TRUE WIND/APPARENT WIND When I first started sailing, this subject always confused me. I understood there were two kinds of wind (true and apparent) but I'd mix them up from a direction standpoint and I did not understand the importance and significance of either. Also, I did not know which wind is used to trim sails. It is one thing to make a sail trim change and another to know why you are making the change. True Wind is the wind you feel when your not moving. It is the wind direction your mast head fly indicates when your sitting at the dock. Apparent Wind is a combination of the speed and direction of the true wind plus the speed and direction of your boat. When your sailing, the mast head fly shows the apparent wind. OK, now that we know the difference between true and apparent wind, what is the importance of knowing the difference between the two. The importance is that you trim your sails to apparent wind, which is the same wind you feel on your face while sailing. Also, the sail trim adjustment you make is always dictated by the wind speed and direction you are sailing in. The actual wind speed, as you'll see, may not be what you think it is. When you are sailing to windward, the wind feels stronger than it is because the boats forward movement is making its own wind. Let's say the wind, while your sitting at the dock, is blowing from the south at 10 knots. This is true wind. When you leave the dock and start sailing, let's assume your making 5 knots. Let's assume you could sail directly into the wind, which you can't, but if you could the combination of true and apparent wind would be 15 knots. Make a mental note of this calculation as it is directly opposite when sailing downwind. We all know we can't sail directly into the wind so what is the speed and direction of the apparent wind while sailing to windward on a port tack in the above example? The apparent wind speed is more than 10 knots but less than 14 knots plus the direction is a little east of north. As the boat starts to accelerate, the apparent wind moves forward and you have to trim your sails accordingly. When the boat reaches full speed, you won't have to make any further changes unless the true wind direction and velocity changes and we all know the wind direction and speed is never constant. What happens in a puff or a lull? The wind direction remains generally steady but the wind speed increases or decreases dramatically. In a puff, the apparent wind moves aft approaching the direction of the true wind. You should make a sail trim adjustment to compensate for this movement, which is to ease the sails. In a lull, the apparent wind moves forward or closer to the boats direction. You should make a sail trim adjustment to compensate for this movement, which is to trim in the sails. Remember that while sailing to windward you added your boat speed to the true wind speed to get the apparent wind speed. While sailing downwind in the direction the true wind is blowing you subtract your boat speed from the true wind speed to get the apparent wind speed. Using our example of 10 knots of true wind speed, use your imagination and assume your also sailing downwind at 10 knots, which would be a thrilling downwind ride. In this case, you would not feel any apparent wind. Continuing to use our imagination, assume you've slowed to 5 knots of boat speed. Even though the true wind is blowing at 10 knots, the apparent wind you would feel on the back of your neck is 5 knots. What is the significance of all this? The significance is that sailing downwind is more of a challenge than you'd think. You have to be ready to adjust your sails quicker than sailing upwind because the boat speed changes more dramatically to a true wind change going downwind than it does while sailing to windward. In a downwind puff, the apparent wind moves aft but as the boat picks up speed the apparent wind moves forward. This can catch the unwary sailor off guard. If he knew what was going to happen when he is hit by a puff, he could anticipate the needed adjustment he is going to have to make. If he is not careful, he ends up chasing the sail. It is like the tail (sail) is wagging the dog (trimmer). Knowing what happens to the apparent wind in a lull or a puff sailing upwind or downwind can make you a better sailor.
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Sail GTrim Asymmetrical
Don, Would you cover this same subject as it would apply to an asymmetrical spinnaker ?? Would like to know about the down wind apparant wind problems with the asym. Going dirctly down wind with a symm spinn has its problems we know. But can an asym be made to compete with the symm spinnaker even if one has to jibe several times ?? Bob Dean
Don, Would you cover this same subject as it would apply to an asymmetrical spinnaker ?? Would like to know about the down wind apparant wind problems with the asym. Going dirctly down wind with a symm spinn has its problems we know. But can an asym be made to compete with the symm spinnaker even if one has to jibe several times ?? Bob Dean
Windward Sailing in Heavy Weather
According to an article I read recently ,over 25 -30 knots of apparent wind,it is almost impossible to sail windward for the regular modern fiber boats. Experienced myself also the same thing many times: When you have strong wind and try to sail to windward,which direction you try to sail (within 60 -70 degrees of both tacks)the appr.wind always comes to you just ahead of the boat.And it's impossible to trim and sail in to the windward points without motoring. Is it really impossible for us(I have H340)and for the other modern boats to sail windward in strong winds ? Thanks..
According to an article I read recently ,over 25 -30 knots of apparent wind,it is almost impossible to sail windward for the regular modern fiber boats. Experienced myself also the same thing many times: When you have strong wind and try to sail to windward,which direction you try to sail (within 60 -70 degrees of both tacks)the appr.wind always comes to you just ahead of the boat.And it's impossible to trim and sail in to the windward points without motoring. Is it really impossible for us(I have H340)and for the other modern boats to sail windward in strong winds ? Thanks..
Sail GTrim Asymmetrical
Bob: Actually,I don't know a lot about spinnaker. My sail trim and seminar business involves dealing primarily with beginners to intermediates and I feel they have to have a good understanding of how to handle the jib before they move to spinnakers. Even when I race on spinn boats, I don't pay much attention to it. I have an idea of how it should work but I don't like to comment on subjects I know little about. Anyway, there is a great book on the subject , which is called "Performance Racing trim" by Bill Gladstone. If I was ever going to race in the spinn class, that book is where I'd start. Also, I wrote an 11 page piece on downwind sailing, which you can view at <http://kindred-spirit.net>. Go to that site and look for "Don Guillette article (11 pages) on downwind sailing". There has never been a lot written about downwind sailing but I think I have compiled most of what has been written in my article. You can easily pick off boats in front of you on that leg especially if they are the ones that use the downwind leg to have a beer and a sandwich.
Bob: Actually,I don't know a lot about spinnaker. My sail trim and seminar business involves dealing primarily with beginners to intermediates and I feel they have to have a good understanding of how to handle the jib before they move to spinnakers. Even when I race on spinn boats, I don't pay much attention to it. I have an idea of how it should work but I don't like to comment on subjects I know little about. Anyway, there is a great book on the subject , which is called "Performance Racing trim" by Bill Gladstone. If I was ever going to race in the spinn class, that book is where I'd start. Also, I wrote an 11 page piece on downwind sailing, which you can view at <http://kindred-spirit.net>. Go to that site and look for "Don Guillette article (11 pages) on downwind sailing". There has never been a lot written about downwind sailing but I think I have compiled most of what has been written in my article. You can easily pick off boats in front of you on that leg especially if they are the ones that use the downwind leg to have a beer and a sandwich.
Spinnaker reply
I have not been able to devise any formula for distinguishing apparent wind from true except to adjust by 45 degrees from true to gain apparent. Put another way, true wind is what you see on the waves and invariably is what you want but cannot seize because the apparent wind is taking you in the wrong direction. I believe Mr. Murphy covered this in one his laws. As to the asymetrical question, deep broad or downwind is fine if you let her balloon out. But a beam reach is often the fastest for the spinnaker, and happily a beam reach doesn't distort true wind from apparent.
I have not been able to devise any formula for distinguishing apparent wind from true except to adjust by 45 degrees from true to gain apparent. Put another way, true wind is what you see on the waves and invariably is what you want but cannot seize because the apparent wind is taking you in the wrong direction. I believe Mr. Murphy covered this in one his laws. As to the asymetrical question, deep broad or downwind is fine if you let her balloon out. But a beam reach is often the fastest for the spinnaker, and happily a beam reach doesn't distort true wind from apparent.
Asymmetrical spinnakers.l
To Don and all. A recent edition of the Hood Sail news letter (cover photo had boats with all black sails) had a good run down on the latest asymm sails and the newer cuts, designs and materials in use. One of their sail designers predicted that the asymm will replace the standard spinnaker/pole combo in 5 years. I like the idea of a big sail without the pole problem(s). Here on the Gulf Coast we can race in the spinnaker class with the asymm. The UK sail web page has a good rundown on asymm sailing - including tips for tacking etc. In any case if we only have 4 years and 300 some days to go - I want to get a head start. Bob Dean Hunter Legend 35
To Don and all. A recent edition of the Hood Sail news letter (cover photo had boats with all black sails) had a good run down on the latest asymm sails and the newer cuts, designs and materials in use. One of their sail designers predicted that the asymm will replace the standard spinnaker/pole combo in 5 years. I like the idea of a big sail without the pole problem(s). Here on the Gulf Coast we can race in the spinnaker class with the asymm. The UK sail web page has a good rundown on asymm sailing - including tips for tacking etc. In any case if we only have 4 years and 300 some days to go - I want to get a head start. Bob Dean Hunter Legend 35
Windward in heavy Weather (answer to Ersin)
Ersin, you must be doing something very wrong! Modern, medium-light finkeelers (and even bulbwingkeelers such as our Legend 43 "Rivendel II") go to windward much, much better than heavy fullkeelers. In fact, "Rivendel II" was one of the very few sailing vessels making regular runs against the strong SE Tradewinds back to Port Vila in the Vanuatu island chain. Although I have not quite figured out what sort of gymnastics you are trying to describe, the whole question of apparent versus true wind becomes relatively unimportant when beating into a 25 knot headwind since boatspeed will tend to be relatively small compared to true wind speed. However, you will need to flatten your sails as much as possible while not reefing the main too far or too early in order to maintain sufficient drive to punch through the waves. If you do have a large genoa which does not reef very well, you will either need to switch to a smaller sail, get a genoa capable of reefing (e.g. by using Aeroluff) or ,best of all, install an inner stay with staysail. Above 30 knots (and corresponding waves) it may be difficult for your 36 footer to keep making much progress (our 43 footer is usually able to keep going till 35 knots or so) and you may have to start thinking about heaving to. If properly done, the transition from slowly jogging against the winds and waves (at 35 - 45 degree apparent wind angles, but probably not doing much better than 50 -60 degrees when measured over the ground) to a hove-to position can be a logical, gradual progression. By deep-reefing the main one can first reduce boatspeed to only 2-3 knots causing the bow to start falling off a bit (as the rudder becomes depowered through the loss of speed). Then, by backwinding the jib (the clew can simply be pulled to windward in smaller or bigger increments and the helm countered proportionally; there is no need to make significant course changes) boatspeed will fall to 1-2 knots and consists now mostly of sideways drift. The deep-reefed, relatively loosely sheeted main still helps keep the bows pointing into wind and waves. Finally, by dropping the main one is left with only 1/2 - 1 knot sideways drift (under backed jib). However, because the bow tends to fall of further now this position is only tenable if wind and waves are slightly misaligned and one has sufficient searoom to chose the most favorable tack (i.e. the tack that keeps the bows best into the waves). Good luck trying some of this out yourself (or invite an experienced heavy weather finkeel sailor to sail with you and give you some pointers). Flying Dutchman "Rivendel II", Port Vila, Vanuatu
Ersin, you must be doing something very wrong! Modern, medium-light finkeelers (and even bulbwingkeelers such as our Legend 43 "Rivendel II") go to windward much, much better than heavy fullkeelers. In fact, "Rivendel II" was one of the very few sailing vessels making regular runs against the strong SE Tradewinds back to Port Vila in the Vanuatu island chain. Although I have not quite figured out what sort of gymnastics you are trying to describe, the whole question of apparent versus true wind becomes relatively unimportant when beating into a 25 knot headwind since boatspeed will tend to be relatively small compared to true wind speed. However, you will need to flatten your sails as much as possible while not reefing the main too far or too early in order to maintain sufficient drive to punch through the waves. If you do have a large genoa which does not reef very well, you will either need to switch to a smaller sail, get a genoa capable of reefing (e.g. by using Aeroluff) or ,best of all, install an inner stay with staysail. Above 30 knots (and corresponding waves) it may be difficult for your 36 footer to keep making much progress (our 43 footer is usually able to keep going till 35 knots or so) and you may have to start thinking about heaving to. If properly done, the transition from slowly jogging against the winds and waves (at 35 - 45 degree apparent wind angles, but probably not doing much better than 50 -60 degrees when measured over the ground) to a hove-to position can be a logical, gradual progression. By deep-reefing the main one can first reduce boatspeed to only 2-3 knots causing the bow to start falling off a bit (as the rudder becomes depowered through the loss of speed). Then, by backwinding the jib (the clew can simply be pulled to windward in smaller or bigger increments and the helm countered proportionally; there is no need to make significant course changes) boatspeed will fall to 1-2 knots and consists now mostly of sideways drift. The deep-reefed, relatively loosely sheeted main still helps keep the bows pointing into wind and waves. Finally, by dropping the main one is left with only 1/2 - 1 knot sideways drift (under backed jib). However, because the bow tends to fall of further now this position is only tenable if wind and waves are slightly misaligned and one has sufficient searoom to chose the most favorable tack (i.e. the tack that keeps the bows best into the waves). Good luck trying some of this out yourself (or invite an experienced heavy weather finkeel sailor to sail with you and give you some pointers). Flying Dutchman "Rivendel II", Port Vila, Vanuatu
Thanks and reply to Henk
Henk,thank you for your detailed answer. But,there is an misunderstanding.I think I couldn't ask it clearly.Hope could do this time. I didn't ask the sailing tactics in heavy weather.... What I'm trying to say is : In strong winds on winward tacks, when your boat speeds up , appr.wind moves forward too ,(and also because of the head waves) you have to bear away... Your VMG (Velocity Made Good) drops dramatically..So it becomes very difficult to reach a windward destinations for us(with modern midsize boats).. Or,let me ask you in another way: Suppose your homeport just 10 miles away on north side of you in late afternoon.And it starts blow 30 from death north. 1)Can you sail up to your destination? 2)Can you point less than 50-60 degrees of true wind? 3)What will your VMG you think? and with that speed,how long will it take you to reach to your homeport? Thanks all of you...
Henk,thank you for your detailed answer. But,there is an misunderstanding.I think I couldn't ask it clearly.Hope could do this time. I didn't ask the sailing tactics in heavy weather.... What I'm trying to say is : In strong winds on winward tacks, when your boat speeds up , appr.wind moves forward too ,(and also because of the head waves) you have to bear away... Your VMG (Velocity Made Good) drops dramatically..So it becomes very difficult to reach a windward destinations for us(with modern midsize boats).. Or,let me ask you in another way: Suppose your homeport just 10 miles away on north side of you in late afternoon.And it starts blow 30 from death north. 1)Can you sail up to your destination? 2)Can you point less than 50-60 degrees of true wind? 3)What will your VMG you think? and with that speed,how long will it take you to reach to your homeport? Thanks all of you...
Don and Henk/others of course...
Will you please read and answer my previous reply to Henk... Thank you. ps:Something wrong happened,it doesn't shown on directly in the response list.
Will you please read and answer my previous reply to Henk... Thank you. ps:Something wrong happened,it doesn't shown on directly in the response list.
Sorry for the late response, Ersin
However, you responded to my post after 6 days, which makes it more difficult to track for me. Most of the answers to the questions you are asking were already in my previous post, though. For instance, two of your questions ask whether you can still make progress to windward at 30 knots. Quoting from my post: "Above 30 knots (and corresponding waves) it may be difficult for your 36 footer to keep making much progress (our 43 footer is usually able to keep going till 35 knots or so) and you may have to start thinking about heaving to." Your remaining question adresses true wind angles and my post tried to address the subtle balance between making progress, keeping your bows into wind
However, you responded to my post after 6 days, which makes it more difficult to track for me. Most of the answers to the questions you are asking were already in my previous post, though. For instance, two of your questions ask whether you can still make progress to windward at 30 knots. Quoting from my post: "Above 30 knots (and corresponding waves) it may be difficult for your 36 footer to keep making much progress (our 43 footer is usually able to keep going till 35 knots or so) and you may have to start thinking about heaving to." Your remaining question adresses true wind angles and my post tried to address the subtle balance between making progress, keeping your bows into wind
Thank you Henk,onemore time,,
...for your close attention and help. I understand that it's a real hustle and a BÝG JOB for us to try to reach on windward points in 30 kn. I wish you and to all sailors we met here, merry christmas and much better year for your country and for all of the world....
...for your close attention and help. I understand that it's a real hustle and a BÝG JOB for us to try to reach on windward points in 30 kn. I wish you and to all sailors we met here, merry christmas and much better year for your country and for all of the world....
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