues we had with the boat the most extreme being getting new sails. The North Sails just didn't cut it strangely enough. The Quantum sails are much superior. Probably relates to my boat being unique and the Quantum salesman taking the time to get them right. (I think there were 7 re-cuts on 5 new sails) I must also say that it isn't easy to get a 55 year old boat to be competitive with more modern boats and it has taken a long time to work out some of the structural issues with the boat so we didn't rip it apart sailing it hard. Below is a picture of my boat leading a T-10 and a C&C-41 into the first mark for your reference.

Posted Image

A pretty boat. From your post I gather the guys at Quantum gave you something (maybe polars) regarding when to change sails re TWS. That would only be an aproximation - a guide. You don't have the means to get TWS or AWS, so the best you will have is a guess.

I trust you will be aware that 20 knots in a hot off the land breeze is considerably weaker than a 20 knot cold (maybe snow threatening) northerly? So if the boat is going slow & laying over, flatten the main and/or change down headsail- don't waste time trying to figure out if the TWS has reached a specific number that your tables suggest you should change sails.


Thanks,

I have not thought about the air density issue you have raised. I race on San Francisco Bay. Hot = no wind. Snow = Well, it doesn't snow. Point is that the weather is pretty much always the same. With this boat, we drop the traveler to flatten the main and bubble it using the sheet to keep the heel at 25 degrees. The full batons help with that a lot.

There are no polars other than the ones I have created from my own measurement on the water. This is an old boat and nobody has polars for it. Mine are based on the measurements I take and the processes I have worked out. They have helped, that is all I can say. I don't claim that they are prefect as they are not. I just have worked out processes to make it possible to use them on the water. I found the Hawk calculator interesting although not sure it is any easier to actually use on the water than what I have worked out but I am studying it. It is surprisingly difficult to do even the simplest math during a race. Doing vector math on graph paper just isn't going to happen on the water. Too much other important stuff happening like keeping the trim correct.

We have three jibs, a 90, a 130 and a 155. The 90 is mylar and the other two Dacron. Quantum said the 155 is good to 12, the the 90 picks up at about 15. We find that 130 is almost useless as the boat can't point with it. I am still trying to work out the switch point between the 90 and the 155 and not sure the 130 has a place. The 130 may be useful depending on the course as a reaching sail so that we might give up a little on the initial short beat to have a better sail on the next leg. As you know, it is not as simple as taking a wind reading and looking on a chart and picking a sail. But it is helpful to know the true wind even if it is at boat level as that is where we always take it. In other words, if 15 TWS at 10 feet off the water was too much wind for a sail last race, why would I think it would not be too much wind this race even thought someone on this thread told me that my reading was wrong?

This thread has a lot of interesting comments. There are people telling me that my 10 feet off the water reading is useless because it is too low. Other people tell me to look at the sea state, which is 0 feet off the water. I understand wind sheer and that my reading would not be the same at different altitudes but it is my reading and it is valid data.


Establishing wind speed by looking at the water? Look at the Beaufort scale. It is general, not specific. You will work out what I mean.

There are too many variables (and looks like I've given you another in air temp., density) to choose a specific wind speed for a sail change - especially when you cannot get an accurate wind speed. Log (boat speed), heel angle, pointing ability, seat state (flat or not), crew weight (numbers) all are the conditions governing sail selection. Can you flatten the main much? Mast does not look like you can bend it very much.

#41 isma

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Posted 29 April 2012 - 08:17 AM

OK,
What JS is trying to convey is stability. Warm air over cold water, stable. Cold air over warm water, unstable. In stable conditions, waves do not grow rapidly. I have sailed on the Great Lakes in calm waters with 12knt winds

#42 bbr

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Posted 29 April 2012 - 01:07 PM

This thread has a lot of interesting comments. There are people telling me that my 10 feet off the water reading is useless because it is too low. Other people tell me to look at the sea state, which is 0 feet off the water. I understand wind sheer and that my reading would not be the same at different altitudes but it is my reading and it is valid data.

Garbage In = Garbage Out

The half-baked system you're now using is like licking your finger and holding it up in the air... it works, in a way, but it's not going to be even close to accurate...

Why not just install wind instruments and get real data?... it's the only way you're going to get any useful numbers...

Bill

#43 allen

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Posted 29 April 2012 - 07:59 PM

Establishing wind speed by looking at the water? Look at the Beaufort scale. It is general, not specific. You will work out what I mean.

There are too many variables (and looks like I've given you another in air temp., density) to choose a specific wind speed for a sail change - especially when you cannot get an accurate wind speed. Log (boat speed), heel angle, pointing ability, seat state (flat or not), crew weight (numbers) all are the conditions governing sail selection. Can you flatten the main much? Mast does not look like you can bend it very much.


Jonnysaint,

The main was designed to have mast bend take out 4 inches of the belly. My backstay can take out 1 inch. That was the re-cut on the main. It is now cut for high winds, inherently flat as around here if there isn't a small craft warning, there isn't any wind. Typical forecast is 15-25. So to answer your question, I can get it flat. As I said, in high winds we drop the traveler to leeward and control the heel of the boat with the mainsheet.

At the risk of repeating myself, from what I have seen of typical TackTick wind readings, I would bet what I am doing is more accurate (note: you have to be aware that there is wind sheer). That is not to say that a top end system with a gyro to measure heel and a computer to make the calculations wouldn't be more accurate, I am sure it would. But I would put what I am doing up against a typical system especially considering I don't really care what the wind really is. All I care about is what did it read when we went fast with the 90 and what did it read when we had too much wind for the 155. That said, I agree there is more that goes into sail selection than just a wind reading. Most important for us is probably is the wind getting stronger or weaker. Is it stronger over there or over here. What sail are we going to want up for the third leg. The list goes on and on. We didn't end up ahead of a boat that owes us over a minute a mile as seen in the picture I posted by being stupid afterall.

Along those lines, how many people who are posting trash in this thread race against boats that owe them over a minute a mile and beat them boat for boat? How many of you have a 55 year old wood boat that can beat a T-10 boat for boat occasionally and corrected usually? How many of the trash talkers have sailed one design and won by over 1/2 minute a mile against a nationally ranked sailor?

Allen

#44 bbr

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Posted 29 April 2012 - 09:10 PM

At the risk of repeating myself, from what I have seen of typical TackTick wind readings, I would bet what I am doing is more accurate (note: you have to be aware that there is wind sheer). That is not to say that a top end system with a gyro to measure heel and a computer to make the calculations wouldn't be more accurate, I am sure it would. But I would put what I am doing up against a typical system especially considering I don't really care what the wind really is. All I care about is what did it read when we went fast with the 90 and what did it read when we had too much wind for the 155. That said, I agree there is more that goes into sail selection than just a wind reading. Most important for us is probably is the wind getting stronger or weaker. Is it stronger over there or over here. What sail are we going to want up for the third leg. The list goes on and on. We didn't end up ahead of a boat that owes us over a minute a mile as seen in the picture I posted by being stupid afterall.

There are several inexpensive wind instrument systems available (without gyros and computers), and any one of these is going to be much, much more accurate than your handheld system... You may think that your system is more accurate, but it's not going to even be close... believe me...

Along those lines, how many people who are posting trash in this thread race against boats that owe them over a minute a mile and beat them boat for boat? How many of you have a 55 year old wood boat that can beat a T-10 boat for boat occasionally and corrected usually? How many of the trash talkers have sailed one design and won by over 1/2 minute a mile against a nationally ranked sailor?

Except for a couple of wankers talking shit to each other, I haven't seen anybody in this thread talking trash to you... What I see is a few people giving you suggestions and constructive criticism... Are you looking for a better way to find true wind or not?... Well, that's what you're getting...

If your intention was to improve your current system then you should be listening to people's advice... if not, then why did you start this thread?

Bill

#45 allen

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Posted 29 April 2012 - 10:43 PM


At the risk of repeating myself, from what I have seen of typical TackTick wind readings, I would bet what I am doing is more accurate (note: you have to be aware that there is wind sheer). That is not to say that a top end system with a gyro to measure heel and a computer to make the calculations wouldn't be more accurate, I am sure it would. But I would put what I am doing up against a typical system especially considering I don't really care what the wind really is. All I care about is what did it read when we went fast with the 90 and what did it read when we had too much wind for the 155. That said, I agree there is more that goes into sail selection than just a wind reading. Most important for us is probably is the wind getting stronger or weaker. Is it stronger over there or over here. What sail are we going to want up for the third leg. The list goes on and on. We didn't end up ahead of a boat that owes us over a minute a mile as seen in the picture I posted by being stupid afterall.

There are several inexpensive wind instrument systems available (without gyros and computers), and any one of these is going to be much, much more accurate than your handheld system... You may think that your system is more accurate, but it's not going to even be close... believe me...

Along those lines, how many people who are posting trash in this thread race against boats that owe them over a minute a mile and beat them boat for boat? How many of you have a 55 year old wood boat that can beat a T-10 boat for boat occasionally and corrected usually? How many of the trash talkers have sailed one design and won by over 1/2 minute a mile against a nationally ranked sailor?

Except for a couple of wankers talking shit to each other, I haven't seen anybody in this thread talking trash to you... What I see is a few people giving you suggestions and constructive criticism... Are you looking for a better way to find true wind or not?... Well, that's what you're getting...

If your intention was to improve your current system then you should be listening to people's advice... if not, then why did you start this thread?

Bill


Bill,

It was my impression that "Seriously, take the dick out of your mouth when you type. You are an A+ asshole. " was directed at me.
Garbage in = Garbage out was not helpful either but perhaps I did get sensitive.

That said, I did get some good comments from Cordur, Oxygen Mask, and particularly LeCanard and Jonnysaint and I appreciate them.

As I said before, a normal mast head system has an error at 25 degrees heal of 10% do to the heal. I am told that there is a downwind error of another about 10% or more due to wash off the sail being different upwind and downwind. Add to that another about 15% from being above the center of effort from the wind sheer and you have a significant error. These are all calibrated out on the top end racers system but not on the typical cruising systems. Combine that with my experience on boats equipped with TackTick systems and I do not believe they are accurate at all and certainly not a good use of money because, as Jonnysaint points out, there are more important things that what the TWS is.

Personally, I think some people are putting too much faith in the masthead systems and they are just not of interest to me. Why should I put more weight on the top of my mast? How will that help me sail faster? I don't see it.

I started this thread to see if anyone else had rules of thumb for converting from AWS to TWS without fancy instruments. Obviously nobody else has any but lots of people think it is a dumb idea. I get that.


Allen

#46 bbr

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Posted 29 April 2012 - 11:12 PM

Bill,

It was my impression that "Seriously, take the dick out of your mouth when you type. You are an A+ asshole. " was directed at me.
Garbage in = Garbage out was not helpful either but perhaps I did get sensitive.

That said, I did get some good comments from Cordur, Oxygen Mask, and particularly LeCanard and Jonnysaint and I appreciate them.

As I said before, a normal mast head system has an error at 25 degrees heal of 10% do to the heal. I am told that there is a downwind error of another about 10% or more due to wash off the sail being different upwind and downwind. Add to that another about 15% from being above the center of effort from the wind sheer and you have a significant error. These are all calibrated out on the top end racers system but not on the typical cruising systems. Combine that with my experience on boats equipped with TackTick systems and I do not believe they are accurate at all and certainly not a good use of money because, as Jonnysaint points out, there are more important things that what the TWS is.

Personally, I think some people are putting too much faith in the masthead systems and they are just not of interest to me. Why should I put more weight on the top of my mast? How will that help me sail faster? I don't see it.

I started this thread to see if anyone else had rules of thumb for converting from AWS to TWS without fancy instruments. Obviously nobody else has any but lots of people think it is a dumb idea. I get that.

Allen


The "Seriously, take the dick out of your mouth..." comment was isma telling johnnysaint that he was being an asshole for talking down to you the way he did... definitely not directed at you...

"Garbage in = garbage out" is a popular expression in the engineering/electronics industry meaning that if the data you put in is wrong then the result that comes out will be even worse... which is very true... getting the apparent wind speed and/or angle wrong by even a small amount will result in the resulting true wind speed and angle being way out... the comment wasn't meant to offend you...

As for the rest of my comments, I was only trying to help... sorry if what I said wasn't what you wanted to hear...

Bill

#47 I'moutahere

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Posted 29 April 2012 - 11:27 PM


Bill,

It was my impression that "Seriously, take the dick out of your mouth when you type. You are an A+ asshole. " was directed at me.
Garbage in = Garbage out was not helpful either but perhaps I did get sensitive.

That said, I did get some good comments from Cordur, Oxygen Mask, and particularly LeCanard and Jonnysaint and I appreciate them.

As I said before, a normal mast head system has an error at 25 degrees heal of 10% do to the heal. I am told that there is a downwind error of another about 10% or more due to wash off the sail being different upwind and downwind. Add to that another about 15% from being above the center of effort from the wind sheer and you have a significant error. These are all calibrated out on the top end racers system but not on the typical cruising systems. Combine that with my experience on boats equipped with TackTick systems and I do not believe they are accurate at all and certainly not a good use of money because, as Jonnysaint points out, there are more important things that what the TWS is.

Personally, I think some people are putting too much faith in the masthead systems and they are just not of interest to me. Why should I put more weight on the top of my mast? How will that help me sail faster? I don't see it.

I started this thread to see if anyone else had rules of thumb for converting from AWS to TWS without fancy instruments. Obviously nobody else has any but lots of people think it is a dumb idea. I get that.

Allen


The "Seriously, take the dick out of your mouth..." comment was isma telling johnnysaint that he was being an asshole for talking down to you the way he did... definitely not directed at you...

"Garbage in = garbage out" is a popular expression in the engineering/electronics industry meaning that if the data you put in is wrong then the result that comes out will be even worse... which is very true... getting the apparent wind speed and/or angle wrong by even a small amount will result in the resulting true wind speed and angle being way out... the comment wasn't meant to offend you...

As for the rest of my comments, I was only trying to help... sorry if what I said wasn't what you wanted to hear...

Bill


I was not intending to talk down to anyone. Believe it or not, but I do know people who have been sailing (not racing) for 30-40 years and they do not have a clue what apparent wind is. More common than one would think.
And I have sailed with some "heavies" (who have won world champs) who were certain the device at the top of the mast reads TW speed & direction (because the instrument displayed it).

I trust that you will note that isma did not contribute anything of value to the thread. Was just being a troll.

#48 Oxygen Mask

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Posted 29 April 2012 - 11:49 PM

Along those lines, how many people who are posting trash in this thread race against boats that owe them over a minute a mile and beat them boat for boat? Allen


Welllll, since you ask, I do. Regularly.

Without instruments other than speed and compass.
And I have not been posting trash, just trying to give you another viewpoint and anecdotal redirection.

#49 allen

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Posted 30 April 2012 - 12:14 AM



Bill,

It was my impression that "Seriously, take the dick out of your mouth when you type. You are an A+ asshole. " was directed at me.
Garbage in = Garbage out was not helpful either but perhaps I did get sensitive.

That said, I did get some good comments from Cordur, Oxygen Mask, and particularly LeCanard and Jonnysaint and I appreciate them.

As I said before, a normal mast head system has an error at 25 degrees heal of 10% do to the heal. I am told that there is a downwind error of another about 10% or more due to wash off the sail being different upwind and downwind. Add to that another about 15% from being above the center of effort from the wind sheer and you have a significant error. These are all calibrated out on the top end racers system but not on the typical cruising systems. Combine that with my experience on boats equipped with TackTick systems and I do not believe they are accurate at all and certainly not a good use of money because, as Jonnysaint points out, there are more important things that what the TWS is.

Personally, I think some people are putting too much faith in the masthead systems and they are just not of interest to me. Why should I put more weight on the top of my mast? How will that help me sail faster? I don't see it.

I started this thread to see if anyone else had rules of thumb for converting from AWS to TWS without fancy instruments. Obviously nobody else has any but lots of people think it is a dumb idea. I get that.

Allen


The "Seriously, take the dick out of your mouth..." comment was isma telling johnnysaint that he was being an asshole for talking down to you the way he did... definitely not directed at you...

"Garbage in = garbage out" is a popular expression in the engineering/electronics industry meaning that if the data you put in is wrong then the result that comes out will be even worse... which is very true... getting the apparent wind speed and/or angle wrong by even a small amount will result in the resulting true wind speed and angle being way out... the comment wasn't meant to offend you...

As for the rest of my comments, I was only trying to help... sorry if what I said wasn't what you wanted to hear...

Bill


I was not intending to talk down to anyone. Believe it or not, but I do know people who have been sailing (not racing) for 30-40 years and they do not have a clue what apparent wind is. More common than one would think.
And I have sailed with some "heavies" (who have won world champs) who were certain the device at the top of the mast reads TW speed & direction (because the instrument displayed it).

I trust that you will note that isma did not contribute anything of value to the thread. Was just being a troll.



OK, I stand corrected and I apparently was a little sensitive. I apologize.

The statement that the TWS is sensitive to the reading of AWA is interesting so I checked it out. Let's say you can only read the masthead fly within 5 degrees. That is afterall half the width of half the flag and that is a pretty big error. Just checking I used a TWS of 10 knots and an TWA of 45 degrees with 6 knots of boat speed. Changing the AWA by +- 5 degrees changes the TWS calculation by about 4 percent. The TWA is another matter. You will obviously never get the TWA any better than you can read the masthead fly and in fact there is a multiplier effect so a 5 degree error in reading the masthead fly will give you a 7 degree TWA error. That is huge. But then again, TWA was not the topic. Checking the 70 degree rule of thumb for the same 5 degree AWA reading error shows a 7% error in the TWS calculation. This is less than a knot in most cases and I would assume more accurate than reading the sea state. Errors in reading the AWS will obviously translate to an error in the TWS result. That will be a 1:1 error. Boat speed error would also enter into it per the rule of thumb formula. Where you stand in taking the measurements will be most important and I don't know the size of the error from that. Aiming the wind meter will cause an error but that is small, likely less than 2%. What I am trying to say is that there are errors no matter how you do this measurement. The masthead measurement has errors that the handheld does not have and visa versa. I don't see it as a garbage in garbage out situation at all. There are errors but I don't think it is garbage. But I respect the opposite opinion. I wonder if anyone with strong opinions has actually taken any data.



#50 allen

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Posted 30 April 2012 - 12:15 AM


Along those lines, how many people who are posting trash in this thread race against boats that owe them over a minute a mile and beat them boat for boat? Allen


Welllll, since you ask, I do. Regularly.

Without instruments other than speed and compass.
And I have not been posting trash, just trying to give you another viewpoint and anecdotal redirection.


And I appreciated your post and said so.

#51 SoAPieceOfStringWalksIntoABar...

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Posted 03 May 2012 - 01:15 AM

I think you're missing that many (most?) wind instruments have built in or adjustable upwind and downwind corrections and calibrations. My less than $2k nexus package had a mini-brain that allowed some laptop tuning, and that was 10 years ago. I think the instrument folks aren't as trig daft as you imply.

#52 allen

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Posted 03 May 2012 - 01:54 AM

I think you're missing that many (most?) wind instruments have built in or adjustable upwind and downwind corrections and calibrations. My less than $2k nexus package had a mini-brain that allowed some laptop tuning, and that was 10 years ago. I think the instrument folks aren't as trig daft as you imply.


I think you are right. The Nexus package at $1300 and a computer at $700 would correct for upwind-downwind. But to get the correction for angle of heal you need the fancy compass at+$700. Mbybe that was only $2000 10 years ago or maybe you are just talking about upwind-downwind. But with all that I think it would definitely be better than a hand held reading on deck, no question. I said $4000 but maybe it is "only" $3000 ish. From the specs, that would be better than any TackTick system, which was my benchmark as it is so popular. As far as I know, the TackTick does not compensate for upwind vs downwind and from my personal observation on the J-105 I race on, it is not very accurate. I could be wrong about it not compensating but I am not wrong about not seeing consistent readings in the same wind with different points of sail.

One thing that bothers me is that the skipper of the J-105 has targets and sails to the true wind target. I think he should sail to the boat speed target. Too many errors are possible in the true wind angle target.

Allen

#53 Balder

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Posted 03 May 2012 - 07:07 AM


Anyone who thinks that the time to change sails is at a given wind speed is barking up the wrong tree.


Shit, something we agree on...what's the world coming to. I still think you and DoRag should do a Thelma and Louise off a cliff.



THAT is the best idea I have heard in a year!

#54 I'moutahere

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Posted 03 May 2012 - 08:09 AM



Anyone who thinks that the time to change sails is at a given wind speed is barking up the wrong tree.


Shit, something we agree on...what's the world coming to. I still think you and DoRag should do a Thelma and Louise off a cliff.



THAT is the best idea I have heard in a year!

And another intelligent comment from a moron who cannot contribute anything but shit to any forum. Why do you bother posting such crap? Does it make you feel good? Like that warm feeling in your pants when you piss yourself because you can't leave the keyboard alone.




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