Mates: When the good folks at Sailboatowners.com gave me the opportunity a while back to host this Forum I started out with an article similiar to this one. A lot of water has passed under our keels since the first article so I thought it would be a good time to re visit the subject. This article will appear in the next Mainsheet Magazine, which is the Catalina owners magazine. THE FOUR ELEMENTS OF SAIL TRIM How many times have you wondered what sail trim is needed for a particular wind condition and point of sail? Do any or all of the sail trim controls on your sail boat confuse you? Your not alone as most sailors are confused and intimidated by all the sail trim controls for the mainsail and jib and consequently, either do not use any of them or use only a few. Additionally, many sailors have little or no idea why they are making a particular sail trim adjustment. This article, and other that will follow, will take the mystery out of mainsail and jib trim. Sail trim is an acquired art and simple to learn and understand but it has to be presented in an easy to understand fashion. Hopefully, I can accomplish that goal. Sail trim is not nuclear research. In other words, it is not a never ending process. It’s like riding a bicycle – once you learn to ride your there. You’ll probably be surprised to know that all the sail trim controls for the mainsail and jib are only adjusting four things and they are draft depth (belly), draft position, twist and angle of attack. Once you have an understanding of those four elements – your almost there. Without an understanding of those element your nowhere! That’s how important they are. Let’s start with the first two elements. Why do we have to understand DRAFT DEPTH (belly) and DRAFT POSITION in the first palce? We have to understand them because they control three things – POWER, ACCELERATION and DRAG. Drag is actually friction, which detract from power and comes from the rudder and keel. A sail is like an airplane wing and if a plane flew sideways it would be called a sailboat! The planes flaps, in the up or down position, produce a deep shape (like a belly) and are used for takeoff and landings. No flaps or a flat wing create less drag and are used for high speed and cruising. Drag on a sail boat has to be minimized or it will simply detract from your speed. Where does the POWER to power a sailboat come from? It comes from three things. The first is the SHAPE OF THE SAIL, which is either deep or flat. The second is the TWIST of the sail. Incidentally, your twist adjustment is one of the most important sail trim adjustments you can make. The third element of power is ANGLE OF ATTACK. The first element of sail trim we’ll discuss is DRAFT DEPTH. What is draft depth (belly)? It is “the % of sail width at a given point”. To understand that definition we have to briefly touch on DRAFT POSITION, which is “the point along the CHORD where the maximum depth falls”. This is probably getting a bit confusing, but hang in there with me and it will shortly become clear. I’m not going to define chord but instead give you a simple procedure to get you into the chord ballpark. I want you to measure the foot of your sail and then mark the halfway point on your boom. In other words, if the foot of your sail is 10’ long, mark the 5’ position with a piece of tape. From a draft position stand point, that 5’ mark is called 50%. The 4’ mark would be called 40% and so on. From a draft depth stand point we also want to continue to use the 10’ length of foot of the sail. So, if the sail had a 1’ belly, the draft depth would be called 10%. If it had a 2’ belly it would be called 20% and so on. There is one more piece we have to look at to put this all together. You have to look at the deepest part of the belly of the sail and imagine a vertical line going from top to bottom and intersecting the boom at some point. Where that imaginary line intersects the boom is called the DRAFT POSITION. If it intersects at the 4’5” mark, it is called 45%. If it intersect at 5’5”, it is called 55%. Let’s put all this together. Assume the skipper decided that the point of sail and wind condition he was sailing in needed a 20% draft depth and a 50% draft position in order to obtain 100% efficiency from his mainsail you would understand that he wants a 2’ belly in the sail and he wants the imaginary line that runs through the deepest part of the belly of the sail to fall at the 5’ mark. The mainsail controls you would use to adjust DRAFT DEPTH are the outhaul and mast bend. Increasing pressure on either of those controls reduces the belly and decreasing pressure increases the belly. The mainsail controls for DRAFT POSITION are the boom vang, Cunningham (or halyard), mainsheet, mast bend and outhaul. Increasing pressure on any of those controls moves the draft position forward and decreasing pressure moves it aft. The next time your on the water try adjusting those controls and watch the draft depth and draft position move. It’s a trip! My next Mainsheet article will deal with TWIST and ANGLE OF ATTACK. Future articles will discuss all the sail trim controls for the mainsail and jib. I’ll describe each one and tell you how each works. You’ll find the future article on telltails very interesting. If you have any questions about any of the above material, please contact me and I’ll do my best to answer your question. In fact, if you have any questions about any elements of sail trim just drop me a note and I’ll get back to you promptly. Don Guillette is the author of The Sail Trim Users Guide and the Sail Trim Chart. His products are available through the sailboatowners.com ships store.
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I'll be waitting
Don I'l be waitting eagerly for your next post, a a new oday owner THis ones has been extremely helpfull. Javier
Don I'l be waitting eagerly for your next post, a a new oday owner THis ones has been extremely helpfull. Javier
I'll be waitting
Don I'l be waitting eagerly for your next post, a a new oday owner THis ones has been extremely helpfull. Javier
Don I'l be waitting eagerly for your next post, a a new oday owner THis ones has been extremely helpfull. Javier
When
I race a 1984 Catalina 30T. I do need new sails but I continue to work on trim. I always struggle with the amount of draft and twist. When, how, where will we see your next article.
I race a 1984 Catalina 30T. I do need new sails but I continue to work on trim. I always struggle with the amount of draft and twist. When, how, where will we see your next article.
When
I race a 1984 Catalina 30T. I do need new sails but I continue to work on trim. I always struggle with the amount of draft and twist. When, how, where will we see your next article?
I race a 1984 Catalina 30T. I do need new sails but I continue to work on trim. I always struggle with the amount of draft and twist. When, how, where will we see your next article?
literacy
Please. The article is simple, informative and well presented. I'm looking forward to the next and to applying the information. However, lest the image of sailors be further besmirched, please your = belonging to you you're = a contraction of 'you are' Thank you.
Please. The article is simple, informative and well presented. I'm looking forward to the next and to applying the information. However, lest the image of sailors be further besmirched, please your = belonging to you you're = a contraction of 'you are' Thank you.
Me too
Don, Thanks for the article. Fleeing from the dark side I have sold my power boat and taken delivery of a Catalina 350 with in-mast furling. It does not have a cunningham. I mention this last point because I see a lot of stuff on sail tuning which looks as if it is targeting a fractional rig with conventional reefing. Is this fair comment? At any rate keep the mast-head cruisers in mind as you continue with your articles. I ordered the chart and book so looking forward to those and your next posting. Make sure you explain what the heck the leach lines are for.
Don, Thanks for the article. Fleeing from the dark side I have sold my power boat and taken delivery of a Catalina 350 with in-mast furling. It does not have a cunningham. I mention this last point because I see a lot of stuff on sail tuning which looks as if it is targeting a fractional rig with conventional reefing. Is this fair comment? At any rate keep the mast-head cruisers in mind as you continue with your articles. I ordered the chart and book so looking forward to those and your next posting. Make sure you explain what the heck the leach lines are for.
May the book be with you
I'm very impressed with Don's helpfulness and generosity in this forum. *box I encourage everyone to buy Don's book. Actually, so does Don from time to time!
I'm very impressed with Don's helpfulness and generosity in this forum. *box I encourage everyone to buy Don's book. Actually, so does Don from time to time!
Mike Aston: Actually, I target most of my stuff towards the masthead rig because it is the most common setup. No matter what type of rig you have - fractional or masthead - the principles are the same. Leech line - it is used when sailing upwind to keep the leech from fluttering or "motor boating" - making a flapping sound. Normally, that's all mates do with the leech line but there is much more it can do. Some sailors over tighten it. When sailing upwind you want to tighten it JUST enough to stop the fluttering. When reaching and running you want to tension it so it bends the battens thus giving the mainsail more shape and depth. What you are doing when you tighten the cord is you are actually preventing the top batten from twisting off because the leech cord is holding the batten in line with the boom. You'll see the importance of that when we discuss TWIST shortly. Twist is a big power robber. Now you know everything there is to know about the leech line. If you want to have some fun, next time your with a gathering of your sailing friends casually throw out leech lines and see the answers you get.They'll all tell you about fluttering but ask them what else does it do. On the cunnigham - actually, the cunnigham is just the halyard in reverse. The both do the same thing to the luff of the sail. I prefer the cunningham becuase everytime I tried to adjust the halyard a few inches I lost a few feet because of the weight of the entire sail. With the cunnigham, which is nothing more than a soft boom vang, you can get a more precise adjsutment with a lot less effort than using the halyard. In your case, you "gots to use what you got", which is the halyard.
Rick Macdonald: Thanks for the plug!! It is a labor of love as I don't want people to go through what I did in order to learn how to sail a silly sail boat. I really like talking about sail trim. When my wife and I go out a social funtion, she always warns me before hand not to bring up sail boats or sail trim because she says people don't want to hear about it and that I should pick some other topic of conversation, which I try to do. I try to explain to her that our friends get me going on the subject. They don't walk away from me either and seem to like to hear about it and I oblige them. Since you were kind enough to mention my book - I have to take the opportunity to jump on a commercial. For those listers that are awaiting the discussion on Twist and angle of attack - you can get a jump on the subjects by visitng the ships store on this site where you'll see my book and sail trim chart. Not only will you learn about twist but you'll learn about the function of every sail trim control and how they effect draft depth, draft position , twist and angle of attack plus a whole bunch of other stuff. Buy my book and chart and give yourself a nice Xmas present!!
Leech line adjustment while running
Hi Don, Since we're talking leech lines, mine is led to the aft end of the boom and tension is controlled with a jam cleat. However, when I'm running, the aft end of the boom is well over the side where the leech line is inaccessible. Obviously properly tensioning the line while the boom is still inboard is one solution. Do you know of any other rigging options to keep the leech line in reach? Thanks for your help. Gary Wyngarden S/V Shibumi H335
Hi Don, Since we're talking leech lines, mine is led to the aft end of the boom and tension is controlled with a jam cleat. However, when I'm running, the aft end of the boom is well over the side where the leech line is inaccessible. Obviously properly tensioning the line while the boom is still inboard is one solution. Do you know of any other rigging options to keep the leech line in reach? Thanks for your help. Gary Wyngarden S/V Shibumi H335
Gary: That reminds me of story - the outhaul on a C30 is inside the boom and it nevers works right, which is a shame because it is a very important control and controls the bottom 2/3 of the mainsail. I converted mine to an external system and I thought my adjustment set up was real trick as I could reach if from the cockpit. Unfortunately, I forgot to take into consideration the fact you are mentioning,when the boom goes over the side of the boat. After the first sail, and I was glad I was alone so no one would see what I had done, I had to re rig the line so it could be adjusted up by the mast where my cunningham is anyway. I'm not sure how you could run the leech line up to the front of the boom. I've never seen that done.
leech line at mast
Gary - this came up a few weeks ago but I'm not sure which forum. I asked about it so if you search the archives for my name and the word leech you might find it. I tried just now but the archives are closed for maintenence. As I recall, the fellow fixed the leech line at the bottom of the main's leech, and ran the line through a block at the head and then down through a pocket added to the luff. From there I don't recall if it was turned and run to the cockpit or terminated at the boom or bottom of the mast. Pretty clever, I thought, but I'm new to this and haven't ever even touched my leech lines yet (don't tell Don!). Don't go by my memory - search the archive!
Gary - this came up a few weeks ago but I'm not sure which forum. I asked about it so if you search the archives for my name and the word leech you might find it. I tried just now but the archives are closed for maintenence. As I recall, the fellow fixed the leech line at the bottom of the main's leech, and ran the line through a block at the head and then down through a pocket added to the luff. From there I don't recall if it was turned and run to the cockpit or terminated at the boom or bottom of the mast. Pretty clever, I thought, but I'm new to this and haven't ever even touched my leech lines yet (don't tell Don!). Don't go by my memory - search the archive!
Don... please clear the confusion
On my Coronado 25 I have a line led from the leach on the main around the inside of the boom and led back to the cockpit. I thought this was the outhaul. What is the difference between the outhaul and a leach line? Steve
On my Coronado 25 I have a line led from the leach on the main around the inside of the boom and led back to the cockpit. I thought this was the outhaul. What is the difference between the outhaul and a leach line? Steve
thanks for the time you put into it!!!!
Don I eagerly await the rest of your articles in the series and the discussion that they will generate. As a 2nd year sailor this is an excellent way to further ones education and become a better sailor Craig S/V Wind Toy 1977 H25
Don I eagerly await the rest of your articles in the series and the discussion that they will generate. As a 2nd year sailor this is an excellent way to further ones education and become a better sailor Craig S/V Wind Toy 1977 H25
Now I can spell leech correctly
Thanks for your reply Don. As you can see I am learning quickly (for an ex power boater)
Thanks for your reply Don. As you can see I am learning quickly (for an ex power boater)
outhaul and leech
The clew is the cringle (grommet) at the foot of the main at the leech. The tack is at the foot of the main at the mast/gooseneck. The outhaul is attached to the clew of the main. When you harden the outhaul, it pulls tight and flattens the lower portion of the sail between the tack and clew for all the trimming reasons that Don writes about. The leech line is a very thin line sewn into a pocket along the leech of the sail, from near the clew to near the head. Tightening this stops the trailing edge (oops, airplane speak for leech) of the sail from flapping (luffing). I may have mentioned in a previous post that I've never adjusted my leech line. It just occured to me that this may because I have a fully battened main. You can't reach the leech line when the boom isn't over the cockpit unless you run it along the boom or mast to the mast base or back to the cockpit.
The clew is the cringle (grommet) at the foot of the main at the leech. The tack is at the foot of the main at the mast/gooseneck. The outhaul is attached to the clew of the main. When you harden the outhaul, it pulls tight and flattens the lower portion of the sail between the tack and clew for all the trimming reasons that Don writes about. The leech line is a very thin line sewn into a pocket along the leech of the sail, from near the clew to near the head. Tightening this stops the trailing edge (oops, airplane speak for leech) of the sail from flapping (luffing). I may have mentioned in a previous post that I've never adjusted my leech line. It just occured to me that this may because I have a fully battened main. You can't reach the leech line when the boom isn't over the cockpit unless you run it along the boom or mast to the mast base or back to the cockpit.
Rick Thanks
Rick: Thanks for your explanation. I think I understand. I have a battened (fully?) main, therefore I probably don't have a leech line and the line that I was talking about IS an outhaul (I think this is one of the ones that is led back to the cockpit). A leech line is sewn in? How heavy a line is it usually? And where it is usually tied off? Thanks again. Steve
Rick: Thanks for your explanation. I think I understand. I have a battened (fully?) main, therefore I probably don't have a leech line and the line that I was talking about IS an outhaul (I think this is one of the ones that is led back to the cockpit). A leech line is sewn in? How heavy a line is it usually? And where it is usually tied off? Thanks again. Steve
Rick Macdonald: Somebody told me you have never touched your leech line!! Naughty, naughty but I'll bet the next time your out sailing you'll be using it - "now that you know the rest of the story" on how and why to use it.
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