Instruments set to True or Apparent wind

[flaming]

I'm not clear if the first part is a quote which you are rebutting. If that is the case, I agree with you. Apparent is what you feel when on board and to which you both adjust your sails and reef or deploy accordingly. It is not uncommon to be enjoying a downwind romp in 25kn of true wind under full sail and be faced with the need to reduce sail when turning the corner.

What you're describing there is the simple fact that your boat can hold more sail when going downwind that when going upwind, a concept familiar to anyone who's flown a spinnaker.

But again, apparent wind is something of a distraction here. If I have my wind instruments set to apparent, how am I supposed to know how much apparent wind I'll have when I turn round and go upwind? I have to do maths... But if I routinely use True wind, then when I'm I'm going downwind in 25 true I know that if I turn around I'm definitely going to need to reef just by looking at the number.

I do understand the basic attraction of apparent, but If you understand that the measure of power that is available to your boat is the difference in velocity between the water and the air then it quickly becomes clear that this is the only number worth displaying if you want anything approaching usable repeatable readings.

 

[johnalison]

What you're describing there is the simple fact that your boat can hold more sail when going downwind that when going upwind, a concept familiar to anyone who's flown a spinnaker.

But again, apparent wind is something of a distraction here. If I have my wind instruments set to apparent, how am I supposed to know how much apparent wind I'll have when I turn round and go upwind? I have to do maths... But if I routinely use True wind, then when I'm I'm going downwind in 25 true I know that if I turn around I'm definitely going to need to reef just by looking at the number.

I do understand the basic attraction of apparent, but If you understand that the measure of power that is available to your boat is the difference in velocity between the water and the air then it quickly becomes clear that this is the only number worth displaying if you want anything approaching usable repeatable readings.

I understand what you are getting at but reject your didactic approach. In the first place, I have no great difficulty with the arithmetic. If I am sailing downwind at seven knots and the apparent wind is seventeen, then it is going to be a bit breezy when I turn round, roughly seventeen plus seven, plus about five, ie nearly thirty. Secondly, it is because sailing to the apparent wind is how I have always done it, before true became available to me, just as I still read my sounder from the transducer without adjustment. Thirdly, as I have said before, apparent gives me the wind angle on my sails and saves me craning my neck to look up, and fourthly, my meter responds more quickly to apparent, which may be important when there is a risk of a gybe. Unlike you, I make no general claims for my practice, only that it is what suits me.

 

[flaming]

I understand what you are getting at but reject your didactic approach. In the first place, I have no great difficulty with the arithmetic. If I am sailing downwind at seven knots and the apparent wind is seventeen, then it is going to be a bit breezy when I turn round, roughly seventeen plus seven, plus about five, ie nearly thirty. Secondly, it is because sailing to the apparent wind is how I have always done it, before true became available to me, just as I still read my sounder from the transducer without adjustment. Thirdly, as I have said before, apparent gives me the wind angle on my sails and saves me craning my neck to look up, and fourthly, my meter responds more quickly to apparent, which may be important when there is a risk of a gybe. Unlike you, I make no general claims for my practice, only that it is what suits me.

The maths isn't hard when you're going DDW, for sure. It just seems unnecessary when the box of tricks will do it for you though, and accurately through the whole range of wind angles. If you are helming in conditions where you really want AWA displayed as you describe, then you can of course switch the instruments over. On most displays it's just a simple button push. However from a cruising context I'm struggling to think of an occasion where I would conceivably drive the boat that close to a crash gybe with only the wind instruments to guide me.

You are of course free to continue to use your instruments exactly as you see fit, however as with the example of not offsetting your depth sounder, I don't think it could be argued that you are getting the most out of them. In some ways it's hard to see what you've really gained from having them over just a piece of wool in the rigging if you leave them to apparent.

 

[johnalison]

You are of course free to continue to use your instruments exactly as you see fit, however as with the example of not offsetting your depth sounder, I don't think it could be argued that you are getting the most out of them. In some ways it's hard to see what you've really gained from having them over just a piece of wool in the rigging if you leave them to apparent.

Passing the sounder issue - my nerves won't stand the business of sailing in 30cm of water - I am essentially a seat-of-pants sailor. Most of my information comes from what I can feel on my face, the feel of the helm, and what I can see around me, and probably my balance organs. I am less likely to be interested in the power available to me than in the dynamic forces acting on my boat in the frame of reference that I am living in. I do make extensive use of the facilities available to me, and my companions tend to think of me as a bit obsessed with detail and sail trim.

 

[Yealm]

But if I routinely use True wind, then when I'm I'm going downwind in 25 true I know that if I turn around I'm definitely going to need to reef just by looking at the number.

I think ground wind maybe even better for this..

 

[BelleSerene]

I think ground wind maybe even better for this..

Why? When you turn about, will you not still be sailing over the same water that’s moving at the same speed and in the same direction over the ground?

 

[wotayottie]

DO says true, DR says apparent...

https://youtu.be/Gmixvf9Ykmc

Thoughts?

Talking lots of nonsense. You sail to the wind not the instruments. You reef when the wind is getting too much for the sail plan , not when the instrument gives a certain reading. The only instrument you really need in coastal waters is your depth sounder - I've sailed for 3 years now without bothering to take out the blanking plug in my log shin fitting, and the wind instrument only works when it wants to do.

As for tidying up the boat before you leave it, I cluck about the thing like an old mother hen, partiularly the mooring ropes which have to be just so. Takes at leat half an hour after first tieing up.

 

[Yealm]

When you turn around the true wind will be current ground wind +/- tide but current true wind +/- (2*tide).

Ie current ground wind gives you a closer approximation to the new true wind when you turn around.

I think! Apolgies if I’ve got it wrong !

Why? When you turn about, will you not still be sailing over the same water that’s moving at the same speed and in the same direction over the ground?

 

[johnalison]

When you turn around the true wind will be current ground wind +/- tide but current true wind +/- (2*tide).

Ie current ground wind gives you a closer approximation to the new true wind when you turn around.

I think! Apolgies if I’ve got it wrong !

You can use the ground wind if you wish, but it just adds another number to be added/subtracted. Your chief frame or reference is the water that you are sailing on. Whether the ground is moving under the water doesn't affect the issue if you choose to ignore it.

If you sail downwind in 15 kn ground wind at 5kn with 5kn tide, your apparent wind will be 5kn, with the instrument showing a true wind of 10kn. When you turn round and sail at 5kn (or motor into the wind directly), the apparent wind will be 15kn and the true wind will still show 10kn.

 

[Yealm]

Apologies, you're absolutely right

You can use the ground wind if you wish, but it just adds another number to be added/subtracted. Your chief frame or reference is the water that you are sailing on. Whether the ground is moving under the water doesn't affect the issue if you choose to ignore it.

If you sail downwind in 15 kn ground wind at 5kn with 5kn tide, your apparent wind will be 5kn, with the instrument showing a true wind of 10kn. When you turn round and sail at 5kn (or motor into the wind directly), the apparent wind will be 15kn and the true wind will still show 10kn.

 

[Babylon]

....I am essentially a seat-of-pants sailor. Most of my information comes from what I can feel on my face, the feel of the helm, and what I can see around me, and probably my balance organs. I am less likely to be interested in the power available to me than in the dynamic forces acting on my boat in the frame of reference that I am living in. I do make extensive use of the facilities available to me, and my companions tend to think of me as a bit obsessed with detail and sail trim.

For me this is completely natural, and more than sufficient for efficient and enjoyable cruising (yacht racing is different).

I've only got a Windex and telltails, and an easily cleaned and therefore fairly accurate paddlewheel log. Remove these aids and I'll still make a good passage by feel and approximation.

With enough experience of any given physical activity, subconscious brain- and muscle-memory becomes highly efficient. (Hence my earlier allusion to golf.)

I therefore use apparent wind, but remain adequately aware at all times of true wind (Bridge).

 

[flaming]

Passing the sounder issue - my nerves won't stand the business of sailing in 30cm of water - I am essentially a seat-of-pants sailor. Most of my information comes from what I can feel on my face, the feel of the helm, and what I can see around me, and probably my balance organs. I am less likely to be interested in the power available to me than in the dynamic forces acting on my boat in the frame of reference that I am living in. I do make extensive use of the facilities available to me, and my companions tend to think of me as a bit obsessed with detail and sail trim.

It all comes down to what you are using your instruments for to be honest. What concerns me on these boards is the number of people who say things like "my boat needs reefing going upwind in 15 knots apparent". That is not a sensible statement as a key element in that measurement is the speed you are going, so I could change the apparent wind figure by sailing faster or slower, but I have not changed the amount of wind there actually is, so I haven't made a fundamental difference to when you need to reef.

So if you are the sort of person who uses their wind instruments to decide (or at least influence) when you reef then apparent is just not a sensible measure to use, especially when deciding what reefs to put in at the start of the trip. This is because the wind when you are hoisting the sail is different to the wind when you crack off and start sailing. And ground wind is equally as terrible as the tidal influence can be large.
In all those instances True wind is the only measure that stays repeatable from hour to hour and day to day to give reliable readings for use with decisions like "Shall I reef? Am I going as fast as I could be? Could I point higher?"
So when you have instruments that are capable of displaying that information it doesn't seem to me to make a lot of sense not to use it. After all, as you say the apparent information is being given to you by the seat of your pants!
For example, when I'm driving the race boat my second to second reactions are essentially dependant on apparent clues, but they are not instrument based. They are telltales, heel angle, rudder angle / pressure. The instruments come into it less frequently. Upwind it's a glance at the TWS and the boats speed. Am I fast enough? A less frequent glance at the TWA, is that correct, could I be higher? And then downwind, TWS and what TWA should I be doing for that windspeed? Ok, find it and then drive to the wave pattern, glancing at the TWA occasionally to check I'm about right.

 

[capnsensible]

I used to race a bit myself so am well aware of the joy of using things to the max. Its a buzz.

However I reckon the average Joe (me cruising) isnt that bothered about the intense use of instruments. It doesnt take much experience to recognise when to reef. Again, are the instruments calibrated anyway? Seen some shockers over the years and as for logs on charter yachts... nuff said.

Happily now back to one yacht so less to worry about. no wind instruments apart from the ever faithful windex. So I can relax in the knowledge that the boat will only ever need reefing about ten minutes after Im off watch......

 

[Yealm]

And ground wind is equally as terrible as the tidal influence can be large.

Disagree.

Tide speed is usually much less than boat speed- and in many places minimal or non-existent- so ground wind is generally a much better approximation to true wind (compared to apparent wind).

Secondly, paddle wheel measurement of true wind is pretty inaccurate, so in some cases, ground wind will be more accurate as a surrogate for ‘true’ true wind than ‘measured’ true wind!

 

[flaming]

Disagree.

Tide speed is usually much less than boat speed- and in many places minimal or non-existent- so ground wind is generally a much better approximation to true wind (compared to apparent wind).

Secondly, paddle wheel measurement of true wind is pretty inaccurate, so in some cases, ground wind will be more accurate as a surrogate for ‘true’ true wind than ‘measured’ true wind!

The ratio between tide speed and boat speed has nothing to do with the accuracy of the figure.

The only ratio that is important is the ration between tide speed and wind speed.

So a 2 knot (hardly uncommon) tide and a 6 knot ground wind could be as much as 8, and as little as 4 knots true. Which makes a massive difference to your boat's ability to sail.

 

[Yealm]

The ratio between tide speed and boat speed has nothing to do with the accuracy of the figure.

The only ratio that is important is the ration between tide speed and wind speed.

So a 2 knot (hardly uncommon) tide and a 6 knot ground wind could be as much as 8, and as little as 4 knots true. Which makes a massive difference to your boat's ability to sail.

I think you’re misunderstanding my post.

I was not comparing ground and true wind (in my first paragraph).
I was comparing ground and apparent wind- as to which is a better approximation of true wind. You stated ground wind is equally terrible. I think it’s much better.

Re my second paragraph- I agree true wind is very useful. But in places with small tides (where I sail- usually less than 1 knot)- ground wind is a reasonable approximation to true wind, particularly as true wind is inaccurately measured, relying on a paddle wheel. Added to that, I find paddlewheel cleaning a nightmare- so ground wind is a no-brainer!

 

[flaming]

I think you’re misunderstanding my post.

I was not comparing ground and true wind (in my first paragraph).
I was comparing ground and apparent wind- as to which is a better approximation of true wind. You stated ground wind is equally terrible. I think it’s much better.

Re my second paragraph- I agree true wind is very useful. But in places with small tides (where I sail- usually less than 1 knot)- ground wind is a reasonable approximation to true wind, particularly as true wind is inaccurately measured, relying on a paddle wheel. Added to that, I find paddlewheel cleaning a nightmare- so ground wind is a no-brainer!

I see what you're getting at, and in areas of no tide I can see the attraction. The problem with boards such as this is that the audience is wide however. And actually most of the audience is probably concerned with sailing on the South coast of England, where tides are large so the ground wind is frequently very misleading if you're using it as a substitute for true wind.
But then in areas of strong tides sailors are I think in general more likely to value a boatspeed reading in addition to a GPS speed, so the issue of an inaccurate paddlewheel far less likely to apply.

As with all these things though, if you know what the figure is actually reading, and the limitations of that, then you're fine. What has concerned me over a number of threads on this topic however is the number of posters who do not see that there is a difference between True and Ground winds.

 

[Yealm]

Yes, totally agree on all points

I see what you're getting at, and in areas of no tide I can see the attraction. The problem with boards such as this is that the audience is wide however. And actually most of the audience is probably concerned with sailing on the South coast of England, where tides are large so the ground wind is frequently very misleading if you're using it as a substitute for true wind.
But then in areas of strong tides sailors are I think in general more likely to value a boatspeed reading in addition to a GPS speed, so the issue of an inaccurate paddlewheel far less likely to apply.

As with all these things though, if you know what the figure is actually reading, and the limitations of that, then you're fine. What has concerned me over a number of threads on this topic however is the number of posters who do not see that there is a difference between True and Ground winds.

 

[noelex]

True, apparent and ground wind are all very usueful on a sailboat.

Apparent and ground wind are normally very accurate, in fact there is no calibration needed, or is possible on most systems, other than perhaps aligning the wind sensor so that it is facing correctly.

Unfortunately, true wind is subject to much more calibration and maintenance to achieve accurate results.

On a cruising boat I have found the combination apparant and ground wind is a great mix. Apparant wind tells me what wind the sails are experiencing, and ground wind tells me what the wind is truly doing without the influence of the boat or water movement. So one wind is referenced to water and the other is refrenced to the earth (so for example I can see if the wind matches the forecast). The main benefit with this combination is I know the the results are always accurate and can be trusted. I never have to wonder if some growth on the hull is creating turbulance and affecting the wind reading (as it will with true wind).

True wind, if accurate, is also nice to have, but even with modern instrument displays it is not easy easy to keep track of three different wind directions and speeds.

I would suggest people try all three options and see which they prefer, but it is important while doing this to understand what the information displayed means.

 

[westhinder]

It all comes down to what you are using your instruments for to be honest. What concerns me on these boards is the number of people who say things like "my boat needs reefing going upwind in 15 knots apparent". That is not a sensible statement as a key element in that measurement is the speed you are going, so I could change the apparent wind figure by sailing faster or slower, but I have not changed the amount of wind there actually is, so I haven't made a fundamental difference to when you need to reef.

So if you are the sort of person who uses their wind instruments to decide (or at least influence) when you reef then apparent is just not a sensible measure to use, especially when deciding what reefs to put in at the start of the trip. This is because the wind when you are hoisting the sail is different to the wind when you crack off and start sailing. And ground wind is equally as terrible as the tidal influence can be large.
In all those instances True wind is the only measure that stays repeatable from hour to hour and day to day to give reliable readings for use with decisions like "Shall I reef? Am I going as fast as I could be? Could I point higher?"
So when you have instruments that are capable of displaying that information it doesn't seem to me to make a lot of sense not to use it. After all, as you say the apparent information is being given to you by the seat of your pants!
For example, when I'm driving the race boat my second to second reactions are essentially dependant on apparent clues, but they are not instrument based. They are telltales, heel angle, rudder angle / pressure. The instruments come into it less frequently. Upwind it's a glance at the TWS and the boats speed. Am I fast enough? A less frequent glance at the TWA, is that correct, could I be higher? And then downwind, TWS and what TWA should I be doing for that windspeed? Ok, find it and then drive to the wave pattern, glancing at the TWA occasionally to check I'm about right.

Flaming, I have no doubt that what you say is good practice on your race boat.
But I feel you are overlooking the fact that whatever the dial is showing, True or Apparent, we always need an additional interpretation before we can make decisions.
Knowing that the TWS is 15 knots is not enough to decide whether to put a reef in the main or not. If I am going upwind, I know I will do a good 7 knots, so AWS will be over 20 and a reef will be needed. If I am going on a broad reach, AWS will be nearer 10, so definitely no reef.
As a cruising man, I tend to use Apparent when going upwind, because it is closest to what I feel and is in fact a visualisation of my own sensations. Going downwind in a fresh breeze I will often switch to True, because it will alert me to what will happen if I have to steer closer to the wind. It avoids an extra step in my mental calculations.
Most of the time my instruments will be on apparent, which reflects the fact that somehow I spend more time beating than running, but that may be just my luck ��