TWIST Apparently every one understands draft depth and draft position. Actually, I think most mates found the concepts pretty easy to understand. So now we are half way home in our understanding of the 4 elements of sail trim. Once you understand these concepts, sail trim becomes a piece of cake. Twist confuses a lot of mates but it is also very easy to understand. On any given day in Long Beach harbor, or any area, 75% of the people sail with a twisted main and jib all the time. The actual definition is “The change in the angle of the chord line of the sail to the centerline of the boat at various heights up and down the sail”. No wonder no one understands what TWIST really is. Simply stated, twist is leeward sag of the leech of the sail. To view it, stand in your cockpit and look up the leech of the sail from bottom to top. Assume your sailing close hauled. The top half of a twisted sail will look like it is on a beam reach. The bottom half will look like it is close-hauled. You will never see a twisted mainsail on an America Cup boat or any race boat because Twist is a power robber. Why do we care about twist anyway? The reason is that there more wind at the top of the sail than at the bottom. Why is that? It is because of friction. Friction occurs when the wind passes over the surface of the water. The wind blows 60% harder at the top of a 50’ mast. Sail makers build twist into their sail because of this friction. The LESS a sail twists - the straighter its back - the more power the mainsail and jib develop. The MORE a sail twists – the more the top sags off to leeward – the less power they develop. Fine tuning twist is the most important adjustment you can make. The controls used to adjust twist in the mainsail are the mainsheet and boom vang. Increasing tension on these controls removes twist and decreasing tension increases twist. The control used to adjust twist in the jib is the fair leads. Moving the fairlead forward decreases twist and powers up the sail. Moving the fairlead aft increases twist and de-powers the sail. Obviously, forum space does not permit a detailed discussion of many of the elements of twist but I do discuss these elements in detail in my book “The sail trim Users Guide”. Next time your out on the water, move your fairleads and mess with the mainsheet and boom vang. Watch the top of the sail sag off and then proceed to eliminate the sag. Watch the power of your boat decrease as you increase twist. Any questions?
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Hey, Don
I used to minimize twist for the reason you describe, but after reading a UK book on sail trim a few years ago, began to induce a little, especially in lighter air. The UK book seemed to indicate that you effectively overtrim the upper sail without some degree of twist. So... ? Rick D.
I used to minimize twist for the reason you describe, but after reading a UK book on sail trim a few years ago, began to induce a little, especially in lighter air. The UK book seemed to indicate that you effectively overtrim the upper sail without some degree of twist. So... ? Rick D.
tell tales
Don, I use my tell tales to adjust the twist in my jib. When I get the outside (leeward) telltale flying at the foot, then I go for twist. After that I try to get the inside (windward) telltales flying by tweaking the sheets and jib fairlead cars. Does that sound about right? I have noticed that ever since I got my sail cleaned, I cannot always tighten the top of the sail to reduce twist. I get flutter and I have my car all the way forward. This seems a little backwards to me. If the sail shrunk a little, I should be able to over tighten the twist( theorctically) cause too much pull back on the clew and foot of the sail. Also, when I furl the jib, the sacrificial no longer covers the sail completely. I am thinking of having the rig tuned and then the sail checked out. Any opinions or advice? Mike D s/v Serenity 1998 H376 110% Jib and furled main (Selden)
Don, I use my tell tales to adjust the twist in my jib. When I get the outside (leeward) telltale flying at the foot, then I go for twist. After that I try to get the inside (windward) telltales flying by tweaking the sheets and jib fairlead cars. Does that sound about right? I have noticed that ever since I got my sail cleaned, I cannot always tighten the top of the sail to reduce twist. I get flutter and I have my car all the way forward. This seems a little backwards to me. If the sail shrunk a little, I should be able to over tighten the twist( theorctically) cause too much pull back on the clew and foot of the sail. Also, when I furl the jib, the sacrificial no longer covers the sail completely. I am thinking of having the rig tuned and then the sail checked out. Any opinions or advice? Mike D s/v Serenity 1998 H376 110% Jib and furled main (Selden)
Rick: When I was researching my book and sail trim chart, I read a million books and articles and watched enough videos to almost break my VCR. Amazingly, I found a lot of contradictory stuff, but the key was I tested EVERY principle on my Catalina 30. I kept what worked for me and discarded what didn’t. There is light air (4-6) and very light air (1-4) and if you can sail in that stuff , you can sail in anything. There are two things to consider in these conditions. One is the wind does not have a lot of power to get around your sail so you don’t want a lot of belly – in very light air you don’t want any . The second thing is that the effect of twist is to spill air (power) out of the top of the sail, which is kind of counter productive to what we are trying to do , which is get as much speed out of the boat as possible. In light air, you have two goals. One is speed and the other is pointing ability. So what you want to do is foot off slightly and ease the sail a bit to build up speed. If you were racing you would want the crew inboard. When you reach the max speed for the conditions, you should try to point up but don’t push it. All your tell tails should be flowing. If you over trim or have too wide an angle of attack (the 4th element of the “the 4 elements of sail trim”), you’ll stall the sail. If the leech is too tight in light air (4-6) you’ll stall the sail but if the sail is too deep you won’t be able to hold the wind. So, what do we do? The following is general because, as you can imagine, every boat and sail is different. In general, you want a deep enough sail but not very much with just enough twist to prevent a stall and a moderately wide angle of attack. As your speed increases, start to head up and trim in and start to reduce twist. What would be the specific settings for your boat? I have no idea!! Now that you have an idea of what your looking for, you will have to go out and experiment. Experiment and record the settings. I hope I’ve been of some help.
Mike DiMario: If we could sit down together for 15 minutes, I could explain to you all there is to know about telltales, twist and fairlead placement. Space here doesn’t permit a detailed discussion but I’ll do the best I can. Let’s start with some basic stuff. I think your boat is a fractional rig and the mainsail is the engine. My boat (Catalina 30) is a masthead rig and the jib is the engine. The 110 jib you have is not really a big jib. The bigger the jib, like a 135 and up, the easier it is to trim. The telltails on your jib that you want to watch are the middle ones. On your mainsail, it is the top one. Here’s a tip on playing your jib telltails – when the inside one starts to flip you should trim IN. When the outside one flips, you should ease OUT. The most important jib sail trim control is the fairlead and it is important to position it properly for the wind conditions you are sailing in. Any time you move a sail trim control, you should have a reason for doing so. It is important to go about sail trim adjustments in a step by step manner. Try these steps the next time your out sailing: 1) sail closehauled 2) Adjust the jib halyard. Light air = less tension. Heavy air = more tension. 3) Head up into the wind and check the luff of the sail. If the foot flutters, bottom luffs or bottom telltails beak first – move the fairleads AFT. If the leech flutters, top luffs or top telltails break first – move the fairleads FORWARD. At this point your fairleads are set. Don’t mess with them unless the wind speed changes or you change your point of sail. Now play with your mainsheet. Reading telltails – There are 5 telltail indicators and all require a particular adjustment. They are pinching, pointing, full speed, acceleration and footing. Your leeward telltail is your most important one to watch. In my book, I devote 7 pages to telltails. I devote 2 pages to the trim sequence for your main and jib. In another section, I provide a simple set by step procedure to set twist in your main. As I said, I can’t sit down with you, but my book “The sail trim Users Guide” and my “Sail Trim Chart” are the next best things. They cost less than a two 12 packs of Sam Adams and the nice part is you get to keep the material as opposed to the beer!!
Rigging the 23' Mac
Once the Boom is in place how do I rig the boom? As you can tell I am new at this. If you could give me resource (book) that describes the process. I also need to know how to furl the sail to fit in a sail bag. Bill
Once the Boom is in place how do I rig the boom? As you can tell I am new at this. If you could give me resource (book) that describes the process. I also need to know how to furl the sail to fit in a sail bag. Bill
Don, What about the clew?
I enjoy reading about triming and try to practice as often as I can. I really like the lessons I have learned from you about the tell tails. But, My Q is what about the clew outhaul. I was previously talking about an automatic clew tensioner and havnt made one strong enough. Other than the basics, Like flat sail for light wind and fat one for the high wind. What good does moving the clew do and what effect does it have on the other parts of trim? Would it be better to find a happy medium and call it a draw? Cole P.S. Mike D, are you still working at the FRB?
I enjoy reading about triming and try to practice as often as I can. I really like the lessons I have learned from you about the tell tails. But, My Q is what about the clew outhaul. I was previously talking about an automatic clew tensioner and havnt made one strong enough. Other than the basics, Like flat sail for light wind and fat one for the high wind. What good does moving the clew do and what effect does it have on the other parts of trim? Would it be better to find a happy medium and call it a draw? Cole P.S. Mike D, are you still working at the FRB?
Twist Again, Like . . .
Don, since the wind at the top of the sail is stronger than the wind at the bottom, it follows that the apparent wind at the top would be farther aft than the apparent wind lower down. Thus, wouldn't a certain amount of twist be desirable?
Don, since the wind at the top of the sail is stronger than the wind at the bottom, it follows that the apparent wind at the top would be farther aft than the apparent wind lower down. Thus, wouldn't a certain amount of twist be desirable?
Bob:On the desirability of twist, actually your stuck with some twist because the sail maker builds it into the sail for exactly the reason you stated. He is trying to balance the sail. If he didn't build in twist, the sail would be almost uncontrolable. Twist does nothing to power the sail. It does just the opposite. It de powers the sail, so on my boat, even when I'm just cruising around the harbor,I try to eliminate as much of it as I can. I really like a nice looking and matched main and jib
Cole: The outhaul is one of the controls used to adjust draft depth (belly) and draft position. The outhual controls the bottom 2/3 of the sail. If it were me, I would not just "set it and forget it" at some happy medium. Your outhaul would be like a broken clock that is only right twice a day!! It would be right for some wind conditions and points of sail but wrong for others. The outhaul is one of your most important sail adjustment controls. The same goes for your fairlead. I notice that on a lot of boats I go on, the fairleads look like they are rusted in place. In other words, the skipper has never moved them. The fairleads are the most important jib adjustment control. Some mates are of the "raise the main and roll out the jib" school. They never adjust anything.They call that sailing and the boat does sail but it performs so much better when you use all the sail trim controls God put on the boat.
Your order please
Don, Which order would I trim my sails. Do I trim the mail then the jib and back to the main as the jib affects it? That is what i have always done. I guess that is why its called the main
Don, Which order would I trim my sails. Do I trim the mail then the jib and back to the main as the jib affects it? That is what i have always done. I guess that is why its called the main
Cole: Nope, you've got it backwards. You trim the jib first and them the main. On boats, I race on, I handle the traveler / mainsheet and sometimes I get impatient waiting for the jib trimmer to get set but I have to. Like everything in life, there is a sequence that you should follow. It is outlined, in detail, on my Sail Trim Chart and in my book but here it is in a nut shell. JIB Step 1 - sail closehauled step 2 - adjust your halyard light air = less tension heavy air = more tension step 3 - adjust fairleads for conditions step 4 - trim sheet until luffing stops step 5 - check telltails and adjust accordingly MAIN step 1 - trim sheet with top batten parallel to boom step 2 - adjust cunningham step 3 - adjust outhaul step 4 - set traveler and adjust for twist On setting twist - On my Chart, I outline a 6 step proceedure on that function. Some of the steps, like setting faileads and the outhaul have sub steps but space does not permit a full outline here. Also, the process may seem time consuming but its not once you get used to it.
Mates: The last couple of sentences dropped off my last article and I could not get them included. What I was saying was that some of the steps, like set the fairleads and adjust the outhaul, have sub steps and space here on the forum does not permit a detailed outline. Also the steps may seem time consuming but once you get used to them, you can do the whole proceedure in seconds and your main and jib sails will look great - until the wind changes and then you'll have to reset!!
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