Is this true of all sailboats? As wind speed builds, you can sail faster and closer to the wind up to a point. Then windage and the ability to carry enough sail takes over and you begin to sail slower into the wind and further off. As the wind continues to build you must sail so far off that you are now sailing downwind.
The nature of sail
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The faster the wind, the less sail you can have up (you have to reduce sail to depower the rig). Also the faster the wind, the closer the apparent wind angle is to the true wind angle which means you can point closer to the true wind angle. However, there comes a time when you've reduced sail so much that the wind forces blowing against the hull exceed the forces generated by the sails so the boat will be blown more off the wind.
So answer is yes and no.
So answer is yes and no.
"As the windspeed builds ..." No, actually this is a mathematical phenomenon of 'apparent wind'. The lighter the wind speed, the higher you can point; conversely, the higher the windspeed the more the apparent wind will 'seem' to be coming more aft.
With super fast planing sailboats and ice boats .... you can be on a 'full beat' and be coming almost 'dead downwind'.
"Then windage and the ability... " Actually the 'restorative forces from the hull' are being overwhelmed by the energy imparted from the wind to sails .... nutherwords the hull shape/bouyancy, etc. isnt strong enough to keep the boat upright.
"As the wind continues to build you must sail so far off that you are now sailing downwind".
True - With super fast planing sailboats and ice boats .... you can be on a 'full beat' and be coming almost 'dead downwind'. Again its a mathematical anomaly of apparent wind.
Not true Rich. With a boat speed of 5 knots and the apparent wind speed of 20 knots and the apparent wind angle of 30 degrees, the true wind angle is 39 degrees. Now if the apparent wind dropped to 10 knots and you kept the same speed and apparent wind angle, then the true wind angle would be 52 degrees. These numbers prove opposite of what you said.
As the true wind speed increases, the true wind angle and the apparent wind angle get closer together.
Note: we are talking about true wind speed, not apparent wind speed. Apparent wind speed can increase because the boat speed increases which will do what you are saying, but it's not what we are talking about here.
As the true wind speed increases, the true wind angle and the apparent wind angle get closer together.
Note: we are talking about true wind speed, not apparent wind speed. Apparent wind speed can increase because the boat speed increases which will do what you are saying, but it's not what we are talking about here.
Sorry your math is off. At the lower wind speeds the boat speed is also diminished; conversely and until you reach 'hull speed', boat speed increases. Its the boat speed versus the trigonmetric function in the Y direction component that yields apparent wind. Only after you reach 'hull speed' does the apparent wind then shift again to 'more forward'.
Just look at any boat's 'polar diagram' and see the graphic geometric progression of 'pointing angle' vs. windspeed. You'll find that 'Pointing angle' drops as windspeed increases for 'displacement' hulls.
.... and I dont think about this when Im closehauled and 'pointing' when coming downwind in my ancient DN iceboat.
No it isn't....came straight from a True Wind calculator. Plug in the numbers I gave you and you will see.
http://www.sailingusa.info/true_wind_calculator.htm
My boat can do 5 knots in 10 knots apparent as well as 20 knots apparent so no, the boat speed doesn't have to change, but to keep the same speed, I'd have to put out more sail and fall off to get back to the 30 degree apparent wind angle that changed when the wind went from 20 knots to 10 knots.
Franklin .... simply look at your (or any) boat's 'polar diagram'. You can sit there with your boat's centerline pointing directly into the true wind, and with the sail 'stalled'/not working except for the leech giving a wee bit of drive .... doesnt prove anything. There's a very fine line between 'pointing' and pinching.
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and if you looked at your example, it proves my point and so does the one I attached. The color red is a much fast wind than the color green and as you can see in the diagram, you can sail at a much lower angle in red than you can in green. Even the maxium VMG is at a lower angle in higher winds as the diagram proves.
http://www.google.com/imgres?imgurl...mage_result&resnum=4&ct=image&ved=0CBMQ9QEwAw
http://www.google.com/imgres?imgurl...mage_result&resnum=4&ct=image&ved=0CBMQ9QEwAw
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however, there is another exception to the rule not including the one I posted earlier. That is, where are we sailing? If we are sailing in protected waters then it's as stated above, but if we are sailing in open waters, then there are other factors to consider.
a) As the wind increases, the size of the waves increase which means:
Summary: where you are sailing and how hard you want to push the boat also has a lot to do with how close you get to the wind.
a) As the wind increases, the size of the waves increase which means:
1) the distance traveled is longer due to having to ride up and down the waves
2) the constant motion of the boat reduces the effectiveness of the sails due to the wind seperating from the sails
3) One will not want to sail so close to the wind, because with the apparent wind angle being much closer to the true wind angle, that means you are beating more directly into the waves and will be bashing down the back end of the steep waves which is very hard on the boat.
In those cases, you may want to fall off the wind a little for a nicer ride, so say you change the awa to 50 and your boat speed over ground increases to 6 with an apparent wind of 28, then the true wind angle is now 61 degrees. Lets compare that to say 5 knots of speed over ground with a AWA of 38 degrees (much more realisitic than 30 that I used before) and an apparent wind speed of 10 knots that will give me a true wind angle of 65 degrees. As you can see here, the angles are much closer (65 - 61 = 4 degrees difference) however, 50 AWA may not be comfortable enough so if you drop down to 60 AWA, then the true angle is 72 degrees and now you are loosing a bit of ground compared to the nice low wind speed of 7 knots true.2) the constant motion of the boat reduces the effectiveness of the sails due to the wind seperating from the sails
3) One will not want to sail so close to the wind, because with the apparent wind angle being much closer to the true wind angle, that means you are beating more directly into the waves and will be bashing down the back end of the steep waves which is very hard on the boat.
Summary: where you are sailing and how hard you want to push the boat also has a lot to do with how close you get to the wind.
oh yeah, and if you also want to throw in the variable of swells from high winds off in the distance that you don't have, then that 7 knots true wind may not provide enough force to keep the boat stable and therefore the wind will seperate from the sails making them less effective, which will slow down the boat. The angle will be the same as the high wind (slower boat makes awa closer to true wind angle also) but the VMG will be much slower so it's a mute point.
Great discussion Franklin & RichH
Would anybody care to come to some conclusions?
Lemme try to make it easier: forget the sea state cr*p, try to answer the apparent wind thing, all by itself. You're at hull speed. Avoid the distractions, just the math, please.
That would be really helpful.
Would anybody care to come to some conclusions?
Lemme try to make it easier: forget the sea state cr*p, try to answer the apparent wind thing, all by itself. You're at hull speed. Avoid the distractions, just the math, please.
That would be really helpful.
Well, first of all, it's not Cr*p. Second of all, I already did prove it but I'll give you another set of numbers.
You said "at hull speed". Well, I have never reached hull speed when trying to go up wind, only on reaches, but I'll give you numbers that I have done with the wind angles.
You said "at hull speed". Well, I have never reached hull speed when trying to go up wind, only on reaches, but I'll give you numbers that I have done with the wind angles.
Boat speed = 7 knots, AWS = 16 knots, AWA = 45, TWA = 69.13
Boat speed = 7 knots, AWS = 20 knots, AWA = 45, TWA = 63.21
With just four knots stronger wind, keeping the same apparent wind angle, I am doing almost 6 degrees closer to true wind angle.
Note: hull speed on my boat is 7.6 knots.Boat speed = 7 knots, AWS = 20 knots, AWA = 45, TWA = 63.21
With just four knots stronger wind, keeping the same apparent wind angle, I am doing almost 6 degrees closer to true wind angle.
And if you want to use polar diagrams, then look at the one I posted for the HannaMaria in the link. The diagram says it can do 5 knots just 30 degrees off true wind with a wind in the range of 13 knots to 17 knots of wind. The diagram also says that the boat can only get to about 40 degrees off of true wind and reach 5 knots with winds between 6 knots and 10 knots.
So, the polars say it and the true wind calculator says it. What more facts do you need?
I know it sounds strange, that a boat can go faster and closer to the wind when the wind is blowing against it, but it's true as long as waves aren't an issue, however, ask any racer and they will tell you that waves are a hugh problem when trying to sail up wind.
So, the polars say it and the true wind calculator says it. What more facts do you need?
I know it sounds strange, that a boat can go faster and closer to the wind when the wind is blowing against it, but it's true as long as waves aren't an issue, however, ask any racer and they will tell you that waves are a hugh problem when trying to sail up wind.
Perhaps I shouldn't have used that word
so please forgive me. I was attempting to get the discussion off a tangent where so many other factors come into play. And I think I understand that you don't reach hull speed on a beat. But that's another of my extraneous factor things.
Gimme some time to digest your latest.
so please forgive me. I was attempting to get the discussion off a tangent where so many other factors come into play. And I think I understand that you don't reach hull speed on a beat. But that's another of my extraneous factor things.
Gimme some time to digest your latest.
Which is closer to the true wind really isn't important at all in most situations because we sail to apparent wind, however, it is important for trip planning and that's why I brought up the wave variables as it's very important information to understand when you are planning to do an upwind leg or trip. Sure, most avoid going to wind for trips but sometimes you just gotta do it and knowing how to plan for it is important.
Basically, don't plan on doing better than 50 degrees of the true wind angle. If the wind is light you will not be able to make any ground pointing higher and if the wind is strong, most likely the waves will make you want to fall off to 50+. Trust me, I've been there. When you come down that wave and the boat bashes into the trough and it sounds like somebody took a sledge hammer to your hull, you'll at least re-think that wind angle.
This is the reason I don't want to take my boat on the Regatta de Amigos race again as it's almost always a beat the whole way and when you get a weather forcast that you don't like just days before the race, most likely you will not want to upset the crew by cancelling at the last minute after they've worked so hard to get ready.
Basically, don't plan on doing better than 50 degrees of the true wind angle. If the wind is light you will not be able to make any ground pointing higher and if the wind is strong, most likely the waves will make you want to fall off to 50+. Trust me, I've been there. When you come down that wave and the boat bashes into the trough and it sounds like somebody took a sledge hammer to your hull, you'll at least re-think that wind angle.
This is the reason I don't want to take my boat on the Regatta de Amigos race again as it's almost always a beat the whole way and when you get a weather forcast that you don't like just days before the race, most likely you will not want to upset the crew by cancelling at the last minute after they've worked so hard to get ready.
I couldn't agree more
Absolutely right, and very well said.
Those three paragraphs are enough to wrap a good short story around! :wow:
Another reason why I just simply don't understand sailboats motoring into a 15 to 20 kt breeze.
Absolutely right, and very well said.
Those three paragraphs are enough to wrap a good short story around! :wow:
Another reason why I just simply don't understand sailboats motoring into a 15 to 20 kt breeze.
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