Mates; Not much going on over at the Sail Trim Forum I host for Sailboatowners.com so I though I'd come over here for a bit and see if anyone is interested in learning some stuff about sail trim. To take the mystery out of sail trim is to essentailly understand that all the controls for the mainsail and jib only adjust four things and they are draft depth (belly), draft position, twist and angle of attack. Once you understand those four items you are miles ahead of 75% of the sailors worldwide. Why do we have to understand draft depth and draft position? The reason is because they control 3 things - power, acceleration and drag. Drag is actually friction, which detracts from power and comes from the keel and rudder. A sail is like an airplane wing and if a plane flew sideways it would be called a sailboat. The plane's flaps, up or down produce a deep shape (like a belly) and that shape is used for take offs and landings. Where does the POWER to power a sailboat come from? It comes from 3 things and they are the shape of the sail, which is either deep or flat. It comes from TWIST, which is the most important sail trim adjustment you can make and it comes from the ANGLE OF ATTACK. What is DRAFT DEPTH? It is "the % of a sails width at a given point".To understand that definition we have to understand Draft POSITION, which is "the point along the chord where the maximum depth falls. To find the chord you measure the foot of the sail and mark the halfway point. If the chord is 10' long then the 5' mark would equal 50%.The 4' mark would equal 40%. So if the sail had a 1' belly the draft depth would be 10%. If it had a 2' belly it would be 20%. Now, if you imagine a vertical line going up the middle of the belly of the sail, where that line intersected the boom would be called the draft position.If it intersected the boom at the 5' mark, the draft postion would be 50%. Now you know what the skipper is talking about when he says set the draft deepth at 20% and set the draft position at 50%. You may not know what sail trim controls to use to adjust your main and jib to get that configureation but at least you know what it is. I hope I didn't bore anyone with the above infomation. If your interested in learning more about sail trim, just let me know.
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Very informative
This was good. If you could include a diagram it would help to explain the concept. I would like more on the subject of balancing the sail trim to the boat. I've heard that when balanced the boat basically sails itself. John Richard s/v Jack's Place
This was good. If you could include a diagram it would help to explain the concept. I would like more on the subject of balancing the sail trim to the boat. I've heard that when balanced the boat basically sails itself. John Richard s/v Jack's Place
Excellent ..................
............. but a sketch to go along with it would be invaluable. Regards, s/v Island Hunter
............. but a sketch to go along with it would be invaluable. Regards, s/v Island Hunter
John S/V AlcyoneMore please
Could you please give more information about twist? The other thing I am interested in is. When you are sailing in heavy air and pointing up as high as the yacht will sail what can you do to stop or minimise sail flogging. (other than bearing away slightly) For example recently we were caught in a very sudden storm with all sails up and little time to reef. Winds up to about 35-40 knots. Because of the amount of sail up it was not possible to sail out of it (beam reach)to shelter. We hauled in the main sheet tight and pointed her up. However when we did this it resulted in the boom shaking violently with the mainsail flogging hard. Of course we had to drop all sails however it would be nice to know if there is a way to stop this massive flogging. (Shakes the whole yacht from bow to stern)
Could you please give more information about twist? The other thing I am interested in is. When you are sailing in heavy air and pointing up as high as the yacht will sail what can you do to stop or minimise sail flogging. (other than bearing away slightly) For example recently we were caught in a very sudden storm with all sails up and little time to reef. Winds up to about 35-40 knots. Because of the amount of sail up it was not possible to sail out of it (beam reach)to shelter. We hauled in the main sheet tight and pointed her up. However when we did this it resulted in the boom shaking violently with the mainsail flogging hard. Of course we had to drop all sails however it would be nice to know if there is a way to stop this massive flogging. (Shakes the whole yacht from bow to stern)
John / Ralph: Thank you for your comments. My answer about the diagrams will sound like a commercial but we are all friends here at sailboatowners.com and if my infomation can help sailors sail more efficiently then that is what this list is all about. If you hot foot it over to the ships store at Sailboatowners.com you will find listed my book THE SAIL TRIM USERS GUIDE. This book contains many diagrams and explains everything you will ever need to know about sail trim. The book tells you WHY you are making a particular sail trim change.You'll also find listed my SAIL TRIM CHART.This chart list every sail trim control for your main and jib and gives you the proper adjustment for every wind condition and point of sail. It tells you WHAT to do. Both products are sold with a money back guarantee. If your not satisfied we will return your money. Also, I gaurantee that after digesting my products you'll know more about sail trim than 75% of the sailors worldwide. Many of the mates on this list have tried my products and are happy with them.
Don
Don, Was wondering about which sail is preferable, I like sailing with jib only in heavier weather but have seen different opinions on this site, any info in reguards to this? was wondering because it seams like I have more control 25 knots plus wind. John
Don, Was wondering about which sail is preferable, I like sailing with jib only in heavier weather but have seen different opinions on this site, any info in reguards to this? was wondering because it seams like I have more control 25 knots plus wind. John
Don, I Will Never .........................
............ buy anything over the net. However, after reading just your brief description of sail trim and assuming the rest of your book is just as well written, I've got to get a copy. But only this once, mind you. Regards, s/v Island Hunter
............ buy anything over the net. However, after reading just your brief description of sail trim and assuming the rest of your book is just as well written, I've got to get a copy. But only this once, mind you. Regards, s/v Island Hunter
Unsolicited heavy weather sail handling comments
While acknowledging Don's superior expertise in sail trim issues (and fully agreeing with the four basic principles he has outlined) I cannot resist jumping into the heavy weather sail handling discussion Mark and John are trying to start up. If a smaller, relatively light cruiser such as the Hunter 260 gets caught in a 35+ knot squall with all sails up, there would indeed seem to be not a whole lot else to do than to take the pressure of the sails by turning into the wind and immediately furling the genoa, followed by dropping the main, unless the latter happens to have a very deep 2nd or 3rd reef in which case it may be possible to try to reef. Speedy reactions are essential to avoid torn sails or worse. At the same time, however, it is important to remember that while turning into the wind, the genoa will tend to start flogging well before the main (unless the latter is baggy) and should thus be furled while trying to keep some pressure on the main in order to avoid having both sails flog like crazy at the same time. Although a flogging main + boom can certainly shake the whole vessel, as described by Mark, my suspicion is that much of the shaking actually came from the flogging jib which jerks the hull directly via the jib sheet while the main jerks primarily on the boom. The entire manoever can be executed most safely by immediately starting the auxiliary engine before turning into the wind in order to keep controlling the bow during the entire procedure. In case no auxiliary engine is available I would try to run off under bare poles or a small slip of (80 % furled) genoa AFTER wrestling the main down. Like John, I am also eager to hear Don's preference for a heavy weather sail. At the same time, however, there is nothing like trying to keep the sail plan balanced under all but the most severe conditions. In other words, a deeply reefed main together with an adequately furled/reefed jib will keep the loads on mast and rigging distributed more evenly while also helping to reduce excessive weather or lee helm. If one really needs to choose for a single sail in heavy weather I personally prefer my deeply reefed main (or trysail) since it will tend to steer the vessel into the wind if the helmsperson (or autopilot) temporarily looses control whereas a single jib might conceivably cause the vessel to broach or jibe if helm control is lost (e.g. in case the helmsperson looses his or her footing or gets disoriented by a boarding wave). Flying Dutchman
While acknowledging Don's superior expertise in sail trim issues (and fully agreeing with the four basic principles he has outlined) I cannot resist jumping into the heavy weather sail handling discussion Mark and John are trying to start up. If a smaller, relatively light cruiser such as the Hunter 260 gets caught in a 35+ knot squall with all sails up, there would indeed seem to be not a whole lot else to do than to take the pressure of the sails by turning into the wind and immediately furling the genoa, followed by dropping the main, unless the latter happens to have a very deep 2nd or 3rd reef in which case it may be possible to try to reef. Speedy reactions are essential to avoid torn sails or worse. At the same time, however, it is important to remember that while turning into the wind, the genoa will tend to start flogging well before the main (unless the latter is baggy) and should thus be furled while trying to keep some pressure on the main in order to avoid having both sails flog like crazy at the same time. Although a flogging main + boom can certainly shake the whole vessel, as described by Mark, my suspicion is that much of the shaking actually came from the flogging jib which jerks the hull directly via the jib sheet while the main jerks primarily on the boom. The entire manoever can be executed most safely by immediately starting the auxiliary engine before turning into the wind in order to keep controlling the bow during the entire procedure. In case no auxiliary engine is available I would try to run off under bare poles or a small slip of (80 % furled) genoa AFTER wrestling the main down. Like John, I am also eager to hear Don's preference for a heavy weather sail. At the same time, however, there is nothing like trying to keep the sail plan balanced under all but the most severe conditions. In other words, a deeply reefed main together with an adequately furled/reefed jib will keep the loads on mast and rigging distributed more evenly while also helping to reduce excessive weather or lee helm. If one really needs to choose for a single sail in heavy weather I personally prefer my deeply reefed main (or trysail) since it will tend to steer the vessel into the wind if the helmsperson (or autopilot) temporarily looses control whereas a single jib might conceivably cause the vessel to broach or jibe if helm control is lost (e.g. in case the helmsperson looses his or her footing or gets disoriented by a boarding wave). Flying Dutchman
But about roller furling mainsails...
Don I bought your trim guides when I owned a Hunter 33.5, and found them to be very valuable. After I bought the Hunter 410, I corresponded with you about trimming the roller furling main, since it is WAY different from sailing a traditional full-roach main. Since you have initiated this thread on the main board, I thought I'd invite my fellow roller-furling main owners to opine on how they get the most performance out of their boats. I've sailed the 410 a lot, and find that up to about 18 knots, I need more than 10% draft depth (big belly) in the sail, and the boom has to be sheeted out more than normal, to get maximum performance out of the boat. When you and I corresponded earlier in the year, you had not yet sailed a boat with a roller furling main. Have you yet? Let's chat!
Don I bought your trim guides when I owned a Hunter 33.5, and found them to be very valuable. After I bought the Hunter 410, I corresponded with you about trimming the roller furling main, since it is WAY different from sailing a traditional full-roach main. Since you have initiated this thread on the main board, I thought I'd invite my fellow roller-furling main owners to opine on how they get the most performance out of their boats. I've sailed the 410 a lot, and find that up to about 18 knots, I need more than 10% draft depth (big belly) in the sail, and the boom has to be sheeted out more than normal, to get maximum performance out of the boat. When you and I corresponded earlier in the year, you had not yet sailed a boat with a roller furling main. Have you yet? Let's chat!
I second that request
for more sail trim information for furling mainsails. We bought your trim guides and follow your instructions to increase draft for moderate wind speeds, and decrease it at the low and high extremes. It would be wonderful to have a sail trim guide just for us, recognizing that we don't have a cunningham, never touch the halyard adjustment, rarely touch the vang, and basically adjust only the sheet, traveler and outhaul.
for more sail trim information for furling mainsails. We bought your trim guides and follow your instructions to increase draft for moderate wind speeds, and decrease it at the low and high extremes. It would be wonderful to have a sail trim guide just for us, recognizing that we don't have a cunningham, never touch the halyard adjustment, rarely touch the vang, and basically adjust only the sheet, traveler and outhaul.
Mark: Twist confuses a lot of sailors. I'll try to simplify it for you. The next time your out sailing, sail closehauled and look up the leech of the sail. Keep that view in mind. Now ease the mainsheet and the boom vang. You'll see the top of the sail open up.The bottom of the mainsail will look like it is closehauled and the top of the sail will looklike it is on a beam reach. What is happening is that the top of the sail is spilling air or depowering the sail. Now trim in your mainsheet and boom vang and watch the top of the sail close up and become more powerfull. The actual definition is "the change in the angle of the of the chord line of the sail to the center line of the boat at various heights up and down the sail". Who in God's name understands that!?! In simple terms it is just the leeward sag of the top of the sail and on any given day you'll see 50% of the sailors sailing their boats that way. Twists main function is to depower the mainsail or the jib.
Four Element Of sail Trim
Mark: Here is the sail trim for sailing in heavy air just before you reef. My answers are none technical and are coming from a common seaman, so unscientifically and simply put, you want your main and jib as flat as possable because a flat sail is a less powereful sail. The more belly you put in the sail (like flaps on a plane) the more powerful it becomes. You also want to induce twist in the top of the sail to splill power and from my last message, you already know what sail trim controls to use to accomplish that end.You also want to reduce the angle of attack but angle of attack is another story.
Mark: Here is the sail trim for sailing in heavy air just before you reef. My answers are none technical and are coming from a common seaman, so unscientifically and simply put, you want your main and jib as flat as possable because a flat sail is a less powereful sail. The more belly you put in the sail (like flaps on a plane) the more powerful it becomes. You also want to induce twist in the top of the sail to splill power and from my last message, you already know what sail trim controls to use to accomplish that end.You also want to reduce the angle of attack but angle of attack is another story.
Ralph: I know how mates feel about buying stuff over the net but how is this for a guarantee. If you are not 100% satisfied with both my book and chart, I'll refund your money and you can keep both items. If they didn't satisfy you, you could give them to a sailor friend, who you don't like, for Xmas!!
Pete: I pondered your request and the only thing I could come up with is to "white out" everything on my Chart except the sheet, traveler and outhaul.JUST KIDDING!! Actually, if you tried adjusting the other controls for the main and jib you'd be plesently surprised how much more efficiently your boat would sail and there would be less wear and tear on your equipment also.
Curt: Nope, I've yet to have a chance to sail on a boat with a mainsail roller furler. I can't imagine much difference but I can't say since I have never had the experience. There has got to be some of these boats in Long Beach. maybe one of these days I'll get the opportunity.
John: Sailing in heavy weather,and maintaining a comfortable control of the boat, is all about reducing sail. For the beginner to intermediate, who I direct the majority of my stuff towards, here's my opinion - its all about reducing sail area. To over simpify it, you start with the main and continually reef it down and down until its down all the way. At the same time, your reducing sail area in the jib until its down to next to nothing. If it got really, really bad you'd sail with a bare pole. On the other hand,I was racing last year at the Catalina 30 National Regatta in Santa Cruz and the wind was in excess of 45 knots. One boat was dismasted and another lost his main. Three boats dropped out. We were in contention for a 1st out of 19 boats (we ended up with a 2nd)so we had everything flying as did the guys that were trying to stomp us, but that was a different situation.I was sailing on a boat with a crew that came together from all over the US for this event and I felt very confident.If it was just my wife and myself going out for a Sunday sail in Long Beach and it was blowing 45 Knots, I'd never leave the dock!!
flat and twisted??
Don, You mentioned that in heavy air one should keep the sails flat and to have a twist at the top of the sail to spill some air. I understand how to trim my sails to make them flat, but how do you make them flat AND twisted??
Don, You mentioned that in heavy air one should keep the sails flat and to have a twist at the top of the sail to spill some air. I understand how to trim my sails to make them flat, but how do you make them flat AND twisted??
Al: Good question. Flat and twisted at the same time seems like a contridiction but here is an over simplified explanation of what is happening. Sails are manufactured with twist built in. The reason they do that is that the wind blows 60% harder at the top of the mast than at deck level. The reason is friction. As the wind blows across the water it looses strength. So you've got some twist already built in. If you didn't you'd have a messy situation to control. To depower the mainsail a bit more you merely ease the two mainsail primary twist sail trim controls, which are the boom vang and the mainsheet, until you get the amount of twist you and your boat are happy with. On your jib, you change twist by moving the fairlead. Forward decreases twist and moving it aft increases twist.
Mark from Western Austalia: I hope you pick up this message. I just received my October issue of Sail Magaazine, which I assume you can get in Australia. On page 56 there is an article called "Time To Shorten Sail", which you should review. It says basically what I said but goes into a lot more detail. It even talks about the flogging mainsail. If you can get a copy of that article, I think you'll find it helpful. I was wondering mate, how do you think the folks from "down under" will do with the Amer Cup next year. I met a lot of your chaps off of your boats when they were in San Deigo a while back. They were a much more friendlier team than the Americans. I wanted to buy your mates a pint but they would not allow me. They bought me a pint! The Americans, on the other hand, would not take the time to talk to me or anyone else.
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