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Old 13-12-2009, 10:43   #91
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I would argue that knowledgeable mariners are already doing precisely that.

I'll give you an example of where the Beaufort system provides more useful data than an anemometer would: I'm Faculty Advisor for a university sailing team. We race three to six boats (Collegiate Flying Juniors) at once, and depending on the regatta each boat will compete in two or three short races before coming in to exchange crews. It would not be legal for us to put someone out in a chase boat and report wind speeds. (A violation of the rule on "outside help.") However, we can stand on shore and observe sea state. Thanks to the Beafort scale we can do this objectively. We use this data to help decide whether to put a lighter or heaver crew with each skipper. For example, I know that Skipper A does better with Crew A in Force 3, but that he'll do better with Crew B in Force 4. And once it reaches Force 5, we yank Skipper A and put Skipper B in with Crew B.
Yes, but can't you do exactly the same with an estimate of wind speed, using the same observation techniques ? It's not the Beaufort scale per see that allows you to do this, but your experience in observing the sea state. I could go down the shore with the written description of the Beaufort scale and estimate the force level. Or I could go down, look at the sea and say to myself "looks about 15-20 knots". The 2nd method would be far more accurate for me, since I have experience using it.
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Old 13-12-2009, 12:37   #92
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now there's an idea

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Yes, but can't you do exactly the same with an estimate of wind speed, using the same observation techniques ? It's not the Beaufort scale per see that allows you to do this, but your experience in observing the sea state. I could go down the shore with the written description of the Beaufort scale and estimate the force level. Or I could go down, look at the sea and say to myself "looks about 15-20 knots". The 2nd method would be far more accurate for me, since I have experience using it.
Truly, I wish we could convince coaches from other colleges to ignore sea state in favor of wind speed. We'd win far more regattas if they did so.
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Old 13-12-2009, 12:55   #93
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I don't think I said anything about ignoring sea state.
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Old 13-12-2009, 15:49   #94
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Only know what I read (not an experienced Sailor) and then, like I said, I just know what I read but not necessarily that what I've read is correct.
Having said that ..... tell me if I've go this right.

The Beaufort system does indeed provide more useful data then windspeed does (for the purpose of safety). Wind speed alone would not take into account tide, current speed (and direction of) or fetch where with the Beaufort system it doesn't care what made the sea this way, it just is. Wind as a component would contribute to the sea state but by it self may only be part of the cause of the observed sea condition. And as some else said, waves (sea state) is generally more dangerous than wind. Of course there is a relationship, just not always the same relationship.

As for racing, perhaps in most sea states, wind speed alone would be more valuable?

Let me know,
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Old 13-12-2009, 16:41   #95
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Erhmmm... no. The resistance of the mechanical indicator is so low that it doesn't matter how dense the air is, it will always turn at the same speed as the windspeed. It has no sensors to measure the force, because those would create friction and slow the indicator down, resulting in a mis-reading for wind speed.

Guys, pick up a book if you don't believe us posters here, this is a well documented thing and known for ages.

cheers,
Nick.
So you are saying that a sailboat in 5kts of wind at 10,000 feet will go slower?
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Old 13-12-2009, 17:31   #96
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this depends on the boat

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As for racing, perhaps in most sea states, wind speed alone would be more valuable?
not in a small boat. certainly not in dinghy sailing or sportboats. or ULDB ultralights.
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Old 13-12-2009, 18:04   #97
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not in a small boat. certainly not in dinghy sailing or sportboats. or ULDB ultralights.
Fair enough.
I got my say nothing, "perhaps in most" line in on the sea state but missed the boat size.

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Old 13-12-2009, 20:52   #98
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So you are saying that a sailboat in 5kts of wind at 10,000 feet will go slower?
If the density of the air is less and the rest is all the same, yes of course the boat will be slower. Less energy equals less speed unless the boat is already at maximum hull speed in which case the extra energy is mostly transferred to a bigger wake.

cheers,
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Old 13-12-2009, 21:08   #99
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Boy oh boy.

I never realised the Beaufort scale was so hard to use!
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Old 13-12-2009, 21:23   #100
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Roger,

It is certainly hard to learn just from the written description, which is all some of us have to go by.
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Old 14-12-2009, 05:29   #101
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Boy oh boy.

I never realised the Beaufort scale was so hard to use!
I realize this post is probably TIC but interestingly (at least interesting to me) was that the problems encountered were far worse before Sir Francis B invented the scale.

Also interestingly regardless of what has already been posted, the original scale was referenced to what sail a Man of War could carry rather than the sea state. It was only with the introduction of steam powered vessels did the scale become referenced to sea state and then later again, wind speed.

From Wikipedia - The initial scale of thirteen classes (zero to twelve) did not reference wind speed numbers but related qualitative wind conditions to effects on the sails of a man of war, then the main ship of the Royal Navy, from "just sufficient to give steerage" to "that which no canvas sails could withstand." [1] At zero, all his sails would be up; at six, half of his sails would have been taken down; and at twelve, all sails would be stowed away

and later : In 1906, to accommodate the growth of steam power, the descriptions were changed to how the sea, not the sails, behaved and extended to land observations. Rotations to scale numbers were standardized only in 1923.
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Old 14-12-2009, 08:29   #102
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If the density of the air is less and the rest is all the same, yes of course the boat will be slower. Less energy equals less speed unless the boat is already at maximum hull speed in which case the extra energy is mostly transferred to a bigger wake.

cheers,
Nick.
So if I push the anemometer with my finger at altitude it is easier or harder to push on?

Rather than play 20 questions the answer is that the anemometer is a mechanical device and the force required to move the device is the same.

Therefore if the air is less dense at altitude you need more windspeed to generate the same mass to push the device. So at a given indicated windspeed the mass is the same.

With the same mass you get the same indicated speed and the sails see the same mass so the performance is the same.

Now density is more sensitive to temperature than altitude so it matters most in the summer at a hot high lake.
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Old 14-12-2009, 09:52   #103
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From a practical standpoint, I don't refer to it (or the anemometer) in the moment. What counts is how the boat is reacting with what's right in front of me. Afterward, it's fun to refer to the scale to put the experience in context, but I don't call for reefs etc. based on numbers, but on what the boat needs (wind state+ sea state)
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Old 14-12-2009, 10:31   #104
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The anemometer on my boat failed about five years ago. I didn't bother getting it fixed. I found that I preferred to get my information about the wind from the sea, the sails, the sounds in the rigging, the feel of it on my face, and the way the boat responded.

The only time I wished I had it working was when I had crew onboard who weren't experienced enough with the boat. They felt lost without a digital display of windspeed and direction.
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Old 14-12-2009, 11:23   #105
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So if I push the anemometer with my finger at altitude it is easier or harder to push on?

Rather than play 20 questions the answer is that the anemometer is a mechanical device and the force required to move the device is the same.

Therefore if the air is less dense at altitude you need more windspeed to generate the same mass to push the device. So at a given indicated windspeed the mass is the same.

With the same mass you get the same indicated speed and the sails see the same mass so the performance is the same.

Now density is more sensitive to temperature than altitude so it matters most in the summer at a hot high lake.
Oh no no no, you asked if the boat would sail faster or slower, not if the anemometer would turn slower or faster. So, my reply was about boat speed, not about the windspeed indication because you told me it would show 5 knots in both situations.

When the indicator shows 5 knots, it's 5 knots no matter how dense the air is. Even when you put it in the water like a water mill and it shows 5 knots then that's the speed of the water flowing by.

The indicator shows wind speed regardless of density. The only "but" is at very very light winds like < 1 knot where the friction in the device will degrade accuracy. From 1 knot up the wind has so much more energy regardless it's density that the friction is not a factor anymore.

Also, just think: the meter shows knots and that is a unit for speed, not for energy. It's like Volts which is the "tension" and not energy.

cheers,
Nick.
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