How to Trim Sails with Carol Hasse, Part 1 – Parts & Points of Sail

October 6, 2014

Knowing the parts and points of sail is important in deepening the understanding of sailing and how to trim sails. In the first of our How to Trim Sails series, master sailmaker Carol Hasse teaches the basics.

Navigate Further...

Carol Hasse is the owner and proprietor of Port Townsend Sails.


How to Trim Sails, Part 2 - The Headsail

How to Trim Sails, Part 3 - The Mainsail

Sails for Blue Water Cruising

A Good Boat, Up Close, the Nordic Folkboat LORRAINE

Points of Sail Guide: click here for the OCH downloadable PDF.

Get Free Videos Start Free Trial Members Sign In


– Pursuit of good sail trim really is something worthwhile, not to be something we’re obsessive about necessarily, but to make the boat not just move faster, but with less leeway, less heel, with that wonderful feeling of predictability and some ineffable magic and joy. So let’s look together then at the basic edges and corners of a three-sided sail. So, in the language of sails that most of us sailors know, the leading edge of a triangular sail is called the luff, whether that sail is a mainsail or a headsail. The word luff is a noun when it refers to the leading edge of the sail and it’s a verb when we get the wind on the wrong side of it. The bottom edge of the sail is called the foot, which actually makes some sense, and the trailing edge, the back end of the sail is called the leech. These are words that are antique, come to us from the Dutch or Old English. So, the corners of the sails are head that we hoist aloft with a halyard. The tack that’s secured closest to the deck, or would be secured to the roller furling drum if we have a roller furling system, or, if it were hanked-on to the headstay, in my preference would be attached to a tack pennant, that which lifts the tack of the sail above the bow pulpit or lifelines so that we have visibility forward, so that we can work our ground tackle or mooring lines ahead of time if we’re coming in under sail. And also, when we ease the sheet, gives our sail less shape distortion and chafe against that bow pulpit. The tack is the corner of the sail that, on our main, would be attached at the intersection of the mast and boom that we refer to as the gooseneck. So, the clue is the after most corner of the sail and to it are attached the sheets. Now, you would think most of us sailors, when we’re new to it, that the sheets are those big white things up in the air, but actually, no, they’re the lines that control the sail. So, let’s look then at how they are really the trim tools of our headsail. So sheets end that halyard. So, let’s back up a minute here and make certain that we understand that when we’re trimming sails, unfortunately, or fortunately for those of us who love to trim sails, it’s not a set it and forget it. It’s gonna completely depend on again wind speed and point of sail. So, let’s talk about point of sail and all that means is the direction your boat is going relative to the wind. So we need to know a few things always. One is where we are. The next thing is where we wanna go. And the third thing is which way the wind is blowing from. Learning to read the wind on the water again is a lifetime skill. One of the beauties of sailing close to land is we can see flagpoles, we can see our paper mill smoke, we can see all sorts of clues as to which way the wind’s coming from. When we’re on our vessel, we’re usually looking aloft at the masthead fly because again it’s the direction of the wind and then our course that determine our point of sail. So, if we’re sailing as close as possible to the wind, we’re close hauled and our sails will be trimmed in as close as possible to the rig. So our genoa might be up against the spreaders, but not poking through them. Our mainsail would be on the center line. Now, if we bear away a little bit, we’re now on what’s called the close reach. A close reach is a little less precise. We’re gonna ease our sails. A close reach is anywhere between as close as we can sail to the wind and something that we can define, a beam reach. A beam reach is when the wind is perpendicular to our center line. As we bear away, or fall off away from the wind, we’re gonna continue to ease our sails. How far do we ease them? Just until they start to luff and then we sheet them back in. That’s the first thing we learn in our sailing lessons. The next point of sail, then, is a broad reach. The broad reach, like the close reach, is a little nebulous. It’s anywhere between a beam reach, where the wind is perpendicular to our center line, and a run, where the wind is parallel to our center line coming over our stern. And at this point our sails are generally wing and wing, and again, we’re on a run. One of the lovely things about the points of sail, even though it’s a lot of words, is they’re the same on the port tack, when the wind’s coming over the port side of our boat, as they are on the starboard tack, when the wind’s coming over the starboard side. So, from a run we’d head up to a broad reach, a beam reach, a close reach, and again we would be close hauled. So those are the points of sail and it’s always a good idea to know the point of sail you’re on, how your vessel is positioned relative to the wind. That’s the first step in how we trim our sails. So, the points of sail are again essential to everything that we’re gonna be doing when we start our sail trim. Less obvious dimensions, but important ones all the same are the L.P., which stands for luff perpendicular, that line that goes at right angles from the left to the clew. And it’s the L.P. that helps us determine the square footage of the sail. So our sail being triangular, we multiply height times base, divide by two, and that tells us how many square feet are in that sail. It’s not essential that we know how many square feet are in that sail, but we have to have an understanding of how that relates to our four triangle and what winds we should be flying this in. So, simple rule, in general, a single sail, not partially furled or reefed, is only gonna be effective in a 10 to 15-knot wind range. So that genoa that might give us steerage way at five knots, 20 knots later, it’s going to be too much sail. So, part of sail trim is having the right size sail up for the right amount of wind. So, another less obvious dimension in this is what drives the sail. And that is its camber, which is synonymous with draft, or fullness. How that’s measured is by taking a chord length, which is a straight line that goes from luff to leech. Let’s put our luff back in here. And that chord has a relationship to the camber. So there can be an infinite number of chords in a headsail. When we look at it as sail makers, we’re looking at three of them at the quarter points and then we’re determining how much camber we want in that sail. So again, camber is synonymous with draft or fullness and it just means the curved shape, the airfoil shape of that sail that actually generates forward drive. So we express the relationship of camber to chord in a percent. So if this chord happens to be 10 feet long, and we have a foot of camber, we have a 10% camber ratio or a one in 10 camber ratio. Again, it’s not critical that you know exactly what that camber ratio is, but as a sail trimmer, you need to know that you can affect two things about it. One is how much fullness there is in that sail at any given time and where that fullness is and that is what we’re doing when we trim a sail. When we build a sail, the sailmakers, whatever fabric we’re using, whether it’s a woven polyester or a laminated exotic, what we do is orient the structural integrity of the fabric along the greatest load path. For our headsails and our mainsails, the greatest load path is gonna be up the leech, so we wanna orient the fabric in a cross-cut woven polyester Dacron sail so that the strongest part of the fabric is taking the load of the sail. So there’s a great example that I love to show about how this works. If we unroll a roll of Dacron or nylon sailcloth, we’ll see that there are fibers that run parallel to the salvage edge, which are referred to as the warp fibers. And then there are fibers that run perpendicular to those. Those are referred to usually as wet fibers but in sailmaking, we call those fill fibers. So they go over under, over under, and it’s along the fill fibers in cloth that’s woven for cross-cut sails, so again, let’s draw this mainsail out here, that would be oriented perpendicular to the trailing edge or the leech of the sail. So the fill fibers are our strong ones. The warp fibers are also very strong, but anything that’s not on the warp or weft, warp or fill, is on the bias and that bias is very stretchy. So if we had a single piece of fabric that was woven we would figure out which is the warp and which is the fill. The fill is a little less stretchier. And anything that’s on the bias, then, when we tension it, is going to change where the fullness of that sail ends up. So what a sailmaker does in orienting the fabric on the sail is to put that bias on the luff of the sail so that when we tension it, the luff of the sail, we are actually pulling the fullness forward. So sail trim in its elemental form, basically is pulling, putting tension on the three sides to achieve the shape that you’re after.


11 Responses So Far to “How to Trim Sails with Carol Hasse, Part 1 – Parts & Points of Sail”:

  1. Avatar Lorenc Kodheli says:

    When is the book coming out? It would be nice if she wrote a book on this.

  2. Avatar Robert (Bob) Godfrey says:

    I have been sailing for many, many years and have often wondered exactly how a sail was constructed in order to achieve good performance and this video is simply excellent! Great work Carol, thank you for sharing your experience with us all. Please keep up the great work.

  3. […] refreshing is this great series on trimming sails. Just good, straightforward information, presented in OCH’s trademark […]

  4. Avatar James Purdy says:

    She is very informative and clearly covers topics not usually mentioned in other videos.

    It’s late November and I can’t wait to test her points. In RI, that will be a while.

  5. Avatar Keith Cheney says:

    Yes, David’s comment (below) is spot on. This is a very informative video that should be seen by new and experienced sailors alike. Thank you, Carol, for a great video series!

  6. Avatar Shaun Wallace says:

    I have yet to build my first boat, but having inherited an industrial strength sewing machine have built two sets of sails myself. However, not until watching Carol’s simple explanation did I understand the relationship of warp, fill, and bias. Needless to say my first set of sails were a terrific lesson in how to fail at constructing a sail. The main setup pitifully largely due to my misunderstanding of bias. The jib was a better attempt though the chamber was minimal. My second set was a kit with pre-cut panels, and what a world of difference. The warp and fill were oriented properly, and the built-in chamber propels my boat noticeably faster. Ironically I still did not comprehend what was making the new sails better. Thank you Carol! In 12 minutes you have helped the puzzle pieces fall together.
    For those of you considering constructing you own sails, I highly recommend the process.

  7. Avatar Edward Childs says:

    What is the easiest way to measure the camber to chord ratio on an existing sail if you don’t have the original spec from the sail maker?

  8. Avatar Paul Atkins says:

    I’ve been sailing for over thirty years and though I knew all of this, but drinking in this great series of videos always teaches me something. Thankyou! I am treating this site like a box of the best chocolates, savouring every post.

  9. Avatar Peter Brackenbury says:

    I agree with David. A wonderful intro to a topic that can be intimidating to a person like me.

  10. Avatar David Gruendel says:

    I’ve certainly never run across a more instructive 12 minutes on sail construction and trim. As usual, Carol is very impressive. I look forward to part 2, and hopefully more thereafter.

Leave a Comment

You must be logged in to post a comment.


Get Immediate Access, Plus
10 More of Our Best Videos

Your email is safe with us.
We'll NEVER share it, and we DON'T spam.

or …


Start Free Trial

Get Instant Access as a Member to the Entire Site

  • Access all 1000 videos/articles
  • No risk! Cancel anytime
  • Get a nice discount if you join