USCG Exam Question: Apparent Wind

[TeddyDiver]

Beebob, having hard time to draw vectors?

[fryewe]

Originally Posted by goboatingnow

Sorry , a beam reach is where the sails are trimmed to roughly the wind coming at right angles to the boat as you sail along

That's apparent wind.

Points of sail refer to that experienced by the boat -again that is apparent wind.

I think this is correct.

Consider a situation with true wind directly on your beam at ten knots, and you are tied to a pier. You cast off lines and unfurl a gennaker, gaining speed until true boat speed is 4 knots, while maintains course at the heading of the pier your just left.

What is apparent wind speed and what is its direction after gaining speed? It's the vector sum of the true wind and the negative boat speed vector, and that is 10.8 knots, blowing from about two points forward of the beam, or about six points off the bow.

That's not a beam reach, but is a close reach.

The diagrams used for sail training are simplistic. The ones I have simply show "wind" from various points relative to a boat on variously points of sail.

Apparent wind determines how we present and shape the sails. The energy delivered to those sails depends on the magnitude of the true wind as a component of that apparent wind.

[Seaworthy Lass]

Originally Posted by beebopbogo

As you can see by these two vector diagrams (One with the boat 90 degrees to true wind, the other 90 to apparent) the coast guard defines a beam reach as relative to the apparent wind.

If you choose to define a beam reach relative to true, you will get the answer wrong on the test.

Here's a reminder of the original question as spit out by the USCG test. They clearly state number 4 is correct:

Question 8. You are sailing at 8 knots on a beam reach in an apparent wind of 25 knots. Which statement is TRUE?:
1. The true wind is a little abaft your beam, at just under 25 knots.
2. The apparent wind at the top of your mast will be slightly stronger than 25 knots and slightly farther forward than the wind at deck level.
3. If you turn to a close reach, the apparent wind will reduce in strength.
4. None of the above are true.
You chose 1. The CORRECT answer was number 4 , None of the above are true..

I agree that the coast guard seem to be referring to beam reach as being relative to apparent wind, but it actually doesn't matter - 1. is wrong regardless, as it states the true wind is abaft your beam.
Strictly speaking "a beam reach" is with the wind perpendicular to your beam, not "a little abaft it".
So 4. is the correct answer regardless .

Personally, I have always personally taken "wind abeam" to mean apparent. Also, if the true wind is at 120° and my apparent wind is at 60°, I would say I was on a shy (or close) reach, not a broad reach. Same goes if the true wind is 140° and the apparent wind is at 90°, I would always say I was on a reach, not a broad reach.

The term "abeam" applies to the boat, so to me it is logical that the term "wind" in "wind abeam" is also relative to the boat (ie apparent). Fast cats with speeds faster than true wind, do put a different spin on the usefulness of this terminology though.

If you consider apparent wind is incorrect, why choose true wind, why not ground wind? A boat does not sail to either true or ground wind, so selecting true seems a bit arbitrary

SWL

[conachair]

Tempting to say it doesn't matter, but apparently that's not true for everyone. Well, it's all relative really

[fryewe]

Originally Posted by beebopbogo

As you can see by these two vector diagrams (One with the boat 90 degrees to true wind, the other 90 to apparent) the coast guard defines a beam reach as relative to the apparent wind.

The second of the two vector diagrams shows an impossibility...a right triangle with a leg longer (greater than 25 knots) than the hypotenuse (25 knots).

[beebopbogo]

Gah! The bottom diagram's "True > 25 kts" should read "True < 25 kts."

[jheldatksuedu]

The only thing that is obvious is the beam reach is not well defined. I choose the true wind definition because then the point of sail has a good reason to sail it, no loss or gain to windward, it also would be an equal heading for all vessels, and accomplish something that might be desirable. Granted the apparent wind definition is more easily sailed, but accomplishes nothing important and would be a different heading for each vessel. If possible points of sail should have some meaning other than just be easy to do while on a moving boat. Any charts that I have seen of points of sail depict it and all points of sail off true wind and never mention apparent wind. I suspect that the problem of the lack of good definition has arose due to the fact it has never been well defined, and it really is not that important to do so. Much like I used to assume I was on a beam reach when the apparent wind was 90 degrees off the centerline of my moving vessel. I have now been forced to really consider the problem. I feel I have now been educated. You can make up your own mind.

[monte]

A couple of points/questions on the subject. When was the term forst coined? Probbaly in the 1800's? Did they define between TWA and AWA then?Did anyone onboard know what a vector was (maybe the Captain?) Did they use the terms (beam reach, broad reach, close hauled etc) for navigation, or did they use them to convey to the crew quickly in simple language how the vessel should be trimmed?
Also, the basic modern diagrams in every sailing book that show points of sail, never define the vessel type, speed, windspeed etc, they simply show the wind direction, point of sail and sail diagram, usually saying a beam reach, wind on the beam, sails set at 45 degrees. Depending on the yacht speed and windspeed, sail setting diagrams couldnt hold true for all vessels if TWS is refered to. As mentioned above, an off the beach cat sailing at 90 degrees to true wind will have Apparent wind well forward, and sails set for a close reach (as per the diagrams)
The main time I would use any of those terms would be explaining the effect of an upcoming course change in basic, simple, easy to understand terminology..
"After we round this bouy we will be gybing and heading toward our next waypoint on a broad reach" to basicly convey how the sails will be set, preperations to make beforehand (adjust travellers. jib track etc) for the new point of sail.
Anyway, chose your poison, whatever works for you. AWA works for me.

[Wotname]

Goboatingnow, SWL and others have it right (IMO ).

Points of sail is simply (and must be) referenced to apparent wind; determining points of sail by reference to true wind is simply hogwash!

A simple explanation:

The other day I sailing down a narrow straight channel setting a cracking pace (for me) and was overtaking a somewhat slower boat. At the same time I was being overtaken by pretty fast cat.

The wind I was experiencing (i.e. the apparent wind) was exactly 90 degrees to my fore aft line. I reckon I was on a beam reach.

The slowcoach had the same wind but it was clearly was about 100 or 110 degrees from his bow. I reckon he was on a broad reach.

The speedy cat had the same wind and it looked about 70 to 80 degrees from his bow. I reckon he was on a close reach.

If we were to reference our points of sail to the true wind, we would have been all on the same point of sail - the true wind was the same and the heading was the same for all three points.

Clearly no sailor would suggest the speedy cat and the slowcoach were on the same point of sail. The speedy cat had the wind afore the beam while the slow coach had the wind abaft the beam (and same heading remember).

The only logical way is to reference the point of sail to the apparent wind of each vessel.

[lancelot9898]

Sails are adjusted to apparent wind direction so that as the boat moves through the water the true wind direction moves aft. ( or to state it the other way..the apparent wind moves forward as the boat speed increases) So if I'm sailing at 8 knots and on a beam reach the true wind direction is aft of the beam. 1 is the correct answer.

[jheldatksuedu]

Originally Posted by Wotname

Goboatingnow, SWL and others have it right (IMO ).

Points of sail is simply (and must be) referenced to apparent wind; determining points of sail by reference to true wind is simply hogwash!

A simple explanation:

The other day I sailing down a narrow straight channel setting a cracking pace (for me) and was overtaking a somewhat slower boat. At the same time I was being overtaken by pretty fast cat.

The wind I was experiencing (i.e. the apparent wind) was exactly 90 degrees to my fore aft line. I reckon I was on a beam reach.

The slowcoach had the same wind but it was clearly was about 100 or 110 degrees from his bow. I reckon he was on a broad reach.

The speedy cat had the same wind and it looked about 70 to 80 degrees from his bow. I reckon he was on a close reach.

If we were to reference our points of sail to the true wind, we would have been all on the same point of sail - the true wind was the same and the heading was the same for all three points.

Clearly no sailor would suggest the speedy cat and the slowcoach were on the same point of sail. The speedy cat had the wind afore the beam while the slow coach had the wind abaft the beam (and same heading remember).

The only logical way is to reference the point of sail to the apparent wind of each vessel.

It all depends upon your reason for defining points of sail, 1. Is it a direction with respect to the wind or 2. Is it a term used to determine the set of the sails. I think it is a direction, since the diagrams, show changes in direction of the boats involved. I admit they also show differences in set of sails, so since it is not defined, one cannot really know until one finds a historical definite answer.

On a cat your basically going to have the sails set mostly for a close reach no matter what direction your going until you start to lose speed going down wind so to used the term on a cat is rather ridiculous for set of sail.

Once again I say, it really makes no difference, there is no right answer, until history proves one of us wrong, but I'll choose directions and true wind and all vessels would have the same direction on the same point. I think that was the point of the direction in the first place. LOL

[jackdale]

My "simple" notes on apparent and true wind.

http://www3.telus.net/jackdale/TrueandApparentWind.pdf

Anyone notice that as you accelerate when close hauled, you need to bear away to maintain the laminar flow over you sails?

[capt jgw]

That's one of the harder questions on the aux sail exam. Most of them are like "what's that pole standing up in the air called?"
These questions were not written by sailors.

[Cadence]

It look academic. I guess the law of sines applies? Those little ribbons on the sail and stays work well.

[OldFrog75]

Originally Posted by lancelot9898

Sails are adjusted to apparent wind direction so that as the boat moves through the water the true wind direction moves aft. ( or to state it the other way..the apparent wind moves forward as the boat speed increases) So if I'm sailing at 8 knots and on a beam reach the true wind direction is aft of the beam. 1 is the correct answer.

But the test results say #1 is incorrect, therefore the USCG is defining beam as relative to True wind.