TWIST

[Don Guillette]

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?

 

[Don Guillette]

Mates: This is a "two for one deal" on twist because space does not permit as much detail as I would like so I have to write two articles.Now that we know what TWIST is, how do we set the proper amount for the sailing conditions we are sailing in? It's easy if you follow this simple proceedure:1)Sail closehauled2)Position the traveler so the boom is near the center line of the boat. 3)Trim the mainsheet until the top batten is parallel to the boom. The top telltail should be streaming. If it isn't and is curling - ease the mainsheet until it does stream.4)Now start to ease the traveler down. Observe the leech from top to bottom. If the TOP breaks first - trim the mainsheet IN as you have TOO MUCH twist. If the BOTTOM breaks first - ease the mainsheet OUT as you DON'T HAVE ENOUGH twist.What you are looking for is an even breeak in the sail from top to bottom.5)When you get an even break your twist is now set for your present point of sail and wind condition. If anything changes you have to obviously re set your twist.6) To pick up more speed - pull the traveler up a bit to obtain 3 to 5 degrees of weather helm. This small amount of weather helm provides LIFT to the rudder and lift equates to more power (speed).A quick way to check your twist is to notice the top telltail. If it curls to leeward more than half the time, you should add twist by easing the mainsheet until the top telltail streams. To get it perfect, go through the simple steps I outlined. With practice, you should be able to go through the proceedure in under 30 seconds!!

 

[Sean]

Great information, Don. Thanks.

 

[Francis]

Don, I have your book and chart and have read it I don't know how many times. It has a lot of great info, but I am a little confused on the twist. You mention that to depower the main with the boom vang to loosen the vang which would add more twist, and to tighten the vang to add less twist. But in high winds you say to tighten the vang. Well, if you tighten the vang isn't that taking away the tiwis that you need to dump air? Also if loosening the vang adds twist, wouldn't that catch more air in your sails? I know you say that in strong winds to tighten up the controls, but by tightening the vang that takes away the twist which I thought wouldn't dump the air? I hope I'm not to confusing, but I still am a little confused on this. I always thought that you want twist in the sails to dump air instead of tightening the vang to lessen twist.Thanks in advance

 

[Don Guillette]

Francis: Thank you for buying my book. Believe me you are not alone in the twist confusion. At every seminar I conduct mates have problems with the concept of twist. Lets take the mainsail and jib sail plane through the entire wind range. With very light winds - under 4 knots - you want the flatest sail you can get. The reason is that the wind does not have enough power to get around a sail with any belly in it. You'll see racers all the time with sails with belly in them in those conditions and if you flatten yours out you'll pass them every time. As the wind picks up, say from the 5 to 15 knot range, you want to induce more and more belly (up to a point) into the sail to produce power because you want to get as much speed out of your boat as it is capable of giving. Sail boats really want to go fast!! How do I know - they talk to me!! Depth or belly produces power. Twist robs power. To harness the power in this wind range, you want the sails to be pretty straight (picture the America Cup boats)with little or no twist. Once the wind gets up in the 15 to 18 knot range you want to induce some twist into the sail to spill power out of the top of the sail so you can control the boat. Assume the wind speed keeps rising and you have induced as much twist as you can. I know this won't make any sense until you try it but the next step is to flatten the sails as much as possable because a flat sail does not generate much power. Only sails with draft depth (belly) do. If that doesn't control the boat, then you reef. If that doesn't work you go to bare poles.How did I do with that explanation? Does it now make sense? Please, if it doesn't make sense just explain where I'm being unclear and I'll try again. Part of my problem is I'm just a common seaman trying to explain a complicated subject but I'll tell you that once the light goes ON it will be very clear to you.

 

[Warren]

We need you here

on the Texas Gulf Coast to give a seminar on sail trim. I've read your book (several times) and while I think I have the concepts down putting them into practice is not always that easy (or maybe I'm just a slow learner). A day in the class room and on the water would be a great help. While we have a ton of sailing schools in the area I don't know of any who offers a course on sail trim. Do you know of anyone in our area who has such a class or does this type of seminar?

 

[Don Guillette]

Warren; Thank you for the kind words. Actually, there is no money in a traveling sail trim show. I barely make a profit just traveling around SO Ca. I charge $75 for the class and that includes my book, chart and 6 handouts (about $35) and people still complain. You can get most of the concepts from the book but it is so much clearer when I demonstrate the principles with diagrams and a Pond Sail Boat.  Here was my problem with sailing schools. after I spent over $800 on sailing lessons and took every class they offered from beginner to advanced, I still didn't understand what was happening to the sails. I was great at backing the boat, flaking sails and working the head but was a lousy sailor.In my case, if they had inserted my book or one like it about half way through the beginner course, sail trim would have been very clear to me. Instead they used terms like draft depth and twist and did not define them. They would talk about positive pressure on one side of the sail and negative on the other. I had no idea what they were talking about and neither did anyone else in the class. Actually, as I looked around I though I was the only idiot but later I found out I wasn't alone.The way my program works is the participant spends 3 solid hours in the class room. My book, charts and 6 handouts are the text for the seminar and everyone understands the material from cover to cover or we don't leave the room. The next day is a 4 hour"on the water session" where the principles they learned are put into practice. I take about 6 people on the boat. They rotate through every boat position on every point of sail. It goes something like this. They get the boat going closehauled as best they can and then I trim it up for them. The boat is then brought head to wind and I mess up every control and they get it going again. Once they get it to full speed, we stop and they rotate positions, I mess everything up and they go at it again. That is done on every point of sail. Additionally, they have to explain every adjustment they are making and why. The first 45 minutes is a mess but boy do they get into after that. They also look at other boat and are able to tell me what is wrong with their sails and how to fix it. At the end of the session, the close hauled top speed run back to the dock brings is a sight to see. After the 3 hour seminar and 4 hours on the water,I will stack these students up against any of the highest intermediate sailors in the world!!When you investigate a sailing school you should question them on the curriculum. They will tell you they follow the ASA plan. That's great but it is a massive general overview on the subject of sailing. I didn't want a massive overview, i wanted to just learn how to sail the boat. Two private lessions finally got me going.I've tried to sell my program to various sailing schools in So Ca but most want to provide the overview and get the folks into chartering boats because that is where the money is.

 

[Don Guillette]

Mates; I just got off the phone with a sailor from FL. He was still having problems actually visualizing twist. With a Pond Sail Boat I could show you twist in 2 seconds and you'd never forget it. You'd also recognize it because 50% of the sailors sail that way all the time.Try this exercise - hold your right hand in front of your face like you were going to give a salute. What you are looking at, with your fingers in a straigth line, is a sail with no twist. The sail is said to be CLOSED. Now turn your fingers counter clockwise. See how the top of your finger open up? The top of your finger are now on a beam reach and your palm is closehauled. Since the top of your hand "opened up" that is called OPENED.Hopefully, you can see how the top of the sail - your fingers - would spill air out and the palm of you hand would still be driving. The more you open up (to an obvius point of no return) the more power you spill away. Conversely, as you close down you can see how you put power back into the sail. In order to get the full potention from the sail you also have to deal with draft depth, draft position and angle of attack. You just can't mess with twist alone no more that you could adjust just one jet on a 4 barrell carb and expect the car to run right.Was that demonstration any help to anyone? Please let me know if it wasn't and I'll try to come up with something else - like a picture. I've got to ask Phil at Sailboatowners.com how to add a picture. I think I'm a fair sailor but I'm lousy with computers. I came from the green eyeshades and pencils era!!

 

[Don Guillette]

Sail trim Users Guide

mates: I was thinking the comments of Warren of Kemah, TX regarding my book. He indicated he had read it a few times and was still picking up new things at each reading.My book is 65 pages and it is chocked full of sail trim material. There are not a lot of wasted words. I don't know how to explain this but I tell seminar participants in the first 5 minutes that I wish I could open their heads and pour the info in all at once. I guess it like the forest and the trees. You have to see the entire forest and not just look at individual trees. In other words, it is not just twist alone or the outhaul or the fairleads. It is EVERYTHING working together. You have to jamb the whole book into your head and then put the Sail Trim Chart in there to. The Chart tells you WHAT to do and the Book tells you WHY you are making a particular sail trim adjustment.Like everything else, sail trim ain't easy when you are learning but the good thing is it is not like nuclear research which goes on and on. It's like riding a bike. Once you learn how to ride it, your home free and there isn't any more to learn.

 

[Rob - "Averyanne" Oday 222]

Ok, No traveller. A boom vang sounds good,

Thanks Don for answering my traveller question so quickly. Maybe there is something else I should buy for the boat (besides a porta-potti). The 222's main sheet is at boom's end. A boom vang sounds like it would be better to control twist while using the main sheet for angle of attack. Seems handy for running too. I noticed the boom lifting quite a bit on my only sail with this boat while running. We had to sheet out so much with the attachment at boom's end.Thanks, Rob

 

[Steve]

Boom Vang Vs Cunningham

Don:Correct me if I am wrong. The Boom Vang is connected to the boom, and keeps the boom from riding up. The Cunningham is connected to the sail (I think from the sail to the mast?) and keeps the luff tight. Am I right?Steve

 

[Trevor - SailboatOwners.com]

Steve, you are right! (nm)

nm

 

[Don Guillette]

Rob of "Averyanne": What a nice boat name. Reminds me of a nice Irish girl I grew up with in RI!!To mates that might be following this thread, the situation Rob is describing is something I've mentioned a couple of times and that is when the boom goes over the side of the boat you lose most of the mechanical advantage of the mainsheet because the pulling angle is so severe. Without a boom vang, the boom goes up so much the mainsail loses most of its effectiveness.The sail trim controls for twist are the boom vang and the mainsheet and they both work together. The mainsheet also works in conjunction with the travel to adjsut the angle of attack.

 

[Jack]

Furled Mainsails

Don, Thank you for explaining sail trim. Whenever I read about sail trim, from you or other authors, they seldom address adjusting sail trim for boats with an inmast furled mainsail. Can you make comments in regard to sail trim for those of us with inmast mainsails (i.e. no battens).Thanks,Jacks/v FriendshipC350, #80

 

[Tom Ehmke]

Tell tales

Don,I have your plastic trim charts on board, but don't often use them because I don't race (consciously, but sometimes when another boat is in the area, and I become aware of my body language.. I'm racing) and I'm lazy enough not to want to try to read and sail at the same time. No comments about walking and chewing gum please. Anyway... I rely on the tell tales on the 155 jenny and the full-batten main. I admit that at certain times at certain wind speeds I can't get all the tell tales to fly in unison no matter what I try. I know that at low wind speed, no tell tale will fly. Is there a range of wind speeds when tell tales are not as reliable as at other wind speeds? I'm not trying to simplify trim by suggesting that tell tales are a cure-all. I just want to know when they are most reliable.Tom

 

[Don Guillette]

Jack: I've never had the opportunity to sail on a boat with in mast furling and no battensbut I'll take a crack at it. Just like the discussion on the traveler where we determined first what it does and used the resulting infomation to determined if we could get away without it. The mainsail need some rigidity to function properly. Without rigidity it would as limp as a dish rag. The luff of the sail gets it rigidity from the mast and the foot gets its from the boom. The purpose of battens is to provide rigidity to the leech of the sail plus they help maintain the shape of the mainsail and are also used to control draft depth.So, without battens, you are missing a big element of sail trim control but all is not lost. Since you don't have the battens, you have to compensate and do a better job at trimming your main. The principals of sail trim are the same no matter what you have for equipment. In other words, I know some guys that could sail a 55 gal drum down wind and beat half the fleet any day of the week on that leg!! My suggestion is that you COMPLETELY understand draft depth, draft position, twist and angle of attack. You should also completely understand the 8 primary controls for the mainsail, which are the traveler,mainsheet, cunningham (or halyard), boom vang, mast bend, outhaul and the leech cord. You should know exactly the function of each of them and what happens when you ease and trim each one. When you get to that point you can easily compensate for any shortcomings of your sail trim system - like no battens. If I had a boat with in mast furling or was sailing on one, that is what I would do. I sail on lots of boats where half the stuff doesn't work. The fairleads are rusted in place and the internal outhaul on older Catalinas is junk and consequently the outhaul doesn't work. The outhaul controls the bottom 2/3 of the sail and is a very important control for draft depth (belly), which is your main power setting. I just do the best I can without it. On the subject of authors of sail trim books - my problem was that if I was looking for infomation on draft depth or the outhaul I found that authors put the infomation all over the book like on pages 25, 52 81, and 125, which made it hard to find and understand. When I wrote my book, I did not make that mistake. Everything you need to know about the outhaul or draft depth is in its individual section. Same with reading telltails - everything you'll ever want to know about telltails is contained in 7 pages.Pop on over to the ships store and take a look at my book. It might be what your looking for.One other point - in my opinion, once you start furling the main or jib, sail trim goes out the window. At that point, all I want to do is control the boat and get it back in one piece. I hope

 

[Don Guillette]

Tom: Any time there are two boats going along together your racing!!Telltails are absolutly the most important sail trim indicator on the boat. No non-electronic devise has been developed that approaches their sensitivity and effectiness. They are the primary system of checks and balance for the mainsail and jib trimmer and an indicator as to whether or not a sail trim adjustemnt is necessary.Sadly, many sailors don't have them and lot of mates who do have them don't know how to read them. On every boat I go on, I take a spare set with me just in case the skipper has not installed them. I can't trim without them. Some guys might be able to but they are better at sail trim than I am. Even America Cup boats, with all their fancy gadgets, have them.As long as there is any wind flowing over your sails, the telltails will fly. The most important one to watch on the mainsail is the top one and the most important ones on the jib is the middle ones. Those are critical.I devote over 7 pages to telltails in my book. That is the importance I attach to them.One other point and it is something I hear all the time. There is no difference between cruising trim and racing trim - there is only a right way and a wrong way to trim your sails. Dennis Conner said that. On my sail trim chart - my suggestion is that if you set up your main and jib exactly the way I suggest for the wind conditions and point of sail you are on that you will be surprised how well your telltails will fly. After a couple of times you won't need the chart anymore.

 

[Rob]

Averyanne-Thanks Don for your kind words!

My son's middle name is Avery and my daughter's middle name is Anne. Both names go back pretty far in my wifes and my families. After much indecision on a boat name, one day the "light went on". It's nice to have some special meaning in the name and I too think it's real nice.And again thanks for all of your advice.

 

[Ken]

Leech Chord

Don

 

[Ken]

Leech Chord

DonI've been very interested in following the discussion on "TWIST".I've learned a lot and find your replies right to the point.I have a question about the leech chord.I know where it is but thats it.I have no idea of its function or how it is used correctly in conjunction with the other trim controls.Can you provide a quick fix?